PHYSIOLOGICAL VARIATIONS DURING A GRADUAL SIX-HOUR SIMULATED HEAT STRESS IN EARLY-AGE ACCLIMATED BROILERS FED LINSEED SUPPLEMENTED DIET

M. Halbouche, A. Mouats, Z. Bengharbi, M. Petkova, S. Dahmouni

Abstract: Panting is the frst and the most visible behavioral mechanism of broilers’ heat stress through which they reduce heat load by evaporation. The aim of the study was to assess the welfare of broilers reared in high ambient temperatures. It was conducted to explore the effects of broilers’ thermal conditioning (TC), 5% linseed dietary supplementation (LS) and their interaction on body weight, mortality rate and some physiological variables during a simulated gradual heat wave stress hours. 400 one-day-old chicks (ISA Hubbard 15) were allotted to 4 treatments for 5 replicates of 20 chickens each as follows: The control non-treated (C), non-acclimated and fed linseed supplemented (CL), acclimated and fed standard diet (AC) and acclimated and fed linseed (ACL). To evaluate the long lasting effects of the treatments on B°C, it was recorded over the last 10 days. Birds, at local marketing age, were exposed to a simulated heat stress during which ambient temperatures were gradually (2°C/hour) increased from 30°C and maintained at 38°C for 6 hours. At each hour, respiratory rate, blood pH and rectal body temperature of 15 birds from each group were measured and recorded and, also (for the surviving birds), their correlation with final growth weight and survival rate at finish. Results show that an impaired body weight was noticed in non-treated broilers compared to the treated birds. Linseed supplementation augmented (P<0.01) the body weight 9.11% and TC 6.52% where their combination increased it 11.35%. TC and LS reduced (P<0.01) mortality in treated birds by 33.33%. Physiological improvements during the simulated heat stress hours in LS fed animals were noticed, such as decrease (P<0.001) in rectal body temperature at 38°C as well as the respiratory rate. Consequently, pH was improved (P<0.001) during all heat stress hours in treated animals compared to C. However, the association of both factors (linseed supplementation and early-age thermal conditioning) improves thermotolerance by increasing the safety fluctuation of B°C (42.20°C to 42.80°C) at 38°C compared to Control birds (45.20°C to 45.80°C). In conclusion, LS (with its bioactive-antioxidant compounds which decrease the oxidative stress) and TC improve both body weight, survival rate and animal’s heat stress resistance of broilers by reducing B°C and blood pH during heat wave stress and, therefore, adverse heat stress impacts on broilers can be partially alleviated dietarily.

Keywords: broilers; heat stress; linseed; mortality; performance

Date published: 2017-09-04