Chick adaptation to diets based on milling fractions of rye varying in arabinoxylans content

The utilization of three milling fractions of rye, bran, flour and shorts was estimated on the basis of the changes that occurred in growth performance parameters, nutrient digestibility and organ weight and size in broiler chicks fed on diets containing these fractions without and with arabinoxylanase supplementation for 3 weeks. Different fractions of rye had differential effects on all estimated parameters and most of their effects appeared to be mostly associated with the content of the soluble and highly viscous arabinoxylans. Growth performance, especially the feed conversion ratio (FCR); nutrient digestibility, especially that of fat; organ size, especially the caeca and ileum were affected to a much greater degree when chicks were fed on the diet containing rye shorts, a fraction with the highest content of soluble arabinoxylans (P < 0.05). The negative effects of the different fractions, especially that of shorts, were greatly reduced when arabinoxylanase was added to the diets (P < 0.05). This effect was more evident during the first week than the third week of the study. Also the negative effects of different fractions were reduced as the time of experiment increased from 1 to 3 weeks (P < 0.05). These studies, therefore, support previous observations that the soluble and highly viscous arabinoxylans are responsible for the main antinutritive effect of rye grain and that enzyme addition to the diet can neutralize these effects. The current study also demonstrated that the negative effects associated with soluble arabinoxylans of rye could be partially overcome by either adaptation of chicks to the diet or by an increase in their age (P < 0.05). Enzyme addition, however, affected all parameters to a greater degree than occurred between the first and third weeks of the feeding period. In addition, the study demonstrated that rye shorts is a good source of the highly viscous arabinoxylans, a compound that markedly depresses chick performance. (C) 2002 Elsevier Science B.V. All rights reserved.