Growth-associated traits in parental and F1 populations of chickens under different feeding programs. 2. Ad libitum and intermittent feeding.

Growth traits and digestive enzyme activities were compared in parental lines and F1 crosses under ad libitum and alternate-day feeding. Responses to the feeding regimens were, in general, dependent on the background genome and age. Population by feeding regimen interactions were more prevalent for growth traits than for enzymatic activities. Although chickens adapted morphologically and physiologically to the particular feeding regimen to which they were exposed, the degree of adaptation was population dependent. Moreover, a line of White Leghorns differed considerably in response compared to a line of White Rocks selected for low body weight, demonstrating that weight is primarily a result of metabolic and behavioral processes rather than the determiner of those processes.