The effect of environmental temperature on episodic growth hormone release of meat-type chickens selected for 6 week body weight or for improved feed efficiency between 3 and 6 weeks of age.
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The effect of a high (33 degrees C) compared to a normal (23 degrees C) ambient temperature on the pulsatile release of growth hormone (GH) has been studied in 4-week-old, cannulated male meat-type chickens selected for high body weight (GL line) or for improved feed efficiency (FC line). When reared in the normal temperature environment, overall circulating mean and amplitude GH values of FC chickens were significantly higher than those of GL chickens. There were no differences in GH pulse length or frequency between genotypes. The high rearing temperature completely abolished the pulsatility of GH in the plasma in both lines, but without affecting overall mean GH levels.