Medroxyprogesterone acetate in reindeer bulls: testes histology, cfos activity in the brain, breeding success, and semen quality.

Autor:	Rowell JE; Institute of Agriculture, Natural Resources and Extension, University of Alaska Fairbanks, Fairbanks, AK 99775, USA., Blake JE; Animal Resources Center, University of Alaska Fairbanks, Fairbanks, AK 99775, USA., Roth KM; School of Veterinary and Biomedical Science, University of Nebraska-Lincoln, Lincoln, NE 68583, USA., Sutton CM; Department of Animal Science, University of Nebraska-Lincoln, Lincoln, NE 68583, USA., Sachse CC; Department of Animal Science, University of Nebraska-Lincoln, Lincoln, NE 68583, USA., Cupp AS; Department of Animal Science, University of Nebraska-Lincoln, Lincoln, NE 68583, USA., Geary TW; Agricultural Research Service, USDA, Fort Keogh, Miles City, MT 59301, USA., Zezeski AL; Agricultural Research Service, USDA, Fort Keogh, Miles City, MT 59301, USA., Alexander BM; Department of Animal Science, University of Wyoming, Laramie, WY 82071, USA., Ziegler RL; Department of Animal Science, University of Wyoming, Laramie, WY 82071, USA., Shipka MP; Institute of Agriculture, Natural Resources and Extension, University of Alaska Fairbanks, Fairbanks, AK 99775, USA.
Jazyk:	angličtina
Zdroj:	Journal of animal science [J Anim Sci] 2022 Jun 01; Vol. 100 (6).
DOI:	10.1093/jas/skac106
Abstrakt:	A previous study reported that a 400-mg dose of medroxyprogesterone acetate (MPA) reduced male reindeer aggression and blocked development of secondary sexual characteristics but did not completely impair fertility. Here we have repeated that protocol in two separate trials. In 2017, tissues and blood samples, collected from MPA and control (CTL) reindeer bulls, euthanized at 30 and 60 d post-treatment were used to evaluate testes histology and morphometrics, cfos activity in the brain and androgen levels. While testes weight tended to decline from August to September in both groups, indices of spermatogenesis remained high. By September, indices of spermatogenesis were declining in both groups with sperm density lower (P = 0.05) in MPA compared to CTL bulls. Aug CTL bulls had the highest concentrations of androstenedione (A4) (P = 0.009) and testosterone (T) (P = 0.08), whereas these androgens were baseline in Aug MPA bulls. By September, A4 and T levels in CTL bulls declined to levels measured in MPA bulls. Cfos activity had a greater number (P = 0.02) of cfos positive neurons in the central amygdala in MPA compared to CTL bulls, suggesting a heightened fear response among the MPA bulls. In the second trial (2019), MPA-treated bulls, with (E, n = 4) and without (IE, n = 4) breeding experience, were blood sampled at key points from July through September when they were put in individual harems with estrous-synchronized cows. Concentrations of T were greatest (P < 0.001) among E bulls prior to MPA treatment but 1 mo after treatment, both T and A4 were baseline in all eight reindeer. Semen collected by electroejaculation at 60 d post-MPA treatment revealed only minor differences in sperm abnormalities between E and IE bulls using both fresh and frozen/thawed semen. Only three bulls (2 E and 1 IE) sired offspring. Breeding success was not related to previous breeding experience, body weight, or bull age. The failure of some MPA bulls to breed appears to be a behavioral, not a physiological, limitation. Limited application of MPA is clearly a useful tool for managing rut-aggression in non-breeding reindeer. However, the possibility that semen could be collected from MPA-treated bulls using restraint and mild sedation rather than general anesthesia should be investigated. This could improve the quality of semen collection while enhancing the safety of both handlers and animals. (© The Author(s) 2022. Published by Oxford University Press on behalf of the American Society of Animal Science. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)
Databáze:	MEDLINE
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