Effects of reduced dietary energy and amino acid density on Pectoralis major myopathies in broiler chickens at 36 and 49 days of age1

Two experiments (Exp) were conducted to determine if reductions in the incidence and severity of wooden breast (WB) and white striping (WS) may be obtained by reducing dietary nutrient density. In each Exp, Yield Plus × Ross 708 male broiler chicks were placed into 63 pens (22 birds/pen). All birds received an identical prestarter diet until 7 d of age, after which time each pen was randomly assigned to 1 of the following 7 dietary treatments (TRT) for the starter (8 to 14 d), grower (15 to 24 d), finisher 1 (Exp 1: 26 to 35 d; Exp 2: 26 to 42 d), and withdrawal (Exp 2: 43 to 48 d) phases: 1) 100% of primary breeder recommendations for digestible amino acid and metabolizable energy density throughout Exp; 2) 95% of TRT 1 until 14 d of age, then as TRT 1; 3) 95% of TRT 1 until 24 d of age, then as TRT 1; 4) 95% of TRT 1 throughout Exp; 5) 90% of TRT 1 until 14 d of age, then as TRT 1; 6) 90% of TRT 1 until 24 d of age, then as TRT 1; 7) 90% of TRT 1 throughout Exp. At 36 d (Exp 1) and 49 d (Exp 2), 18 birds per pen were processed and evaluated for WS and WB. In Exp 1, reduced dietary density in the starter phase (TRT 2 and TRT 5) resulted in increased (P ≤ 0.05) incidences of severe WB (32.9% and 34.7%) relative to TRT 1 (18.2%). In Exp 2, broilers assigned to TRT 7 had reduced (P < 0.01) incidences of severe WB (20.8%) and WS (42.3%) relative to the control (WB: 36.5%; WS: 64.5%). In both Exp, plasma creatine kinase and lactate dehydrogenase increased (P ≤ 0.05) with increasing scores for WB and WS. Reducing dietary nutrient density from 8 to 14 d may exacerbate fillet myopathies in broilers reared to 35 d of age. Although reducing dietary energy and amino acid density to 90% of recommendations from 1 to 48 d reduced the severity of myopathies, these reductions occurred with compromises in live performance. Altogether, these results indicated that concurrent manipulation of dietary amino acid and energy density is not a viable practical solution for breast myopathies.

Growth performance and meat yields of broiler chickens fed diets containing low and ultra-low oligosaccharide soybean meals during a 6-week production period

Two experiments were conducted to determine the effects of diets containing low oligosaccharide soybean meals (SBM) on growth performance, meat yields, and physiological variables of broilers during a 6-wk production period. In experiment 1, six hundred Ross × Ross 708 male chicks were randomly distributed to 24 floor pens (25 birds per pen; 0.09 m(2) per bird at 1 d of age). Birds were fed corn-soybean meal-poultry by-product meal-based diets with either low oligosaccharide (LOSBM) or control SBM (CSBM) from 1 to 40 d of age. In experiment 2, one thousand five hundred Ross × Ross 708 male chicks were randomly distributed to 60 floor pens (25 birds per pen; 0.09 m(2) per bird at 1 d of age). Broilers were fed corn-soybean meal-poultry by-product meal-based diets containing 1 of 3 SBM sources [CSBM, LOSBM, or ultra-low oligosaccharide SBM (ULSBM)] and formulated with moderate or reduced AMEn concentrations (25 kcal/kg reduction) resulting in a 3 × 2 factorial design. Diets were formulated using AMEn and digestible amino acid values determined from previous research utilizing the same SBM types. Variables measured consisted of BW gain, feed intake, feed conversion ratio, mortality, carcass weight and yield, abdominal fat percentage, total breast meat weight and yield, digesta viscosities and pH, plasma nonesterfied fatty acids, plasma glucose, and plasma triglycerides. In experiment 1, broilers fed diets containing LOSBM had increased BW gain (P = 0.020) and decreased (P < 0.001) feed conversion from 1 to 14 d of age. Abdominal fat percentage was higher (P < 0.001) for birds fed LOSBM vs. CSBM. In experiment 2, no differences were observed for interaction effects or main effects of energy concentration. Feed conversion ratio was lower (P < 0.001) for broilers fed diets containing ULSBM vs. LOSBM and CSBM from 1 to 28 and 1 to 42 d of age. Broilers fed diets formulated with ULSBM had higher (P < 0.05) carcass yield vs. birds fed diets with CSBM. Total breast yield was higher (P = 0.021) for birds fed diets containing LOSBM and ULSBM vs. CSBM. Abdominal fat percentage was higher (P = 0.027) for broilers fed diets containing LOSBM vs. CSBM. Diets formulated with LOSBM and ULSBM required approximately 45% less supplemental fat, and broilers fed these diets exhibited no adverse effects on growth performance and meat yields compared with broilers fed diets containing CSBM.