A Comprehensive Review on Reproductive Tract Infections Causing Fetal Deaths and Abortions in Large Ruminants

Abortion in dairy cattle is commonly defined as a loss of the fetus between the age of 42 days and approximately 260 days. Pregnancies lost before 42 days are usually referred to as early embryonic deaths, whereas a calf that is born dead between 260 days and full term is defined a stillbirth Each abortion leads to significant economic loss depending on such factors as the current value of replacement stock, feed and milk prices, and the stage of gestation when the abortion occurs. The diagnosis of abortions often presents a challenge to the herd owner and the herd veterinarian. Although a gradual increase in the abortion rate in a herd may be noted over a period of many years, a sudden and dramatic increase is more commonly seen. For this reason, prompt and thorough action is required when abortions do occur. Well kept records will often be of benefit during the investigation of abortion problems. With the increased use of natural service in many dairy herds, the potential exists for venereal diseases to affect reproductive performance. These diseases have generally been of very minor concern to the dairy industry because of the widespread adoption of artificial insemination. The bacteria may not cause disease symptoms in the cow, the fetus appears to be more susceptible, in large part because of its immature immune system. The resulting growth of bacteria can cause the death of the fetus, which in turn results in it being expelled (aborted) from the uterus. Some laboratory data suggests that these bacteria are the most commonly identified cause of bacterial abortions in dairy cattle