Use of GnRH agonist implants for long term suppression of fertility in extensively managed heifers and cows

D'Occhio, Michael J., Fordyce, Geoffry, Whyte, Tim R., Jubb, Tristan F., Fitzpatrick, Lee A., Cooper, Neil J., Aspden, William J., Bolam, Matt J., and Trigg, Timothy E. (2002) Use of GnRH agonist implants for long term suppression of fertility in extensively managed heifers and cows. Animal Reproduction Science, 74 (3). pp. 151-162.

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Abstract

The ability of gonadotrophin releasing hormone (GnRH) agonist implants to suppress ovarian activity and prevent pregnancies, long-term, was examined in heifers and cows maintained under extensive management. At three cattle stations, heifers (2-year-old) and older cows (3- to 16-year-old) were assigned to a control group that received no treatment, or were treated with high-dose (12 mg, Station A) or low-dose (8 mg, Station B and Station C) GnRH agonist implants. The respective numbers of control and GnRH agonist-treated animals (heifers + cows) at each station were: Station A, 20 and 99; Station B, 19 and 89; Station C, 20 and 76. Animals were maintained with 4% bulls and monitored for pregnancy at 2-monthly intervals for approximately 12 months. Pregnancy rates for control heifers and control cows ranged from 60-90% and 80-100%, respectively, depending on the study site. The respective number of animals (heifers + cows) treated with GnRH agonist that conceived, and days to first conception, were: Station A, 9 (9%) and 336 +/- 3 days; Station B, 8 (10%) and 244 +/- 13 days; Station C, 20 (26%) and 231 +/- 3 days. Treatment with high-dose GnRH agonist prevented pregnancies for longer (approximately 300 days) than treatment with low-dose GnRH agonist (approximately 200 days). In the majority of heifers and cows treated with GnRH agonist, ovarian follicular growth was restricted to early antral follicles (2-4mm). The findings indicate that GnRH agonist implants have considerable potential as a practical technology to suppress ovarian activity and control reproduction in female cattle maintained in extensive rangelands environments. The technology also has broader applications in diverse cattle production systems.

Item ID: 13457
Item Type: Article (Refereed Research - C1)
Keywords: GnRH agonist; Ovarian Function
ISSN: 0378-4320
Date Deposited: 09 Nov 2010 23:19
FoR Codes: 07 AGRICULTURAL AND VETERINARY SCIENCES > 0702 Animal Production > 070206 Animal Reproduction @ 51%
07 AGRICULTURAL AND VETERINARY SCIENCES > 0707 Veterinary Sciences > 070799 Veterinary Sciences not elsewhere classified @ 49%
SEO Codes: 83 ANIMAL PRODUCTION AND ANIMAL PRIMARY PRODUCTS > 8303 Livestock Raising > 830301 Beef Cattle @ 51%
83 ANIMAL PRODUCTION AND ANIMAL PRIMARY PRODUCTS > 8399 Other Animal Production and Animal Primary Products > 839999 Animal Production and Animal Primary Products not elsewhere classified @ 49%
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