Effect of different supplements on eggshell quality, some characteristics of gastrointestinal tract and performance of laying hens.

This study was performed to investigate the effects of antibiotic, organic acid, probiotic and prebiotic supplementation on performance, egg shell quality, pH value of gastrointestinal (GI) tract and small intestinal morphology of laying hens. The experiment was a completely randomized design with 160 laying hens strain (W-36) from 32 to 42 weeks of age, with five treatments, four replicates and eight hens in each replicate. The experimental treatments consisted of: 1-basal diet, 2-basal diet + 150 g per ton antibiotic (oxytetracycline), 3-basal diet + 3 kg per ton mixture of organic acids supplementation, 4- basal diet + 50 g per ton probiotic (protoxin) and 5-basal diet + 2 kg per ton prebiotic (mannan oligosaccharide).