Abstract:
The main aim of the present study was to investigate the changes in the relative growth of digestive organs of broilers as influenced by whole wheat feeding and age of birds. The secondary aim was to examine the effects of whole wheat feeding on broiler performance over a 5-week feeding period. Diets containing ground wheat and whole wheat (100 and 200�g/kg whole wheat replacing ground wheat during 1?21 days and 22?35 days, respectively) were placed in 4 replicate pens (46 birds/pen) each. Throughout the 5-week trial, the birds offered feed containing wheat as whole grain grew slower (P < 0.05) and consumed less (P < 0.05) feed than those offered feed containing ground wheat. Feed-to-gain ratio was not influenced (P > 0.05) by the form of wheat during the first 2 weeks, but was significantly lowered (P < 0.05) by whole wheat feeding from 3 weeks onwards. Over the 5-week period, the feed-to-gain ratio of birds fed the whole-wheat diet was 7 points better (P < 0.05) than of those fed the ground wheat diet. Improved feed efficiency from Week 3 onwards coincided with significant increases (P < 0.05) in the relative weights of the gizzard in birds fed the whole-wheat diet. Whole-wheat inclusion had no effect (P > 0.05) on the relative weights of crop, proventriculus, and pancreas or on the relative weight and length of the small intestine. The relative weights of storage sections of the gastrointestinal tract (crop, proventriculus, and gizzard) steadily declined during the 5-week period. The relative weights of pancreas and liver increased to Day 14 and decreased thereafter. The relative weights of intestinal segments were maximal during Weeks 1 and 2 of life, and declined rapidly with age. In general, the growth of different segments of the small intestine (duodenum, jejunum, and ileum) followed a similar pattern. The intestinal mass, measured as g tissue/cm tissue, steadily increased over the trial period, indicating that, although the relative size of the intestine declines with age, this decline is compensated by increased intestinal mass to support the nutrient supply function to the demand tissues.