Environment

The Role of Prolactin in Reproductive Failure Associated with Heat Stress in the Domestic Turkey

Abstract
Reproductive failure associated with heat stress is a well known phenomenon in avian species. The increased prolactin (PRL) levels in response to heat stress have been suggested as a mechanism involved in this reproductive malfunction. To test this hypothesis, laying female turkeys were subjected to 40°C for 12 hr, daily or maintained under thermoneutral conditions (24-26°C). Birds in each group received oral treatment with parachlorophenyalanine (PCPA; 50 mg/kg BW/day for 3 days), an inhibitor of serotonin (5-HT) biosynthesis, or immunized against vasoactive intestinal peptide (VIP). Either treatment is known to reduce circulating PRL levels. Non-treated birds were included as controls. In the control group, high ambient temperature terminated egg laying, induced ovarian regression, reduced plasma luetinizing hormone (LH) and ovarian steroids (progesterone, testosterone, estrogen) levels and increased plasma PRL levels and the incidence of incubation behavior. Pretreatment with PCPA reduced (P<0.05) heat stress induced-decline in egg production, -increase in PRL levels, and -expression of incubation behavior. Plasma LH and ovarian steroids levels of heat stressed birds were restored to that of controls by PCPA treatment. As in PCPA treated birds, VIP immunoneutralization of heat stressed turkeys reduced (P<0.05) circulating PRL levels and prevented the expression of incubation behavior. But, it did not restore the decline in LH, ovarian steroids and egg production (P> 0.05). The present findings indicate that the detrimental effect of high temperature on reproductive performance may not be related to the elevated PRL levels in heat stressed birds, but to mechanism(s) that involve 5-HT neurotransmission and the induction of hyperthermia.

Key words: Ovary • Luteinizing hormone • Pituitary hormones • Prolactin • Stress

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				I. Rozenboim, E. Tako, O. Gal-Garber, J. A. Proudman, and Z. Uni The Effect of Heat Stress on Ovarian Function of Laying Hens Poult. Sci., August 1, 2007; 86(8): 1760 - 1765. [Abstract] [Full Text] [PDF]

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