Effect of dietary probiotics and stocking density on carcass traits, meat quality, microbial populations and ileal histomorphology in broilers under hot-climate conditions

Abstract

The objective of the present study was to investigate the potential effects associated with dietary probiotic inclusion and the stocking density on carcass traits, meat chemical composition, meat sensory quality, microbial populations and ileal histomorphology in broiler chickens raised under hot climate conditions. In total, 1800 1-day-old unsexed broiler chicks (Ross 308) were randomly allocated in a completely randomised design according to a 3 × 2 factorial arrangement, with three concentrations of a dietary probiotic (0, 200 and 400 mg/kg) containing 4 × 109 cfu/g of Bacillus subtilis and two stocking densities (12 or 18 birds/m2), forming six treatments, with three pens (replicates) each. The probiotic concentration had no significant (P > 0.05) effect on bodyweight gain, feed consumption, feed conversion ratio, carcass percentage and meat chemical composition. Dietary probiotic inclusion significantly (P = 0.02) increased the scores of meat colour and odour. The acceptability score was significantly (P < 0.03) affected by the stocking density. Dietary supplementation of the probiotic at both 200 and 400 mg/kg significantly (P = 0.05) reduced the counts of Escherichia coli and Salmonella in the gut and litter. In meat, dietary supplementation of the probiotic at 200 and 400 mg/kg significantly (P = 0.03) reduced the counts of E. coli, compared with those of the control group. Moreover, Salmonella was not detected in meat. Regarding the ileal villi and crypt morphology, dietary probiotic supplementation significantly (P = 0.05) increased the height of the villus. There were no significant probiotic concentration × stocking density interactions for any of the investigated parameters, except for the gizzard percentage. Thus, dietary probiotic supplementation in broilers raised under a high ambient temperature had a significantly positive effect on the ileal villus height and a significantly negative effect on the counts of E. coli and Salmonella in the gut and litter. No negative effects on growth performance, carcass parts and meat quality were detected.