Screening and characterization of Bacillus velezensis LB-Y-1 toward selection as a potential probiotic for poultry with multi-enzyme production property

Bacillus spp. have gained increasing recognition as an option to use as antimicrobial growth promoters, which are characterized by producing various enzymes and antimicrobial compounds. The present study was undertaken to screen and evaluate a Bacillus strain with the multi-enzyme production property for poultry production. LB-Y-1, screened from the intestines of healthy animals, was revealed to be a Bacillus velezensis by the morphological, biochemical, and molecular characterization. The strain was screened out by a specific screening program, possessed excellent multi-enzyme production potential, including protease, cellulase, and phytase. Moreover, the strain also exhibited amylolytic and lipolytic activity in vitro. The dietary LB-Y-1 supplementation improved growth performance and tibia mineralization in chicken broilers, and increased serum albumin and serum total protein at 21 days of age (p < 0.05). Besides, LB-Y-1 enhanced the activity of serum alkaline phosphatase and digestive enzyme in broilers at 21 and 42 days of age (p < 0.05). Analysis of intestinal microbiota showed that a higher community richness (Chao1 index) and diversity (Shannon index) in the LB-Y-1 supplemented compared with the CON group. PCoA analysis showed that the community composition and structure were distinctly different between the CON and LB-Y-1 group. The beneficial genera such as Parasutterella and Rikenellaceae were abundant, while the opportunistic pathogen such as Escherichia-Shigella were reduced in the LB-Y-1 supplemented group (p < 0.05). Collectively, LB-Y-1 can be considered as a potential strain for further utilization in direct-fed microbial or starter culture for fermentation.

Vulnerability assessments in dairy cattle farms based on individual sensitivity to heat stress

Climate change (CC) is expected to increase temperatures and the frequency of extreme weather events, which renewed interest in heat stress (HS) effects on dairy cattle farms. Resilience is a key concept that should be considered to better understand the dairy farms exposure to HS and to combat CC-related risks. Thus, this study aimed to investigate the aspects of HS vulnerability for Tunisian dairy cattle farming systems. Historical milk test-day records from official milk recording were merged with temperature and humidity data provided by public weather stations. Firstly, different models relying in two heat load indices were applied for HS exposure assessment. Secondly, broken line models were used to estimate HS thresholds, milk losses, and rates of decline of milk production associated with temperature-humidity index (THI) across parities. Thirdly, individual cow responses to HS estimated using random regression model were considered as key measures of dairy farming system sensitivity assessment to HS. Dairy farms are annually exposed for 5 months to high THI values above 72 in Tunisia. The tipping points, at which milk yield started to decline over parities with 3-day average THI, ranged between 65 and 67. The largest milk decline per unit of THI above threshold values was 0.135 ± 0.01 kg for multiparous cows. The milk losses estimated due to HS in the Holstein breed during the summer period (June to August) ranged between 110 and 142 kg/cow in north and south, respectively. A high HS sensitivity was proved especially in dairy farms characterized by large herd size and high milk production level. Hence, providing knowledge of dairy farms vulnerability to HS may provide the basis for developing strategies to reduce HS effects and plan for CC adaptation.

Xylo-Oligosaccharides, Preparation and Application to Human and Animal Health: A Review

Xylo-oligosaccharides (XOS) are considered as functional oligosaccharides and have great prebiotic potential. XOS are the degraded products of xylan prepared via chemical, physical or enzymatic degradation. They are mainly composed of xylose units linked by β-1, 4 bonds. XOS not only exhibit some specific physicochemical properties such as excellent water solubility and high temperature resistance, but also have a variety of functional biological activities including anti-inflammation, antioxidative, antitumor, antimicrobial properties and so on. Numerous studies have revealed in the recent decades that XOS can be applied to many food and feed products and exert their nutritional benefits. XOS have also been demonstrated to reduce the occurrence of human health-related diseases, improve the growth and resistance to diseases of animals. These effects open a new perspective on XOS potential applications for human consumption and animal production. Herein, this review aims to provide a general overview of preparation methods for XOS, and will also discuss the current application of XOS to human and animal health field.

Effects of graded levels of xylo-oligosaccharides on growth performance, serum parameters, intestinal morphology, and intestinal barrier function in weaned piglets

The objective of this study was to investigate the effects of xylo-oligosaccharides (XOSs) supplementation on growth performance, serum parameters, small intestinal morphology, intestinal mucosal integrity, and immune function in weaned piglets. A total of 240 weaned piglets with an average body weight (BW) of 8.82 ± 0.05 kg (28 d of age) were assigned randomly to four dietary treatments in a 28-d trial, including a control (CON) diet and three diets with XOS supplementation at the concentration of 100 (XOS100), 500 (XOS500), and 1,000 (XOS1000) mg/kg. There were four replicates per treatment with 15 pigs per pen. From day 1 to 14, there were no differences (P > 0.05) in average daily gain (ADG), average daily feed intake, and gain to feed ratio (G:F) during the different treatments. The different doses of XOSs showed a quadratic effect on BW on day 28, ADG, and G:F on day 1 to 28 of piglets (P < 0.05). From day 15 to 28, ADG of pigs fed the XOS500 diet was higher (P < 0.05) than pigs fed the CON diet. During the overall period (day 1 to 28), pigs fed the XOS500 diet had a higher BW, ADG, and G:F than pigs fed the CON diet (P < 0.05). In addition, compared with the CON group, the XOS500 group had significantly higher serum total antioxidant capacity, total superoxide dismutase and catalase levels, and lower malondialdehyde levels on days 14 and 28 (P < 0.05). The serum immunoglobulin G (IgG) concentration in the XOS500 group was also significantly higher compared with the CON group on days 14 and 28 (P < 0.05). However, serum immunoglobulin A and immunoglobulin M were not affected by the dietary treatments. Supplementation of XOS500 to the feed significantly increased the villus height (VH) and VH to crypt depth ratio in the jejunum and ileum in comparison with the CON and XOS1000 groups. Moreover, the XOS500 group significantly elevated the expression levels of occludin and zonula occludens protein-1 in the ileum compared with the CON group. The ileal interleukin (IL)-1β, IL-8, and interferon (IFN)-γ mRNA expression levels in the XOS100 and XOS500 groups were markedly lower than in the CON group. In contrast, the ileal IL-10 mRNA expression levels were remarkably higher in the XOS500 than in the CON group. In conclusion, XOSs have a beneficial effect on growth performance by improving serum antioxidant defense system, serum IgG, small intestinal structure, and intestinal barrier function in weaned piglets.

Red clover-rich grassland increases equol concentration in eggs from free-range laying hens

1. The aim of this study was to evaluate the production of equol (4',7-isoflavandiol; a bacterial polyphenol metabolite which is an isoflavandiol oestrogen metabolised from daidzein from plants) enriched eggs from free-range hens fed different pasture species. Four species were tested: red clover, white clover, ryegrass and chicory.2. The study was conducted from June to September 2017 on eight free range, outdoor areas, each containing fifteen laying hens and sown with a single pasture species3. Precursors of equol (daidzein, formononetin) were analysed every fortnight from the fresh pasture cover in each area, as well as equol and daidzein levels in eggs.4. Daidzein and formononetin concentrations in the fresh pasture samples differed significantly according to species (P < 0.001), whereby red clover had the highest concentrations of daidzein and formononetin (85 and 996 µg/g DM, respectively).5. Equol concentration in eggs differed according to pasture species (P < 0.001). Equol concentrations reached about 1,200 ng/g DM in eggs from hens with access to red clover. These eggs can represent a valuable source of equol in the human diet.

Effects of Xylo-Oligosaccharides on Growth and Gut Microbiota as Potential Replacements for Antibiotic in Weaning Piglets

Xylo-oligosaccharides (XOS) is a well-known kind of oligosaccharide and extensively applied as a prebiotic. The objective of this study was to investigate the effect of XOS supplementation substituting chlortetracycline (CTC) on growth, gut morphology, gut microbiota, and hindgut short chain fatty acid (SCFA) contents of weaning piglets. A total of 180 weaned piglets were randomly allocated to three treatments for 28 days, as follows: control group (basal diet, CON), basal diet with 500 mg/kg (XOS500) XOS, and positive control (basal diet with 100 mg/kg CTC). Compared with the CON group, the piglets in the XOS500 group improved body weight (BW) on days 28, average daily gain (ADG) and reduced feed: gain ratio during days 1–28 (P < 0.05). The XOS500 supplementation increased Villus height and Villus height: Crypt depth ratio in the ileum (P < 0.05). Villus Height: Crypt Depth of the ileum was also increased in the CTC treatment group (P < 0.05). Meanwhile, the XOS500 supplementation increased significantly the numbers of goblet cells in the crypt of the cecum. High-throughput 16S rRNA gene sequencing revealed distinct differences in microbial compositions between the ileum and cecum. XOS500 supplementation significantly increased the bacterial diversity. However, CTC treatment markedly reduced the microbial diversity (P < 0.05). Meanwhile, XOS500 supplementation in the diet significantly increased the abundance of Lactobacillus genus compared to the CON and CTC group in the ileum and cecum (P < 0.01), whereas the level of Clostridium_sensu_stricto_1, Escherichia-Shigella, and Terrisporobacter genus in the XOS500 group were markedly lower than the CON and CTC group (P < 0.05). In addition, dietary supplementation with XOS500 significantly increased the total short-chain fatty acids, propionate and butyrate concentrations and decreased the acetate concentration compared to the CON group in the cecum (P < 0.05). In summary, dietary supplemented with XOS500 could enhance specific beneficial microbiota abundance and decrease harmful microbiota abundance to maintain the structure of the intestinal morphology and improve growth performance of weaned piglets. Thus, XOS may potentially function as an alternative to in-feed antibiotics in weaned piglets in modern husbandry.

The Walloon farmers position differently their ideal dairy production system between a global-based intensive and a local-based extensive model of farm

Dairy farming systems are evolving. This study presents dairy producers’ perceptions of their ideal future farm (IFF) to ensure revenue, and attempts to determine the reasons for this choice, the environmental aspects related to this choice, the proximity between the current farm and the IFF and the requirements for reaching this IFF. Just before the end of the European milk quota, a total of 245 Walloon dairy producers answered a survey about the characteristics of their IFF and other socio-environmental-economic information. A multiple correspondence analysis (MCA) was carried out using seven characteristics of the IFF (intensive vs. extensive, specialised vs. diversified, strongly vs. weakly based on new technologies, managed by a group of managers vs. an independent farmer, employed vs. familial workforce, local vs. global market, standard vs. quality-differentiated production) to observe the relationships between them. Based on the main contributors to the second dimension of the MCA, this axis was defined as an IFF gradient between the local-based extensive (LBE) producers (26%) and the global-based intensive (GBI) producers (46%). The differences of IFF gradient between modalities of categorical variables were estimated using generalised linear models. Pearson correlations were calculated between the scores on the IFF gradient and quantitative variables. Finally, frequencies of IFF characteristics and the corresponding characteristic for the current situation were calculated to determine the percentages of “unhappy” producers. Some reasons for the choice of IFF by the producers have been highlighted in this study. Environmental initiatives were more valued by LBE than GBI producers. Low similarity was observed between the current farm situation of the respondents and their IFF choice. LBE and GBI producers differed significantly regarding domains of formation (technical and bureaucratic vs. transformation and diversification respectively) and paths of formation (non-market vs. market respectively). Two kinds of farming systems were considered by dairy producers and some socioeconomic and environmental components differed between them.

The drying temperature and the moisture content at harvest affect the apparent metabolisable energy of two maize varieties in broiler chickens

1. The grain drying process may affect the feeding value of maize but until now, no general consensus has been reached. This knowledge is essential to manage maize nutritional value in feed and ensure optimal growth performance of broiler chickens. 2. A total of 72 male Ross 308 were used in a complete randomised block design to assess the effect of initial moisture content (MC) at harvest (high or low MC after the appearance of the black layer) and drying temperature (54°C, 90°C or 125°C) on the apparent faecal digestibility and the AMEn value of two maize grain types (flint and flint-dent varieties). Moreover, the relationship between in vitro dry matter digestibility coefficient (IVDMD) and salt-soluble protein (SSP) content of dried maize grain with AMEn was assessed. 3. High drying temperature (125°C) significantly decreased the AMEn (by 0.41 MJ/kg) of the maize. Maize with high-moisture content at harvest had significantly higher AMEn than maize with low moisture content (0.38 MJ/kg) depending on the variety. Based on the combination of MC at harvest and drying temperature, an AMEn difference of about 0.65 MJ per kg of dry matter was measured during this experiment. The faecal digestibility of starch remained close to 98% with low variation between the treatments. The decrease in AMEn at high drying temperature was related to the decrease in non-starch organic matter retention (NSOM_R). IVDMD and SSP content were not correlated with AMEn of dried maize (R² < 0.1). 4. This study showed that using drying temperature below 90°C for maize grain harvested at high MC, just after the black layer development, can enhance its AMEn. The IVDMD and SSP content failed to predict the AMEn of the dried maize, but further research is required to validate the results of this study.

Effect of dietary tannins on milk yield and composition, nitrogen partitioning and nitrogen use efficiency of lactating dairy cows: A meta-analysis

Tannins are secondary plant compounds which have been extensively studied in order to improve the nitrogen use efficiency (NUE) of ruminants. A meta-analysis was performed of 58 in vivo experiments comparing milk yield, composition and nitrogen metabolism of lactating dairy cows fed diets with or without tannins. The meta-analysis shows that tannins have no impact on corrected milk yield, fat and protein content or NUE (p > .05). However, tannins reduce ruminal ammoniacal nitrogen (N) production by 16% (from 10.95 to 8.47 mg/dl on average), milk urea by 9% (from 15.82 to 14.03 mg/dl) and urinary N excretion (-11%; p < .05). This is compensated for by a lower apparent N digestibility (61.51% with dietary tannins compared to 66.17% without). The effect of tannin on N metabolism parameters increases with tannin dose (p < .05). The shift from urinary to faecal N may be beneficial for environment preservation, as urinary N induces more harmful emissions than faecal N. From a farmer's perspective, tannins seem unable to increase fat- and protein-corrected milk yield or reduce feed protein requirements and thus have no direct economic benefit. Potentially less costly than tannin extracts, forage or by-products naturally rich in tannins could still be useful to reduce the environmental impact of ruminant protein feeding.

The use of inulin and wheat bran only during the starter period or during the entire rearing life of broilers: effects on growth performance, small intestinal maturation, and cecal microbial colonization until slaughter age

Inulin and wheat bran were added to broiler diets during the starter period or during the entire rearing period to investigate whether the effects of using these ingredients remained until slaughter age. Diets containing no inulin and no wheat bran (CON), 2% inulin (IN), 10% wheat bran (WB), or 2% inulin + 10% wheat bran (IN+WB) were provided until day 11. Thereafter, each dietary treatment was further divided into a continued diet with supplementation or a control diet, resulting in 7 groups (CON, IN/IN, IN/CON, WB/WB, WB/CON, IN+WB/IN+WB, or IN+WB/CON). On day 40, 12 chickens per group were euthanized. The IN/IN group increased the cecal molar ratio of butyrate but had a lower relative abundance of Lactobacillus (P < 0.05). Additionally, the cecal molar ratio of propionate was higher in the IN/CON group compared to the IN/IN group (P = 0.034). The WB/CON group had the best results on BW and feed conversion ratio (FCR) (P < 0.05). Only the cecal molar ratio of iso-butyrate was higher in the WB/WB group (P = 0.013). Moreover, compared to the CON group, both WB/WB and WB/CON groups reduced the relative abundances of Bifidobacterium and Escherichia coli, and only the WB/WB group reduced the relative abundance of Enterobacteriaceae (P < 0.05). Both IN+WB/IN+WB and IN+WB/CON groups increased BW until day 21 and lowered the relative abundance of Bifidobacterium (P < 0.05). The IN+WB/IN+WB group increased the cecal molar ratio of butyrate but reduced the molar ratio of propionate with a higher relative abundance of Enterobacteriaceae (P < 0.05). In conclusion, the lack of positive effects induced by inulin might be explained by the dose being too high. The beneficial effects on BW, FCR, and microbiota induced by wheat bran during the starter period were lasting when supplementation was stopped, suggesting that wheat bran could be a favorable ingredient during the starter period.

Influence of adding fibrolytic enzymes on the ruminal fermentation of date palm by-products

This study was conducted in order to assess the influence of four doses (0, 0.5, 1, and 2 mg (g dry matter) - 1 of commercial fibrolytic enzymes (MAXFIBER-I ® , SHAUMANN GmbH, Wahlstedt, Germany) on in vitro fermentation of date palm (Phoenix dactylifera) by-products: date kernels, wasted dates, floral stems, and palm fronds. Rumen contents were obtained from two non-lactating Holstein cows. Enzyme supplementation to by-products was carried out 12 h prior to incubation. Compared to the control, the enzymatic supplementation quadratically increased the extent but not the gas production rate of date kernel fermentation. Indeed, the potential gas production increased notably by 14.8 % with the lowest enzymes dose following recorded gas production after 48, 72, and 96 h of incubation. The estimated organic-matter digestibility, metabolisable energy, and total volatile fatty acids in the incubation fluid tended to be increased with the lowest dose by 7.8 %, 8.4 %, and 13.9 % respectively. For the wasted dates, this feed additive tended to linearly increase the gas production rate of fermentation with the highest dose. On the other hand, this supplementation had no effect on the ruminal fermentation of the floral stems and palm fronds. The exogenous fibrolytic enzymes were more effective on fibrous but not on lignified date palm by-products.

The effect of inulin and wheat bran on intestinal health and microbiota in the early life of broiler chickens

Inulin and wheat bran were added to the starter diets of broiler chickens to investigate the potential of these ingredients to improve the host's health and growth performance, as well as the underlying mechanisms of their effects. A total of 960 1-day-old chicks were assigned to 4 treatments: control (CON), 2% inulin (IN), 10% wheat bran (WB), and 10% wheat bran +2% inulin (WB+IN). On day 11, 6 chicks per treatment were euthanized. A general linear model procedure with Tukey's multiple range test was performed to compare a series of parameters between treatments. The WB-containing treatments improved BW on day 7, day 11, day 35, and BW gain until day 11 (P < 0.05), but only the WB+IN treatment showed a lower feed conversion ratio than the CON treatment (P = 0.011). Furthermore, the WB+IN treatment showed the highest villus height in the jejunum and ileum (P < 0.05), and the highest jejunal ratio villus height/crypt depth (P = 0.035). The concentration of acetate in the ceca was higher in the CON treatment compared to the IN treatment (P = 0.040). The IN treatment increased the concentration (P = 0.003) and ratio (P = 0.004) of iso-butyrate compared to the WB+IN and the CON treatments (P < 0.05). A clustering result exhibited similar intestinal microbiota profiles in the chicks receiving the IN and the WB+IN diets (P > 0.05), but these profiles were different from those found in chicks receiving the WB and the CON diets (P < 0.05). In conclusion, wheat bran and the combination of wheat bran and inulin ameliorated the growth performance and gut morphology of the starter chicks, which resulted in a higher BW until day 35. Inulin, on the other hand, had a greater ability to influence the microbiota profile. The beneficial results found in relation to BW and gut morphology during the starter period suggested a synergistic effect of inulin and wheat bran.

Urea Metabolism and Regulation by Rumen Bacterial Urease in Ruminants – A Review

Urea is used as non-protein nitrogen in the rations of ruminants as an economical replacement for feed proteins. Urea transferred from the blood to the rumen is also an important source of nitrogen for rumen microbial growth. It is rapidly hydrolyzed by rumen bacterial urease to ammonia (NH3) and the NH3 is utilized for the synthesis of microbial proteins required to satisfy the protein requirements of ruminants. Urea has commonly become an accepted ingredient in the diets of ruminants. In recent decades, urea utilization in ruminants has been investigated by using traditional research methods. Recently, molecular biotechnologies have also been applied to analyze urea-degrading bacteria or urea nitrogen metabolism in ruminants. Combining traditional and molecular approaches, we can retrieve better information and understanding related to the mechanisms of urea metabolism in ruminants. This review focuses on urea utilization in ruminants and its regulation by rumen bacterial urease in the host. The accumulated research provides foundations for proposing further new strategies to improve the efficiency of urea utilization in ruminants.

Agroforestry for ruminants: a review of trees and shrubs as fodder in silvopastoral temperate and tropical production systems

Among the oldest agroforestry systems, silvopastoralism uses shrubs and trees to feed ruminants. The practice is common in extensive livestock production systems, whereas the intensification of grass-based systems in the past century has led to the removal of woody species from agricultural temperate landscapes. In Europe however, woody species are promoted again on grasslands through environment-friendly policies due to the ecosystem services they provide such as carbon sequestration, control of soil erosion, limitation of airborne pollutants and biodiversity conservation. Positive effects of browse on rumen digestion and parasite control have also been documented across different plant species and regions. Under optimal conditions, feeding ruminants from woody fodder sustains animal production. Nonetheless, limitations can restrict the use of woody forage into animal diets, such as the presence of anti-nutritive and toxic compounds. The incorporation of this resource in ruminant feeding systems raises the question of the management of the interface between the plant and the animal. Various management systems are practiced. Temperate species such as Salix spp. and Populus spp. are fed to sheep and cattle in fodder blocks or by pruning trees in New Zealand, and Fraxinus spp. or Corylus avellana in hedgerows supply forage to livestock in Belgium, whereas Leucaena leucocepahala and Desmanthus spp. browsing is common in Australia. Nowadays, ensiling and pelleting techniques are being developed as a way to store browse forage. As the renewed interest in using shrubs and trees to feed ruminants is recent, especially in temperate regions, additional research about the optimal introduction of this resource within systems is needed.

Characterization of fructans and dietary fibre profiles in raw and steamed vegetables

Dietary fibre (DF) has many positive effects on human health associated with its functionality in the gastrointestinal tract. These benefits vary according to the type of DF. Vegetables can be a natural source of DF in the diet. However, to provide adequate nutritional advice, the content and profile of their various DF types must be characterised. This study aimed to determine the DF profile of 29 vegetables cultivated in Wallonia (Belgium) and the impact of steaming on these profiles. Using a combination of enzymatic, gravimetric and chromatographic methods, fructans, total dietary fibre (TDF), low- and high-molecular-weight soluble dietary fibre (SDF), and insoluble dietary fibre (IDF) were analysed. Results show that the DF content varies considerably among the 29 investigated vegetable varieties and species, but the influence of steaming is limited to a shift from IDF to high-molecular-weight SDF for 18 of the 29 tested vegetables, while fructans are preserved with not actual reduction in the DP.

Illumina Sequencing Approach to Characterize Thiamine Metabolism Related Bacteria and the Impacts of Thiamine Supplementation on Ruminal Microbiota in Dairy Cows Fed High-Grain Diets

The requirements of thiamine in adult ruminants are mainly met by ruminal bacterial synthesis, and thiamine deficiencies will occur when dairy cows overfed with high grain diet. However, there is limited knowledge with regard to the ruminal thiamine synthesis bacteria, and whether thiamine deficiency is related to the altered bacterial community by high grain diet is still unclear. To explore thiamine synthesis bacteria and the response of ruminal microbiota to high grain feeding and thiamine supplementation, six rumen-cannulated Holstein cows were randomly assigned into a replicated 3 × 3 Latin square design trial. Three treatments were control diet (CON, 20% dietary starch, DM basis), high grain diet (HG, 33.2% dietary starch, DM basis) and high grain diet supplemented with 180 mg thiamine/kg DMI (HG+T). On day 21 of each period, rumen content samples were collected at 3 h postfeeding. Ruminal thiamine concentration was detected by high performance liquid chromatography. The microbiota composition was determined using Illumina MiSeq sequencing of 16S rRNA gene. Cows receiving thiamine supplementation had greater ruminal pH value, acetate and thiamine content in the rumen. Principal coordinate analysis and similarity analysis indicated that HG feeding and thiamine supplementation caused a strong shift in bacterial composition and structure in the rumen. At the genus level, compared with CON group, the relative abundances of 19 genera were significantly changed by HG feeding. Thiamine supplementation increased the abundance of cellulolytic bacteria including Bacteroides, Ruminococcus 1, Pyramidobacter, Succinivibrio, and Ruminobacter, and their increases enhanced the fiber degradation and ruminal acetate production in HG+T group. Christensenellaceae R7, Lachnospira, Succiniclasticum, and Ruminococcaceae NK4A214 exhibited a negative response to thiamine supplementation. Moreover, correlation analysis revealed that ruminal thiamine concentration was positively correlated with Bacteroides, Ruminococcus 1, Ruminobacter, Pyramidobacter, and Fibrobacter. Taken together, we concluded that Bacteroides, Ruminococcus 1, Ruminobacter, Pyramidobacter, and Fibrobacter in rumen content may be associated with thiamine synthesis or thiamine is required for their growth and metabolism. In addition, thiamine supplementation can potentially improve rumen function, as indicated by greater numbers of cellulolytic bacteria within the rumen. These findings facilitate understanding of bacterial thiamine synthesis within rumen and thiamine's function in dairy cows.

Thiamine supplementation facilitates thiamine transporter expression in the rumen epithelium and attenuates high-grain-induced inflammation in low-yielding dairy cows

An experiment was conducted to uncover the effects of increasing dietary grain levels on expression of thiamine transporters in ruminal epithelium, and to assess the protective effects of thiamine against high-grain-induced inflammation in dairy cows. Six rumen-fistulated, lactating Holstein dairy cows (627 ± 16.9 kg of body weight, 180 ± 6 d in milk; mean ± standard deviation) were randomly assigned to a replicated 3 × 3 Latin square design trial. Three treatments were control (20% dietary starch, dry matter basis), high-grain diet (HG, 33.2% dietary starch, DM basis), and HG diet supplemented with 180 mg of thiamine/kg of dry matter intake. On d 19 and 20 of each period, milk performance was measured. On d 21, ruminal pH, endotoxic lipopolysaccharide (LPS), and thiamine contents in rumen and blood, and plasma inflammatory cytokines were detected; a rumen papillae biopsy was taken on d 21 to determine the gene and protein expression of toll-like receptor 4 (TLR4) signaling pathways. The HG diet decreased ruminal pH (5.93 vs. 6.49), increased milk yield from 17.9 to 20.2 kg/d, and lowered milk fat and protein from 4.28 to 3.83%, and from 3.38 to 3.11%, respectively. The HG feeding reduced thiamine content in rumen (2.89 vs. 8.97 μg/L) and blood (11.66 vs. 17.63 μg/L), and the relative expression value of thiamine transporter-2 (0.37-fold) and mitochondrial thiamine pyrophosphate transporter (0.33-fold) was downregulated by HG feeding. The HG-fed cows exhibited higher endotoxin LPS in rumen fluid (134,380 vs. 11,815 endotoxin units/mL), and higher plasma concentrations of lipopolysaccharide binding protein and pro-inflammatory cytokines when compared with the control group. The gene and protein expression of tumor necrosis factor α (TNFα), IL1B, and IL6 in rumen epithelium increased when cows were fed the HG diet, indicating that local inflammation occurred. The depressions in ruminal pH, milk fat, and protein of HG-fed cows were reversed by thiamine supplementation. Thiamine supplementation increased thiamine contents in rumen and blood, and also upregulated the relative expression of thiamine transporters compared with the HG group. Thiamine supplementation decreased ruminal LPS (49,361 vs. 134,380 endotoxin units/mL) and attenuated the HG-induced inflammation response as indicated by a reduction in plasma IL6, and decreasing gene and protein expression of pro-inflammatory cytokines in rumen epithelium. Western bottling analysis showed that thiamine suppressed the protein expression of TLR4 and the phosphorylation of nuclear factor kappa B (NFκB) unit p65. In conclusion, HG feeding inhibits thiamine transporter expression in ruminal epithelium. Thiamine could attenuate the epithelial inflammation during high-grain feeding, and the protective effects may be due to its ability to suppress TLR4-mediated NFκB signaling pathways.

Differences in Ureolytic Bacterial Composition between the Rumen Digesta and Rumen Wall Based on ureC Gene Classification

Ureolytic bacteria are key organisms in the rumen producing urease enzymes to catalyze the breakdown of urea to ammonia for the synthesis of microbial protein. However, little is known about the diversity and distribution of rumen ureolytic microorganisms. The urease gene (ureC) has been the target gene of choice for analysis of the urea-degrading microorganisms in various environments. In this study, we investigated the predominant ureC genes of the ureolytic bacteria in the rumen of dairy cows using high-throughput sequencing. Six dairy cows with rumen fistulas were assigned to a two-period cross-over trial. A control group (n = 3) were fed a total mixed ration without urea and the treatment group (n = 3) were fed rations plus 180 g urea per cow per day at three separate times. Rumen bacterial samples from liquid and solid digesta and rumen wall fractions were collected for ureC gene amplification and sequencing using Miseq. The wall-adherent bacteria (WAB) had a distinct ureolytic bacterial profile compared to the solid-adherent bacteria (SAB) and liquid-associated bacteria (LAB) but more than 55% of the ureC sequences did not affiliate with any known taxonomically assigned urease genes. Diversity analysis of the ureC genes showed that the Shannon and Chao1 indices for the rumen WAB was lower than those observed for the SAB and LAB (P < 0.01). The most abundant ureC genes were affiliated with Methylococcaceae, Clostridiaceae, Paenibacillaceae, Helicobacteraceae, and Methylophilaceae families. Compared with the rumen LAB and SAB, relative abundance of the OTUs affiliated with Methylophilus and Marinobacter genera were significantly higher (P < 0.05) in the WAB. Supplementation with urea did not alter the composition of the detected ureolytic bacteria. This study has identified significant populations of ureolytic WAB representing genera that have not been recognized or studied previously in the rumen. The taxonomic classification of rumen ureC genes in the dairy cow indicates that the majority of ureolytic bacteria are yet to be identified. This survey has expanded our knowledge of ureC gene information relating to the rumen ureolytic microbial community, and provides a basis for obtaining regulatory targets of ureolytic bacteria to moderate urea hydrolysis in the rumen.

Cooking Has Variable Effects on the Fermentability in the Large Intestine of the Fraction of Meats, Grain Legumes, and Insects That Is Resistant to Digestion in the Small Intestine in an in Vitro Model of the Pig's Gastrointestinal Tract

This study aimed to evaluate the fermentation in the large intestine of indigestible dietary protein sources from animal, insect, and plant origin using an in vitro model of the pig's gastrointestinal tract. Protein sources were used raw and after a cooking treatment. Results showed that the category of the ingredient (meats, insects, or grain legumes) exerts a stronger impact on enzymatic digestibility, fermentation patterns, and bacterial metabolites such as short-chain fatty acids (SCFA) and hydrogen sulfide (H₂S) than the cooking treatment. The digestibility and the fermentation characteristics of insects were more affected by the cooking procedure than the other categories. Per gram of consumed food, ingredients from animal origin, namely, meats and insects, were associated with fewer fermentation end-products (gas, H₂S, SCFA) than ingredients from plant origin, which is related to their higher small intestinal digestibility.

Relationship between thiamine and subacute ruminal acidosis induced by a high-grain diet in dairy cows

Two experiments were conducted to reveal the effects of grain-induced subacute rumen acidosis (SARA) on thiamine status in blood and rumen fluid in dairy cows. In both experiments, 6 multiparous, rumen-fistulated Holstein dairy cows were used in a 2-treatment, 2-period crossover design. Each experimental period consisted of 21d (total of 42d). Experiment 1 was to investigate the effects of SARA on thiamine status in blood and rumen fluid. Treatments were either control (20% starch, dry matter basis) or SARA-inducing diet (SAID, 33.2% starch, dry matter basis). In experiment 2, the effects of dietary thiamine supplementation on attenuating SARA and ruminal fermentation characteristics in dairy cows were studied. All cows received the same SAID diet during the whole experimental period; treatments were with or without thiamine (180mg of thiamine/kg of dry matter intake). In both experiments, rumen fluid samples were collected at 0, 3, 6, 9, and 12h after morning feeding on d 21 and 42 of the experiments for measurement of pH, thiamine, volatile fatty acid, and lactate contents. Peripheral blood was also collected at 3h after morning feeding on d 21 and 42 to measure thiamine, carbohydrate metabolites, and enzyme activities. In experiment 1, cows fed the SAID diet had lower ruminal and plasma thiamine concentrations and higher lactate than cows fed the control diet. The ruminal thiamine contents were positively related to pH and the concentrations of acetate in the rumen, and negatively correlated with the lactate contents. Experiment 2 demonstrated that ruminal pH and the concentrations of thiamine, acetate, and total volatile fatty acids in the rumen were increased, whereas ruminal lactate contents were reduced by thiamine supplementation. The concentrations of lactate and the activity of lactate dehydrogenase in blood were reduced in the thiamine supplemented group, and the opposite was true for the nonesterified fatty acids and α-ketoneglutarate dehydrogenase contents. In conclusion, the thiamine status was affected by SARA in dairy cows and ruminal infusion of thiamine could help attenuate SARA by improving theproportions of ruminal volatile fatty acids and reducing lactate contents in rumen fluid and blood.

Insights into Abundant Rumen Ureolytic Bacterial Community Using Rumen Simulation System

Urea, a non-protein nitrogen for dairy cows, is rapidly hydrolyzed to ammonia by urease produced by ureolytic bacteria in the rumen, and the ammonia is used as nitrogen for rumen bacterial growth. However, there is limited knowledge with regard to the ureolytic bacteria community in the rumen. To explore the ruminal ureolytic bacterial community, urea, or acetohydroxamic acid (AHA, an inhibitor of urea hydrolysis) were supplemented into the rumen simulation systems. The bacterial 16S rRNA genes were sequenced by Miseq high-throughput sequencing and used to reveal the ureoltyic bacteria by comparing different treatments. The results revealed that urea supplementation significantly increased the ammonia concentration, and AHA addition inhibited urea hydrolysis. Urea supplementation significantly increased the richness of bacterial community and the proportion of ureC genes. The composition of bacterial community following urea or AHA supplementation showed no significant difference compared to the groups without supplementation. The abundance of Bacillus and unclassified Succinivibrionaceae increased significantly following urea supplementation. Pseudomonas, Haemophilus, Neisseria, Streptococcus, and Actinomyces exhibited a positive response to urea supplementation and a negative response to AHA addition. Results retrieved from the NCBI protein database and publications confirmed that the representative bacteria in these genera mentioned above had urease genes or urease activities. Therefore, the rumen ureolytic bacteria were abundant in the genera of Pseudomonas, Haemophilus, Neisseria, Streptococcus, Actinomyces, Bacillus, and unclassified Succinivibrionaceae. Insights into abundant rumen ureolytic bacteria provide the regulation targets to mitigate urea hydrolysis and increase efficiency of urea nitrogen utilization in ruminants.

Improving adjuvant systems for polyclonal egg yolk antibody (IgY) production in laying hens in terms of productivity and animal welfare

The antibody production in the egg yolks of immunized laying hens is seen as a way of improving animal welfare compared with conventional production by mammals. Immunoglobulin Y (IgY) technology, however, has still to address welfare issues linked to the widespread use of an adjuvant in vaccines. Currently, Freund's adjuvants, complete (FCA) or incomplete (FIA), remain the standard. This study sought to evaluate various approaches used to enhance egg yolk antibody production in terms of both productivity and avian welfare. The outer membrane protein (OMP) of Salmonella Typhimurium was used as the prototype antigen. At 20 weeks of age, 56 ISA Brown hens, with specific-Salmonella-free status, were divided into seven groups (n=8) and received an initial intramuscular immunization. Hens in the two negative control groups received phosphate buffered saline (PBS) or FIA alone. Hens in the other groups received 80μg of Salmonella OMP emulsified with one of the following adjuvants: 200μl of FIA alone (T1); 200μl of FIA supplemented with 8μg of C-phosphate-guanosine oligodeoxynucleotides (CpG-ODN) (T2); and 280μl of Montanide ISA 70 VG (T4). Birds in the T3 group received the antigen in emulsion with FIA and were given the tested immunostimulatory component (l-carnitine) via their feed (100mg/kg). A positive control group (PC) received FCA for the first and final immunizations and FIA for the other boosters. Immunization was repeated after 20, 46, 82 and 221 days. Eggs were collected regularly until 242 days after the first immunization and the anti-Salmonella Typhimurium activities in the yolk were determined by ELISA. After 242 days, the birds were euthanized and the injection sites were evaluated for gross and microscopic lesions. Among the tested immunostimulatory approaches, supplementation of FIA with CpG-ODN led to a significant and long-lasting enhancement of the specific antibody response. This treatment was even higher than the positive benchmark using FCA in the first immunization. The study results showed that a clinical examination of injection sites is insufficient for drawing conclusions about the local tolerance of vaccines. Tissue damage was noticeable in all treatment groups. The birds receiving the Montanide adjuvant, however, had fewer and less severe lesions. Given these limited side-effects, Montanide ISA 70 VG could provide the depot effect needed to ensure the immunomodulatory efficiency of CpG-ODN. The association of these two adjuvants could prove a promising alternative to Freund's adjuvants (FA).

Chemical composition of silage residues sustaining the larval development of the Culicoides obsoletus/Culicoides scoticus species (Diptera: Ceratopogonidae)

Culicoides (Diptera: Ceratopogonidae) are biological vectors of bluetongue virus (BTV). Bluetongue is a viral disease that affects domestic and wild ruminants. Since its recent emergence in northern Europe, this disease has caused considerable economic losses to the sheep and cattle industry. The biotopes, and more particularly the chemical characteristics which are suitable for larval development of the main vector species, are still relatively unknown. This study shows that the larvae of biting midges belonging to the species Culicoides obsoletus and Culicoides scoticus are able to breed in different types of silage residue (maize, grass, sugar beet pulp and their combinations). The chemical composition of substrates strongly influences the presence of the immature stages of these biting midges. Higher lignin and insoluble fibre contents seem to favour their presence and could play the role of a physical support for semi-aquatic larvae. In contrast, higher concentrations of magnesium and calcium are negatively correlated with the presence of these two species. These data will help to locate and monitor the breeding sites of these species and could contribute to the control of these insects on farms.

Effect of bovine colostrum on the serum insulin-like growth factor-I (IGF-I), the IGF binding proteins-2 and -3 and the thyroid hormones in weaning piglets

Abstract. This study examined the effect of a bovine colostrum supplementation on growth performance, feed intake and the hormonal response of piglets at weaning. Ninety-six newly-weaned piglets were assigned for four weeks to one of the two treatments: Control (diet with bovine milk whey) and Colostrum (diet with bovine colostrum whey) treatments. The supplements were incorporated in a commercial diet at 20 g/kg during the first 2 weeks after weaning and lowered to 10 g/kg for the next 2 weeks. Body weight and feed intake were measured weekly. Blood samples were taken weekly for determination of circulating IGF-I, its binding proteins and the thyroid hormones (T3 and T4). During the first week of the trial, the Colostrum-fed piglets presented improved growth performance, feed intake and feed efficiency and a higher concentration in circulating IGF-I (+15 %) compared to the Control piglets. In both treatments, the circulating thyroid hormones were reduced by weaning and the levels measured at weaning were recovered earlier by the Colostrum-fed piglets compared to the Control group (P<0.05). It is concluded that hormonal response observed after the bovine colostrum supplementation is, at least in part, consequent of the positive action of bovine colostrum on the feed intake.

Effect of the bacterial or fungal origin of exogenous xylanases supplemented to a wheat-based diet on performance of broiler chickens and nutrient digestibility of the diet

Two identical experiments were carried out to study the effects of four xylanases from bacterial or fungal origin supplemented to a wheat-based diet, on growth performance of broiler chickens and nutrient digestibilities. Experimental treatments consisted of a control basal diet containing 600 g kg-1 wheat (C), and the basal diet supplemented with 0.1 g kg-1 Grindazyme G from Aspergillus niger (G), 0.1 g kg-1 Belfeed B1100MP from Bacillus subtilis (B), 0.1 g kg-1 Roxazyme G from Trichoderma viride (R), or 0.0125 g kg-1 of a xylanase from Aspergillus aculeatus (A). Each experimental diet was given to four groups of six chickens each. Growth performance and feed conversion ratio (FCR) were recorded weekly, from 7 to 21 d of age. In the second experiment, a digestion balance trial was performed from 27 to 31 d of age to evaluate the nitrogen-corrected apparent metabolizable energy (AMEn) and the digestibilities of nitrogen, crude fat, starch and crude fibre. From 7 to 21 d of age, xylanase supplementation led to increased final body weight and daily weight gain, by 3.7 and 4.5 % (P < 0.05), respectively, without significant difference according to the xylanase origin. Xylanase supplementation significantly increased the AMEn (+2.6 %), and the digestibilities of crude fibre (+58.9 %) and nitrogen (+1.6 %). Increase in AMEn as well as in crude fat and starch digestibilities were significantly different according to the xylanase, but were not dependent on fungal or bacterial origin. In conclusion, the microbial origin of xylanases supplemented to wheat-based diets influenced neither the performance of broiler chickens nor the improvement in nutrient digestibilities.Key words: Broiler, growth performance, nutrient digestibility, wheat, xylanase

Salmonella in chicken: current and developing strategies to reduce contamination at farm level

Salmonella is a human pathogen that frequently infects poultry flocks. Consumption of raw or undercooked contaminated poultry products can induce acute gastroenteritis in humans. Faced with the public health concerns associated with salmonellosis, the European Union has established a European regulation forcing member states to implement control programs aimed at reducing Salmonella prevalence in poultry production, especially at the primary production level. The purpose of the present review article is to summarize the current research and to suggest future developments in the area of Salmonella control in poultry, which may be of value to the industry in the coming years. The review will focus especially on preventive strategies that have been developed and that aim at reducing the incidence of Salmonella colonization in broiler chickens at the farm level. In addition to the usual preventive hygienic measures, other strategies have been investigated, such as feed and drinking water acidification with organic acids and immune strategies based on passive and active immunity. Modification of the diet by changing ingredients and nutrient composition with the intent of reducing a bird's susceptibility to Salmonella infection also has been examined. Because in ovo feeding accelerates small intestine development and enhances epithelial cell function, this approach could be an efficient tool for controlling enteric pathogens. Feed additives such as antibiotics, prebiotics, probiotics, and synbiotics that modify the intestinal microflora are part of another field of investigation, and their success depends on the additive used. Other control methods such as the use of chlorate products and bacteriophages also are under study.

Production of hen egg yolk immunoglobulins simultaneously directed against Salmonella enteritidis and Salmonella typhimurium in the same egg yolk

The present study was an attempt to raise hen egg yolk Ig (IgY) simultaneously directed against Salmonella Enteritidis (SE) and Salmonella Typhimurium (ST) in the same egg yolk. The immunopotentiating effect of 2 different adjuvants—Freund’s adjuvants (FA) and immunostimulating complexes matrix (IM)—on antibody response was also evaluated. Bacterial outer membrane proteins (OMP) were selected as target antigens. The ISA Brown hens, specific-Salmonella spp.-free status, divided into 6 groups were intramuscularly injected with a mono-compound antigen preparation: SE-OMP (treatment SE-FA or SE-IM) or ST-OMP (treatment ST-FA or ST-IM), or a combined antigen preparation: ½ SE-OMP and ½ STOMP (treatment SEST-FA or SEST-IM). Titers of antibodies in yolk were evaluated biweekly with ELISA. There was no antigen × adjuvant interaction on antibody titers. Anti-SE IgY titers in hens that received treatment SEST-FA or SEST-IM were statistically similar (P > 0.05) as compared with those obtained from hens immunized with treatment SE-FA or SE-IM. Anti-ST IgY titers in hens immunized with treatment SEST-FA or SEST-IM were slightly lower than those of hens that received treatment ST-FA or ST-IM. The cross-reactivity of anti-SE IgY, induced by treatment SE-FA or SE-IM, with ST-OMP antigen and that of anti-ST IgY, induced by ST-FA or ST-IM, with SE-OMP antigen were arbitrarily assessed on d 43 and 155 by ELISA. The average cross-reactivity of anti-SE IgY with ST-OMP antigen was 71.7%. The average cross-reactivity of anti-ST IgY with SE-OMP antigen was 78.8%. In FA groups, antibody titers were found higher (P < 0.05) than those in IM groups. Furthermore, no extensive lesions or clinical abnormalities were detected in hens injected with FA. These findings showed the opportunity to raise IgY antibody against 2 Salmonella serovars in the same yolk and that FA was more efficient than IM in mediating antibody response.

Effect of various levels of imbalance between energy and nitrogen release in the rumen on microbial protein synthesis and nitrogen metabolism in growing double-muscled Belgian Blue bulls fed a corn silage-based diet1

Seven double-muscled Belgian Blue bulls (initial BW: 341 +/- 21 kg) with cannulas in the rumen and proximal duodenum were used in an incomplete replicated Latin square. The study examined the effect of imbalance between energy and N in the rumen on microbial protein synthesis and N metabolism by giving the same diet according to 3 different feeding patterns. The feed ingredients of the diet were separated into 2 groups supplying the same amount of fermentable OM (FOM) but characterized by different levels of ruminally degradable N (RDN). The first group primarily provided energy for the ruminal microbes (12.5 g of RDN/kg of FOM), whereas the second provided greater N (33.3 g of RDN/kg of FOM). These 2 groups were fed to the bulls in different combinations with the aim of creating 3 levels of imbalance (0, 20, and 40 g/ kg of DM) between energy and N supplies in the rumen. Imbalance was measured by the variation of the degradable protein balance (OEB value in the Dutch system) of the diet between the 2 meals each a day. Diurnal variations in ruminal NH3-N concentrations and plasma urea concentrations were greatly influenced by the feeding patterns of the diet. Introduction of imbalance affected neither microbial N flow at the duodenum (P = 0.97) nor efficiency of growth (P = 0.54). The feeding patterns of the diet had no negative impact on NDF degradation in the rumen (P = 0.33). Nitrogen retention was not affected by imbalance (P = 0.74) and reached 49.7, 52.0, and 51.3 g/d, respectively for 0, 20, and 40 g of OEB/kg of DM imbalance. It seems that introduction of an imbalance between energy and N supplies for the ruminal microbes by altering the feeding pattern of the same diet does not negatively influence the microbial activity in the rumen nor N retention of the animal. Nitrogen recycling in the rumen plays a major role in regulating the amount of ruminally available N and allows a continuous synchronization of N and energy-yielding substrates for the microorganisms in the rumen. Therefore, imbalance between dietary energy and N created over a 24-h interval was not detrimental to rumen microbial growth for the animal as long as the level of imbalance did not exceed 40 g of OEB/kg of DM. Thus, these feeding patterns of the diet can be used under practical feeding conditions with minimal impact on the performance of ruminant animals for meat production.

Effect of imbalance between energy and nitrogen supplies on microbial protein synthesis and nitrogen metabolism in growing double-muscled Belgian Blue bulls1

Six double-muscled Belgian Blue bulls (initial weight: 345 +/- 16 kg) with cannulas in the rumen and proximal duodenum were used in two juxtaposed 3 x 3 Latin squares to study the effect of a lack of synchronization between energy and N in the rumen on microbial protein synthesis and N metabolism by giving the same diet according to three different feeding patterns. The feed ingredients of the diet were separated into two groups supplying the same amount of fermentable OM (FOM), but characterized by different levels of ruminally degradable N (RDN). The first group primarily provided energy for the ruminal microbes (14.6 g of RDN/kg of FOM), and the second provided N (33.3 g of RDN/kg of FOM). These two groups were fed to the bulls simultaneously or alternately with the aim of creating three different time periods of imbalance (0, 12, or 24 h) between energy and N supplies in the rumen. The introduction of imbalance affected neither microbial-N flow at the duodenum (P = 0.65) nor efficiency of growth (P = 0.69), but decreased (P = 0.016) the NDF degradation in the rumen 12.2% for a 12-h period of imbalance. N retention was not affected by imbalance (P = 0.53) and reached 57.8, 58.5, and 54.7 g/d, respectively, for 0-, 12- and 24-h imbalance. It seems that the introduction of an imbalance of 12 or 24 h between energy and N supplies for the ruminal microbes by altering the feeding pattern of the same diet does not negatively influence microbial protein synthesis or N retention by the animal. Nitrogen recycling in the rumen plays a major role in regulating the amount ofruminally available N and allows for continuous synchronization of N- and energy-yielding substrates for the microorganisms in the rumen. Therefore, a lack of synchronization in the diet between the energy and N supplies for the ruminal microbes is not detrimental to their growth or for the animal as long as the nutrient supply is balanced on a 48-h basis. Thus, these dietary feeding patterns may be used under practical feeding conditions with minimal effect on the performance of ruminant animals.

Rumen escape of methionine and lysine administered intraruminally to growing double-muscled Belgian Blue bulls

In many dietary conditions, methionine (Met) and lysine (Lys) are the most limiting amino acids (AA) for ruminants. The AA protected from ruminal fermentation are not commercially available, with the exception of Met which is not always economical, especially for meat production. This study measured ruminal escape of free Met and Lys supplemented intraruminally to fast growing bulls. Six double-muscled Belgian Blue bulls, fed a high concentrate diet and fitted with a rumen cannula, received free Met (40 g x d(-1)) and free Lys (60 g x d(-1)), individually or simultaneously, in a duplicated Latin square design. The mean ruminal escape of Met and Lys reached 37 and 45% respectively, and did not differ if administered separately or together. Plasma Lys and Met concentrations were increased by 504 and 126%, respectively. Substantial proportions of free AA escaped ruminal fermentation and were available for absorption from the small intestine when they were administered at physiologically high levels.

Determination of the methionine requirement of finishing double-muscled Belgian blue bulls with a three-step method

A three-step technique was used to determine total amino acids (AA) and the first limiting AA requirements in finishing double-muscled Belgian Blue (dmBB) bulls. In a first experiment, three dmBB bulls (505 ± 21 kg) received a low metabolizable protein diet containing 25% meadow hay and 75% concentrate. Net energy supply was adequate for maximizing daily gains because of continuous infusion of dextrose into the duodenum. The intestinal apparent disappearance of essential AA (EAA) averaged 70.8% and was the lowest for histidine (61.3%) and the highest for arginine (79.9%). In a second experiment, four dmBB bulls (517 ± 16 kg) received the same diet supplemented with duodenal infusion of dextrose and four doses of Na-caseinate (17, 33, 50 and 66% of metabolizable dietary AA) in a 4 × 4 Latin square design. Nitrogen retention for the basal diet alone and the four increasing supplements of Na-caseinate averaged 61, 64, 74, 75 and 78 g d–1, respectively. A supply of 720 g d–1 of metabolizable AA was defined as optimising the N utilization for animal growth. Based on patterns of plasma concentrations, methionine and phenylalanine were probably the limiting AA. In a third experiment, five dmBB bulls (513 ± 60 kg) fed the basal diet received duodenal infusion of dextrose and AA, equivalent to the second dose in exp. 2 except for the supply of metabolizable methionine (12.8, 15.1, 17.6, 20.1, 22.6 and 25.1 g d–1) that varied in a 6 × 6 Latin square design with one missing animal. On the basis of N retention, the metabolizable methionine requirement was estimated to 22.8 g d–1 and corresponded to 360 mg of metabolizable methionine per gram of N retained. Key words: Ruminant, amino acid, duodenal infusion, requirement, plasma, nitrogen pollution

Determination of the methionine requirement of growing double-muscled Belgian blue bulls with a three-step method

The three-step technique was used to determine the requirements of total amino acids (TAA) and the first-limiting amino acid (AA) in growing double-muscled Belgian Blue bulls (BBb). In Exp. 1, three double-muscled BBb weighing initially 306 +/- 28 kg received a basal diet consisting of 30% meadow hay and 70% concentrate that was poor in digestible protein but had adequate NE because of continuous infusion of dextrose into the duodenum. The intestinal apparent digestibility of essential AA (EAA) was defined according to their duodenal and ileal flows. It averaged 72% but varied between 60% for Met and 79% for Arg. In Exp. 2, five double-muscled BBb (334 +/- 22 kg) received the same diet supplemented with duodenal infusions of dextrose and four doses of Na-caseinate (28, 56, 84, and 112% of intestinal digestible dietary AA) in a 4 x 4 Latin square design with one additional animal. Nitrogen retention for the basal diet alone and the four increasing supplements of Na-caseinate reached 49, 61, 70, 80, and 86 g/d, respectively. Nitrogen utilization improved from 34.3% without Na-caseinate supplementation to a maximum of 40.6%, with the third dose supplying 788 g/d of apparently digestible AA. Based on patterns of plasma concentrations, Met, Phe, and Arg were probably the limiting AA when animals optimized N utilization. In Exp. 3, six double-muscled BBb (315 +/- 25 kg) fed the basal diet received duodenal infusions of dextrose and AA, equivalent to the third dose in Exp. 2, except for digestible Met (9.3, 14.4, 18.4, 22.4, 26.4, and 30.4 g/d) in a 6 x 6 Latin square design. The Met requirement was close to 26.4 g/d on the basis of N retention.