J. Anim Sci.
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J. Anim Sci. 1979. 49:543-553.
© 1979 American Society of Animal Science
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Secretory Patterns and Circadian and Seasonal Changes in Luteinizing Hormone, Follicle Stimulating Hormone, Prolactin and Testosterone in the Male Pygmy Goat1

D. S. Muduuli2 ,4,, L. M. Sanford2 ,3,, W. M. Palmer2 and B. E. Howland3

University of Manitoba, Winnipeg, Canada R3T 2N2

Abstract

Four male pygmy goats were 9 months of age when assigned to this experiment. They were maintained for 1 year beginning in June 1975 under natural photoperiod changes characteristic of southern Canada and ambient barn temperatures ranging from 5 to 25 C. During the third week of each month, bucks were bled from a jugular vein by venipuncture at 30-min intervals for either 12 or 24 hr (August, November, February and May). Sera were assayed for luteinizing hormone (LH), follicle stimulating hormone (FSH), prolactin (PRL) and testosterone (T) by radioimmunoassay. Both LH and T were secreted episodically, and increases in serum LH were generally followed by increased serum T concentrations which peaked within 60 minutes. Mean serum LH, T and PRL concentrations fluctuated considerably over the 24-hr periods with peak PRL concentrations generally occurring during the dark period. However, serum FSH concentrations did not show a pulsatile profile and variations over the 24-hr were minimal.

Serum LH and T increased with decreasing daylength and attained maximum mean values (± SE) in October of 1.9 ± .5 ng NIH-LH-S14/ml and 15.4 ± .9 ng/ml, respectively. These increases were a result of higher baseline levels and peak frequencies. Lowest mean serum concentrations of LH (.4 ± ,1 ng/ml) and T (2.3 ± .5 ng/ml) occurred in November and June, respectively. Serum FSH increased slightly in September, but the highest concentration occurred in April (67.8 ± 4.4 ng NIH-FSH-S6/ml). Changes in serum PRL concentration paralleled changes in daylength (r = .58, P<.05). Seasonal changes in serum concentrations of LH, PRL, and T in the male pygmy goat follow closely the changes that have been reported for rams, which are also a seasonal breeder under temperate climatic conditions.

Footnotes

1 Presented in part at the 70th Annual Meeting of the American Society of Animal Science, East Lansing, MI. The study was supported by grants from the Canadian International Development Agency (CIDA-Project No. 942-00101) and the National Research Council of Canada (Grant No. A6251). The authors gratefully acknowledge the technical assistance of Mr. D. B. Beaton and Drs. F. Chebib and C. Dawes for their advice and help with the statistical analysis.

2 Department of Animal Science.

3 Department of Oral Biology.

4 Recipient of a CIDA scholarship.






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