Effect of diet form and enzyme supplementation on stress indicators and bone mineralisation in heat-challenged broilers fed wheat-soybean diet

Abstract

A study was carried out to evaluate the effect of dietary xylanase supplementation and feed form on the bone mineralisation and tibia breaking strength, serum enzyme activities, plasma minerals concentration, and heat stress biomarkers of broilers fed wheat-based diet under high ambient temperature (33 °C for 10 h, from 07.00 to 17.00 h, and 22 °C from 17.00 to 07.00 h). Two hundred and forty 1-d-old Ross 308 male broilers were allocated in six experimental treatments, each of which was replicated five times with eight broilers per replicate. A 2 × 3 factorial design was used in the study, and the main factors were composed of xylanase (with or without 300 mg/kg) and feed form (mash, crumbles, and pellets). Broilers fed crumbles or pellets had higher tibia breaking strength, plasma P concentration, and serum ALP activity than broilers fed mash. The tibia ash, Ca, and P contents in ash were greater (p < .001) for broilers fed pellets than for broilers fed mash or crumbles. The circulating heterophil-to-lymphocyte ratio, creatine kinase level, and heat shock protein 70 mRNA of breast muscle were also decreased (p < .05) by the crumbles and pellets diets. Xylanse significantly increased tibia ash, tibia Ca and P contents, ALP activity, plasma Ca and P concentrations (p < .05). The results indicate that crumbling or pelleting of the diets improved minerals retention and down-regulated heat stress biomarkers of broilers subjected to heat challenge. The results of the current study suggested that dietary addition xylanase has the potential to improve bone mineralisation. It could be concluded that feeding crumbled and pelleted diets may effective in partially ameliorating the resistance to heat stress in the birds under high ambient temperature.