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Neonatally-induced thermotolerance: physiological responses
A A Arjona1, D M Denbow, W D Weaver
1Poultry Science Department, Virginia Polytechnic Institute and State University, Blacksburg 24061-0332.
Comparative Biochemistry and Physiology. A, Comparative Physiology
|January 11, 1990
Summary
Neonatal heat exposure in broiler chicks significantly reduced later mortality from heat stress. This early stress did not affect physiological responses but altered immune markers, suggesting different survival mechanisms.
Area of Science:
- Animal Science
- Poultry Physiology
- Environmental Stress Biology
Background:
- High environmental temperatures pose a significant threat to poultry production, leading to increased mortality and reduced performance.
- Understanding the long-term effects of early-life stress on heat tolerance is crucial for improving broiler chicken resilience.
Purpose of the Study:
- To investigate the impact of neonatal heat exposure on the subsequent thermotolerance of broiler cockerels.
- To determine if early heat stress influences physiological and immunological responses to later heat challenges.
Main Methods:
- Broiler cockerels were subjected to a 24-hour heat exposure (35-37.8°C) at 5 days of age (neonatal stress group).
- Control groups did not receive neonatal heat exposure.
- Both groups were later exposed to elevated temperatures (35-37.8°C) at 43-44 days of age, with mortality and physiological parameters assessed.
Main Results:
- Neonatally heat-stressed cockerels exhibited significantly lower mortality rates when exposed to high temperatures later in life compared to controls.
- No significant differences were observed in water consumption, core/surface temperatures, plasma T3/T4, protein, or glucose levels between groups during juvenile heat stress.
- Heterophil to lymphocyte ratios were significantly lower in the neonatally stressed group when challenged with heat at 44 days of age.
Conclusions:
- Neonatal heat exposure enhances survival during subsequent heat challenges in broiler cockerels.
- The improved thermotolerance appears to be mediated by mechanisms distinct from direct physiological acclimation, potentially involving immune system modulation.
- Early life environmental manipulation may offer a strategy to improve poultry resilience to heat stress.