Effect of bee pollen and propolis (bee glue) on growth performance and biomarkers of heat stress in broiler chickens reared under high ambient temperature

This study investigated the supplemental effects of bee pollen (BP) and propolis (bee glue; BG) on broiler performance, intestinal morphometry, haematological profile and biomarkers of heat stress in broilers reared under high ambient temperature. Two hundred and forty one-day-old male broiler chickens were divided into 4 treatment groups: control; BP – supplemented with 20 g of BP · kg^–1 of feed; BG – supplemented with 3 g of BG · kg^–1 of feed; and BP + BG – supplemented with 20 g of BP · kg^–1 + 3 g of BG · kg^–1. It was estimated that dietary BP and BG improved average daily gain and average daily feed intake of broilers particularly during the starter period (P < 0.05). The relative weights of spleen and bursa of Fabricius were higher in groups fed supplemented diets when compared to the control group (P < 0.05). Biomarkers of heat stress including the circulating heterophil : lymphocyte ratio, creatine kinase level and mRNA expression of 70 kD heat shock protein (HSP70) levels in breast muscle were decreased in supplemented birds. In birds fed diets with BP and BG addition, crypts were deeper and villus : crypt ratios were higher in the jejunum segment (P < 0.05). The obtained results suggest that the dietary use of both BP and BG as a feed additive may offer a practical nutritional strategy in high temperature environment to prevail the harmful effects of heat stress in broiler.