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This Article Full Text Full Text (PDF) All Versions of this Article: jas.2006-589v1 85/4/944    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Shipka, M. P. Articles by Sousa, M. C. Search for Related Content PubMed PubMed Citation Articles by Shipka, M. P. Articles by Sousa, M. C.

Steroid hormone secretion during the ovulatory cycle and pregnancy in farmed Alaskan reindeer¹

M. P. Shipka^*,,2, J. E. Rowell^* and M. C. Sousa^*,

^* Department of Plant, Animal and Soil Sciences, School of Natural Resources and Agricultural Sciences, University of Alaska, Fairbanks 99775; and Department of Allied Health, Tanana Valley Campus, University of Alaska, Fairbanks 99775; and and Center for Reproductive Biology, Washington State University, Pullman 99164

² Corresponding author: ffmps{at}uaf.edu

Seasonal endocrine changes in 5 non-bred and 10 pregnant Alaskan reindeer have been documented. Blood samples were collected from early September until early May, spanning the breeding season, gestation, or the anovulatory period. Plasma was analyzed by RIA for progesterone (P₄), estradiol-17ß, estrone, and estrone sulfate. Elevated P₄ in 80% of the reindeer at the onset of the study indicated that ovarian activity had been initiated. The median date for the onset of the first recorded full-length ovulatory cycle was September 23. In nonbred reindeer, the mean ovulatory cycle length from September to May was 24 ± 1 d (range 18 to 29 d). Nonbred females continued to cycle throughout the winter, displaying 6 to 8 ovulatory cycles after the beginning of blood sampling. Cycle length (mean 22 to 24 d) did not vary between individuals (P = 0.170) or over the course of the winter (P = 0.244). In early April, ovulatory cycles ceased with normal demise of the corpus luteum in 2 females, whereas the remaining 3 females formed apparently persistent corpora lutea. Natural service breeding occurred between September 10 and October 2, and P₄ profiles indicated that all breeding females conceived to the first mating. Concentrations of P₄ rose steadily after conception and remained elevated throughout gestation, with mean concentrations not varying significantly (P = 0.104) from 4 to 28 wk of gestation. Estrogens all followed patterns similar to each other, remaining at baseline concentrations until approximately 24 wk of gestation and rising coincidently as P₄ declined just before parturition. There was a continual overlap throughout the winter in peak P₄ concentrations observed in cycling and pregnant reindeer. Calving occurred between April 8 and May 2, resulting in a mean gestation length of 211 ± 2.2 d (range 198 to 221 d). Information from this study can be used by Alaskan reindeer producers to improve management and profitability of reindeer production.

Key Words: estrogen • gestation length • ovulatory cycle • pregnancy • progesterone • reindeer