EFFECTS OF GROWTH-HORMONE INJECTION TO EMBRYOS ON GROWTH AND MYOSIN HEAVY-CHAIN ISOFORMS IN GROWING TURKEYS (MELEAGRIS-GALLOPAVO)

Effects of embryonic imprinting with growth hormone (GH) on growth and myosin heavy chain (MyHC) isoforms in pectoralis muscle were determin ed by injecting turkey embryos with ovine growth hormone (oGH) at a do se of 10 mu g three times a day. Injections were made on days 20 and 2 6 (Treatment 1), days 14 and 20 (Treatment 2) or days 14 and 26 (Treat ment 3) of incubation. In Treatement 1 poults, plasma GH concentration s were elevated at 3 days posthatch and in Treatment 3 poults, plasma GH concentrations were elevated at 15 days posthatch, as compared to c ontrol poults. At 4 weeks of age, in males, body weights, shank length and weights of pectoralis, gastrocnemius and sartorius muscles were i ncreased in Treatment 3, and in females, body weights, shank length an d weights of gastrocnemius muscle of female turkeys were increased in Treatment 1. The growth rate of female turkeys from 4 weeks through 16 weeks was increased by Treatment 1. Treatment 1 resulted in a delay i n the transition from the embryonic MyHC isoform to the neonatal MyHC isoform and to the adult MyHC isoform. Treatment 3 induced. an earlier appearance of the adult MyHC isoform. No effects on body and muscle g rowth and MyHC isoforms were observed by Treatment 2.