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Summary: The Cobb MV × Cobb 700 male broiler was evaluated for BW and feed conversion ratio (FCR) when fed diets of increasing levels of digestible lysine (Lys) and ME within each growing phase (0–12 D, 12–26 D, 26–35 D, and 35–55 D). Male BW was highest (P < 0.0001) at 12 D of age for birds fed 1.24% digestible Lys and 3,194 ME vs. birds fed 1.20% digestible Lys and 3,084 ME. Male BW were also highest (P < 0.0001) at 26 D of age for birds fed 1.23% digestible Lys and 3,194 ME. However, birds were able to compensate with increased FCR (P < 0.0001) when fed diets with lower levels of digestible Lys and ME from 26 to 55 D to achieve similar BW (P > 0.05) compared with the birds on the highest level and duration of digestible Lys and ME. The control group, that is, industry standard digestible Lys and ME levels, had the lowest levels of digestible Lys and ME for the duration of the experiment and had the highest (P < 0.0001) FCR and the lowest (P < 0.0001) BW. The results for BW and FCR suggest that the digestible Lys needs are higher than previously established. More investigations within each growing phase should be performed to better define the requirements of the Cobb MV × Cobb 700 broiler for digestible Lys.

Summary The percentage of broiler complex processing plants slaughtering big birds (e.g., those greater than 3.5 kg) has steadily increased in the United States the past 15 yr. Precision amino acids in dietary formulation is key as the growing cycle for these birds is extended, as well as total feed consumed. Furthermore, broilers reared for big-bird slaughter plants are destined for specialty breast meat yield portioning, making digestible Lys one of the key nutrients in feed formulation. This work assesses dietary Lys levels in graduations across feed phases to 53 D in Cobb MV × Cobb 700 female and male broilers. Optimizing digestible Lys in the starter phase (to 14 D) occurred between 1.26 and 1.31%. On average, dietary Lys intake per bird needed to optimize live performance, and white meat yield was higher in male birds (64 g) than in female birds (58 g). Optimization of Lys amino acid density in the Cobb MV × Cobb 700 broilers resulted in increased white meat yields in larger broilers, resulting in increased fillet weights per bird with white striping and woody breast being unaffected.

Published literature elucidating dietary valine (Val) requirements for female broilers is limited and lacks data for the finisher phase. Three experiments (Exp) were conducted to determine the Val requirement for Cobb MX × 500 females during the grower (Exp 1; 14–28 days), finisher (Exp 2; 28–42 days), and withdraw periods (Exp 3; 42–56 days). Two additional Exp were conducted to determine the Val requirement for Cobb MV × 500 male (Exp 4) and female (Exp 5) broilers from 14–35 days. Corn-soybean meal diets were fed in the experimental period of all Exp to create Val dose response titration diets. Dietary titration levels of digestible Val to digestible Lys (Val/Lys) ratios were: 64–82 in Exp 1; 65–83 in Exp 2 and 3; and 57–92 in Exp 4 and 5. Body weight (BW) gain, feed intake, and feed conversion ratio were determined for each experimental period. At the conclusion of Exp 2 through 5, broilers were processed to determine carcass traits. Requirements were determined using regression analysis, considering the requirement to be 95 % of the quadratic response. No significant linear or quadratic responses were determined for Exp 1 through 3. In Exp 4 and 5, significant responses were observed for feed conversion ratio, but not processing yields. The lack of responsiveness in Exp 1 through 3 are likely due to an inadequate reduction in dietary Val to observe female quadratic responses. Valine requirements were determined to be 78 and 77 Val/Lys for males and females, respectively, based on feed conversion responses.

Data pertaining to the branched-chain amino acids (BCAA) are of particular importance due to the positioning of valine (Val) and isoleucine (Ile) as limiting amino acids (AA) in conventional diets. Similarly, current research evaluating their potential interaction is sparse. Therefore, two experiments were conducted using Box-Behnken design (BBD) to determine performance and carcass responses to BCAA and glycine (Gly) supplementation in male broilers from 15–34 days (Experiment 1) and 15–35 days (Experiment 2). In Experiment 1, 13 experimental diets were formulated to contain various levels of digestible BCAA supplementation based on BBD. Inclusion levels for the BCAA were based on ratios to digestible lysine (Lys) and included: 65, 75, and 85 for digestible Val; 58, 66, and 74 for digestible Ile; and 110, 130, and 150 for digestible leucine (Leu). Diets for Experiment 2 were formulated in a similar manner and design, but total glycine + serine (Gly + Ser) inclusions were substituted for Leu. Inclusion levels were the same for Val and Ile as in Experiment 1 and ratios to digestible Lys of 131, 151, and 171 for total Gly + Ser. Fifteen-hundred and sixty male broilers were distributed across 78 pens and randomly assigned to 13 experimental diets in each Experiment. Body weight (BW) gain, feed intake, and feed conversion ratio (FCR) were determined for the experimental grower period in both Experiments. On day 35 (Experiment 1) or 36 (Experiment 2), six birds per pen were processed for the evaluation of carcass traits. Data were analyzed for linear, quadratic, and interactive effects. In Experiment 1, increased Leu inclusion linearly increased (P

The present study was conducted to evaluate the responses of growth performance and carcass traits in Cobb MV × 500 fast feathering broiler chickens fed maize, soybean meal (SBM) and peanut meal based diets containing different levels of digestible (dig) lysine (Lys). Dietary treatments consisted of 6 concentrations of dig Lys that ranged from 8.4 to 12.9 g/kg in increments of 0.9 g/kg. Two control diets with the medium level of dig Lys concentration of 11.1 g/kg were included where the positive control (PC) diet was a typical commercial diet based on maize and SBM and the negative control (NC) diet replaced part of SBM with100 g/kg peanut meal to allow higher supplementations of feed grade amino acids. Each of the eight experimental diets were offered to either male or female broiler chickens to form 16 experimental treatments and each treatment included 6 floor pens with 12 birds per pen. Broiler chickens were offered experimental diets from 14 to 35 days post-hatch. All diets were balanced with essential amino acids (EAA) by using ideal protein ratio approach and were offered to broiler chickens from 14 to 35 days post-hatch. Predictably, male broiler chickens had better weight gain (WG), feed intake (FI), feed conversion ratio (FCR) and breast meat yield (P