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

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 sel ected for high body weight (GL line) or for improved feed efficiency ( FC line). When reared in the normal temperature environment, overall c irculating mean and amplitude GH values of FC chickens were significan tly higher than those of GL chickens. There were no differences in GH pulse length or frequency between genotypes. The high rearing temperat ure completely abolished the pulsatility of GH in the plasma in both l ines, but without affecting overall mean GH levels. (C) 1994 Academic Press, Inc.