Protein source and diet structure influence growth performance and gut health in broilers

A study was conducted by using 1-day-old mixed sex (ross 308) broilers (n=240) to test the hypothesis that a coarsely ground diet increased growth performance of broilers fed on a low digestible protein source. a high digestible soybean meal was gradually replaced by a poor digestible diet based on rapeseed meal (rsm) in three steps (rsm-0%,rsm-50%,and rsm-100%). two diet structures (fine and coarse),as an extra factor,were investigated in a factorial design with six dietary treatments. the results indicated that an increase in indigestible dietary protein decreased feed intake (fi) (p=0.005),bw gain (p=0.006) and feed conversion ratio (fcr) (p=0.023). this increase in dietary indigestible protein contents by an increase in the indigestible protein level,from rsm-0% to rsm-100%,resulted in decreased (p=0.023) villi heights (1677 vs. 1462 μm); whereas,crypt depths increased (p=0.013; 227vs. 282μm). a coarse diet improved fi (p=0.006),bw gain (p=0.014) and fcr (p=0.009). birds fed coarsely ground diets had about 12,21 and 11% lower relative empty weights of the crop,proventriculus and jejunum,respectively. the gizzard weight was approximately 15% improved in coarsely ground diets fed birds compared with those fed the fine diets. dietary coarseness resulted in approximately16% lower gizzard ph,21% greater villi heights,27% lower crypt depths,in comparison with broilers fed fine diets. in conclusion,irrespective of digestibility of the diet,coarse particles feeding improved the performance of broilers.