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Growth performance and carcass characteristics of MV × Cobb 700 broilers fed diets varying in apparent metabolizable energy from 34 to 46 days of age

Philpot, S., J. Caldas and W. Dozier

Limited data are available defining the optimum apparent metabolizable energy (AMEn) specification of MV × Cobb 700 broilers during the finisher phase. An experiment was conducted to determine the effects of AMEn on growth performance, carcass characteristics, and breast quality of MV × Cobb 700 broilers from 34 to 46 D of age. Fourteen hundred and eight broilers were vent sexed and randomly distributed by sex into 64 floor pens (22 birds; 0.10 m2/bird). A 2 × 4 factorial arrangement of treatments was used, with male and female broilers fed diets formulated to AMEn of 3,108, 3,152, 3,196, or 3,241 kcal/kg from 34 to 46 D of age. Each treatment was represented by eight replicate pens. Broilers were fed common starter and grower diets (1 to 18 and 19 to 33 D of age, respectively) formulated to the primary breeder guidelines. Corn, soybean meal, and dried distillers grains with solubles were the primary ingredients during all feeding phases. Body weight gain, feed intake, feed conversion ratio, and mortality were determined from 34 and 46 D of age. At 47 D of age,12 birds per pen were processed and the weights and yields of the abdominal fat, carcass, and breast fillets and tenders were assessed. Breast fillets were evaluated for prevalence and severity of wooden breast and white striping using a subjective scoring system of normal, mild, moderate, or severe defects. Data were analyzed with a two-way analysis of variance. No interactive effects (P ≥ 0.07) were observed between sex and AMEn for growth performance or processing characteristics. A sex × AMEn interaction was observed for white striping where males fed diets containing 3,152 kcal/kg had increased (P = 0.038) incidence of moderate white striping compared with females fed diets containing 3,108 kcal/kg. For the main effect of AMEn, broilers fed diets containing 3,196 kcal/kg had higher BW gain (P = 0.032), reduced feed conversion ratio (P = 0.020), and reduced abdominal fat weight and percentage (P ≤ 0.045) compared with birds fed diets containing 3,108 kcal/kg. Breast meat yield was highest in broilers fed diets containing 3,108 (P = 0.0030) compared with broilers provided with all other treatments. Breast quality characteristics were not affected by AMEn (P ≥ 0.11). Males had higher BW gain and feed intake, lower feed conversion ratio, heavier carcass, breast fillets, and tenders, and increased incidence of wooden breast scores of moderate and severe compared with females (P ≤ 0.001).

These results indicate that increasing AMEn above 3,196 kcal/kg in MV × Cobb 700 broilers has little impact in performance or breast quality characteristics during the finisher period, which may allow for reductions in feed cost.