Energy and protein relationships in the broiler. 1. Effect of protein levels and feeding regimens on growth, body composition, and in vitro lipogenesis of broiler chicks.

Male broiler chicks were fed ad libitum diets containing 18, 23, or 30% protein for 3 weeks. In addition, chicks were fed diets containing 12, 23, or 30% protein on a 3-day rotation. Finally, chicks were fed either the 23 or 30% protein on a schedule of 2 days on feed and 1 day off feed. These feeding schemes allowed chicks to consume low to excess protein coupled with either adequate or inadequate energy intake. Feed intakes were equal for the 18, 23, and rotational percent protein dietary groups and lower (P less than .05) for the 30% ad libitum group. Chicks fed the 18% protein diet ad libitum were the least efficient (P less than .05) at utilizing feed and the most efficient (P less than .05) at utilizing protein for weight gain. Compared to the ad libitum situation, restricted feeding improved feed and protein efficiency of chicks fed 30% protein diets but not of chicks fed 23% protein diets. Body composition data on a dry matter basis supported a positive relationship between dietary protein and percent lean tissue. Conversely, expressing data on a whole bird basis indicated that lean body mass was favored by feeding the diet containing 23% protein. In vitro lipogenesis was greatest (P less than .05) in chicks fed a 18% protein diet ad libitum and least (P less than .05) in chicks fed a 30% protein diets ad libitum.(ABSTRACT TRUNCATED AT 250 WORDS)