Strategies for healthy pregnancies

There are a variety of factors that can impact the viability of cattle pregnancies. Some are within a producer’s control and others are not. The good news is there are management practices producers can put in place to prevent pregnancy loss in their herds.

First, consider some of the causes for aborted or stillborn calves. Diseases, viruses, genetics, physical trauma and severe stress can all cause an animal to lose her calf. However, in some cases, the cause is simply unknown. “In a biological unit, sometimes it just happens,” Johnny Gunsaulis, county extension agent with the University of Arkansas Division of Agriculture, said. 

Nutritional factors can lead to a loss of pregnancy. For example, high nitrates in hay or forages can lead to pregnancy loss. Additionally, improper nutrition contributes to an animal’s poor body condition which can result in a failed pregnancy. 

Diseases such as leptospirosis, vibriosis, brucellosis or trichomoniasis can all directly cause pregnancy loss. Other diseases impact pregnant cattle as well. “Pregnant animals coming into contact with either a BVD (Bovine Viral Diarrhea) carrier animal or naïve pregnant animals coming into contact with animals that have been vaccinated with modified live BVD vaccines, can experience pregnancy loss or complications with fetal development,” Gunsaulis explained.

Addressing some of these factors from a management perspective can reduce pregnancy problems. First, ensure the mommas-to-be have proper nutrition. “You have to have them in the right flesh to get them bred to start with, and to keep them there, for them to maintain that pregnancy,” Andy McCorkill, livestock field specialist with the University of Missouri Extension, said.

Livestock specialists recommend cows have a body condition score between 4 1/2 and a 7. If they are in good flesh, it reduces stress and gives them the health to fight off diseases and viruses. 

A thorough and regular vaccination protocol helps to ward off diseases that could cause cattle to abort a fetus or deliver a stillborn calf. Regardless of where producers are located, they may want to ask their veterinarian about incorporating brucellosis vaccinations for their herd. “Missouri is considered a brucellosis-free state and we don’t have to vaccinate any more for it by law,” McCorkill said. “But I still feel it is a good tool to have in our toolbelt because we are only one midnight run of a cow across a state line from somewhere from bringing it back.”

Before bringing new animals to the farm, ask the previous owners about their vaccination history. “Keep new animals quarantined from the rest of your herd for a month before mixing with your own herd,” Gunsaulis stated. 

Additionally, experts recommend when purchasing replacement females at a livestock auction, they should be at least in the second stage of pregnancy or have a calf at side. Breeding bulls should either be virgin bulls or have passed a trichomoniasis test.

To avoid pregnancy loss, producers should think about their breeding season in relation to weather conditions and fescue toxicity. When cattle are exposed to high toxins in fescue, their body temperature rises. “It funnels down to blood flow basically,” McCorkill explained. “The blood flow is restricted because of the toxins in the fescue, which makes the cow get hot quicker.”

Heat stress negatively impacts pregnancy. The first 45 days of pregnancy is the time a female is at the most risk of complications.

If producers start experiencing pregnancy loss or failed breeding in their herds, they may want to seek the advice of their veterinarian. “Consult with a vet on individual operations about what you have seen if you have a lot of problems with breeding percentages and the like, then you probably need to get a vet involved and pull some samples and see pathologically what might be going on,” McCorkill said.

There is a chance the problems are not with the females in the herd. Cattle that are open after breeding season has ended could be the result of an infertile bull. Therefore, semen testing herd bulls prior to the start of breeding season will answer that piece of the reproductive puzzle. 


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