The dynamics of body composition and body energy content in broilers.

Body composition (BC) analysis is important because the modern broiler is one of the most efficient animals in producing protein for human consumption, and a proper nutrition could potentiate this meat production. BC by chemical analysis was analyzed in 151 broilers from 1to 60 d of age. Birds were fed mash feeds ad libitum in four phases (starter 1 to 14d, grower 15 to 28 d, finisher 29 to 42 d, and withdrawal 43 to 60 d). Gompertz 3P model, multiple linear regression, and CRD with ANOVA analysis were used in the experimental design using JMP pro 2015. The growth in terms of body weight, protein, fat, minerals (Ca and P) followed a Gompertz 3P model with similar growth rates of about 4.9% per day and the maximum growth was obtained at about 34 d of age. Body weight ranged from 56 to 4184 g, water from 683 to 751 g/kg, protein from 154 to 182 g/kg, fat from 53 to 101 g/kg, minerals (ash) from 17.9 to 22.5 g/kg (AS IS basis). Broiler protein ranged from 563 to 613 g/kg, fat 197 to 317 g/kg, minerals 65.2 to 86.6 g/kg, calcium 11.7 to 18.9 g/kg, and phosphorus 10.3 to 15.3 g/kg dry matter (DM) basis. The calorific coefficients for protein and fat were determined by multiple regressions and resulted in 5.45 ± 0.09 kcal/g for protein and 8.95 ± 0.16 kcal/g for fat. These two coefficients can be used to predict the body energy content or energy of gain. The protein: fat ratio was the highest at day 1 and decreased gradually until day 60. The BC in terms of water, protein, and fat changes with age, water being reduced and protein and fat increased towards d60. Mineral composition remained constant at the end of growth but some fluctuations occurred during the grower period. The understanding of the dynamics of BC will bring new opportunities to study and change feed strategies and increase the feed efficiency for meat in the modern broiler.

The effect of ß-mannanase on nutrient utilization and blood parameters in chicks fed diets containing soybean meal and guar gum.

The present study was conducted to determine whether the addition of ß-mannanase in broiler feed changes hormonal profiles in the blood and broiler performance and nutrient availability. Five hundred and four Cobb male chickens were studied during d 7 to 21. Three corn-soybean meal (SBM) based diets 1) Low SBM (18% SBM); 2) High SBM (31% SBM); and 3) High SBM+GG (31% SBM + Guar Gum (GG) 0.5%) with 3 levels of ß-mannanase (0, 200, and 400 ppm) were mixed to produce 9 diets. A factorial design 3 × 3 was performed with JMP pro 13 (SAS, 2017). Analysis of variance and contrast analysis were used to test significance level at P < 0.05. Glucose (190 and 188 mg/dL) was increased with 200 and 400 ppm of ß-mannanase, respectively, compared to control (182 mg/dL) in the fasted state (P < 0.037). Glucose was higher in chicks fed with the High SBM and High SBM + GG diets but lower in the fasted re-fed state (P < 0.01). Insulin was higher with 200 and 400 ppm added ß-mannanase in the fed state (P < 0.021). Insulin-like growth factor-1 was higher with 400 ppm added to High SBM+GG. ß-mannanase improved feed conversion ratio (FCR) 9 points with 400 ppm in High SBM diet (P < 0.01) and 16 and 18 points with 200 and 400 ppm, respectively, added to the High SBM+GG diet (P < 0.01). Viscosity decreased from 19.2 to 7 cps with both enzyme doses in the High SBM + GG diet (P < 0.01). Digestible energy was +152 kcal/kg with 400 ppm ß-mannanase in the High SBM diet and +200 kcal/kg with both levels of enzyme in High SBM+GG diet. Digestibility of amino acids was improved from 0.8 to 3.6% with ß-mannanase in High SBM+GG diet (P < 0.05). In conclusion, chicks fed with High SBM and High SBM+GG diets with added ß-mannanase significantly improved blood glucose and anabolic hormone homeostasis, FCR, digestible energy, and digestible amino acids compared to chicks fed with same diets without ß-mannanase.

Dynamics of nutrient utilization, heat production, and body composition in broiler breeder hens during egg production.

Changes in heat production (HP) and body composition (BC) in modern broiler breeders can provide means to understand nutrient utilization. Twelve Cobb 500 breeders were evaluated 10 times from 26 to 59 wk of age. The same wired caged breeders were moved to respiratory chambers connected to an indirect calorimetry to obtain oxygen consumption (VO2) and carbon dioxide production (VCO2), HP, and respiratory exchange ratio (RER). The same hens were evaluated for BC using a dual X-ray absorptiometry (DEXA). Data were analyzed during light (16 h) and dark (8 h) period using a mixed model to evaluate calorimetry parameters, a factorial design 2 × 10 for normalized calorimetry parameters, and Complete Randomized Design (CRD)-one way ANOVA for BC. Means were separated by Tukey-Honest Significant difference (HSD). HP increased with age (d) in 0.152 kcal/d, VO2 and VCO2 were 0.031 and 0.024 L/d per each increase in age (d), respectively. In the light period, hens consumed +17.4 L/d VO2 and produced +18.9 L/d VCO2 (P < 0.01). HP during the dark period was 84 kcal/kg0.75 and during the light period was 115 kcal/kg0.75. RER decreased with age until 43 wk and remained the same until 59 wk suggesting more fat and/or protein being oxidized at later periods of production. Lean body mass ranged from 642 to 783 g/kg during the whole study reaching the lowest at 37 and 50 wk and the highest at 26 to 33 wk (P < 0.01). Body fat ranged from 168 to 261 g/kg with the lowest at 26 to 33 wk and the highest at 50 wk of age (P < 0.01). Broiler breeder females may be catabolizing fat energy reserves from 50 wk onwards when the egg production is reduced, and HP increased at 54 and 59 wk (P < 0.01) due to higher energy required for maintenance of a higher lean mass structure. Broiler breeders change nutrient fuel use during egg production. Indirect calorimetry and DEXA can be used to pursue further feed strategies to maximize egg production and maintain a healthy breeder.

The effect of sexual maturity and egg production on skeletal muscle (pectoralis major and gastrocnemius) protein turnover in broiler breeder pure lines.

A study was conducted to evaluate the effect of sexual maturity on pectoralis major and gastrocnemius muscle protein turnover in broiler breeder pure lines. Protein turnover in skeletal muscle tissue was determined in 4 broiler breeder pure lines (Line A, Line B, Line C and Line D) at 22, 27, 33, 37, 44, and 50 wk of age. A completely randomized design with a factorial arrangement 4 × 6 (4 lines and 6 time periods (ages)) was used. There were 5 replicates per line/time and each hen represented a replicate. Five hens/line at each age were given an intravenous flooding-dose of 15N-phenylalanine (150 mM, 40 atom percent excess (APE) at a dose of 10 mL/kg. After 10 min, birds were euthanized using CO2 asphyxiation and the breast and leg muscle excised and snap frozen in liquid nitrogen for protein turnover analysis. Excreta was collected from each breeder for 3-methyl histidine (3-MH) analysis. There was a significant age effect for the breast muscle fractional synthesis rate (FSR), but no main effects (age and line) for leg muscle FSR. The FSR in breast muscle tissue decreased in hens from wk 22 (first egg) to wk 33 (peak egg production). There was a significant age effect on fractional breakdown rate (FBR) in breast and leg muscle. The FBR in breast muscle increased in hens from wk 22 to wk 33 and remained high through wk 37. Breast muscle FBR significantly decreased in hens from wk 37 to wk 50. The FBR in leg muscle tissue increased in hens from wk 33 to wk 37 and then decreased at wk 50. No line effect was seen for FSR or FBR. There is a large increase in skeletal muscle FBR during the transition for the pullet to sexual maturity with increases in skeletal muscle FBR in the breast and leg muscle through peak egg production. Protein turnover in skeletal muscle tissue is believed to be a source of nutrients for egg production.

Effect of white striping myopathy on breast muscle (Pectoralis major) protein turnover and gene expression in broilers.

WS: A study was conducted to evaluate the effect of white striping ( ) of broiler breast muscle ( Pectoralis major ) on protein turnover and gene expression of genes related to protein degradation and fatty acid synthesis. A total of 560 day-old male broiler chicks Cobb 500 were allocated in a total of 16 pens, 35 chicks per pen. A completely randomized design was conducted with a 2 × 3 factorial arrangement (2 scores: severe and normal, and 3 breast meat samples sites). At d 60, 20 birds were randomly selected, euthanized, and scored for white striping. Scoring was either normal ( , no WS) or severe ( ). Also, the same day, 17 birds (16 infused, one control) were randomly selected and infused with a solution of 15 N Phen 40% ( ). Breast muscle tissue was taken for gene expression analysis of the following genes: MuRF1, atrogin-1, IGF-1, insulin receptor ( ), fatty acid synthetase, and acetyl CoA carboxylase ( ). Each bird was humanely euthanized after 10 minutes of infusion and scored for WS (NORM or SEV). Samples of the breast muscle ( Pectoralis major ) were taken at different layers (3 samples per bird: ventral, medial, dorsal), along with a sample of excreta for 3-methylhistidine analysis. Out of the 16 breast samples taken, only 10 were selected for analysis based on the WS score (5 NORM and 5 SEV). No significant differences ( P > 0.05) were found in fractional synthesis rate ( ) between SEV WS, NORM and sample sites for breast meat. However, fractional breakdown rate ( ) was significantly higher in birds with SEV WS compared to NORM (8.2 and 4.28, respectively, P < 0.0001). Birds with SEV WS showed significantly higher ( P < 0.05) relative expression of MuRF1 and slightly higher ( P = 0.07) relative expression of atrogin-1 than the NORM birds. These birds also showed lower ( P < 0.05) relative expression of IGF-1 than NORM birds. Further studies are needed to better understand why birds with severe white striping are degrading more muscular protein and mobilizing more fat.

The effect of four different feeding regimens from rearing period to sexual maturity on breast muscle protein turnover in broiler breeder parent stock.

A study was conducted to evaluate the effect of four different feeding regimens on breast muscle protein turnover in broiler breeder Cobb-500 parent stock (PS) pullets and breeder hens. The four feeding regimens based on BW curves utilized for the study were as follows: Everyday feeding (STD-ED) (Cobb Standard BW curve), skip-a-day feeding (STD-SKIP) (Cobb Standard BW curve), lighter BW (LBW-SKIP) (BW curve 20% under), and heavier BW (HBW-SKIP) (BW curve 20% over). Each feeding regimen was provided to pullets from 4 wk to 21 wk of age. Protein turnover was determined in PS pullets/breeders at 6, 10, 12, 16, 21, 25, 31, 37, 46, and 66 wk of age. A completely randomized design was used with a 4 × 10 factorial arrangement (four feeding regimens, 10 ages), each pullet represented a replicate. Five pullets/breeders at each age were given an intravenous flooding-dose of 15N-Phe (15N phenylalanine 150 mM, 40 APE (atom percent excess)) at a dose of 10 mL/kg BW for the determination of fractional synthesis rate (FSR). After 10 min, birds were euthanized and the breast muscle (pectoralis major) excised for protein turnover and gene expression analysis. Excreta was collected from each pullet or breeder for 3-methylhistidine (3-MH) analysis. No feeding regimen affected protein turnover. There was an age effect for breast muscle FSR. The FSR in breast muscle of pullets significantly increased from 6 wk to 12 wk and then decreased significantly for 31 wk-old breeders. FSR in breeder breast muscle increased significantly from 31 wk to 66 wk. There was an age effect for breast muscle fractional breakdown rate (FBR). FBR in breast muscle significantly increased from 21 wk to 25 wk and 31 wk (peak egg production), then significantly decreased at 66 wk. The expression of the genes related to protein degradation (Atrogin-1, MURF-1) in breast muscle was significantly higher at peak egg production. Protein turnover in skeletal muscle tissue is believed to be a source of nutrients for egg production.

25-Hydroxycholecalciferol Enhances Male Broiler Breast Meat Yield through the mTOR Pathway.

BACKGROUND: In recent years, there has been a growing body of evidence indicating that replacing cholecalciferol (vitamin D3) with 25-hydroxycholecalciferol [25(OH)D3] through dietary supplementation enhances breast meat yield in broiler chickens. However, the underlying molecular mechanisms are still unknown. OBJECTIVE: We investigated the effect of 25(OH)D3 on male broiler growth performance (body weight, feed intake, feed conversion ratio, and breast meat yield), muscle protein synthesis, and the potential underlying molecular mechanisms. METHODS: Male Cobb 500 broiler chickens were divided into 4 body weight-matched groups and received a control diet with normal cholecalciferol (2760 IU/kg feed) for 42 d, a diet with high concentrations of cholecalciferol (5520 IU/kg feed) for 42 d, or a diet with 25(OH)D3 (5520 IU/kg feed) for 42 d (HyD-42). A fourth group consumed the HyD-42 for 21 d and then control feed for 21 d (HyD-21) (n = 360 birds, 12 replicates/treatment). Food and clean water were available for ad libitum consumption. At the end of the 42-d experiment, protein turnover was measured by phenylalanine flooding dose. Breast muscle tissues were collected and protein synthesis-related gene and protein expression were measured by real time polymerase chain reaction and Western blot, respectively. Functional studies were performed in vitro with the use of a quail myoblast (QM7) cell line. QM7 cells were treated with 2 doses (1 nM and 10 nM) of cholecalciferol or 25(OH)D3 alone or in combination with 100 nM rapamycin, and cell proliferation was determined by cell proliferation assay. Protein synthesis-related gene and protein expression were also determined. RESULTS: The HyD-42 increased 25(OH)D3 circulating concentrations by 126% (P < 0.05), enhanced breast meat yield (P < 0.05), and increased the fractional rate of protein synthesis by 3-fold (P < 0.05) compared with the control diet. Molecular analyses revealed that breast muscle from chickens consuming the HyD-42 expressed significantly higher concentrations of vitamin D receptor (VDR), phospho mechanistic target of rapamycin(Ser2481), phospho ribosomal P70 S6 kinase (RPS6K)(Thr421/Ser424), and antigen Ki-67 (Ki67) compared with the other groups. In line with the in vivo data, in vitro functional studies showed that cells treated with 25(OH)D3 for 24 h had increased VDR expression, and activated the mechanistic target of rapamycin (mTOR)/S6 kinase (S6K) pathway, enhanced Ki67 protein concentrations, and induced QM7 cell proliferation compared with untreated or cholecalciferol-treated cells. Blocking the mTOR pathway with rapamycin reversed these effects. CONCLUSION: Taken together, our findings provide evidence that the effects of 25(OH)D3 on male broiler breast muscle are likely mediated through the mTOR-S6K pathway.