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Biology of Reproduction, Vol 15, 335-342, Copyright © 1976 by Society for the Study of Reproduction
1 Reproduction Research Section,
University of Melbourne, and
Department of Agriculture, Victoria,
S. S. Cameron Laboratory,
Werribee, 3030, Australia The concentrations of FSH (ng NIH-FSH-S6/ml) were measured by specific radioimmunoassay
in jugular vein plasmas of 3 groups of ewes fed complete rations of alfalfa hay providing either 1/3
of a maintenance (M) requirement (1/3M, n=16), M (n=12) or 2M (n=9). The ewes were bled on
different, known days of their estrous cycle and records of live weight (LW) and ovulation rate
(OR) at the time of blood sampling were recorded. After 7 weeks the mean LW of the 3 groups
(1/3M, 35 kg; M, 42 kg; 2M, 49 kg) reflected the differential nutrition. The OR (1/3M, 0.94; M,
1.17; 2M, 1.89) was highest (P<0.05) in the 2M group, but there were no significant differences in
FSH concentration (1/3M, 79 ng/ml; M, 67 ng/ml; 2M, 67 ng/ml). The major sources of variation
in FSH level were attributed to animals (75 percent), day (16 percent) and hour (9 percent) of
blood sampling. There was no correlation of either LW or OR with FSH concentration. In a second experiment ewes were fed on similar planes of nutrition (1/3M, n=3; M, n=10; 2M,
n=3) for 6 weeks. On Days 10-12 of the estrous cycle the metabolic clearance rate (MCR) (0.605
ml/min/kg) in 7 ewes with one ovulation was not significantly different (P>0.05) than the MCR of
FSH (0.621 ml/min/kg) in 8 ewes with 2 ovulations. The FSH response to GnRH (2.5 µg/h for 4.5
h), measured 2 days after the MCR studies, appeared to be inversely related to number of corpora
lutea (0.05<P<0.10). The peripheral concentration of FSH (72.7 ng/ml) in 37 ewes during the breeding season was
higher (P<0.05) than in 13 lactating(58.4 ng/ml) or 45 nonlactating (59.4 ng/ml) anestrous ewes.
Note:
ACKNOWLEDGMENTS
These investigations were supported by grants from
the Australian Wool Research Trust Fund and the
Australian Meat Research Committee. We are indebted
to the NIH, Bethesda and Dr. H. Papkoff, University
of California for supplying preparations of FSH and
Mr. W. White of Abbott Laboratories, Illinois for
supplying GnRH. The technical assistance of Peter
Langdon, Ron Parr and Robert Baxter in conducting
the experiments and Julie Robinson and Enid Pruysers
for the hormone assays is gratefully acknowledged.
Our thanks to Lyn Bourke for typing the manuscript.
This article has been cited by other articles:
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  C Vinoles, M Forsberg, G B Martin, C Cajarville, J Repetto, and A Meikle Short-term nutritional supplementation of ewes in low body condition affects follicle development due to an increase in glucose and metabolic hormones Reproduction, March 1, 2005; 129(3): 299 - 309. [Abstract] [Full Text] [PDF]
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