Predicted essential fatty acid intakes for a group of dairy cows also apply at individual animal level

The ruminant requirements for essential fatty acids (EFAs), particularly linoleic acid (LA) and alpha-linolenic acid (ALA), have not been fully determined, although evidence suggests that an adequate supply of polyunsaturated fatty acids (FAs) could improve immunity and reproduction in transition cows. In previous studies, we predicted EFA intake for a group of cows based on animal characteristics and milk EFA secretions. However, to support precision livestock feeding, we need to match the nutrient requirements and intakes of each cow as closely as possible. Our group-level predictions may not be accurate enough to estimate the EFA intake of an individual cow, due to inter-individual variations in EFA digestion and metabolism related to differences in feed intake, intake patterns, and the composition and functioning of the rumen microbiota. To address this issue, here we set out to establish specific equations that predict EFA intake for an individual cow based on the difference (i.e. the residuals) between observed EFA intake and the predicted EFA intake based on our group-level equations. We studied a database of individual dairy cows (26 experiments; 503 datapoints from three research teams) and we predicted the residuals from (1) dietary and animal-related factors (i.e. full predictions) and (2) animal-related factors only (i.e. field predictions), which are considered more field-amenable. The variance of predicted LA and log ALA intake was explained to 68% by observed LA intake and 66% by observed log ALA intake, respectively. The residuals of LA intake were predicted by dietary ALA content, total FA intake, BW, milk yield and fat content in full predictions, and by BW, feeding level, milk yield and fat content, and sum of milk C4:0 to C14:0 FA in field predictions. The log residuals of ALA intake were predicted by dietary NDF and total FA contents, NDF intake, BW, milk protein, LA and ALA contents, and fat yield in full predictions, and by BW, DM intake, milk LA and ALA contents, and fat yield in field predictions. The field predictions showed a moderate loss of accuracy compared to full predictions based on RMSE of prediction (from 38 to 54 g/d for LA and from 0.090 to 0.12 log (g/d) for ALA). This work is the first to predict the EFA intake of an individual cow based on previously established group-level predictions of EFA intake adjusted for dietary and animal-related factors.

Milk metabolites can characterise individual differences in animal resilience to a nutritional challenge in lactating dairy goats

The aim of this study is built in two phases: to quantify the ability of novel milk metabolites to measure between-animal variability in response and recovery profiles to a short-term nutritional challenge, then to derive a resilience index from the relationship between these individual variations. At two different stages of lactation, sixteen lactating dairy goats were exposed to a 2-d underfeeding challenge. The first challenge was in late lactation, and the second was carried out on the same goats early in the following lactation. During the entire experiment period, samples were taken at each milking for milk metabolite measures. For each metabolite, the response profile of each goat was characterised using a piecewise model for describing the dynamic pattern of response and recovery profiles after the challenge relative to the start of the nutritional challenge. Cluster Analysis identified three types of response/recovery profiles per metabolite. Using cluster membership, multiple correspondence analyses (MCAs) were performed to further characterise response profile types across animals and metabolites. This MCA analysis identified three groups of animals. Further, discriminant path analysis was able to separate these groups of multivariate response/recovery profile type based on threshold levels of three milk metabolites: β-hydroxybutyrate, free glucose and uric acid. Further analyses were done to explore the possibility of developing an index of resilience from milk metabolite measures. Different types of performance response to short-term nutritional challenge can be distinguished using multivariate analyses of a panel of milk metabolites.

Dietary Phosphorus and Calcium Utilization in Growing Pigs: Requirements and Improvements

The sustainability of animal production relies on the judicious use of phosphorus (P). Phosphate, the mined source of agricultural phosphorus supplements, is a non-renewable resource, but phosphorus is essential for animal growth, health, and well-being. P must be provided by efficient and sustainable means that minimize the phosphorus footprint of livestock production by developing precise assessment of the bioavailability of dietary P using robust models. About 60% of the phosphorus in an animal's body occurs in bone at a fixed ratio with calcium (Ca) and the rest is found in muscle. The P and Ca requirements must be estimated together; they cannot be dissociated. While precise assessment of P and Ca requirements is important for animal well-being, it can also help to mitigate the environmental effects of pig farming. These strategies refer to multicriteria approaches of modeling, efficient use of the new generations of phytase, depletion and repletion strategies to prime the animal to be more efficient, and finally combining these strategies into a precision feeding model that provides daily tailored diets for individuals. The industry will need to use strategies such as these to ensure a sustainable plant–animal–soil system and an efficient P cycle.

66 Strategies to Improve Phosphorus Utilization in Growing Pigs: Depletion-repletion Protocols

To optimize the use of dietary P by pigs, 5 feeding strategies were studied in a 3-phase feeding trial on 240 pigs (initial bodyweight (BW) of 31 kg): 1) C-C-C providing 100% of digestible phosphorus (Pdig, 4.3 g/kg STTD) and calcium (Ca, 9.7 g/kg) requirement to maximize bone mineralization, 2) L-L-L 60% of the Pdig and Ca requirements of C-C-C, 3) Phyt-Phyt-Phyt (phosphate-free, with phytase, 750, 686, 390 FTU/kg), providing 60% of Pdig and Ca requirements in phase 1, then 100%, 4) and 5) C in phases 1 and 3, and 60% of the need for Pdig in phase 2, associated with 65% of the requirements for Ca (N) or 80% (H), namely C-N-C and C-H-C. The BW and bone mineral content (BMC) were measured at the beginning and end of each phase. The BMC gain (gBMC), average daily gain (ADG) and average daily feed intake (ADFI) were calculated by phase. In phase 1, ADG was lower in the Phyt group than the C group (1.05 vs 1.10 kg/d, P < 0.01) and the BMC of group C and gBMC were higher than those of the Phyt and B groups (P < 0.05). In phase 2, C-C and Phyt-Phyt groups had similar BMC due to higher gBMC in the Phyt-Phyt (27.1 vs 18.4 g/d, P < 0.01). At the end of phases 2 and 3, C-C-C, C-N-C and C-H-C groups had similar BMC. The Phyt and B groups showed an increased phosphorus-use efficiency during phases 1 and 2 (+20% vs C). Phosphorus retention was also higher in the C-N-C and C-H-C groups, during the depletion in phase 2 (+24% vs C, P< 0.05). These results showed the potential of a depletion-repletion strategy including free phosphate diet to reduce phosphorus intake and excretion without affecting final growth performance and bone mineralization because of increased minerals utilization efficacies.

290 Phosphorus and calcium requirements of growing pigs predicted by mechanistic modelling

Phosphorus (P) is a key element for the sustainability of pork production systems. The response of pigs to P intake is complex and optimize P utilization requires a multicriteria approach. A mechanistic mathematical model representing the P and Ca absorption and bone and soft tissues deposition was developed and used to optimize these minerals utilization. Model P and Ca requirements (g/kg) were also compared to those of INRA (Jondreville and Dourmad, 2005; apparent total tract digestible P, ATTD-P) and NRC (2012; standardized total tract digestible P, STTD-P) requirements in different bone mineralisation scenarios (100 and 85%). The proposed model showed lower ATTD-P and STTD-P requirements than INRA (6%) and NRC (7%), between 29 to about 98 kg of body weight (BW) and higher (up to 17%) at other weights. The proposed model Ca requirements increase after 95 kg BW unlike NRC and INRA Ca requirements that decrease. For 100 % of bone mineralisation, INRA show the highest Ca requirements (21%) while NRC requirements are similar between 35 to 65 kg and the model requirements are higher for other weights. For 85% objective, the model showed lower Ca requirements than NRC from 25 to 82 kg of BW (9%). The Ca:ATTD-P ratio increased curvilinearly with BW varying from 2.2 to 2.6. The differences observed with the current model and NRC and INRA are due to the structure of the model, that simulates the bone independently of the protein, the first evolving linearly with the weight while the second follows a Gompertz function. Therefore a non-fixed Ca:ATTD-P (or STTD-P) ratio could be consider to maximize bone mineralisation. By predicting bone and muscle growth independently the model offers greater allometric insight into nutrient requirements and their interactions. Studies such as this one will help to usher in a new era of sustainable and eco-friendly livestock production.

Histidine: A Systematic Review on Metabolism and Physiological Effects in Human and Different Animal Species

Histidine is an essential amino acid (EAA) in mammals, fish, and poultry. We aim to give an overview of the metabolism and physiological effects of histidine in humans and different animal species through a systematic review following the guidelines of PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). In humans, dietary histidine may be associated with factors that improve metabolic syndrome and has an effect on ion absorption. In rats, histidine supplementation increases food intake. It also provides neuroprotection at an early stage and could protect against epileptic seizures. In chickens, histidine is particularly important as a limiting factor for carnosine synthesis, which has strong anti-oxidant effects. In fish, dietary histidine may be one of the most important factors in preventing cataracts. In ruminants, histidine is a limiting factor for milk protein synthesis and could be the first limiting AA for growth. In excess, histidine supplementation can be responsible for eating and memory disorders in humans and can induce growth retardation and metabolic dysfunction in most species. To conclude, the requirements for histidine, like for other EAA, have been derived from growth and AA composition in tissues and also have specific metabolic roles depending on species and dietary levels.

Intestinal Availability and Metabolic Effects of Dietary Camelina Sphingolipids during the Metabolic Syndrome Onset in Mice

Sphingolipids appear as a promising class of components susceptible to prevent the onset of the metabolic syndrome (MetS). Gut availability and effects of Camelina sativa sphingolipids were investigated in a mouse model of dietary-induced MetS. Seed meals from two Camelina sativa lines enriched, respectively, in C24- and C16-NH_2^- glycosyl-inositol-phosphoryl-ceramides (NH₂GIPC) were used in hypercaloric diets. After 5 weeks on these two hypercaloric diets, two markers of the MetS were alleviated (adiposity and insulin resistance) as well as inflammation markers and colon barrier dysfunction. A more pronounced effect was observed with the C16-NH₂GIPC-enriched HC diet, in particular for colon barrier function. Despite a lower digestibility, C16-NH₂GIPC were more prevalent in the intestine wall. Sphingolipids provided as camelina meal can therefore counteract some deleterious effects of a hypercaloric diet in mice at the intestinal and systemic levels. Interestingly, these beneficial effects seem partly dependent on sphingolipid acyl chain length.

In vitro fermentation of total mixed diets differing in concentrate proportion: relative effects of inocula and substrates

BACKGROUND

In vitro techniques are used to predict ruminant feedstuff values or characterise rumen fermentation. As the results are influenced by several factors, such as the relative effects of inocula and substrates, this study aimed to examine in vitro incubation of two total mixed rations (substrates) differing in their proportion of concentrate [low (L): 350 g kg(-1) vs. high (H): 700 g kg(-1)] incubated in inocula provided by goats fed either a L or a H diet. Gas production and composition in carbon dioxide (CO2), methane (CH4 ) and hydrogen (H2), volatile fatty acids (VFAs), soluble carbohydrates (SCs) and ammonia (NH3) concentrations, and pH of the fermentation fluid were measured.

RESULTS

In comparison with the L inoculum and L substrate, the H ones produced more CO2 and CH4 gas, which led to higher SCs and VFA concentrations, and lower acetate-to-propionate ratio and NH3 concentration, with a predominant effect of the inoculum.

CONCLUSION

The effects of the inocula and of the substrates were additive using donor animals adapted to the diets.

Effects of the percentage of concentrate on rumen fermentation, nutrient digestibility, plasma metabolites, and milk composition in mid-lactation goats

The aim of this work was to study the effects of the dietary percentage of concentrate on patterns of intake, the evolution of rumen fermentation characteristics and plasma metabolites after a meal, nutrient digestibility, and milk production and composition in a medium-term trial in dairy goats. These effects have been well studied in dairy cattle but seldom in goats. Thirteen ruminally and duodenally cannulated dairy goats (95±4 d in milk) fed ad libitum were used in this study. Goats were assigned to 1 of 2 dietary treatments: high-concentrate (70% concentrate on dry matter basis) or a low-concentrate (35%) total mixed rations. The experiment was conducted over a period of 10 wk, including 3 wk of adaption to the diets. Patterns of intake, rumen fermentation characteristics, and plasma metabolites after a meal and fatty acids profile of milk fat were compared at the onset and at the end of the experiment. The increase in dietary percentage of concentrate decreased rumen pH, acetate to propionate ratio, ammonia-N concentration, and plasma urea concentration. The percentage of concentrate did not affect total volatile fatty acid concentrations. The high-concentrate diet increased the rate of intake during the morning meal at the onset of the experiment, whereas it decreased total dry matter intake and the rate of intake during the morning meal at the end of the experiment. The high-concentrate diet resulted in greater organic matter digestibility. Raw milk yield and protein yield were greater in goats fed the high-concentrate diet, whereas fat yield was not affected by dietary treatments. The milk fat content was lower in goats fed the high-concentrate diet. Proportions of the trans-C18:1 isomer relative to total fatty acids in milk were higher with the high-concentrate diet, but no modification of the proportion of total trans-C18:1 was detected, in particular no shift from trans-11 C18:1 to trans-10 C18:1 was observed. Further, the isomer trans-10,cis-12 C18:2 was not detected. Data from this study could be used for a new modeling approach or to improve existing models.

Utilization of extruded linseed to modify fatty composition of intensively-reared lamb meat: effect of associated cereals (wheat vs. corn) and linoleic acid content of the diet

Sixty male lambs were used in two trials to study the efficiency of transfer and elongation of linolenic acid (ALA) in muscle and caudal adipose tissue and to assess factors affecting this process and related changes in fatty acid (FA) profile. In experiment 1, lambs were fed a control diet or extruded linseed (L) diet either with wheat (W, rapid starch) or corn (C, slow starch). In experiment 2, lambs were fed L with "normal" rapeseed, or high-oleic rapeseed, or soybean. In experiment 1, L increased ALA proportion and total n-3 PUFA in muscle and adipose tissue. In adipose tissue but not in muscle, LC lambs had higher proportion of ALA than LW lambs. In experiment 2, increasing linoleic acid (LA) intake increased LA proportion in muscle and adipose tissue but did not modify ALA proportion. Moreover, in muscle, it did not change the desaturation and elongation processes of ALA to long-chain n-3 PUFA.

[Control of milk composition and quality on the farm]

Milk and milk products have a reputation for quality among consumers. Yet the raw material--milk collected on the farm--varies widely in its composition and quality depending on the farming conditions, animal genetics, feed, and environmental determinants. The micronutrient content of milk and milk products, their organoleptic qualities, and the factors that influence these characteristics are now better known. Thus, the dairy industry is better able to develop foods meeting modern demands for taste, safety and health-promoting qualities.

Effect of duodenal infusion of trans10,cis12-CLA on milk performance and milk fatty acid profile in dairy goats fed high or low concentrate diet in combination with rolled canola seed

The effect of t10,c12-C18:2 on milk production, and fatty acid (FA) profile of milk fat was studied in 8 goats infused duodenally with t10,c12-C18:2 (2 g.10 h-1) during 3 days, followed by a 2-day infusion of skim milk (SM). The goats were assigned to 4 diets in a factorial arrangement constituted by low (L = 45%) or high (H = 65% of the diet DM) percentage of concentrate without (CS0) or with (CS20) rolled canola seed (20% of the concentrate DM). Milk samples were collected before (basal), and during the t10,c12-C18:2 and SM infusions. The t10,c12-C18:2 in milk fat increased from undetectable basal values to an average of 0.39% of total FA in the 3rd day of t10,c12-C18:2 infusion. DMI, milk yield, and the contents and yield of milk fat, protein, and lactose were similar between basal and the t10,c12-C18:2 infusion. The concentration of saturated FA with 4 to 16C did not change during the t10,c12-C18:2 infusion, whereas C18:0 increased, particularly in the milk fat of the CS20 group. The t10,c12-C18:2 infusion increased the t10- and t11-C18:1 (except a reduction in t11-C18:1 for the H-CS20 group), and it decreased the c9,t11-C18:2 in milk fat, particularly for the H-CS20 group. The t10,c12-C18:2 infusion reduced the c9,t11-C18:2/t11-C18:1 ratio, particularly for the CS0 group. The results indicate that mammary lipogenesis in dairy goats was not decreased by t10,c12-C18:2, however, the desaturation of long chain FA appeared to be equally affected as in dairy cows. This reduction in the desaturase index of milk fat could have been a direct effect of t10,c12-C18:2, or mediated via an increase in t10-C18:1.

Influence of extruded soybeans with or without bicarbonate on milk performance and fatty acid composition of goat milk

The effects of extruded soybeans (ESB) included at 0, 10, or 20% of dry matter (DM) of the diet in combination with sodium bicarbonate (0 vs. 1% bicarbonate added to DM) on rumen fermentation characteristics, production parameters, and fatty acid (FA) profiles of milk fat were examined in 30 midlactation goats and 6 rumen-cannulated goats fed high-concentrate diets (30:70 forage-to-concentrate ratio) ad libitum in a 3 x 2 factorial design. Diets were fed as total mixed rations. The trial lasted 13 wk with the final 9 wk as the test period. Milk yield and composition were recorded each week throughout the trial. Individual samples of milk were taken in wk 4, 7, 10, 11, and 13 to determine FA profile of milk fat. Dry matter intake and intake of net energy for lactation were not affected by dietary treatments. Feeding ESB did not modify ruminal pH or volatile fatty acids concentration in the rumen fluid, but it increased the molar proportion of propionate. Feeding ESB increased fat-corrected milk, milk fat content, and fat yield compared with the control diets. There was no change in milk protein content when ESB were fed. Feeding ESB increased the proportions of oleic, linoleic, and linolenic acids in milk fat at the expense of most of the saturated FA. It also increased the n-6 to n-3 FA ratio of milk. The largest changes in milk yield and milk composition were generally obtained with ESB included at 20% of DM. The addition of sodium bicarbonate tended to increase ruminal pH, VFA concentrations in the rumen fluid, and the molar proportions of acetate. The addition of sodium bicarbonate increased milk fat content and fat yield, with no change in milk FA composition. It is concluded that during midlactation, the inclusion of ESB to 20% of DM prevented low milk fat content for goats fed high-concentrate diets, with no decrease in milk protein content. The addition of sodium bicarbonate may enhance the effects of ESB on milk fat content and fat yield.

Effect of dietary propionate on intake patterns and fatty acid composition of adipose tissues in lambs

The aim of the present trial was to study the effect of dietary propionate supplementation on growth performance, intake patterns and on the proportion of odd-numbered and methyl-branched chain fatty acids in internal or in subcutaneous adipose tissues. These fatty acids are responsible, in part, for abnormally soft subcutaneous adipose tissue. Eleven male lambs were fed ad libitum carbohydrate-rich diets based mainly on barley, supplemented (P diet) or not supplemented (C diet) with 5.6% DM of sodium propionate. During the trial, the intake patterns were recorded on three non-consecutive days over a 9h-period. The fatty acid compositions of four adipose tissue sites, two subcutaneous (dorsal, caudal) and two internal (omental, perirenal) were analysed. The ME intake (3.32+/-0.44Mcal per day) and average daily gain (316+/-64g per day) were not different (P>0.10) between the C and P treatments. The intake patterns of these lambs given ad libitum access to feed did not show any large meal even after the morning distribution of feed. No differences in intake patterns were observed between the two diets. The dietary propionate supplementation increased (P<0.05) the proportion of odd-numbered fatty acids (Odd FA) in both internal (increase of 0.7wt.% of total fatty acids) and subcutaneous adipose tissues (increase of 1.7% of total fatty acids). The effect of dietary propionate supplementation on branched-chain fatty acids was less conclusive although it tended to increase (P=0.09) the proportion of branched-chain fatty acids other than the iso and anteiso fatty acids (BCFAO) in dorsal adipose tissue. This experiment confirms the role of propionate as an important precursor of odd-numbered and methyl-branched chain fatty acids. Moreover, the dorsal adipose tissue seems to be the most sensitive adipose tissue to dietary increment in ruminal propionate content. A positive relationship between the mean ME intake rate measured over 8.5h and the proportions of Odd FA and BCFA in dorsal adipose tissue was shown. However, it does not appear to play a predominant role in the explanation of the individual variability in dorsal fatty acid composition.

Influence of feed intake and source of dietary carbohydrate on the metabolic response to propionate and glucose challenges in lactating goats

The influence of type of nutrients in the diet (rapidly degraded starch plus rapidly degraded N or highly digestible fiber plus slowly degraded N) and amount of feed offered (2.40 +/- 0.10 or 2.00 +/- 0.10 kg of dry matter/d) on plasma constituents after a glucose tolerance test or a propionate challenge test were studied using 12 multiparous dairy goats. Type of diet and interaction between type of diet and amount of feed offered had no effect on the concentrations of any plasma metabolite measured during propionate challenge. During propionate challenge, goats fed at the high dry matter intake (DMI) had a higher clearance of propionate and glucose and a higher ratio of plasma insulin to glucose. During glucose challenges, goats fed diets that were rich in highly digestible fiber tended to have lower peak concentrations of glucose, and goats fed at the high DMI had a higher clearance of glucose. The plasma insulin response to the glucose test was not altered by treatment. The ratio of plasma insulin to glucose was numerically, although nonsignificantly, higher for goats fed at the high rate of DMI. Most of the differences concerning glucose metabolism, insulin response, and tissue responsiveness to insulin appeared to be primarily due to the amount of feed offered and not to the type of diets fed to dairy goats in midlactation.

Influence of feed intake and source of dietary carbohydrate on milk yield and composition, nitrogen balance, and plasma constituents of lactating goats

The influence of diet (synchronized or not synchronized for the degradation rate of the carbohydrate and N fractions) and amount of feed offered [2.40 +/- 0.10 or 2.00 +/- 0.10 kg of dry matter (DM)/d] on milk yield and composition, N balance, and some plasma constituents was studied using 32 multiparous dairy goats (100 +/- 16 d in milk) that were fed a mixed diet for 9 wk. Diets were 40% concentrate with rapidly degraded starch and rapidly degraded N or highly digestible fibers and slowly degraded N. Nitrogen balance was determined at wk 4 and 8. Goats that were fed greater amounts of DM had higher yields of milk, fat-corrected milk, and protein, but lower milk fat concentrations during the whole trial. Raw milk yield was higher at wk 4 and from wk 6 to 7 for goats consuming the rapidly degraded diet than for goats fed the slowly degraded diet at a high feed intake. Concentrations of milk fat tended to be greater for goats fed the rapidly degraded diet at wk 5, 7, and 8. At wk 5 and 6, an interaction between feed intake and diet was observed for milk protein concentration. Nitrogen digestibility, milk N, and N balance were increased for goats fed at high intakes. The output of N in urine and the efficiency of N use for milk output was greater, and N balance was lower, for goats fed the rapidly degraded diet. Plasma concentrations of nonesterified fatty acids, beta-hydroxybutyrate, and urea (wk 2 to 6) were lower, and insulin concentrations were transiently increased, for goats fed at high intakes. Goats fed the rapidly degraded diet compared with goats fed the slowly degraded diet had higher plasma concentrations of urea, which may indicate inefficient use of ruminal N.

Quantitative review of ruminal and total tract digestion of mixed diet organic matter and carbohydrates

The mean response and main factors of variation (level of concentrate, nature of carbohydrate in the concentrate and level of intake) for organic matter, cell wall material, starch digestion and microbial synthesis in the gastrointestinal tract of ruminants were quantitatively reviewed using a data base involving 157 papers. The ruminal digestion (mean +/- SE%) of organic matter, cell wall material, and starch were 45.2 +/- 11.2 (n = 553), 47.7 +/- 17.7 (n = 348), and 74.1 +/- 16.2 (n = 140), respectively and the proportion of each component digested in the rumen in relation to total tract digestibility was 64.7 +/- 12.3, 78.8 +/- 18.5 and 80.5 +/- 16.3, respectively. The efficiency of microbial synthesis (g of microbial protein/kg of organic matter truly fermented in the rumen) and the proportion of microbial nitrogen in the total amount of nitrogen leaving the stomachs (%) were, 23.6 +/- 9.3 (n = 320) and 55.1 +/- 16.5 (n = 289), respectively. The ruminal digestion of organic matter increased by 2 points for every 10 percent increase in concentrate incorporation. The ruminal digestion of cell wall material was maximal when the concentrate incorporation in the diet was 30%. When the ruminal digestion of cell wall decreased, the substitution of ruminal digestion by intestinal digestion was partial (10%). The efficiency of microbial synthesis was optimal when the level of concentrate incorporation was 40%. The nature of the carbohydrates in the concentrates had a significant effect on the efficiency of the microbial synthesis, which was higher (+6.6 g of nitrogen/kg of fermentable organic matter in the rumen) with slowly degradable starch (SS) or digestible fiber (DF) than with rapidly degradable starch (RS). Moreover, the mean depression of cellulolysis in the rumen was higher with RS (-13 points) comparatively to SS (-7 points) or DF (-5 points).

Influence of trenbolone acetate combined with estradiol-17 beta on growth performance, body characteristics, and chemical composition of goat kids fed milk and slaughtered at different ages

The effects of anabolic agents (5 mg of estradiol-17 beta + 30 mg of trenbolone acetate) on body characteristics and chemical composition of gain were studied in 58 intact male goat kids fed milk replacer. Four kids were slaughtered at 7 d of age to constitute the initial group. The other kids were allotted in a 2 x 3 factorial arrangement with slaughter age (41, 49, and 56 d of age) and treatment (control and implanted at 21 d old) as factors. Energy intake decreased during the first 4 wk after treatment; implanted kids had the same ADG as controls but a better energy efficiency (P < .05). During the last week of the trial, energy intake was the same; treated kids tended (P < .10) to have a higher empty body gain (EBG). Anabolic agents increased carcass (P < .10) and hide proportions (P < .01) in empty BW and in EBG for all groups (except for carcass at 56 d old). Anabolic agents reduced the contribution of adipose tissues (P < .05), empty digestive tract (P < .05), and other organs (P < .01) to EBG. At all slaughter ages, the chemical composition of carcass and hide wet tissues, all dissectible adipose tissues, and EBG were altered by treatment. In these tissues (except for mesenteric fat tissue), water content increased and lipid content decreased (P < .05), but these effects diminished with age. Expressed on a DM basis, the CP content of the treated carcasses was increased in all groups (P < .05). Implanting high doses of steroids altered nutrient partitioning, which reduced fat and increased water and protein in the body.