An Adaptive Growth Response of Chicks Fed Rye

Day-old Arbor Acre male broiler chicks were fed 55%-rye diets with or without antibiotic supplements in three 14-day experiments. Procaine penicillin, chlortetracycline, or bacitracin methylene disalycilate were added individually to the rye basal diet at a concentration of 55 p.p.m. Weight gain and feed consumption were calculated at two-day intervals in all experiments. Chicks fed the antibiotic supplemented diets grew better than chicks on the basal diet. In each experiment chicks fed the unsupplemented diet gained weight at a linear rate for about the first eight days and exponentially thereafter. Feed conversion ratios (feed/gain) for chicks on the basal diet, calculated for each two-day interval, increased rapidly reaching a peak after eight days on the diet. Thereafter, the feed conversion ratios of the chicks on the unsupplemented diet declined until the 13—14 day interval when the experiments were terminated. All chicks exhibited a sticky feces condition regardless of the presence of antibiotics in their diet. It is concluded that young chicks adapt to diets containing rye. The adaptive response in these experiments occurred after the chicks had been on the diet for about eight days. Since the adaptation occurred only in chicks fed the unsupplemented diets, it is suggested that the adaptation is due to a change in the gut bacterial population.