Acta Veterinaria Scandinavica Research Fixed-time artificial insemination in beef cattle Juhani Taponen BioMed Central Open Access Address: Department of Clinical Veterinary Sciences, Faculty of Veterinary Medicine, University of Helsinki, Paroninkuja 20, 04920 Saarentaus, Finland Email: Juhani Taponen - juhani.taponen@helsinki.fi Published: 30 November 2009 Acta Veterinaria Scandinavica 2009, 51:48 doi:10.1186/1751-0147-51-48 This article is available from: http://www.actavetscand.com/content/51/1/48 Received: 19 August 2009 Accepted: 30 November 2009 © 2009 Taponen; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract Background: The study was designed to test the effect of fixed-time artificial insemination (fixed- AI) after the slightly modified Ovsynch protocol on the pregnancy rate in beef cattle in Finnish field conditions. The modification was aimed to optimize the number of offsprings per AI dose. Methods: Ninety Charolais cows and heifers were entered into the program an average of 1.8 times. Thus, 164 animal cases were included. Animals were administered 10-12 μg of buserelin. Seven days later animals without a corpus luteum (CL) were rejected (20.7%) while the remaining 130 cases with a CL were administered prostaglandin F2α, followed 48 h later with a second injection of buserelin (8-10 μg). Fixed-AI was performed 16-20 hours after the last injection. Results: The pregnancy rate was 51.5% (67/130). The pregnancy rate after a short interval (50-70 d) from calving to entering the program was significantly higher than that after a long interval (>70 d). Conclusion: This protocol seems to give acceptable pregnancy results in beef herds and its effect on saving labour is notable. Background In breeding beef herds that produce genetically high merit breeding animals, it is necessary to use artificial insemina- tion (AI) to import new genetic material from progeny tested bulls. Oestrus detection may, however, often be fairly problematic. Animals are usually kept in big herds and they are more difficult to approach and manage than dairy cattle. It may be difficult to identify a single animal from a big herd since in many beef breeds all animals are coloured similarly. Also, time spent with beef animals is much less than with dairy cattle. In some cases, catching a single animal for AI may be problematic. Because of these reasons, the use of AI after oestrus detection in some beef herds is either impossible or at least results in a poor preg- nancy rate. According to Geary et al. [1], it is estimated that less than 5% of beef cows in the United States are arti- ficially inseminated each year. Perhaps the biggest reason that so few beef cattle are artificially inseminated is the problem of accurate detection of oestrus. Several hormonal treatments have been established to synchronise oestrus in order to facilitate and reduce time consumed on oestrus detection. Since the 1970s, when preparations of prostaglandin F2α were introduced into veterinary medicine [2-6], developing oestrus synchroni- sation programs has aroused great interest. During the first two decades, the AI after synchronisation programs was based, however, on oestrus detection, or alternatively, double inseminations on consecutive days [7-9]. In Fin- land, where the number of beef cattle is small, the semen used for breeding purposes has to be imported from abroad, and thus, it is fairly expensive. Owing to this, the Page 1 of 6 (page number not for citation purposes)