Reproductive efficiency in lactating dairy cows has sharply declined in the last two decades and the two major components of infertility in cattle are low conception rates and suboptimal embryo survival. Our current and future research plans are directed towards improving conception rates and embryo survival in high producing lactating dairy cows through nutritional and hormonal means. We have conducted a series of experiments to evaluate the effects of fatty acids and gossypol on fertility of dairy cattle. We have also studied hormonal methods to manipulate the estrous cycle of dairy cattle to improve reproductive efficiency by minimizing anestrous and improving response to synchronization programs. Some of those studies involved basic aspects of fertilization and embryo development. A substantial component of our research program is implementation of reproductive programs in large scale dairy farms to evaluate their impacts on fertility of cattle.
References for some of the projects:
Cerri et al. 2004. Timed artificial insemination with estradiol cypionate or insemination at estrus in high-producing dairy cows. J. Dairy Sci. 87: 3704-3715.
Chebel et al. 2004. Factors affecting conception rate after insemination and pregnancy loss in lactating dairy cows. Anim. Reprod. Sci. 84:239-255.
Santos et al. 2004. The effect of embryonic death rates in cattle on the efficacy of estrous synchronization programs. Anim. Reprod. Sci. 82-83C: 513-535.
Santos et al. 2004. Effect of bST and reproductive management on reproductive and lactational performance of Holstein dairy cows. J. Dairy Sci. 87: 868-881.
Santos et al. 2004. Effect of timing of first clinical mastitis occurrence on lactational and reproductive performance of Holstein dairy cows. Anim. Reprod. Sci. 80: 31-45.
Santos et al. 2004. Effect of a deslorelin implant in a timed artificial insemination protocol on follicle development, luteal function and reproductive performance of lactating dairy cows. Theriogenology 61:421-435.
Thatcher et al. 2003. Regulation of embryo survival in cattle. Reproduction Supplement 61: 253-266.
Santos et al. 2003. Type of cottonseed and gossypol in diets of lactating dairy cows: Plasma gossypol, reproduction, and health. J. Dairy Sci. 86: 892-905.
Contact Dr. José Santos for additional information: jsantos@vmtrc.ucdavis.edu