Enhanced Luteinizing Hormone Release by Luteinizing Hormone ...

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(FSH)-induced steroidogenesis (Camper and Burke, ... Ope1 (1981) and Burke et al. ..... Garcia A, Herbon A, Barkan A, Papavasiliou S, Marshall JC, 1985.
BIOLOGY OF REPRODUCTION 36,884-889 ( 1 9 8 7 )

Enhanced Luteinizing Hormone Release by Luteinizing Hormone-Releasing Hormone in Incubating Female Turkeys (Meleagris gallopavo)' M. E. EL HALAWANI,' S. C. FEHRER, and J . L. SILSBY Department o f A n i m a l Science University of Minnesota S t . Paul, Minnesota 55108 ABSTRACT

To determine what role pituitary responsiveness plays in the suppression of gonadotropin level during incubation in the turkey, the ability o f the pituitary to release luteinizing hormone ( L H ) in response t o luteinizing hormonereleasing hormone ( L H R H ) was compared in incubating, laying, and photorefractory birds. In all three groups, the i.m. injection of LHRH (4 pg/kg) increased serum LH levels; however, the LH response was markedly enhanced in the incubating turkeys as compared with the laying (6.6-fold increase over preinjection levels vs. 1.9-fold; p c 0 . 0 5 ) or the photorefractory birds (9.'/-fold vs. 3.1 -fold; p c 0 . 0 5 ) . The LHRH-induced LH release was also determined in turkeys as t h e y shifted f r o m the laying to the incubating phase of the reproductive cycle. This response increased (p