Cow and Reproductive Performance

Sex preselection in cattle: a field trial D.G. Cran, L.A. Johnson, C. Polge Veterinary Record (1995) 136, 495-496 Producing livestock progeny of a predetermined sex has been a long sought goal of producers worldwide. Benefits would be expected to follow in terms of genetic improvement and farm management and the tailoring of offspring to meet particular market demands. In spite of numerous approaches to the problem only one procedure has stood the test of laboratory validation and appropriate skewness of the sex ratio of the progeny. This procedure (Beltsville Sperm Sexing Technology) is based on the well established difference in total DNA content between mammalian Xand Y-chromosome bearing sperm (Johnson 1992). The separation is carried out by flow cytometric sorting of individual sperm (Johnson and others 1989, Johnson 1991, Cran and oth42 L.C., R.H. Ingraham and E.B. Morgan. 1984. Plasma copper concentration and packed ALI volume and their relationships to fertility and milk production in Holstein cows. Am. J. Vet. Res. 45:346. 14. King, J.O.L. 1971. Nutrition and fertility in dairy cows. Vet. Rec. 89:230. 15. Maas, J. 1987. Relationship between nutrition and reproduction in beef cattle. Vet. Clin. N. Amer.: Food Anim. Prac. 3:633. 16. Manspeaker, J.E., M.G. Rohl, G.H. Edwards and L.W. Douglass. 1987. Chelated minerals: Their role in bovine fertility. Vet. Med. 82:951. 17. McDowell, L.R. 1985. Nutrition of grazing ruminants in warm climates.Academic Press Inc., NewYork. 18. O'Dell, B.L. 1984. Bioavailability of trace elements. Nutr. Rev. 42:301. 19. Phillippo M., W.R. Humphries, T. Atkinson, et al. The effect of dietary molybdenum and iron on copper status, puberty, fertility and estrus cycles in cattle. J. Agric. Sci. 109:321. 20. Pitts, W.J., W.J. Millers, O.T. Fosgate, et al. 1966. Effects of zinc deficiencies and restricted feeding from two to five months of age on reproduction in Holstein bulls. J. Dairy Sci. 49:321. 21. Pugh, D.G. et al. 1985. A review of the relationship between mineral nutrition and reproduction in cattle. Bou. Prac. 20:10. 22. Puls, R. 1991. Mineral levels in animal health. Sherpa International. Clearbrook, British Columbia, Canada. 23. Spears, J.W. 1994. Minerals in forages. In: Forage quality, evaluation, and utilization. G.C. Fahey, Jr. (ed.),American Society of Agronomy, Inc. Madison, Wisconsin. 24. Thomas,. J.W. and S. Moss. The effect of orally administered molybdenum on growth, spermatogenesis and testes histology in young dairy bull. J. Dairy Sci. 34:929. 25. Underwood, E.J. 1966. The mineral nutrition oflivestock. The Central Press, Ltd., Great Britain. 26. Wilson, T.G. 1966. Bovine functional fertility in Devon and Cornwall: Response to manganese therapy. Vet. Rec. 79:562. ers 1993) and the separated sperm populations may be either inseminated surgically or used for in vitro fertilization (IVF). These reports have demonstrated skewness of the sex ratio in rabbits, pigs and cattle ranging from 70 to 90 percent. In an initial study to produce progeny in cattle, Cran and others (1993) reported the birth of six calves using this technology; all the calves were of the predicted sex. The present report is an extension of these studies carried out in a field trial in which Y sperm only were sorted, then used for IVF to produce embryos for transfer to recipient cows. They reportthe birth of 41 calves that had a sex ratio of 90 percent male. THE BOVINE PRACTITIONER-NO. 29