Effect of different feed particle size on digestive tract morphology, digesta viscosity, nutrient retention, and blood biochemical parameters in slow-growing broiler chickens.

The study evaluated the effect of feed particle size on health and performance indicators in slow-growing broiler chickens. Performance traits, digestive tract morphology, digesta viscosity, nutrient retention, and blood biochemical parameters were assessed in 120 one-day-old male Hubbard JA57 broilers divided into three dietary groups with five replicates, differing only in feed particle size: coarse (CG), medium (MG), and fine (FG). The Geometric Mean Diameter (GMD) of grower and finisher was 1.06 mm for CG, 0.89 mm for the MG and 0.66 mm for the FG. Broilers fed by coarse diet had higher weight (P< 0.05) of the proventriculus and the gizzard and higher weight of ileum. Duodenal villi were higher (P< 0.05) in the CG than in the FG. Jejunal and ileal crypts were deeper (P< 0.05) in the CG in contrast with the MG. Ratio between the villus height and crypt depth differed in jejunal and ileal part, where the MG reached higher values (P< 0.05). There were observed differences (P< 0.05) in nutrient retention, where nitrogen and starch retention were increased by CG. On the other hand, the ether extract retention increased (P< 0.05) in fine mashed particles in the diet. The differences in feed intake, performance parameters, digesta viscosity and the blood biochemical parameters were not significant. Under the conditions of the present study in slow-growing broiler chickens, dietary particle size did not affect growth performance or blood biochemical indices but significantly influenced digestive tract morphometry and nutrient retention.