An “abortion” is the discharge of the fetus prior to the end of the normal gestation period, according to Gerald Stokka, North Dakota State University Extension veterinarian and livestock stewardship specialist. Many abortions occur within the first 45 days of conception (called early embryonic death), and the embryos or fetuses are so small that they may not be seen.
Other abortions may occur near normal calving time, and determining whether the cow has aborted or a premature birth has occurred is difficult. A stillbirth is when a full-term calf is born dead, with no obvious evidence of the cause of death.
Abortions have many causes, including physiological causes such as extreme environmental or handling stress and hormonal imbalances, metabolic problems, toxicoses and/or infectious diseases caused by protozoa, fungi, bacteria or viruses, says Brett Webb, director of the NDSU Veterinary Diagnostic Laboratory.
Abortions and stillbirths can be the result of a direct effect, such as viral, bacteria or protozoal organisms gaining access to the fetus. The fetus also may have abnormal development (congenital defects) that results in abnormalities at delivery, such as a lack of the anus opening or inside-out calf, or inherited genetic defects such as “curly calf” or “fawn calf” syndrome.
Indirectly, abortions and stillbirths can be a result of an interruption of the connection between the fetus and the dam, or the illness of the dam. The fetus receives nourishment and oxygen via the organ called the placenta. Any disruption in that process can impact the fetus negatively or result in its death, Stokka says.
Inflammation of this organ is called “placentitis.” Bacterial, fungal and protozoal infections can cause placentitis. Mycotic abortions are one of the more common results of fungal infections. Mouldy feeds are implicated as the source of most fungal infections.
Stillbirths can be frustrating because producers often see no indication of the cause or evidence of excessive labour. Stillbirths can result from an umbilical cord rupture, premature separation of the placenta or the placenta blocking the calf’s nostrils after the delivery of an otherwise healthy calf.
Regardless of the cause, abortions may be sporadic or they may occur as “storms.” The normal abortion or stillbirth rate would be one to two per cent of cows in a herd. Losses greater than this are abnormal, and producers should talk to their veterinarian for assistance in identifying the cause, NDSU Extension livestock systems specialist Karl Hoppe advises. Hoppe also recommends producers to keep good records of calf and cow losses because indemnity payments may be available to offset some of the losses.
“The best chance of identifying what caused an abortion is prompt submission of fetal and placental tissues and maternal blood or serum to a diagnostic laboratory,” Stokka says. “Contact your veterinarian for assistance with diagnostic efforts, sample submission and identifying management strategies to reduce the risk of future abortions.”