Effect of Feed or Water Restriction on Basal and TRH-Stimulated Growth Hormone Secretion in the Growing Turkey Poult

Abstract

Both feed and water restriction of growing turkeys resulted in an increase in the basal levels of plasma growth hormone (GH). Restricted birds also showed an increased response to thyrotropin-releasing hormone (TRH) stimulation. These changes were significantly greater in feed-restricted birds than in the water-restricted birds. After return to ad lib conditions, basal plasma GH levels remained elevated above control levels in both previously restricted groups. However, the GH response to TRH stimulation returned to normal during this period. The increase in GH secretion during undernutrition is a metabolic adjustment consistent with the known role of GH in glucose, protein and fat metabolism. The elevated GH levels present after return to adequate nutrition may aid compensatory growth.Feed and water restriction were equally effective in limiting the growth of young turkey poults. Body weight gain and feed efficiency were severely affected during the first 3 weeks of restriction, but improved during the 4th week. Return to ad lib conditions resulted in compensatory growth and markedly improved feed efficiency in both restricted groups.Feed-restricted birds showed a significant increase in water consumption after 8 days of restriction. This polydipsia may result from intermittent feeding of hungry animals. Water consumption returned to normal after 1 week of ad lib feeding. Birds restricted in water consumption voluntarily limited their feed intake to a level only slightly higher than that of the feed-restricted group. When water was supplied ad lib, these birds immediately resumed normal feed consumption.