Effect of bee pollen and propolis (bee glue) on growth performance and biomarkers of heat stress in broiler chickens reared under high ambient temperature
In tropical and subtropical regions, heat stress (HS) is considered as a critical problem in the poultry industry. High ambient temperatures not only cause heavy economic losses in this industry by reducing feed consumption and increasing mortality rate but have negative influence on meat quality (Chiang et al. 2008) too. Also, HS has been associated with an increased number of heterophils and decreased number of lymphocytes. In addition, HS increases heat shock proteins expression in skeletal and cardiac muscles, which may enhance the tolerance to stress and increase the survival rate of stressed cells (Kamboh et al. 2013) Recent studies showed that supplementation of natural antioxidants is a suitable strategy to minimize the deleterious effects of heat stress in broiler chickens. Propolis (bee glue; BG) which exhibits a strong antioxidant properties, was reported to improve the growth performance and egg quality in birds reared under high ambient temperatures (Seven, 2008) BG is a resinous and balsamic material collected by worker honeybees (Apis mellifera L. from tree buds, sap ABSTRACT. 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. Received: 17 March 2015 Revised: 24 February 2016 Accepted: 7 March 2016