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Evaluation of growth, hormonal, and hematological responses of neonatal chickens to reduced temperature brooding
Insights
Reduced brooding temperatures in broiler chicks led to lower body weight and altered hormone levels, including corticosterone and thyroxine. Further research can improve cold tolerance through genetic selection.
Area of Science:
- Animal Science
- Poultry Science
- Environmental Physiology
Background:
- Neonatal broiler chicks are sensitive to environmental temperatures.
- Brooding temperature significantly impacts early growth and physiological responses.
Purpose of the Study:
- To investigate the physiological and growth responses of neonatal male broiler chicks to reduced brooding temperatures.
- To assess the impact of cold stress on key serum hormone levels.
Main Methods:
- Broiler chicks were subjected to different brooding temperatures (26.7°C vs. 32.2°C) in multiple trials.
- Body weight, weight gain, and serum levels of corticosterone, thyroxine, growth hormone, total protein, albumin, and globulin were measured.
Main Results:
- Lower brooding temperatures (26.7°C) resulted in reduced body weight and weight gain.
- Elevated serum corticosterone and thyroxine levels were observed in chicks brooded at reduced temperatures.
- Serum growth hormone levels showed initial depression followed by elevation under cold stress.
Conclusions:
- Reduced brooding temperatures induce physiological stress responses in neonatal broiler chicks.
- Hormonal responses, particularly corticosterone and thyroxine, are indicative of cold adaptation.
- Evaluating genetic variation in hormone responsiveness could enhance tolerance to reduced brooding temperatures through selective breeding.
Abstract:
A series of experiments was conducted to examine the response of neonatal, male broiler chicks to brooding at a reduced temperature. In Trials 1 and 2, chicks brooded at 26.7 C generally had lower body weights and higher serum corticosterone levels during the first week after hatch than those brooded at 32.2 C. However, significant differences in body weight were observed only on Day 6 in Trial 1 and on Days 1 and 5 in Trial 2. Serum corticosterone levels, likewise, were not significantly different on all days in Trials 1 and 2. These hormone levels were statistically different on Days 1 and 5 in Trial 1 and on Days 1 and 3 in Trial 2. Brooding neonates at 26.7 C for 3 days in Trials 3 and 4 resulted in consistently lower body weights and gain and higher serum corticosterone, thyroxine, total protein, albumin, and globulin. Serum growth hormone levels in chicks brooded at 26.7 C were initially depressed the first day but were elevated on the 2 subsequent days, compared with chicks brooded at 32.2 C. Considering the physiological importance of corticosterone and thyroxine in the adaptation of chickens to cold environmental temperatures, it would be useful to evaluate the genetic variation associated with the responsiveness of these hormones in a randombred population and to improve tolerance of neonatal chickens to reduced temperature brooding through selection.