Effects of feed form and particle size, and pellet binder on performance, digestive tract parameters, intestinal morphology, and cecal microflora populations in broilers

Abstract

This study was conducted to assess the effects of feed form (FF), particle size (PS), and pellet binder (PB) on performance, digestive tract parameters, intestinal morphology, and cecal microflora populations in broiler chicks. Two FF (mash and pellet), two feed PS (fine and coarse), and two levels of PB (0 and 3%) were evaluated in a completely randomized design with a 2 × 2 × 2 factorial arrangement of treatments. A total of 256 one-day-old male Ross 308 chicks were allocated into 8 treatments consisting of 8 replicates (4 birds/cage) with equal weight from 25 to 42 d of age. The results showed a three-way interaction among FF, PS, and PB for growth performance in broilers. The growth performance parameters were significantly improved by feeding the pellet-coarse PS-3% PB diet in comparison to the other treatments (P < 0.05). Birds fed pelleted diets had lower relative weight of the gizzard and pancreas, goblet cell (GC) number of the duodenum, crypt depth (CD) of the jejunum, higher villus height (VH) of the duodenum, and cecal spore-forming bacteria population (P < 0.05). Coarse PS resulted in lower jejunum CD and higher cecal count of lactic acid bacteria (LAB) and spore-forming bacteria (P < 0.05). Adding PB significantly improved pellet durability index (PDI) (P < 0.05). In addition, coarse PS-3% PB diets had higher pellet hardness. Also, adding PB to diets significantly (P < 0.05) decreased cecal spore-forming bacteria population. Pellet-coarse PS-3% PB diets fed broilers had a lower (P < 0.05) cecal Clostridium spp. bacterial population. The main factors had no significant effect (P > 0.05) on cecal Coliform spp. levels. Birds fed pellet-3% PB diets had higher VH:CD ratio both in the duodenum and jejunum, and those fed mash-3% PB diets had significantly (P < 0.05) lower VH in the jejunum than other treatments. Overall, pellet-coarse PS-3% PB diets improved growth performance through the positive changes on intestinal morphology of broilers under short-term conditioning (STC).