J. Anim Sci.
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J. Anim. Sci. 2003. 81:E28-E36
© 2003 American Society of Animal Science

The use of controlled internal drug release devices for the regulation of bovine reproduction1

R. J. Mapletoft*,2, M. F. Martínez*, M. G. Colazo* and J. P. Kastelic{dagger}

* Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada and and {dagger} Agriculture and Agri-Food Canada, Research Centre, Lethbridge, AB T1J 4B1, Canada

2 Correspondence: 52 Campus Dr. (phone: 306-966-7149; fax: 306-966-7159; E-mail: reuben.mapletoft{at}usask.ca).

Our knowledge of bovine estrous cycle physiology has expanded greatly in recent years, primarily with the advent of ultrasonography to monitor ovarian follicles. With increased knowledge, new methods of manipulating ovarian function have become available. The use of controlled internal drug release (CIDR) devices for the synchronization of estrus in cattle is now well accepted throughout the world. In fact, Canada and the United States are among the last countries in the world to have CIDR devices available for use in bovine practice. The use of CIDR devices, along with other hormones that are already on the market (e.g., gonadotropin releasing hormone) has permitted fixed-time artificial insemination with high pregnancy rates in beef cattle. New approaches, such as the use of estradiol in CIDR-based protocols, offer novel and exciting ways to manipulate the bovine estrous cycle. Recent studies suggest that steroid hormones readily available on the veterinary pharmaceutical market, such as estradiol cypionate and injectable progesterone, can be successfully used to synchronize follicular wave emergence and ovulation in CIDR-based, fixed-time artificial insemination programs. Experiments described in this report include several protocols that do not require detection of estrus, thereby permitting fixed-time artificial insemination in beef cattle. Over a 5-yr period, pregnancy rates to a single fixed-time artificial insemination have ranged from 55 to 77% in heifers and slightly less in lactating beef cows.

Key Words: Artificial Insemination • Cattle • Controlled Release • Estradiol • Gonadotropin-Releasing Hormone • Luteinizing Horomone






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