Live Performance and Meat Yield Responses of Straight-run Broilers to Progressive Concentrations of Di- Etary Energy Maintained at a Constant Me:protein Ratio

s of papers 37 151 Live performance and meat yield responses of straight-run broilers to progressive concentrations of dietary energy maintained at a constant ME:Protein ratio. M. A. Hidalgo*, W. A. Dozier, III, A. J. Davis, and M. E. Freeman, University of Georgia. According to a popular benchmark reporting service, a diverse array of metabolizable energy values is being used in formulating diets for broiler chickens. Reducing dietary energy concentration while maintaining a constant ME:Protein ratio has been shown to result in equivalent broiler performance as compared to utilizing high energy diets when broilers are marketed at 6.5 lb. This study examined the effects of progressive concentrations of dietary energy at a constant ME:Protein ratio on live performance and processing yields of broilers during a 37-d production period. A total of 2,592 Ross x Ross 308 straight-run broilers were sexed and 27 of each sex were commingled and randomly assigned to one of 48 floor pens. Birds were given a three-phase feeding program, which consisted of starter (0-17 d), grower (18-30 d), and finisher (31-37 d). Dietary treatments consisted of six feeding regimens (8 reps/trt): Regimen 1: starter 1,350 kcal/lb, grower 1,370 kcal/lb, and finisher 1,400 kcal/lb; Regimen 2: starter 1,370 kcal/lb, grower 1,390 kcal/lb, and finisher 1,420 kcal/lb; Regimen 3: starter 1,390 kcal/lb, grower 1,410 kcal/lb, and finisher 1,440 kcal/lb; Regimen 4: starter 1,410 kcal/lb, grower 1,430 kcal/lb, and finisher 1,460 kcal/lb; Regimen 5: starter 1,430 kcal/lb, grower 1,450 kcal/lb, and finisher 1,480 kcal/lb; Regimen 6: starter 1,450 kcal/lb, grower 1,470 kcal/lb, and finisher 1,500 kcal/lb. In general, body weight measurements were lower (P<0.05) when broilers consumed Regimen 1 compared with the other regimens throughout each phase of growth. Feed conversion ratio was improved (P<0.05) with Regimens 4, 5, and 6 compared with Regimen 1 from 18-30 d, 30-37 d, and 0-37 d as was feed consumption (P<0.05) from 30-37 d and 0-37 d. Dietary treatments did not alter the incidence of mortality, abdominal fat percentage, chilled carcass yield, or the recovery of carcass parts. These data indicate reducing metabolizable energy content of the diet at a constant ME:Protein ratio allows similar live performance to be obtained without affecting meat recovery, but decreasing the energy content of the diets to sub-optimum concentrations adversely affected performance, which may be related to inadequate caloric and protein consumption.