Live Performance and Meat Yield Responses of Broilers to Progressive Concentrations of Dietary Energy Maintained at a Constant Metabolizable Energy-to-Crude Protein Ratio

In the US, a wide array of ME values ranging from deficient to adequate is being used to formulate diets for broilers to accommodate performance, meat yield, or economics. When formulating diets to minimize live production cost, cumulative live performance and meat recovery may be adversely affected when diets contain a suboptimum caloric concentration. Diets formulated to contain progressive concentrations of dietary energy at a constant ME:CP ratio were provided to Ross × Ross 308 male and female broilers in equal numbers to simulate straight-run birds on live performance responses during a 38-d production period. Processing yields corresponded only to males. Dietary treatments consisted of 6 feeding regimens that provided ME concentrations from 1,350 to 1,450 kcal/lb in the starter period (0 to 17 d), from 1,370 to 1,470 kcal/lb in the grower phase (from 18 to 30 d), and from 1,400 to 1,500 kcal/lb in the final phase of production (from 31 to 38 d). In general, body weight gain and feed conversion ratio suffered when broilers consumed the regimen formulated to contain the lowest ME content compared with the 2 regimens having the highest ME concentrations. Dietary treatments did not alter the incidence of mortality, abdominal fat percentage, chilled carcass yield, or yield of carcass parts. Decreasing the energy content of diets formulated to contain a constant ME:CP ratio to suboptimum concentrations can adversely affect performance, and this may be related to inadequate caloric and CP consumption.