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Impacts of Variable Amino Acid Densities during Withdrawal Phase Diets on Growth Performance, Yield, and Meat Quality of Broilers
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Two experiments were conducted to investigate the impact of variable AA densities on broiler live performance, processing yield and meat quality parameters. The objective in experiment I was to evaluate 4 diets of increasing AA density in 35 d male broilers. All broilers were fed a common diet until 12 d of age and then switched to dietary treatments from d 13 to 35. On d 13, broilers were fed 1 of 4 dietary treatments of increasing AA density (0.95/0.82, 1.00/0.87, 1.05/0.92, and 1.10/0.97% dig lysine for d 13 to 25/25 to 35). Evaluated parameters included average body weight (BW), body weight gain (BWG), mortality corrected feed conversion ratio (FCR), feed consumption (FC) and processing yields. Increasing the dig lysine level improved growth performance as incremental improvements were observed in BW, BWG, FCR, and processing weights were observed. However, whole carcass yield percentage was not impacted. In general, increasing dig lysine increased breast meat yield and decreased abdominal fat pad yield. In experiment II, a similar approach was taken with 4 levels of increasing dig lysine fed in the final 2 diets of grow-out. However, the age of the birds evaluated increased to 48 d of age and all broilers were fed a common diet through 28 d of age. The 4 treatment diets had increasing AA densities and were fed as WD 1 from d 28 to 38 and WD 2 from d 38 to 48 (0.91/0.85, 0.96/0.89, 1.00/0.94, and 1.05/0.98% dig lysine for WD 1 and WD 2, respectively). All measured parameters were similar to that of experiment I however, breast fillets were observed for the presence and severity of woody breast and white striping. Similar to experiment I, increased dietary AA density improved growth performance parameters to include increased BW and decreased FCR through both phases of the experimental period. Reducing the dig lysine level increased FC. Whole carcass yield percentage increased when broilers were fed the highest AA density diet compared to those fed the lowest AA density diet. Breast weight and yield percentage increased in broilers fed the diet with a higher AA density as compared to the other diets. As AA density increased, the severity of woody breast also increased. In conclusion, dietary AA content will impact growth performance and can be used to improve profitability dependent upon ingredient prices.
Portillo Gattas, Danny Alberto (2016). Impacts of Variable Amino Acid Densities during Withdrawal Phase Diets on Growth Performance, Yield, and Meat Quality of Broilers. Master's thesis, Texas A & M University. Available electronically from