Effects of early-age thermal conditioning on growth performance, dressing yield, and fear response of pasture-raised broilers under acute heat stress

Le résumé fourni par la source

Heat stress is a major environmental challenge affecting the poultry industry worldwide. Early-age thermal conditioning (TC) has been studied as a strategy to mitigate heat stress in broilers, but most research has focused on conventional indoor systems. Limited information is available on the effectiveness of TC in alternative systems such as pasture-raised poultry. This study evaluated the effects of TC on growth performance, dressing yield, relative weight of immune organs, and fear response of pasture-raised broilers exposed to acute heat stress (HS) . Three hundred thirty-six Ross 308 broiler chicks were randomly assigned to four treatments. Birds were either subjected to TC or maintained at non-TC temperatures on day 5 and later exposed to either HS or non-HS conditions on days 28 and 41. Birds were processed on day 47, and growth performance, dressing yield, relative weight of spleen and bursa of Fabricius, and mortality were recorded. Fear response was assessed using the tonic immobility (TI) test before and after the first HS event. TI duration significantly decreased with repeated testing ( p ≤ 0.05), suggesting habituation to the restraint procedure. HS significantly reduced feed intake on days 28 and 41 ( p ≤ 0.05), reflecting short-term physiological responses under elevated temperatures. However, no significant interaction between TC and HS was observed for any measured variables ( p > 0.05), indicating that TC did not influence the responses to HS later in life. Under the conditions of this study, TC alone may not adequately mitigate HS in pasture-raised broilers, highlighting the need for additional management strategies.

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