The effect of saturation, chain length of pure triglycerides, and age of bird on the utilization of rye diets.

Four experiments were conducted with growing chicks to study the effects on performance and fat absorption of feeding rye and wheat diets supplemented with fats of different chain length and degree of saturation. In Experiment 1 it was shown that there was a much greater decrease in feed intake and fat absorption when tallow replaced safflower oil in the diets of chicks fed rye as compared to those fed wheat-based diets. Experiment 2 established the effects on chick performance of supplementing diets based on either rye or wheat with variably saturated fats. Substituting the most saturated triglyceride (C18:0) with the most unsaturated triglyceride (C18:2) in the rye diets improved the respective feed intake, weight gain, and feed conversion efficiency by 11, 75, and 40%, whereas the corresponding changes for the wheat-fed birds were -9, 9, and 16%, respectively. Experiment 3 investigated the effects on chick performance of supplementing rye-based or wheat-based diets with fats of varying chain lengths. Substituting fats containing long chain fatty acids (C18) for those containing shorter chain fatty acids (C12) resulted in respective improvements in weight gain and feed conversion efficiency of 27 and 30% in rye-fed birds and corresponding improvements of only 1 and 9% in the wheat-fed birds. A similar trend also occurred for fat absorption. The results of Experiment 4 demonstrated that older birds (35 versus 6 days of age) fed wheat-based diets absorbed only 1% more fat than younger birds, whereas when rye diets were fed, older birds absorbed 55% more fat than the younger birds. Overall it may be concluded that fat absorption in chicks is affected by chain length and degree of saturation of the fat and the age of the birds and that these factors affect rye-fed birds to a much greater degree than those birds fed wheat-based diets.