Pork carcass composition, meat and belly qualities as influenced by feed efficiency selection in replacement boars from Large White sire and dam lines

This study evaluated carcass attributes, meat and belly qualities in finisher boars (n = 79) selected for feed efficiency (low, intermediate and high) based on estimated breeding value for feed conversion ratio within a Large White dam and sire genetic lines. The sire line had lower trimmed fat proportions and higher lean than the dam line (P < 0.01). Genetic lines expressed slight colour changes and drip losses (P < 0.05), with no differences in pH, marbling and cooking traits (P > 0.05). High-efficient animals presented the highest lean yield (P < 0.01), the lowest trimmed fat proportion (P < 0.01) and no effect on meat and belly quality attributes (P > 0.05) compared with other efficient groups. Interaction between efficiency group and genetic line was only detected for belly weight and thickness (P < 0.01). High-efficient animals offer a greater leanness level, with minimal impact on meat and belly quality traits.

Hydroponic barley supplementation fed with high protein diets improves the production performance of lactating dairy cows

The study investigated the effects of dietary protein level and the inclusion of hydroponic barley sprouts (HB) on lactation performance, blood biochemistry and N use efficiency in mid-lactation dairy cows. Treatments were arranged in a 2 × 2 factorial design with 2 crude protein (CP) levels [16.8% and 15.5% of dry matter (DM)], with HB (4.8% of DM, replacing 4.3% of alfalfa hay and 0.5% of distillers dried grains with solubles (DDGS)) or without HB. Forty-eight multiparous Holstein dairy cows (146 ± 15 d in milk, 40 ± 5 kg/d of milk) were randomly allocated to 1 of 4 diets: high protein diet (16.8% CP, HP), HP with HB (HP+HB), low protein diet (15.5% CP, LP), or LP with HB (LP+HB). An interaction between CP × HB on dry matter intake (DMI) was detected, with DMI being unaffected by HB inclusion in cows fed the high CP diets, but was lower in cows fed HB when the low CP diet was fed. A CP × HB interaction was also observed on milk and milk protein yield, which was higher in cows fed HB with HP, but not LP. Inclusion of HB also tended to reduce milk fat content, and feeding HP resulted in a higher milk protein and milk urea N content, but lower milk lactose content. Feed efficiency was increased by feeding HP or HB diets, whereas N efficiency was higher for cows fed LP or HB diets. There was an interaction on the apparent total-tract digestibility of DM and CP, which was higher when HB was fed along with HP, but reduced when fed with LP, whereas the digestibility of ADF was increased by feeding low protein diets. In conclusion, feeding a low protein diet had no adverse effect on cow performance, while feeding HB improved milk and milk component yield, and N efficiency when fed with a high CP diet, but compromised cow performance with a low CP diet.

An across breed, diet and tissue analysis reveals the transcription factor NR1H3 as a key mediator of residual feed intake in beef cattle

BACKGROUND

Provision of feed is a major determinant of overall profitability in beef production systems, accounting for up to 75% of the variable costs. Thus, improving cattle feed efficiency, by way of determining the underlying genomic control and subsequently selecting for feed efficient cattle, provides a method through which feed input costs may be reduced. The objective of this study was to undertake gene co-expression network analysis using RNA-Sequence data generated from Longissimus dorsi and liver tissue samples collected from steers of two contrasting breeds (Charolais and Holstein-Friesian) divergent for residual feed intake (RFI), across two consecutive distinct dietary phases (zero-grazed grass and high-concentrate). Categories including differentially expressed genes (DEGs) based on the contrasts of RFI phenotype, breed and dietary source, as well as key transcription factors and proteins secreted in plasma were utilised as nodes of the gene co-expression network.

RESULTS

Of the 2,929 DEGs within the network analysis, 1,604 were reported to have statistically significant correlations (≥ 0.80), resulting in a total of 43,876 significant connections between genes. Pathway analysis of clusters of co-expressed genes revealed enrichment of processes related to lipid metabolism (fatty acid biosynthesis, fatty acid β-oxidation, cholesterol biosynthesis), immune function, (complement cascade, coagulation system, acute phase response signalling), and energy production (oxidative phosphorylation, mitochondrial L-carnitine shuttle pathway) based on genes related to RFI, breed and dietary source contrasts.

CONCLUSIONS

Although similar biological processes were evident across the three factors examined, no one gene node was evident across RFI, breed and diet contrasts in both liver and muscle tissues. However within the liver tissue, the IRX4, NR1H3, HOXA13 and ZNF648 gene nodes, which all encode transcription factors displayed significant connections across the RFI, diet and breed comparisons, indicating a role for these transcription factors towards the RFI phenotype irrespective of diet and breed. Moreover, the NR1H3 gene encodes a protein secreted into plasma from the hepatocytes of the liver, highlighting the potential for this gene to be explored as a robust biomarker for the RFI trait in beef cattle.

Polymorphisms of PLIN1 and MOGAT1 genes and their association with feed efficiency in Hu sheep

Feed cost accounts for a high proportion of sheep production, and improving sheep's utilization of feed will reduce production costs and improve economic benefits. The purpose of this study was to investigate the expression characteristics of PLIN1 and MOGAT1 genes and the relationship between their polymorphisms and feed efficiency traits in Hu sheep, and to find molecular Genetic marker that can be used in breeding. The expression levels of PLIN1 and MOGAT1 genes in various tissues were determined using quantitative real-time PCR (qRT-PCR). The results showed that PLIN1 and MOGAT1 genes were widely expressed in heart, liver, spleen, lungs, kidneys, rumen, duodenum, muscle, lymph, and tail fat. The PLIN1 gene had the highest expression level in in the tail fat compared to the other nine tissues. The expression levels of MOGAT1 gene in liver, tail fat, lung and heart was significantly higher than in kidney, muscle and lymph. The expression level of MOGAT1 was lowest in muscle compared to the other tissues (heart, liver, spleen, lung, rumen and tail fat). We recorded the body weight (BW80 and BW180) and feed intake (FI) information of 985 male Hu sheep at 80 and 180 days of age, and calculated the daily average feed intake (ADFI), average daily gain (ADG), and feed conversion rate (FCR) from 80 to 180 days of age. Two intronic mutations, g.18517910 A > G and g.224856118 G > C, were identified in PLIN1 and MOGAT1 genes by PCR amplification and Sanger sequencing. MassARRAY ® SNP detection technology was used to genotype the DNA of 985 Hu sheep and analyze its association with feed efficiency traits. The results showed that the SNP g.18517910 A > G was significantly associated with BW80, BW180, FI, ADFI and FCR (P < 0.05), while SNP g.2248561118 G > C was significantly associated with FCR (P < 0.05). Meanwhile, significant differences were also observed in different combinations of genotypes (P < 0.05). Therefore, these two polymorphic loci can serve as candidate molecular markers for improving feed utilization efficiency in Hu sheep.

Short communication: Correlation of methane production, intensity, and yield with residual feed intake throughout lactation in Holstein cows

The environmental impact of dairy production can be reduced in several ways, including increasing feed efficiency and reducing methane (CH4) emissions. There is no consensus on their relationship. This study aimed at estimating the correlations between residual feed intake (RFI) and CH4 emissions expressed in g/d methane production (MeP), g/kg of fat- and protein-corrected milk methane intensity (MeI), or g/kg of DM intake methane yield (MeY) throughout lactation. We collected CH4 data using GreenFeed devices from 107 Holstein cows, as well as production and intake phenotypes. RFI was predicted from DM intake, fat- and protein-corrected milk, BW, and body condition score. Five-trait random regression models were used to estimate the individual variance components of the CH4 and production traits, which were used to calculate the correlations between RFI and CH4 traits throughout lactation. We found positive correlations of RFI with MeP and MeI ranging from 0.05 to 0.47 throughout the lactation. Correlations between RFI and MeY are low and vary from positive to negative, ranging from -0.18 to 0.17. Both MeP and MeI are favorably correlated with RFI, as is MeY during the first half of lactation. These correlations are mostly favorable for genetic selection, but the confirmation of these results is needed with genetic correlations over a larger dataset.

Transcriptomic analysis of intestinal organoids, derived from pigs divergent in feed efficiency, and their response to Escherichia coli

BACKGROUND

There is increasing interest in using intestinal organoids to study complex traits like feed efficiency (FE) and host-microbe interactions. The aim of this study was to investigate differences in the molecular phenotype of organoids derived from pigs divergent for FE as well as their responses to challenge with adherent and invasive Escherichia coli (E. coli).

RESULTS

Colon and ileum tissue from low and high FE pigs was used to generate 3D organoids and two dimensional (2D) monolayers of organoid cells for E. coli challenge. Genome-wide gene expression was used to investigate molecular differences between pigs that were phenotypically divergent for FE and to study the difference in gene expression after challenge with E. coli. We showed, (1) minor differences in gene expression of colon organoids from pigs with low and high FE phenotypes, (2) that an E. coli challenge results in a strong innate immune gene response in both colon and ileum organoids, (3) that the immune response seems to be less pronounced in the colon organoids of high FE pigs and (4) a slightly stronger immune response was observed in ileum than in colon organoids.

CONCLUSIONS

These findings demonstrate the potential for using organoids to gain insights into complex biological mechanisms such as FE.

Chromium in the Diet of Dairy Calves: Benefits for Growth Performance, Feed Efficiency, Digestibility, and Health

Chromium (Cr) is a mineral that helps animals subjected to stressful conditions. The suckling period is characterized by several stressful episodes, particularly during the first hours after birth and at weaning. There is little consumption of concentrate by calves in the first weeks of life; consequently, consuming any supplement added to feed would be negligible. Thus, the hypothesis was that the calves would take it in earlier if Cr were consumed in a milk replacer instead. Therefore, our study aimed to determine whether including organic Cr in calf feed (via milk replacer or concentrate) during the suckling phase would improve calf health and growth performance. Twenty-four male Holstein calves with an average age of 8 ± 4 days and 39.8 ± 6.9 kg average body weight were used. Calves were randomly divided into three groups: (a) Chromium-Milk (CR-M), receiving 4 mg Cr/animal/day via milk replacer during the 60 experimental days of suckling (n = 8); (b) Chromium-Concentrate (CR-C), receiving 4 mg Cr/animal/day via concentrate (n = 8); (c) Control (C), animals that did not receive Chromium (n = 8). The experiment lasted 75 days, divided into two well-defined stages: suckling (1-60 days) and weaning (61-75 days). Body weight weekly, daily feed intake, and blood samples taken every two weeks during the experiment were evaluated. At the end of the experiment, the apparent digestibility evaluation was carried out, with the results of weight and consumption carried out, and a feed efficiency analysis was carried out. It was observed that the inclusion of organic Cr (regardless of whether it was milk or concentrate) increased body weight gain (kg) for the CR-C group: 41.8 kg, CR-M: 40.4 kg compared to the C: 34.2 kg (p = 0.01). The protein digestibility was higher in the CR-M group (52%, p = 0.05). Cr consumption increased Cr concentrations in the serum of the calves and was higher in the first week in the animals in the CR-M group. This did not happen for the C group; however, with higher concentrate consumption, Cr concentrations increased and remained high until the end of the experiment. Glucose concentrations were higher in the groups that consumed Cr. Total protein concentrations were higher in the CR-M and CR-C groups than in group C. Immunoglobulin A concentrations were higher in groups CR-C and CR-M than in group C (days 40 and 60). In conclusion, the adding Cr to calf feed improves their health, indirectly favors growth performance, and increases protein digestibility.

Interaction between residual feed intake and thermal environment on performance, nitrogen balance, ingestive behavior and carcass yield of dorper lambs

Residual feed intake (RFI) is a nutritional variable used in genetic improvement programs, the relationship between the environment and the availability of energy and protein in the diet has not yet been explored. Thus, the aim was to evaluate interactions between RFI and thermal environment on performance, nitrogen balance, ingestive behavior and carcass yield of Dorper lambs receiving diets containing different concentrate levels. Dorper lambs (male, n = 64, 17.83 ± 2.43 kg and 110 ± 10 days of age) were confined individually for 40 days for RFI classification. Lambs were separated into positive RFI (n = 30) and negative RFI (n = 30) and remained confined for another 60 days. The animals were distributed in a randomized block design, with a 2 × 2 × 3 factorial scheme, with 2 confinement environments (full sun or shade), 2 groups of feed efficiency (RFI positive or RFI negative) and three diets containing different concentrate levels (30, 45 and 60%), with 5 replications in each treatment. Isolated effects of concentrate level were observed for dry matter intake and digestibility, feeding, rumination, idle and chewing times, feeding efficiency, ingested, excreted and absorbed nitrogen, and on cooling losses, hot and cold carcass yield (P < 0.05). There was an effect of environment × concentrate interaction on performance, retained nitrogen and nitrogen balance (P < 0.05). There was an effect of RFI × environment interaction on the dry matter rumination efficiency, hot and cold carcass weight (P < 0.05). Under experimental conditions, RFI did not influence the productive performance of Dorper lambs. Interactions between environment and diet indicate better performance for Dorper lamb confined in the shade and receiving a higher proportion of concentrate. Animals with negative RFI show better performance and carcass weight when confined in shade, while animals with positive RFI showed better responses to these variables when confined in full sun.

Comparison of the effects of zinc oxide and zinc aspartic acid chelate on the performance of weaning pigs

In this research, the growth efficiency, nutritional utilization, fecal microbial levels, and fecal score of weaned pigs were evaluated using therapeutic zinc oxide (ZnO) and zinc aspartic acid chelate (Zn-Asp). In a 42-day feeding trial, 60 weaned pigs ([Yorkshire × Landrace] × Duroc) were arbitrarily allotted (age: 21 days; 7.01 ± 0.65 kg preliminary body weight) to 3 different treatment groups with 5 repetitions (2 male and 2 female piglets) in each pen. The trial had 2 different phases, including 1-21 days as phase 1, and 22-42 days as phase 2. The nutritional treatments were: basal diet as control (CON), basal diet incorporated with 3,000 ppm ZnO as TRT1, and basal diet incorporated with 750 ppm Zn-Asp as TRT2. In comparison to the CON group, the pigs in the TRT1 and TRT2 groups had greater (p < 0.05) body weight on day 42; an average daily gain, and an average daily feed intake on days 22-42. Furthermore, during days 1-42, the average daily gain in the treatment groups trended higher (p < 0.05) than in the CON group. Additionally, the fecal score decreased (p < 0.05) at week 6, the lactic acid bacteria count tended to increase (p < 0.05), and coliform bacteria presented a trend in reduction (p < 0.05) in the TRT1 and TRT2 groups compared to the CON group. However, there was no difference in nutrient utilization (p > 0.05) among the dietary treatments. Briefly, the therapeutic ZnO and Zn-Asp nutritional approaches could decrease fecal score and coliform bacteria, increase lactic acid bacteria, and improve growth efficiency; moreover, Zn-Asp (750 ppm) can perform a comparable role to therapeutic ZnO (3,000 ppm). So we can use Zn-Asp (750 ppm) instead of therapeutic ZnO (3,000 ppm) for the better performance of weaning pigs and the reduction of environmental pollution, as therapeutic ZnO is responsible for environmental pollution.

Strategies of virginiamycin supplementation in the postweaning phase on growth performance and carcass quality of beef cattle

The present study evaluated the effects of supplementing VM in grazing cattle during the rearing phase on performance and carcass quality of beef cattle in the finishing phase. Two experiments with a randomized block design were conducted in consecutive years to contrast two post-weaning supplementation strategies using VM at 45 mg/100 kg body weight (BW). In the first year, treatments were protein supplement in the dry season and mineral supplement in the rainy season versus the addition of VM both in the protein and mineral supplements. In the second year, was contrasted with protein supplement in the dry season and protein-energy supplement in the rainy season. Performance, carcass traits, and carcass quality were evaluated at the end of both phases. In Year 1, adding VM in mineral supplement increased final backfat thickness (P=0.05), backfat gain (P=0.06), final rump fat thickness (P=0.02), and rump fat gain (P=0.01). In the finishing phase, VM-treated cattle had a greater dry matter intake (P=0.03) and tended to show a greater backfat thickness than non-treated cattle (P=0.07). In Year 2, no VM effects were observed on post-weaning phase performance and carcass traits. However, cattle-fed VM during the post-weaning phase tended to show a lower feed conversion ratio (P=0.09) and had a significantly higher gross feed efficiency (P=0.03) than non-treated cattle at slaughter. Virginiamycin supplementation during rearing on pasture improves performance and carcass fattening in the growth phase and has a residual effect in the finishing phase that may reflect greater backfat thickness and gross feed efficiency.

Effects of particle size of corn and stocking densities on the performance, carcass traits and gastrointestinal tract development of Muscovy ducks in housing

The current investigation was conducted to investigate the effects of different particle sizes of corn and stocking densities on performance, carcass traits and gastrointestinal tract (GIT) development of Muscovy ducks in housing. 200 Muscovy ducks were distributed in a factorial scheme (2 × 2) where the treatments were constituted by two stocking densities (2 or 3 birds/m2) and two particle sizes of corn (6 or 8 mm), with five replicates of 10 birds each. At 1, 35, 70, and 90 days old, Muscovy ducks were slaughtered to evaluate the development of heart and GIT. Muscovy ducks managed in the density of 3 birds/m2 presented higher (P < 0.05) GIT development, performance and carcass traits regardless of age evaluated. In the same way, Muscovy ducks fed diets using a particle size of corn of 6 mm (Mean Geometric Diameter (MGD) = 781 μm) presented higher (P < 0.05) GIT development, performance and carcass traits regardless of age evaluated. Conclusively, the stocking density of 3 birds/m2 and the particle size of corn of 6 mm (MGD = 781 μm) were considered ideal recommendations for Muscovy ducks, providing higher GIT development, which resulted in better performance and carcass traits.

Short communication: Impact of corn grain particle size on production performance of lactating dairy cows

Corn grain particle size has the potential to influence the performance of lactating dairy cows and the overall profitability of a dairy farm. The objective of this study was to evaluate the productive performance of lactating cows fed diets containing finely or coarsely ground corn grain. Fifty lactating Holstein cows (n = 50; 10 primiparous and 40 multiparous), averaging (mean ± standard deviation, SD) 658 ± 64 kg of BW, 38.8 ± 7.3 kg of milk/d, and 155 ± 80 DIM, were fed diets with finely ground corn grain (FGC) or coarsely ground corn grain (CGC) in a randomized block design with a 28-d treatment period. Finely and coarsely ground corn grain had an average particle size of 660 and 915 µm, respectively. Dry matter intake (DMI) was reduced (p < 0.01) for cows fed FGC (22.1 vs. 21.2 kg d-1). Milk yield and efficiency were not affected by treatments (37.9 vs. 36.8 kg d-1; p = 0.12 and 1.78 vs. 1.79; p = 0.15). Concentrations of milk protein and fat, as well as other milk solids, were unaffected (p > 0.05) by treatments. Fecal starch (FS) concentrations were greater (p < 0.01) for cows fed CGC (7.0 vs. 4.9%), whereas plasma concentrations of D-lactate were greater (p < 0.05) for cows fed FGC (98.5 vs. 79.7 µM). Overall, feeding finely ground corn grain increased total-tract starch digestibility and reduced DMI while maintaining milk yield.

Aerobic physical exercise modifies the prostate tumoral environment

Exercise is recognized for its potential role in reducing the risk of certain cancers. However, the molecular mechanisms behind this risk reduction are not fully understood. Here, we hypothesized that aerobic physical exercise induces cancer attenuating effects through the modulation of oxidative stress and inflammation. To test this hypothesis, twenty male Sprague Dawley rats with chemically induced prostate tumors were divided into two groups: Prostate cancer (PC) in the absence and presence of exercise (PC + Ex). Rats in the PC + Ex group performed exercises on a treadmill for 8 weeks, 5 sessions per week, at an intensity of 60 % of maximum capacity. Weight and feed efficiency, Ki-67, apoptosis, prostatic inflammation, and markers of oxidative stress were analyzed. We found that aerobic physical exercise significantly decreased prostate cell proliferation (p < 0.05) across modulation, tumor size, and prostate weight. The PC + Ex group also significantly reduced anti-apoptosis protein expression (p < 0.05) and increased pro-apoptotic protein expression. Furthermore, physical exercise increased enzymatic antioxidant defenses in the prostate, plasma, and whole blood. Moreover, PC + Ex reduced lipid peroxidation and protein carbonyl levels (p < 0.05). In the prostate, there was an increase in anti-inflammatory cytokines (IL-10), and a reduction in pro-inflammatory cytokines (IL-6, TNF-α, and NF-κB) after 8 weeks of physical exercise. In conclusion, we found that aerobic physical exercise is a functional, beneficial, and applicable approach to control PC progression, because it modifies the systemic environment, including the regulation of glucose and circulating lipids. This modification of the cancer cells environment has anti-inflammatory and antioxidant effects that attenuate tumor growth.

Small networks of expressed genes in the whole blood and relationships to profiles in circulating metabolites provide insights in inter-individual variability of feed efficiency in growing pigs

BACKGROUND

Feed efficiency is a research priority to support a sustainable meat production. It is recognized as a complex trait that integrates multiple biological pathways orchestrated in and by various tissues. This study aims to determine networks between biological entities to explain inter-individual variation of feed efficiency in growing pigs.

RESULTS

The feed conversion ratio (FCR), a measure of feed efficiency, and its two component traits, average daily gain and average daily feed intake, were obtained from 47 growing pigs from a divergent selection for residual feed intake and fed high-starch or high-fat high-fiber diets during 58 days. Datasets of transcriptomics (60 k porcine microarray) in the whole blood and metabolomics (1H-NMR analysis and target gas chromatography) in plasma were available for all pigs at the end of the trial. A weighted gene co-expression network was built from the transcriptomics dataset, resulting in 33 modules of co-expressed molecular probes. The eigengenes of eight of these modules were significantly ([Formula: see text]) or tended to be ([Formula: see text]) correlated to FCR. Great homogeneity in the enriched biological pathways was observed in these modules, suggesting co-expressed and co-regulated constitutive genes. They were mainly enriched in genes participating to immune and defense-related processes, and to a lesser extent, to translation, cell development or learning. They were also generally associated with growth rate and percentage of lean mass. In the whole network, only one module composed of genes participating to the response to substances, was significantly associated with daily feed intake and body adiposity. The plasma profiles in circulating metabolites and in fatty acids were summarized by weighted linear combinations using a dimensionality reduction method. Close association was thus found between a module composed of co-expressed genes participating to T cell receptor signaling and cell development process in the whole blood and related to FCR, and the circulating concentrations of polyunsaturated fatty acids in plasma.

CONCLUSION

These systemic approaches have highlighted networks of entities driving key biological processes involved in the phenotypic difference in feed efficiency between animals. Connecting transcriptomics and metabolic levels together had some additional benefits.

Non-invasive methods to quantify the carcass parameters of sheep: Interaction between thermal environment and residual feed intake

The thermal environment is important in unit production because the perception of thermal stress can reduce fertility, and productive performance, therefore its management is necessary. The use of non-invasive methods, such as infrared thermography and real-time ultrasonography, are widely used to evaluate indicators in animal production, without the need to slaughter the animals. Thus, we aimed to assess the effect of the thermal environment on the physiological parameters and carcass characteristics of Dorper sheep with positive and negative residual feed intake (RFI) using infrared thermography and real-time ultrasonography techniques. Twenty uncastrated male Dorper sheep (17.8 ± 2.4 kg) were confined for 40 days for RFI classification. Sheep were separated into positive RFI (n = 10) and negative RFI (n = 10). The experimental design was in randomized blocks, in a 2 × 2 factorial arrangement, with 2 thermal environments (full sun or shade) and two feed efficiency groups (positive RFI or negative RFI), with 5 replications. The sheep remained in confinement for 60 days. The animals were slaughtered at the end of the experiment and the carcasses dissected for tissue separation. Rectal temperature (RT) and respiratory rate (RR) were measured at two times (14:00 h and 18:00 h) for periods of 5 days. The RR was determined by indirect auscultation of heart sounds at the level of the laryngotracheal region. The RT was measured introduced a digital clinical thermometer into the animal's rectum. Surface temperature (ST) was obtained using a thermographic infrared camera, collecting the temperatures of the eyeball and skin surface in the regions of the head, ribs, rump, flank and shin. Sheep confined in full sun showed higher RR (P = 0.0001), ST ribs (P = 0.0020), ST rumb (P = 0.0055), ST flank (P = 0.0001) and heat tolerance coefficient (HTC) (P = 0.0010). For sheep confined in full sun, a strong correlation was observed between the RR and the mean ST (MST; r = 0.6826; P = 0.0236) and between the final loin eye area (LEAf) with the real LEA (LEAr) (r = 0.9263; P = 0.0001) and slaughter body weight (SBW) (r = 0.7532; P = 0.0325). For negative RFI sheep, a positive correlation was observed between the RR and the ST rump (r = 0.7343; P = 0.0025) and ST ribs (r = 0.6560; P = 0.0178) and the MST (r = 0.7435; P = 0.0001), between the MST and the LEAr (r = 0.6837; P = 0.0025) and the final LEA (r = 0.6771; P = 0.0144), and between the final LEA and LEAr (r = 0.9942; P = 0.0001), BW (r = 0.8415; P = 0.0277) and MST (r = 0.6771; P = 0.0045). Positive RFI sheep confined to shade showed a high correlation between final LEA and LEAr (r = 0.9372; P = 0.0001). The use of shading in confined Dorper sheep, regardless of the RFI classification, reduces the effects of heat stress on physiological parameters.

Determining and predicting feed intake in crossbred sheep from weaning until maturity

Access to simple, accurate feed intake models would facilitate decision-making in feedlots as feed costs are a major part of operational expenditure. This study aimed to develop genotype-specific feed intake models for South African feedlot lambs. Four ram and four ewe lambs each of eight genotypes were raised under ideal growth conditions from weaning until 1 year of age. Feed intake and growth were monitored throughout this period. The intake data were then used to fit various models to predict daily feed intake, intake as percentage of body weight, cumulative intake and feed conversion ratio. No satisfactory univariate models could be found for the prediction of daily or percentage intake, but a good fit was found for cumulative intake data (R2 >0.80, P <0.01). The slope parameters of these linear models show a strong correlation (72%) with feed conversion and can therefore also serve as proxies for feed conversion. A model was also developed that can predict feed conversion ratio with a moderate accuracy (R2 =0.5, P <0.05) at a given body weight. The cumulative intake model was deemed accurate and simple enough for practical use.

Combined effect of microbially derived cecal SCFA and host genetics on feed efficiency in broiler chickens

BACKGROUND

Improving feed efficiency is the most important goal for modern animal production. The regulatory mechanisms of controlling feed efficiency traits are extremely complex and include the functions related to host genetics and gut microbiota. Short-chain fatty acids (SCFAs), as significant metabolites of microbiota, could be used to refine the combined effect of host genetics and gut microbiota. However, the association of SCFAs with the gut microbiota and host genetics for regulating feed efficiency is far from understood.

RESULTS

In this study, 464 broilers were housed for RFI measuring and examining the host genome sequence. And 300 broilers were examined for cecal microbial data and SCFA concentration. Genome-wide association studies (GWAS) showed that four out of seven SCFAs had significant associations with genome variants. One locus (chr4: 29414391-29417189), located near or inside the genes MAML3, SETD7, and MGST2, was significantly associated with propionate and had a modest effect on feed efficiency traits and the microbiota. The genetic effect of the top SNP explained 8.43% variance of propionate. Individuals with genotype AA had significantly different propionate concentrations (0.074 vs. 0.131 μg/mg), feed efficiency (FCR: 1.658 vs. 1.685), and relative abundance of 14 taxa compared to those with the GG genotype. Christensenellaceae and Christensenellaceae_R-7_group were associated with feed efficiency, propionate concentration, the top SNP genotypes, and lipid metabolism. Individuals with a higher cecal abundance of these taxa showed better feed efficiency and lower concentrations of caecal SCFAs.

CONCLUSION

Our study provides strong evidence of the pathway that host genome variants affect the cecal SCFA by influencing caecal microbiota and then regulating feed efficiency. The cecal taxa Christensenellaceae and Christensenellaceae_R-7_group were identified as representative taxa contributing to the combined effect of host genetics and SCFAs on chicken feed efficiency. These findings provided strong evidence of the combined effect of host genetics and gut microbial SCFAs in regulating feed efficiency traits. Video Abstract.

Opportunities and limits of commercial farm data to study the genetic determinism of feed efficiency throughout lactation in dairy sheep

The collective economic and environmental interest of the whole dairy sheep sector is to reduce feed costs and the negative impact of milk production on the environment. Thus, this study focused on the characterisation and genetic selection potential of feed efficiency in the Lacaune breed. Estimates for feed efficiency in dairy ewes are limited, mainly due to a lack of individual feed intake measurements in the sheepfold or in the pasture. We estimated the genetic parameters for two approximated (not entirely based on individual data) feed efficiency traits (lactation feed conversion ratio (LFCR) and residual energy intake (REI)) and daily milk yield (DMY) at different stages of lactation and throughout lactation. The accuracy of the efficiency traits was first evaluated on samples from Lacaune dairy ewes that were monitored individually, especially for their feed intake. Then, feed efficiency estimation methods were applied on eight commercial farms corresponding to 4 680 Lacaune dairy ewes over two milk lactations (30 854 records). Animals were collectively (for a large part of feed intake) or individually (for milk performance and dynamics of body fat reserves) monitored at different lactation stages. The heritabilities of LFCR and REI were estimated over lactations at 0.10 ± 0.01 and 0.11 ± 0.01, respectively. High genetic correlations were observed between the two efficiency traits and milk production traits, with a genetic correlation between LFCR and DMY of 0.74 ± 0.04 and between REI and DMY of -0.79 ± 0.04. A strong influence of environmental factors such as farm, year of milk production and lactation stage affected the genetic link between REI and milk production traits. Efficiency values observed in early lactation when animals were bred in the sheepfold were less genetically correlated with values obtained later in lactation when animals were grass-fed. However, individual characterisation of feed efficiency remains difficult due to the collective feeding context in dairy ewe farms.

Effect of dietary inclusions of different types of Acacia mearnsii on milk performance and nutrient intake of dairy cows

This study investigated the effects of including different types of Acacia mearnsii (tannin extract and forage) on nutrient intake and milk performance in dairy cattle. Holstein-Friesian x Jersey dairy cows (n per Experiment = 24) that had 200 days in milk were selected for this study in a completely randomized study design. This study was conducted under on-farm conditions at Springfontein dairy farm, a farm that lacked a functional bodyweight scale to measure the cow bodyweight and a computer system to register cow parity. Cows were assigned Acacia mearnsii tannin extract (ATE) pellets which were added with 0 (0ATE), 0.75 (0.75ATE), 1.5 (1.5ATE) or 3 (3ATE) % ATE in pellets while 0ATE was a commercial protein concentrate (Experiment 1). Cows were assigned Acacia mearnsii forage (AMF) at a rate of 0 (0AMF), 5 (5AMF), 15 (15AMF) or 25 (25AMF) % AMF inclusion in corn silage-based diet (Experiment 2). For both Experiments, treatments had six cows each, in which they were adapted (14 d) to diets before data collection (21 d). All AMF inclusions decreased (P<0.0001) dry matter intake (DMI), crude protein intake (CPI), neutral detergent fibre intake (NDFI), acid detergent fibre intake (ADFI) and organic matter intake (OMI) at 25AMF. Linear (P<0.0001) and quadratic (P<0.001) effects were observed on DMI, CPI, NDFI, ADFI and OMI. Inclusions of AMF in corn silage diets affected milk yield, protein yield, lactose yield and milk protein percentage (P<0.001). Linear effect was present in milk yield per DMI (P<0.0001). In conclusion, the dairy cow diet supplemented with ATE pellets did not have a beneficial effect on the nutrient intakes and milk yield. However, the AMF supplemented in corn silage of the dairy cow diet, increased milk production due to positive effects on nutrient intake, which was favourably influenced from a nutritional point of view.

Blood parameters associated with residual feed intake in beef heifers

Blood chemistry may provide indicators to greater feed efficient cattle. As a side objective to previous research, 17 Angus heifers approximately two years old underwent a feed efficiency trial to determine residual feed intake (RFI) and identify variation in blood chemistry in beef cattle divergent in feed efficiency. Heifers were categorized as high- or low-RFI based ± 0.25 standard deviations around mean RFI. Blood samples were analyzed using an i-STAT handheld blood analyzer to measure sodium, potassium, glucose, blood urea nitrogen (BUN), creatinine, hematocrit, and hemoglobin. BUN was greater in high-RFI heifers (µ = 8.7 mg/dL) contrasted to low-RFI heifers (µ = 6.5 mg/dL; P = 0.01), whereas glucose was greater in low-RFI heifers (µ = 78.1 mg/dL) contrasted to high-RFI heifers (µ = 82.0 mg/dL; P = 0.05). No other blood chemistry parameters differed by RFI. The greater abundance of BUN in high-RFI heifers may indicate inefficient utilization of protein or mobilization of tissue protein for non-protein use. Greater blood glucose concentrations in low-RFI heifers may indicate greater utilization of energy precursors, such as volatile fatty acids, or metabolites. These data suggest there are readily measurable indicators of physiological variation in nutrient utilization; however, this warrants additional studies to explore.

Metagenomic approach to infer rumen microbiome derived traits of cattle

Ruminants enable the conversion of indigestible plant material into animal consumables, including dairy products, meat, and valuable fibers. Microbiome research is gaining popularity in livestock species because it aids in the knowledge of illnesses and efficiency processes in animals. In this study, we use WGS metagenomic data to thoroughly characterize the ruminal ecosystem of cows to infer positive and negative livestock traits determined by the microbiome. The rumen of cows from Argentina were described by combining different gene biomarkers, pathways composition and taxonomic information. Taxonomic characterization indicated that the two major phyla were Bacteroidetes and Firmicutes; in third place, Proteobacteria was highly represented followed by Actinobacteria; Prevotella, and Bacteroides were the most abundant genera. Functional profiling of carbohydrate-active enzymes indicated that members of the Glycoside Hydrolase (GH) class accounted for 52.2 to 55.6% of the total CAZymes detected, among them the most abundant were the oligosaccharide degrading enzymes. The diversity of GH families found suggested efficient hydrolysis of complex biomass. Genes of multidrug, macrolides, polymyxins, beta-lactams, rifamycins, tetracyclines, and bacitracin resistance were found below 0.12% of relative abundance. Furthermore, the clustering analysis of genera and genes that correlated to methane emissions or feed efficiency, suggested that the cows analysed could be regarded as low methane emitters and clustered with high feed efficiency reference animals. Finally, the combination of bioinformatic analyses used in this study can be applied to assess cattle traits difficult to measure and guide enhanced nutrition and breeding methods.

Orange molasses as a new energy ingredient for feedlot lambs in Brazil

The objectives of this experiment were to evaluate the effects of increasing levels of orange molasses in replacement of flint corn grain in high-concentrate diets on dry matter intake (DMI), average daily gain (ADG), and feed efficiency (FE) of feedlot lambs. Thirty male lambs without defined racial pattern (30.3 ± 5.3 kg of initial BW; mean ± SD) were used in a randomized complete block design with 10 blocks and 3 treatments. The treatments were defined by partial replacement of flint corn by orange molasses in the diet with 90% of concentrate and 10% of Cynodon spp. hay, as follows: 0OM-control diet without orange molasses; 20OM-20% of orange molasses replacing flint corn; and 40OM-40% of orange molasses replacing flint corn (DM basis). The experiment lasted 72 days divided into 3 subperiods, with 1 subperiod of 16 days and 2 subperiods of 28 days. Animals were weighed after a 16-h fast on days 1, 16, 44, and 72 of the experimental periods to determine the ADG and FE. The DMI, ADG, and FE showed an interaction between treatments and experimental periods. The DMI in the first period decreased linearly (P < 0.01); in the third period, there was no effect of treatments (P > 0.05) on DMI. The ADG decreased linearly (P < 0.01) in the first period as the orange molasses increased. Otherwise, in the third period, ADG increased linearly (P = 0.05) as flint corn was replacement by orange molasses. The FE showed an interaction between treatment and period (P = 0.09). The first period had a decreased linear effect; in the third period, there was a trend (P = 0.07) of increased linear effect. There was no difference between the diets regarding the final BW of the lambs. In conclusion, the orange molasses can replace up to 40% of flint corn in diets for feedlot lambs without affecting final BW. However, it is important to consider the adaptation time proved to be very important for better use of orange molasses as a source of energy in diets for lambs.

Review: Diving into the cow hologenome to reduce methane emissions and increase sustainability

Interest on methane emissions from livestock has increased in later years as it is an anthropogenic greenhouse gas with an important warming potential. The rumen microbiota has a large influence on the production of enteric methane. Animals harbour a second genome consisting of microbes, collectively referred to as the "microbiome". The rumen microbial community plays an important role in feed digestion, feed efficiency, methane emission and health status. This review recaps the current knowledge on the genetic control that the cow exerts on the rumen microbiota composition. Heritability estimates for the rumen microbiota composition range between 0.05 and 0.40 in the literature, depending on the taxonomical group or microbial gene function. Variables depicting microbial diversity or aggregating microbial information are also heritable within the same range. This study includes a genome-wide association analysis on the microbiota composition, considering the relative abundance of some microbial taxa previously associated to enteric methane in dairy cattle (Archaea, Dialister, Entodinium, Eukaryota, Lentisphaerae, Methanobrevibacter, Neocallimastix, Prevotella and Stentor). Host genomic regions associated with the relative abundance of these microbial taxa were identified after Benjamini-Hoschberg correction (Padj < 0.05). An in-silico functional analysis using FUMA and DAVID online tools revealed that these gene sets were enriched in tissues like brain cortex, brain amigdala, pituitary, salivary glands and other parts of the digestive system, and are related to appetite, satiety and digestion. These results allow us to have greater knowledge about the composition and function of the rumen microbiome in cattle. The state-of-the art strategies to include methane traits in the selection indices in dairy cattle populations is reviewed. Several strategies to include methane traits in the selection indices have been studied worldwide, using bioeconomical models or economic functions under theoretical frameworks. However, their incorporation in the breeding programmes is still scarce. Some potential strategies to include methane traits in the selection indices of dairy cattle population are presented. Future selection indices will need to increase the weight of traits related to methane emissions and sustainability. This review will serve as a compendium of the current state of the art in genetic strategies to reduce methane emissions in dairy cattle.

Dietary administration of l-carnitine during the fattening period of early feed restricted lambs modifies lipid metabolism and meat quality

Early feed restriction of lambs promotes a permanent mitochondrial dysfunction that impairs β-oxidation of fatty acids along the whole life. Therefore, dietary l-carnitine might help to improve the mitochondrial function of these lambs, thus modifying lipid metabolism and meat quality traits. In order to test this hypothesis an experiment was carried out with 22 Merino lambs that were subjected to an early feed restriction during the suckling period. Once weaned, the lambs were allocated to a control group (CTRL, n = 11) being fed ad libitum a complete pelleted diet during the fattening phase, whereas the second group (CARN, n = 11) received the same diet formulated with 3 g/kg of l-carnitine. Carcass characteristics were not affected (P > 0.05) by treatment. However, lambs fed l-carnitine showed higher amounts of intramuscular fat (26.5 vs. 33.6 g/kg fresh matter; P = 0.047) with a lower ratio between polyunsaturated and saturated fatty acids (0.425 vs 0.333; P = 0.023) and a higher atherogenic (0.507 vs 0.597; P < 0.001) and thrombogenic index (1.23 vs 1.42; P < 0.001). An increase in lightness (P < 0.05) and a tendency to improved oxidative stability in cooked meat (P = 0.066) were also observed in the CARN group. Consequently, dietary l-carnitine supplied during the fattening period of early feed restricted lambs modifies meat quality traits thus increasing lightness, oxidative stability and intramuscular fat content, but worsening the fatty acid profile.

Residual feed intake breeding value associated with growth, carcass traits, meat quality, bone properties and humoral immunity in Japanese quail

Improved feed efficiency (FE) is one of the most important achievements in animal breeding programs. The present investigation aimed to determine the phenotypic correlations of residual feed intake (RFI) breeding value with some traits in growing Japanese quail. A total of 48 birds (24 males and 24 females) were selected from 220 quail chicks divided into three classes based on breeding values (BV) for RFI including low (LBV; n = 16), medium (MBV; n = 16), and high-BV (HBV; n = 16) were used to test FE. The effects of three groups of BV on the studied traits including carcass traits, meat quality, humoral immunity, and bone properties were evaluated. The BV for RFI was positively correlated with feed conversion ratio (FCR) and feed intake (FI) but not with metabolic BW (MBW^0.75). Live body weight, carcass, breast, and thigh weight in the LBV-RFI group were significantly greater than those in the HBV-RFI group. The BV for RFI had a negative correlation with live body weight and thigh weight. Our findings suggested that the selection of LBV-RFI quails may be useful to increase live body weight without any adverse impact on meat quality and bone properties, and live body weight can be implemented in breeding programs as an indirect selection indicator for improvement of FE in quails.

Processing methods of flint corn and protein supplement in forage-free diets for feedlot lambs

Diets without forage increase the productivity in less time and favor greater practicality and better quality carcass. The corn grain is mostly used associated with pellets but processing these ingredients can bring benefits. The present study evaluated the effect of diets without forage based on whole or coarse ground corn associated with pelleted or ground protein supplement on performance, eating behavior, carcass characteristics, and ruminal morphology of feedlot lambs. Thirty-five Dorper × Santa Inês lambs were used, with 23.85 ± 3.88 kg of initial body weight and 88 ± 9 days old. The experimental design was in a randomized complete block, defined by body weight and age. The experimental diets were control (CONT), containing 90% of concentrate and 10% of forage (coastcross hay), and 4 diets without forage: WC+P, 70% whole flint corn and 30% pelleted protein supplement; WC+G, 70% whole flint corn and 30% ground protein supplement; GC+P, 70% ground flint corn and 30% pelleted protein supplement; and GC+G, 70% ground flint corn and 30% ground protein supplement. There was an interaction between treatments and experimental periods for DMI in kg/day (P = 0.01) and g/kg of BW^0.75 (P < 0.01; Table 3). For the DMI in kg/day, no significant differences were observed between the treatments in any of the experimental periods. However, for DMI expressed in g/kg of BW^0.75, the animals fed WC+P had lower DMI than the animals on the CONT (P < 0.01) only in the first period. The ADG, FBW, and FE were not affected by the treatments. Compared to CONT, forage-free diets decreased ingestion time (min/day) and rumination and chewing (min/day and min/g of dry matter). There was no effect of treatments for any of the carcass traits evaluated. The diets did not cause lesions suggestive of ruminitis. Forage-free diets containing whole or ground corn associated with pelleted or ground protein supplement can be used successfully for feedlot lambs; they provide proper performance and carcass characteristics, without harming the animal's health.

Identification of gut microbes associated with feed efficiency by daily-phase feeding strategy in growing-finishing pigs

Feed efficiency is one of the most important issues for sustainable pig production. Daily-phase feeding (DPF) is a form of precision feeding that could improve feed efficiency in pigs. Gut microbiota can regulate host nutrient digestion, absorption, and metabolism. However, which key microbes may play a vital role in improving the feed efficiency during DPF remains unclear. In the present study, we used a DPF program compared to a three-phase feeding (TPF) program in growing-finishing pigs to investigate the effects of gut microbiota on feed efficiency. A total of 204 Landrace × Yorkshire pigs (75 d) were randomly assigned into 2 treatments. Each treatment was replicated 8 times with 13 to 15 pigs per replicate pen. Pigs in the TPF group were fed with a commercial feeding program that supplied fixed feed for phases I, II, and III, starting at 81, 101, and 132 d of age, respectively, and pigs in the DPF group were fed a blend of adjacent phase feed from 81 to 155 d at a gradual daily ratio and phase III feed from 155 to 180 d of age. Daily feed intake and body weight were recorded by a computerized device in the feeders. Feces and blood samples were collected from 1 pig per replicate at 155 and 180 d of age. The results showed that the DPF program remarkably improved the feed efficiency at 155 d (P < 0.001) and 180 d of age (P < 0.001), with a significant reduction of the intake of crude protein (P < 0.01), net energy (P < 0.001), crude fiber (P < 0.001), ether extract (P < 0.01), and ash (P < 0.001). The daily-phase feeding program increased the abundance of Prevotella copri (P < 0.05) and Paraprevotella clara (P < 0.05), while it decreased the abundance of Ocilibacter (P < 0.05) at 155 d of age. The results of correlation analysis indicated that the differentially abundant microbiota communities were closely associated with 20 metabolites which enriched amino acid and phenylalanine metabolism. Our results suggest that 2 key microbes may contribute to feed efficiency during daily-phase feeding strategies in pigs.

Genomic prediction ability and genetic parameters for residual feed intake calculated using different approaches and their associations with growth, reproductive, and carcass traits in Nellore cattle

This study aimed to estimate prediction ability and genetic parameters for residual feed intake (RFI) calculated using a regression equation for each test (RFI_test) and for the whole population (RFI_pop) in Nellore beef cattle. It also aimed to evaluate the correlations between RFI_pop and RFI_test with growth, reproductive, and carcass traits. Genotypic and phenotypic records from 8354 animals were used. An analysis of variance (ANOVA) was performed to verify the adequacy of the regression equations applied to estimate the RFI_test and RFI_pop. The (co)variance components were obtained using the single-step genomic best linear unbiased prediction under single and two-trait animal model analyses. The genetic and phenotypic correlations between RFI_test and RFI_pop with dry matter intake, frame, growth, reproduction, and carcass-related traits were evaluated. The prediction ability and bias were estimated to compare the RFI_test and RFI_pop genomic breeding values (GEBV). The RFI_pop ANOVA showed a higher significance level (p < 0.0001) than did the RFI_test for the fixed effects. The RFI_pop displayed higher additive genetic variance estimated than the RFI_test, although the RFI_pop and RFI_test displayed similar heritabilities. Overall, the RFI_test showed higher residual correlations with growth, reproductive, and carcass traits, while the RFI_pop displayed higher genetic correlations with such traits. The GEBV for the RFI_test was slightly biased than GEBV RFI_pop. The approach to calculate the RFI influenced the decomposition and estimation of variance components and genomic prediction for RFI. The application of RFI_pop would be more appropriate for genetic evaluation purpose to adjust or correct for non-genetic effects and to decrease the prediction bias for RFI.

Identification and characterization of hypothalamic circular RNAs associated with bovine residual feed intake

Residual feed intake (RFI) is crucial economic indicator used for calculating the feed efficiency of growing beef cattle. circRNA plays an important biological role in gene transcriptional regulation, but little is known about its potential functional regulation underlying RFI phenotypic variation. As the core center of regulation of animal feeding, the hypothalamus is closely associated with RFI. Therefore, the present study aimed to identify the key genes and functional pathways contributing to variance in cattle RFI phenotypes using RNA sequencing from hypothalamic tissue samples, in order to gain insight into the potential regulatory role of circRNAs in bovine RFI phenotypic variation. Differentially expressed genes were detected by RNA sequencing for beef cattle in the high and low RFI groups, followed by GO, KEGG enrichment, and circRNA-miRNA co-expression network analysis. A total of 257 circRNAs were differentially expressed between the two groups, with 128 significantly upregulated and 129 significantly downregulated genes in H group compared to L group. Among them, 9 unique circRNAs were present in group L and 4 unique circRNAs were present in group H. GO and KEGG enrichment analysis of the source genes of the differentially expressed circRNAs revealed that they were mainly involved in metabolic processes, such as cellular metabolic processes, cellular macromolecular metabolic processes, and regulatory pathways related to nutrient metabolism, including protein and amino acid metabolism, as well as vitamin metabolism and pancreatic secretion associated with the animal feeding behavior. The circRNAs detected in this study were mostly novel, and have not been investigated directly to be associated with the RFI phenotype. Interestingly, most miRNAs of differentially expressed circRNAs predicted based on the circRNA-miRNA co-expression network analysis by using top 50 differentially expressed circRNAs and 13 unique circRNAs, have been reported to be related to animal RFIs, implying that circRNAs in bovine hypothalamic tissue may regulate phenotypic variation in RFI through miRNAs. The study results illustrate the complex biological functions of the hypothalamus in regulating feed efficiency and showing the potential role of circRNAs in the feeding behavior regulation of livestock, which would contributing to expanding the understanding of circRNA.

Suckling behavior, performance, and Kleiber index in calves of different genetic groups under shaded and unshaded environments

The aim of this study was to evaluate the effect of heat stress on the suckling behavior and performance of Nelore (NE), ½ Nelore × ½ Angus (NA), and ½ Nelore × ½ Pantaneiro (NP) crossbred calves, in environments shaded or unshaded, using the temperature-humidity index (THI) and Kleiber index (KI) equations. Twenty-five animals were evaluated, from 30 days of age distributed as follows: 9 NE, 8 NA, and 8 NP calves, from 7:00 A.M. to 5:00 P.M., under shaded and unshaded environments. Data were collected on number of suckling episodes per day (NS), mean suckling duration (MSD), surface body temperature (SBT), THI, weight gain, and KI. THI showed difference (P < 0.05) between environments, being lower in the shaded area. NA cattle had higher SBT (33.00 ± 2.31), differing (P < 0.05) from NE (31.71 ± 1.65) and NP (31.38 ± 1.99), and lower (P < 0.05) suckling activity, suggesting reduced thermal comfort. However, their weight gain and KI were higher, differing (P < 0.05) from the other genetic groups. NE and NP cattle did not differ (P > 0.05) in weight gain and KI. Thus, the results suggest that NA calves, despite the greater thermal discomfort, used thermolysis mechanisms to maintain higher weight gain and feed efficiency (KI) than the other groups. NP showed greater thermal adaptability, in addition to weight gain and KI similar to NE cattle.

Meta-analysis of Zinc Supplementation on Laying Performance, Egg Quality Characteristics, and Blood Zinc Concentrations in Laying Hens

There are inconsistent results on the influence of zinc (Zn) supplementation levels on productive indices of laying hens. This study, therefore, uses meta-analysis to synthesis evidence on the effect of inclusion of Zn in chicken diets on performance, egg quality, and blood Zn status of laying hens. Eleven studies were identified and used to analyze the effect of diets with or without Zn supplementation on feed intake, feed conversion ratio (FCR), hen day egg production (HDEP), egg weight (EW), egg mass (EM), Haugh unit (HU) scores, eggshell thickness (EST), eggshell weight (ESW), and blood Zn concentrations in laying hens. Data extracted from the 11 studies included in the meta-analysis were pooled using a random-effects model and expressed as standardized mean differences (SMDs) at a 95% confidence interval (CI). Results indicate that dietary Zn supplementation reduced FCR (SMD =  - 0.50 g feed/g egg; 95% CI: - 0.68 to - 0.31) and increased HDEP (SMD = 0.33%; 95% CI: 0.18 to 0.48), EW (SMD = 0.14 g; 95% CI: 0.03 to 0.25) and EM (SMD = 0.58 g/hen/day; 95% CI: 0.22 to 0.95), HU (SMD = 0.64; 95% CI: 0.42 to 0.85), EST (SMD = 0.84 mm; 95% CI: 0.45 to 1.23), and plasma Zn concentration (SMD = 4.20 mg/dl; 95% CI: 2.99 to 5.40) compared with the controls. In contrast, feed intake and ESW were not significantly different from controls. Restricted subgroup analysis indicated that chosen moderators (age of hen, inclusion level, chicken breed/strain, and supplementation duration) influenced the results of this meta-analysis. There was evidence of significant heterogeneity, and meta-regression indicated that moderators explained most of the sources of heterogeneity. We conclude that dietary zinc supplementation had positive effect on feed conversion ratio, laying performance, aspects of egg quality traits, and blood zinc concentrations in laying hens. The findings from this meta-analysis will help in policy advancements and sustainable use of zinc in the egg production industry.

Detection of potential functional variants based on systems-biology: the case of feed efficiency in beef cattle

BACKGROUND

Potential functional variants (PFVs) can be defined as genetic variants responsible for a given phenotype. Ultimately, these are the best DNA markers for animal breeding and selection, especially for polygenic and complex phenotypes. Herein, we described the identification of PFVs for complex phenotypes (in this case, Feed Efficiency in beef cattle) using a systems-biology driven approach based on RNA-seq data from physiologically relevant organs.

RESULTS

The systems-biology coupled with deep molecular phenotyping by RNA-seq of liver, muscle, hypothalamus, pituitary, and adrenal glands of animals with high and low feed efficiency (FE) measured by residual feed intake (RFI) identified 2,000,936 uniquely variants. Among them, 9986 variants were significantly associated with FE and only 78 had a high impact on protein expression and were considered as PFVs. A set of 169 significant uniquely variants were expressed in all five organs, however, only 27 variants had a moderate impact and none of them a had high impact on protein expression. These results provide evidence of tissue-specific effects of high-impact PFVs. The PFVs were enriched (FDR < 0.05) for processing and presentation of MHC Class I and II mediated antigens, which are an important part of the adaptive immune response. The experimental validation of these PFVs was demonstrated by the increased prediction accuracy for RFI using the weighted G matrix (ssGBLUP+wG; Acc = 0.10 and b = 0.48) obtained in the ssGWAS in comparison to the unweighted G matrix (ssGBLUP; Acc = 0.29 and b = 1.10).

CONCLUSION

Here we identified PFVs for FE in beef cattle using a strategy based on systems-biology and deep molecular phenotyping. This approach has great potential to be used in genetic prediction programs, especially for polygenic phenotypes.

Heat abatement during the pre-weaning period: effects on growth, feed efficiency, metabolites, and insulin of male Holstein calves

Heat stress abatement strategies for pre-weaned dairy calves are seldom evaluated. An experiment was conducted to evaluate the effects of housing calves under a barn and provision of fans to calves housed under a barn on calfhood performance. The experiment was conducted in a dairy in southern Georgia, USA. Male Holstein calves (n = 60; 0 to 68 day of age) were assigned randomly at birth (day 0) to 1 of 3 treatments: hutch outdoors with 50% of its area covered with plywood (control = 20), hutch in a barn with no cooling (SH = 21), and hutch in a barn with ceiling fans (SHF = 19). Body weight (BW) was measured at birth, and total serum protein and wither-height were measured 24 to 48 h after birth. A sub-set of hutches was evaluated for air speed and temperature, and rectal temperature (RT) and respiratory frequency (RF) of calves housed in these hutches were measured at 0900 and 1500 h. Intakes of liquid feed (days 14 to 63) and starter (days 14 to 68) were recorded daily, BW and wither-height were measured weekly, and feed efficiency was calculated weekly. Blood was sampled on days 1, 14, 28, 42, 49, 52, 56, 58, 63, and 65 for the measurement of fatty acids, β-hydroxybutyrate, glucose, and insulin. The SHF treatment resulted in air velocity 0.56 to 0.83 m/s greater (P < 0.01) than the control and SH treatments, respectively, whereas the control treatment resulted in air temperature 1.2 to 3.2 °C greater (P < 0.01) than the SH and SHF treatments, respectively. The RT of calves in the control treatment was 0.1 to 1.1 °C greater (P ≤ 0.03) than the SH and SHF treatments, respectively, and the control treatment resulted in RF 39.4 to 60.2 mov/min greater (P < 0.01) than the SH and SHF treatments, respectively. Treatment did not (P ≥ 0.27) affect feed efficiency and concentrations of metabolites and insulin, but calves in the control treatment were 2.6 cm shorter (P = 0.03) than calves in the SHF treatments at weaning. Provision of fans to calves housed under a barn reduced RT, RF, but only had a minute impact on wither-height.

Apparent digestibility and ingestive behavior of Nellore bulls with low and high residual feed intake

The objective of this study was to determine the correlation between ingestive behavior, apparent digestibility, and residual feed intake (RFI) of finishing Nellore bulls fed a high concentrate diet. One hundred and twenty Nellore bulls, housed in individual pens, were evaluated in individual performance tests. The animals were fed a high concentrate diet (23:77 roughage/concentrate ratio). The animals were classified as low RFI, medium RFI, and high RFI. Data from ten animals from each group were used. Fecal production and nutrient digestibility were calculated using indigestible neutral detergent fiber as an internal marker. The feeding behavior was evaluated over 24 h by direct observation every 5 min. The most efficient animals (low RFI, 8.58 kg DM/day) consumed 27.62% less feed than the least efficient animals (high RFI, 10.95 kg DM/day). Animals with medium efficiency (mean RFI, 9.49 kg DM/day) consumed 15.39% less than high RFI. Nutrient digestibility coefficients were similar except for ether extract (P < 0.03) which was 8% greater for the high-RFI animals. No effect was observed for ingestive behavior (P > 0.05). Animals spent, on average, 3 h 28 min feeding, 7 h 32 min ruminating, and 13 h 40 min in idle time. In the present study, ingestive behavior and dry matter digestibility were not responsible for between-animal variation in residual feed intake in Nellore bulls fed a high concentrate diet.

Prediction of dry matter intake and gross feed efficiency using milk production and live weight in first-parity Holstein cows

Direct measurement of dry matter intake (DMI) presents a major challenge in estimating gross feed efficiency (GFE) in dairy cattle. This challenge can, however, be resolved through the prediction of DMI and GFE from easy-to-measure traits such as milk production (i.e. milk yield, energy-corrected milk (ECM), butterfat, protein, lactose) and live weight (LW). The main objective of this study was, therefore, to investigate the feasibility of predicting dry matter intake and gross feed efficiency for first-parity Holstein cows using milk production traits and LW. Data comprised of 30 daily measurements of DMI and milk production traits, and 25 daily LW records of a group of 100 first-parity Holstein cows, fed a total mixed ration. Gross feed efficiency was calculated as kg ECM divided by kg DMI. The initial step was to estimate correlations of milk production traits and LW with DMI and GFE, to identify the best potential predictors of DMI and GFE. Subsequently, a forward stepwise regression analysis was used to develop models to predict DMI and GFE from LW and milk production traits, followed by within-herd validations. Means for DMI, butterfat yield (BFY) and LW were 21.91 ± 2.77 kg/day, 0.95 ± 0.14 kg/day and 572 ± 15.58 kg/day, respectively. Mean GFE was 1.32 ± 0.22. Dry matter intake had positive correlations with milk yield (MY) (r = 0.32, p < 0.001) and LW (r = 0.76, p < 0.0001) and an antagonistic association with butterfat percent (BFP) (r =  - 0.55, p < 0.001). On the other hand, GFE was positively associated with MY (r = 0.36, p < 0.001), BFP (r = 0.53, p < 0.001) and BFY (r = 0.83, p < 0.0001), and negatively correlated with LW (r =  - 0.23, p > 0.05). Dry matter intake was predicted reliably by a model comprising of only LW and MY (R² = 0.79; root mean squared error (RMSE) = 1.05 kg/day). A model that included BFY, MY and LW had the highest ability to predict GFE (R² = 0.98; RMSE = 0.05). Live weight and BFY were the main predictor traits for DMI and GFE, respectively. The best models for predicting DMI and GFE were as follows: DMI (kg/day) =  - 54.21 - 0.192 × MY (kg/day) + 0.146 × LW (kg/day) and GFE (kg/day) = 4.120 + 0.024 × MY (kg/day) + 1.000 × BFY (kg/day) - 0.008 × LW (kg/day). Thus, daily DMI (kg/day) and GFE can be reliably predicted from LW and milk production traits using these developed models in first-parity Holstein cows. This presents a big promise to generate large quantities of data of individual cow DMI and GFE, which can be used to implement genetic improvement of feed efficiency.

Phenotypic correlations between feed efficiency, growth, and meat quality of slow-growing chickens

1. Korat (KR) chicken is a new meat-type chicken breed established with the purpose of developing Small and Micro Community Enterprise Production. This slow-growing chicken has been recognised for its good texture and flavour, but its low feed efficiency is associated with high cost of production which can hamper the development of local production. This has highlighted the importance of studying the trade-off between feed efficiency and meat quality in KR chicken.2. This study investigated the phenotypic correlations between feed efficiency, growth performance, and meat quality in KR chicken. Individual body weight and feed intake were recorded weekly for 75 male KR chickens for the calculation of feed conversion ratio (FCR) and residual feed intake (RFI). The growth curve was modelled by Gompertz function and meat quality evaluated at 10 weeks of age, through the measurement of pH (pH_u), water-holding capacity (WHC) and drip loss (DL) in breast and thigh muscle.3. Faster growth rate at young age appeared favourable, regarding feed efficiency, since a moderate negative correlation was found between FCR and initial growth rate. Chickens with a higher initial growth and maturation rates were characterised by lower water-holding capacity in meat. This was not associated with acidic meat, since a higher speed of growth (especially in the first weeks) was positively associated with final pH in breast meat. Relationships between RFI and meat quality traits appeared to be weak. While better FCR could be achieved by increased initial growth rate, this seemed to negatively impact water-holding capacity of the meat.4. RFI appeared as an interesting alternative as a compromise between FCR and meat quality.

Protein metabolism, body composition and oxygen consumption in young bulls divergent in residual feed intake offered two contrasting forage-based diets

Protein metabolism and body composition have been identified as major determinants of residual feed intake (RFI) in beef cattle fed high-starch fattening diets. This study aimed to evaluate if these two identified RFI determinants in beef cattle are the same across two contrasting silage-based diets. During two consecutive years, an 84-day feed efficiency test (Test A) immediately followed by a second 112-day feed efficiency test (Test B) was carried out using a total of 100 animals offered either one of two diets (either corn silage- or grass silage-based) over 196 days. At the end of Test A, the 32 animals most divergent for RFI (16 extreme RFI animals per diet, eight low RFI and eight high RFI) were identified and evaluated during Test B for their i) N use efficiency (NUE; N retention/N intake) calculated either from a 10-d nitrogen balance trial or from estimations based on body composition changes occurring during the whole experiment (Test A and Test B; 196 days), ii) carcass and whole-body protein turnover rates analysed through the 3-methyl-histidine urinary excretion and the N isotopic turnover rates of urine, respectively, and iii) body composition measured at the slaughterhouse at the end of Test B. Oxygen consumption was measured during Test B for the 100 animals by two GreenFeed systems. Irrespective of the diet, efficient RFI animals tended (P = 0.08) to improve their NUE when N retention was estimated for 196 days or when considering their lower urinary urea-N to total N ratio (P = 0.03). In contrast, NUE calculated during the 10-d N balance showed no differences (P = 0.65) across RFI groups suggesting that this method may not be suitable to capture small NUE differences. Efficient RFI individuals presented higher dressing percentage and muscle deposition in the carcass (P = 0.003) but lighter rumen (P = 0.001), and a trend for lower oxygen consumption (P = 0.08) than inefficient RFI animals irrespective of the diet. Lower protein degradation rates of skeletal muscle and lower protein synthesis rates of plasma proteins were found in efficient RFI cattle but only with the corn silage-based diet (RFI × Diet; P = 0.02). The higher insulinaemia associated with the corn silage-based diet (P = 0.001) seemed to be a key metabolic feature explaining the positive association between protein turnover and RFI only in this diet. Feed N was more efficiently used for growth by efficient RFI animals regardless of the diet but lower protein turnover rates in efficient RFI animals were only observed with corn silage-based diets.

Using the natural abundance of nitrogen isotopes to identify cattle with greater efficiency in protein-limiting diets

The difficulty in selecting cattle for higher feed and nitrogen use efficiency (NUE) is an important factor contributing to poor growth and reproductive performance in dry-tropics rangelands. Therefore, the objectives were to examine the cattle variation in retaining nitrogen in a protein-deficient diet and the natural abundance of stable isotopes in body tissues as a practical alternative for the detection of more efficient cattle. In experiment 1, feed efficiency parameters were determined in 89 Brahman steers fed a protein-limiting diet for 70 days, followed by 7 days in metabolism crates for total collection of urine and faeces and calculation of nitrogen retention and NUE. The diet-animal fractionation of nitrogen isotopes (Δ¹⁵N) was quantified in tail hair and plasma proteins using isotope-ratio MS. There was a large variation in growth performance, feed efficiency and nitrogen losses among steers. Quantifying Δ¹⁵N in tail hair (Δ¹⁵N_{tail hair}) resulted in stronger correlations with feed efficiency and nitrogen metabolism parameters than when quantified in plasma proteins. Δ¹⁵N_{tail hair} was positively correlated with nitrogen losses in urine (r = 0.31, P < 0.01) and faeces (r = 0.25, P = 0.04), leading to a negative correlation with NUE (r = -0.40, P < 0.01). The group of steers with lower Δ¹⁵N_{tail hair} had greater feed efficiency, lower nitrogen losses, and greater NUE. In experiment 2, for evaluation of isotope fraction as a predictor of reproductive performance, 630 Brahman-crossed cows were classified for reproductive performance for 2 years. From this group, 25 cows with poor reproductive performance and 25 cows with good reproductive performance were selected. Tail hair representing 7 months of growth were segmented and analysed for carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope enrichment. Reproductive performance was not associated with diet selection, as there was no difference in tail hair δ¹³C between groups. However, more productive cows had lower (P < 0.05) tail hair δ¹⁵N during the dry season, indicating differences in N metabolism and possibly lower N losses. In addition, cows with better reproductive performance and, therefore, greater nutrient demands, had similar body condition scores and a tendency (P = 0.09) for higher live weight at the end of the trial. In conclusion, the findings of the present study confirm that nitrogen isotope fractionation in tail hair can be used as a predictor of nitrogen losses, NUE, and reproductive performance of Brahman cattle on low-protein diets.

Aquaculture wastewater-raised Azolla as partial alternative dietary protein for Pangasius catfish

Azolla is a freshwater floating aquatic fern found in the tropical, subtropical and temperate regions with a high nitrogen-fixing rate from the result of symbiotic relationship with the blue-green cyanobacterium, Anabaena azollae. Azolla can effectively remediate aquaculture wastewater owing to its high production capacity and the ability to absorb nutrients and toxic compounds. The Azolla biomass generated as a by-product is currently underutilized and could potentially benefit the aquafeed industry in replacing the unfeasible and expensive fishmeal protein at a certain level. This study evaluates the incorporation of red tilapia wastewater-raised Azolla as a dietary protein for the growth performance, feed efficiency, survival, body indices, body composition and nutrient utilization of Pangasius catfish Pangasianodon hypophthalmus during a 90-days feeding experiment. Dried Azolla was incorporated into four isonitrogenous (30 g kg^-1) and isolipidic (12 g kg^-1) practical diets containing 0 g kg^-1 (Control), 10 g kg^-1 (A10), 20 g kg^-1 (A20) and 30 g kg^-1 (A30) fishmeal protein replacement. One hundred and twenty juveniles with an initial mean weight of 45 ± 15 g were distributed into 12 tanks representing four dietary treatments in triplicates. Results showed significant (p < 0.05) improvement in weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER) and feed conversion ratio (FCR) in Pangasius catfish fed 10 g kg^-1 Azolla protein. Beyond that, WG, SGR, PER and FCR decreased to the lowest value when fed with 30 g kg^-1 Azolla protein. No significant (p > 0.05) effects were recorded for feed intake, survival, body indices and nutrient utilization amongst all dietary treatments. In conclusion, Azolla raised from red tilapia aquaculture wastewater can replace fishmeal protein up to 10 g kg^-1 in the diet of Pangasius catfish juveniles having better growth, feed efficiency and nutrient utilization without affecting its survival, body indices and body composition.

Integrated meta-omics reveals new ruminal microbial features associated with feed efficiency in dairy cattle

BACKGROUND

As the global population continues to grow, competition for resources between humans and livestock has been intensifying. Increasing milk protein production and improving feed efficiency are becoming increasingly important to meet the demand for high-quality dairy protein. In a previous study, we found that milk protein yield in dairy cows was associated with the rumen microbiome. The objective of this study was to elucidate the potential microbial features that underpins feed efficiency in dairy cows using metagenomics, metatranscriptomics, and metabolomics.

RESULTS

Comparison of metagenomic and metatranscriptomic data revealed that the latter was a better approach to uncover the associations between rumen microbial functions and host performance. Co-occurrence network analysis of the rumen microbiome revealed differential microbial interaction patterns between the animals with different feed efficiency, with high-efficiency animals having more and stronger associations than low-efficiency animals. In the rumen of high-efficiency animals, Selenomonas and members of the Succinivibrionaceae family positively interacted with each other, functioning as keystone members due to their essential ecological functions and active carbohydrate metabolic functions. At the metabolic level, analysis using random forest machine learning suggested that six ruminal metabolites (all derived from carbohydrates) could be used as metabolic markers that can potentially differentiate efficient and inefficient microbiomes, with an accuracy of prediction of 95.06%.

CONCLUSIONS

The results of the current study provided new insights into the new ruminal microbial features associated with feed efficiency in dairy cows, which may improve the ability to select animals for better performance in the dairy industry. The fundamental knowledge will also inform future interventions to improve feed efficiency in dairy cows. Video Abstract.

Digestive efficiency traits in growing pigs are genetically correlated with sow litter traits in the Large White breed

Digestive efficiency traits are promising selection criteria to improve feed efficiency in pigs. However, the genetic relationships between digestive efficiency and sow reproductive traits are mostly unknown and need to be estimated. In this study, reproductive traits were available for 61 601 litters recorded on 21 719 Large White purebred sows. The traits were comprised of the number of born alive (NBA) and the number of weaned piglets (NWP), the number of stillbirths (NSB) and piglet mortality during suckling (PM). For a subset of 32518 litters, the mean (MBW) and CV of piglet birth weights (CVBW) were deduced from individual piglet weights as well as the proportion of piglets weighing less than 1 kg (PPL1K). Growth and feed efficiency traits were available for 4 643 Large White male pigs related to sows with reproductive performances. They comprised average daily gain (ADG), daily feed intake (DFI) and feed conversion ratio (FCR). A subset of 1 391 pigs had predictions for digestibility coefficients (DC) of energy, organic matter and nitrogen obtained by analysing faecal samples with near-infrared spectrometry. Estimated heritabilities were low for NBA, NSB, NWP and PM (0.08 ± 0.01 to 0.11 ± 0.01) and low to moderate for litter weight characteristics (0.14 ± 0.02 to 0.38 ± 0.01). Heritability estimates were moderate to high for ADG, DFI and FCR (0.37 ± 0.04 to 0.54 ± 0.05) and moderate for DC traits (0.26 ± 0.06 to 0.38 ± 0.07). Genetic correlations were low between ADG, or alternatively FCR, and reproductive traits. They were significantly different from zero with MBW (0.19 ± 0.06 with ADG and -0.15 ± 0.06 with FCR) and PPL1K (-0.19 ± 0.07 with ADG and 0.18 ± 0.07 with FCR). All genetic correlations between DFI and reproductive traits were low and not significantly different from zero. Genetic correlations between DC traits and NBA were significantly different from zero for DC of organic matter and energy (<-0.25 ± 0.11). DC traits were moderately correlated with MBW (>0.30 ± 0.11), CVBW (<-0.36 ± 0.11) and PPL1K (<-0.37 ± 0.11) at the genetic level. Genetic correlations between DC traits and PM were significantly negative and hence favourable (<-0.38 ± 0.12). Finally, genetic correlations between DC traits and NWP were close to zero. These results suggested that sows closely related to growing pigs with the best digestive efficiency would produce heavier and more homogeneous piglets, with slightly smaller litter sizes at birth but better survival. Hence, there is usable genetic variation in DC that could be exploited to define new selection strategies in maternal lines aiming at improving not only feed efficiency but also piglet survival.

Exploring the pathways towards the mitigation of the environmental impacts of food consumption

Agriculture constitutes a quarter and more than a third of Denmark's global greenhouses gas (GHG) emissions and natural resource consumption, respectively. This paper aims to estimate the potential to lower Denmark's global food-related GHG, blue water and land footprints using the most recent version of a hybrid global multi-regional input-output (MRIO) database, EXIOBASE of the reference year, 2011. Specifically, we apply the 'what if' scenario-based MRIO approach to EXIOBASE and quantify the impact of increased livestock feed efficiency (FE), dietary changes, food loss and waste (FLW) reduction/prevention and food waste treatment scenarios on Denmark's global food-related GHG and resource footprints. We obtain modest reductions in Denmark's global food-related GHG, blue water and cropland footprint from the combination of livestock FE improvements and FLW reduction; 61 kt CO₂e, 2 Mm³ and 30 kha, respectively. In contrast, dietary change towards no/less meat and dairy diets embodies the most significant reductions potential for Denmark's total global food-related GHG, blue water, croplands and grassland footprint by up to 34% (3.63 Mt. CO₂e), 8% (90 Mm³), 23% (371 kha) and 78% (386 kha) respectively. A key policy priority should therefore be the nudging of Danish consumers towards sustainable diets. Also, this study's findings emphasise that FLW prevention remains the most effective food waste-related climate mitigation and resource efficiency strategy despite the benefits of food waste valorisation.

Synergistic Effects of Selenium and Zinc Oxide Nanoparticles on Growth Performance, Hemato-biochemical Profile, Immune and Oxidative Stress Responses, and Intestinal Morphometry of Nile Tilapia (Oreochromis niloticus)

This study was aimed to investigate the synergistic effects of selenium (Se-NP) and zinc oxide (ZnO-NP) nanoparticles on growth performance, hemato-biochemical profile, immune and oxidative stress responses, and intestinal morphometry of Nile tilapia (Oreochromis niloticus). Monosex Nile tilapia (12.50 ± 1.03 g, N= 180) were randomly allocated into 4 groups in triplicates. Fish were fed diet supplemented with 0 Se-NP and Zn-NP (control group, CG), while fish in the other experimental groups were fed diet supplemented with 1 mg/kg diet Se-NP (Se-NP group), 10 mg/kg diet ZnO-NP (Zn-NP group), and a mixture of 1 and 10 mg/kg diet Se-NP and Zn-NP, respectively (Se/Zn-NP group) for 60 days. Fish fed diet containing Se-NP, Zn-NP, and Se/Zn-NP showed higher final body weight, weight gain, weight gain rate, specific growth rate, and lower feed conversion ratio with respect to CG (P<0.05) with the highest being in fish fed with Se/Zn-NP. Fish fed with Se/Zn-NP showed higher hemoglobin, red blood cells, and globulin (P<0.05). The highest phagocytic activity, phagocytic index, lysozyme activity, and immunoglobulin M was recorded in fish that received Se/Zn-NP followed by Se-NP, Zn-NP, and the lowest in CG (P<0.05). Fish that received diet supplemented with Se-NP, Zn-NP, and Se/Zn-NP significantly (P<0.05) increased superoxide dismutase and catalase while reduced malonaldehyde activity compared to CG. Intestinal morphometry revealed significantly (P<0.05) increased villi length and goblet cells number in fish fed with Se-NP and/or Zn-NP. In conclusion, dietary supplementation of Nile tilapia with Se-NP and Zn-NP induces synergistic effects that improve growth performance, blood health, and intestinal histomorphology.

Distinctive roles between rumen epimural and content bacterial communities on beef cattle feed efficiency: A combined analysis

Rumen content-associated (RC) and epithelial tissue-attached (RT) bacterial communities are composed of different phylotypes and play distinctive roles. This study aimed to compare the composition of the RT and RC bacterial communities of steers differing in feed efficiency. The microbiota of RT and RC samples collected from sixteen beef steers with high or low residual feed intake (RFI) were analyzed through sequencing of partial 16S rRNA gene amplicons. Bacteroidetes, Proteobacteria and Firmicutes were the predominant phyla and Prevotella was the most abundant genus in both RC and RT bacterial communities. In total, 19 OTUs of the RC samples and 19 OTUs of the RT samples were differentially abundant (DA) between H-RFI and l-RFI steers. Among them, a common DA OTU belonged to Prevotella genus was identified in both RC and RT samples, making it the potential key microbial marker for indicating feed efficiency of steers. The co-occurrence of the DA OTUs among RT and RC samples suggest the importance of these two communities function as a complete system in influencing host feed efficiency.

Identifying active rumen epithelial associated bacteria and archaea in beef cattle divergent in feed efficiency using total RNA-seq

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The most active archaea in the epimural community were different from that of the liquid and content-associated community, but the exact taxonomy requires further identification.

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Rumen epithelial attached methanogens may not contribute to differences in CH₄ production and variations in feed efficiency.

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Families Campylobacteraceae and Neisseriaceae, which contain oxygen scavenging bacteria were significantly more active on the epithelium of efficient cattle.

To date, the role of ruminal epithelial attached microbiota in cattle feed efficiency is undefined. In this study, we aimed to characterize transcriptionally active bacteria and archaea attached to the rumen epithelial wall and to determine whether they differ in cattle with varied feed efficiency. RNA-sequencing was performed to obtain the rumen epithelial transcriptomes from 9 of the most efficient (low RFI) and 9 of the most inefficient (high RFI) animals. The bacteria and archaea 16S rRNA transcripts were identified using an in-house developed pipeline, enriched from filtered reads that did not map to the bovine genome. Archaea from unclassified genera belonging to the Euryarchaeota phylum showed the most activity on the rumen epithelium of low RFI (81.3 ± 1.9%) and high RFI (76.4 ± 3.0%) steers. Bacteria from the Succinivibrionaceae family showed the greatest activity of bacteria on the low RFI (28.7 ± 9.0%) and high RFI (33.9± 8.8%) epithelium. Of the bacterial families, Campylobacteraceae and Neisseriaceae had significantly greater activity on the low RFI epithelium (p < 0.05) and are known to play a role in oxygen scavenging. Greater activity of rumen epithelial attached oxygen scavenging bacteria may provide more optimal feed fermentation conditions, which contributes to high fermentation efficiency in the rumen.

Combining datasets in a dynamic residual feed intake model and comparison with linear model results in lactating Holstein cattle

A new method to estimate residual feed intake (RFI) was recently developed based on a multi-trait random regression model. This approach deals with the dynamic nature of the lactation, which is in contrast with classical linear approaches. However, an issue remains: pooling data across sites and years, which implies dealing with different (and sometimes unknown) diet energy contents. This will be needed for genomic evaluation. In this study, we tested whether merging two individual datasets into a larger one can lead to valuable results in comparison to analysing them on their own with the multi-trait random regression model. Three datasets were defined: the first one with 1 063 lactations, the second one with 205 lactations from a second farm and the third one combining the data of the two first datasets (1 268 lactations). The model was applied to the three datasets to estimate individual RFI as well as variance components and correlations between the four traits included in the model (fat and protein corrected milk production, BW, feed intake and body condition score), and a fixed month-year-farm effect was used to define the contemporary group. The variance components and correlations between animal effects of the four traits were very similar irrespective of the dataset used with correlations higher than 0.94 between the different datasets. The RFI estimates for animals from their single farm only were also very similar (r > 0.95) to the ones computed from the merged dataset (Dataset 3). This highlights that the contemporary group correction in the model adequately accounts for differences between the two feeding environments. The dynamic model can thus be used to produce RFI estimates from merged datasets, at least when animals are raised in similar systems. In addition, the 205 lactations from the second farm were also used to estimate the RFI with a linear approach. The RFI estimated by the two approaches were similar when the considered period was rather short (r = 0.85 for RFI for the first 84 days of lactation) but this correlation weakened as the period length grew (r = 0.77 for RFI for the first 168 days of lactation). This weakening in correlations between the two approaches when increasing the used time-period reflects that only the dynamic model permits the regression coefficients to evolve in line with the physiological changes through the lactation. The results of this study enlarge the possibilities of use for the dynamic RFI model.

Accelerated discovery of novel glycoside hydrolases using targeted functional profiling and selective pressure on the rumen microbiome

BACKGROUND

Carbohydrate-active enzymes (CAZymes) form the most widespread and structurally diverse set of enzymes involved in the breakdown, biosynthesis, or modification of lignocellulose that can be found in living organisms. However, the structural diversity of CAZymes has rendered the targeted discovery of novel enzymes extremely challenging, as these proteins catalyze many different chemical reactions and are sourced by a vast array of microbes. Consequently, many uncharacterized members of CAZyme families of interest have been overlooked by current methodologies (e.g., metagenomic screening) used to discover lignocellulolytic enzymes.

RESULTS

In the present study, we combined phenotype-based selective pressure on the rumen microbiota with targeted functional profiling to guide the discovery of unknown CAZymes. In this study, we found 61 families of glycoside hydrolases (GH) (out of 182 CAZymes) from protein sequences deposited in the CAZy database-currently associated with more than 20,324 microbial genomes. Phenotype-based selective pressure on the rumen microbiome showed that lignocellulolytic bacteria (e.g., Fibrobacter succinogenes, Butyrivibrio proteoclasticus) and three GH families (e.g., GH11, GH13, GH45) exhibited an increased relative abundance in the rumen of feed efficient cattle when compared to their inefficient counterparts. These results paved the way for the application of targeted functional profiling to screen members of the GH11 and GH45 families against a de novo protein reference database comprised of 1184 uncharacterized enzymes, which led to the identification of 18 putative xylanases (GH11) and three putative endoglucanases (GH45). The biochemical proof of the xylanolytic activity of the newly discovered enzyme validated the computational simulations and demonstrated the stability of the most abundant xylanase.

CONCLUSIONS

These findings contribute to the discovery of novel enzymes for the breakdown, biosynthesis, or modification of lignocellulose and demonstrate that the rumen microbiome is a source of promising enzyme candidates for the biotechnology industry. The combined approaches conceptualized in this study can be adapted to any microbial environment, provided that the targeted microbiome is easy to manipulate and facilitates enrichment for the microbes of interest. Video Abstract.

Identification of candidate genes and enriched biological functions for feed efficiency traits by integrating plasma metabolites and imputed whole genome sequence variants in beef cattle

BACKGROUND

Feed efficiency is one of the key determinants of beef industry profitability and sustainability. However, the cellular and molecular background behind feed efficiency is largely unknown. This study combines imputed whole genome DNA variants and 31 plasma metabolites to dissect genes and biological functions/processes that are associated with residual feed intake (RFI) and its component traits including daily dry matter intake (DMI), average daily gain (ADG), and metabolic body weight (MWT) in beef cattle.

RESULTS

Regression analyses between feed efficiency traits and plasma metabolites in a population of 493 crossbred beef cattle identified 5 (L-valine, lysine, L-tyrosine, L-isoleucine, and L-leucine), 4 (lysine, L-lactic acid, L-tyrosine, and choline), 1 (citric acid), and 4 (L-glutamine, glycine, citric acid, and dimethyl sulfone) plasma metabolites associated with RFI, DMI, ADG, and MWT (P-value < 0.1), respectively. Combining the results of metabolome-genome wide association studies using 10,488,742 imputed SNPs, 40, 66, 15, and 40 unique candidate genes were identified as associated with RFI, DMI, ADG, and MWT (P-value < 1 × 10-5), respectively. These candidate genes were found to be involved in some key metabolic processes including metabolism of lipids, molecular transportation, cellular function and maintenance, cell morphology and biochemistry of small molecules.

CONCLUSIONS

This study identified metabolites, candidate genes and enriched biological functions/processes associated with RFI and its component traits through the integrative analyses of metabolites with phenotypic traits and DNA variants. Our findings could enhance the understanding of biochemical mechanisms of feed efficiency traits and could lead to improvement of genomic prediction accuracy via incorporating metabolite data.

Genetic analyses of metabolic body weight, carcass weight and body conformation traits in Nordic dairy cattle

Improving feed efficiency in dairy cattle by animal breeding has started in the Nordic countries. One of the two traits included in the applied Saved feed index is called maintenance and it is based on the breeding values for metabolic BW (MBW). However, BW recording based on heart girth measurements is decreasing and recording based on scales is increasing only slowly, which may weaken the maintenance index in future. Therefore, the benefit of including correlated traits, like carcass weight and conformation traits, is of interest. In this study, we estimated genetic variation and genetic correlations for eight traits describing the energy requirement for maintenance in dairy cattle including: first, second and third parity MBW based on heart girth measurements, carcass weight (CARW) and predicted MBW (pMBW) based on predicted slaughter weight, and first parity conformation traits stature (ST), chest width (CW) and body depth (BD). The data consisted of 21329 records from Finnish Ayrshire and 9780 records from Holstein cows. Heritability estimates were 0.44, 0.53, 0.56, 0.52, 0.54, 0.60, 0.17 and 0.26 for MBW1, MBW2, MBW3, CARW, pMBW, ST, CW and BD, respectively. Estimated genetic correlations among MBW traits were strong (>0.95). Genetic correlations between slaughter traits (CARW and pMBW) and MBW traits were higher (from 0.77 to 0.90) than between conformation and MBW traits (from 0.47 to 0.70). Our results suggest that including information on carcass weight and body conformation as correlated traits into the maintenance index is beneficial when direct BW measurements are not available or are difficult or expensive to obtain.

Impact of varied time of feeding on the lactation and growth performance of West African Dwarf goat

This study was conducted to evaluate the effect of time of feeding on production performance of West African Dwarf (WAD) goats. Two experiments involving twenty-seven goats (15 bucks and 12 gravid does) were conducted. In Experiment I, the bucks were randomly allocated into three treatments of five replicates and fed for 115 days. In experiment II, pregnant goat-does were randomly allocated into three experimental treatments of four replicates per treatment  1 month to kidding. Goats were either fed in the morning (06:00 h), afternoon (12:00 h), or evening (18:00 h) respectively under natural light cycles. In experiment I, dry matter intake, weight gain, carcass characteristic, and meat chemical composition were not affected (P > 0.05) by time of feeding. In experiment II, data collection on feed intake, feed efficiency (FE), and milk yield spanned 6 weeks and were analyzed. From the results, milk yield in morning-fed goat-does was higher than evening-fed does while afternoon-fed does have the lowest yield at P < 0.001. Energy corrected milk in evening-fed does was higher (P = 0.006) than other treatments. Feed efficiency for milk yield and energy corrected milk yield (P < 0.001) in evening-fed does were higher than morning and afternoon-fed does. Milk component yield (g/day) for lactose (P = 0.002) was the highest in morning-fed does; evening-fed does had the highest (P = 0.001) crude fat while afternoon-fed does had the lowest yield for all milk component parameters. Conclusively, feeding in the morning and evening is recommended for milk production and component yield per day. However, for improved energy corrected milk yield and feed efficiency in lactating goats, feeding in the evening is recommended. It is recommended that further studies should be conducted on improving milk productivity in evening-fed goats due to the advantage it had over other feeding regimes. Thus, altering time of feeding could be a suitable alternative feeding strategy in a changing climate with a potential to improve production efficiency, especially in the tropics.