Benefits and Risks of Preventing Twin Pregnancies

SIMPLE SUMMARY: While cows usually give birth to singletons, the incidence of twin births has increased considerably during the past few decades alongside milk production. In most cases, multiple pregnancies arise from the simultaneous formation of two or more ovulatory follicles in either the same ovary or both ovaries. Twin pregnancies have devastating effects on cow welfare and the economy of dairy herds. To prevent them, strategies proposed have been the transfer of a single female beef cow embryo produced in vitro to a cow that is not suitable for producing replacements, or the drainage of co-dominant follicles at insemination to prevent twin pregnancies in cows with genetic merit. Developing strategies to reduce the incidence of multiple ovulations and twin pregnancies should be a main focus of clinicians responsible for reproduction in dairy herds. The two procedures mentioned could be components of a weekly reproductive control program and applied to synchronized cows. As a result, embryo survival should improve, avoiding economic losses associated with twin pregnancies, and beef output from the herd will accordingly increase. Last but not least, if twin pregnancies are prevented, the cow’s general health and welfare state will certainly improve. ABSTRACT: Clinical problems associated with twin pregnancies have been well established, and twin births are now considered undesirable or even disastrous for the dairy cattle industry and the individual cow. The high incidence of early fetal loss, abortion during the mid-lactation period, dystocia, stillbirth, and placenta retention should be considered a preventable consequence of management, as these disorders greatly compromise the welfare and productive lifespan of a cow carrying or delivering twins. The use of sexed semen generates herd replacements and additional heifers, so a proposed strategy for twin pregnancy prevention is the transfer of a single in vitro-produced female beef cow embryo to cows not suitable for producing replacements. Another proposed strategy is drainage at insemination of co-dominant follicles to prevent twin pregnancies in cows with genetic merit. As a result, embryo survival should improve, economic losses associated with twin pregnancies will be prevented, beef output from the herd will be increased, and the health and welfare of the cow will certainly benefit. In this review, the clinical prospects of preventing or avoiding twin pregnancies using both procedures are discussed.