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Journal of Animal Science, Vol 79, Issue 11 2895-2901, Copyright © 2001 by American Society of Animal Science

JOURNAL ARTICLE

Nocturnal melatonin and prolactin plasma concentrations in sheep selected for fertility in autumn lambing'

D. R. Notter and P. Chemineau
Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24060, USA. drnotter@vt.edu

Ewes selected for fertility in autumn lambing were used to evaluate correlated responses in nocturnal hormone levels. Four jugular blood samples were obtained during nighttime in August from each of 113 selected and 69 control ewes. Melatonin levels were lower for selected ewes (143 +/- 14 pg/mL) than for control ewes (184 +/- 13 pg/mL), and melatonin levels decreased with increases in estimated breeding values (EBV) for fertility (-2.23 +/- 0.79 pg mL(-1) x %(-1)). Prolactin levels were higher for selected ewes (90 +/- 7 ng/mL) than for control ewes (52 +/- 7 ng/mL), but significant line x ewe age interaction was also observed, with smaller differences in prolactin levels in 2-yr-old and older ewes (74 +/- 7 vs. 56 +/- 9 ng/mL for select and control ewes, respectively; P < 0.20 before and P = 0.05 after logarithmic transformation). Prolactin levels increased with both fertility EBV (1.23 +/- 0.53 ng mL(-1) x %(-1)) and maternal birth weight EBV (9.0 +/- 4.0 ng x ml(-1) kg(-1)). Heritability estimates were 0.43 (P < 0.02) for melatonin levels and 0.11 (P > 0.25) for prolactin levels. Thus, we conclude that selection for fertility in autumn lambing has affected patterns of melatonin and prolactin secretion during the dark phase.


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D. R. Notter, N. E. Cockett, and T. S. Hadfield
Evaluation of melatonin receptor 1a as a candidate gene influencing reproduction in an autumn-lambing sheep flock
J Anim Sci, April 1, 2003; 81(4): 912 - 917.
[Abstract] [Full Text] [PDF]


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Copyright © 2001 by the American Society of Animal Science.