Implants and vaccines are proven to have positive impacts on production, but their potential for negative impacts on reproduction are sometimes overlooked.

Presenting at the 3 State Beef Conference, held in Greenfield, Iowa, Savannah, Missouri, and Syracuse, Nebraska, Craig Payne, University of Missouri Veterinary Extension and Continuing Education director, presented information producers may want to take into consideration when implanting heifer calves or vaccinating cows and heifers.

“The data is pretty conclusive that implants increase rate of gain in suckling calves,” says Payne. Implants transfer nutrient use toward increased synthesis of muscle tissue and reduced deposition of body fat. He cites a paper that summarizes the results of numerous implant studies and on average it shows a daily rate of gain increase of .1 lbs. during the payout period when compared to non-implanted calves. “In the broad range, the data suggests an increase of 10-40 lbs. on the calf during the implant period. That’s definitely a positive effect on production.”

But, implanting a replacement heifer can also impact reproductive performance, and not in a good way. Implanting heifer calves soon after birth can have a negative impact on later reproductive performance and that impact can be significant. Implanting heifers near weaning time or twice can also have a negative effect on reproductive performance.

“The general recommendation,” says Payne, “is don’t implant heifers you know will be kept as replacements.” He says those wanting to implant heifers without knowing for sure which ones they will keep, should implant heifers born in the last half of the calving season, since it is most likely producers will retain the earliest born heifers. Or, at the very least, if wanting to implant all, make sure to use an implant approved for use in suckling heifers and follow the label recommendations regarding implant timing.

Modified Live Vaccines

The decision to administer vaccines requires balancing the need for vaccination to prevent animal health issues and the future effects on the animal’s reproductive potential. Payne says producers often ask which vaccine they should use to prevent reproductive losses in the breeding herd – modified live (MLV) or killed viral vaccine. He stresses that decision should always be made with a veterinarian’s advice. “Your vet knows your operation, and the disease risk,” says Payne. “Depend on that expert opinion.”

MLV is often thought of as providing better protection because of how it stimulates the immune system. However, precautions are needed when using these vaccines in the breeding herd.

A pregnant cow or heifer should not be vaccinated with an MLV, unless the vaccine is approved for that use and she has been previously vaccinated according to label directions. “Depending on the circumstances, there is risk of causing abortion if you don’t follow the label recommendations,” says Payne.

Another precaution is related to vaccinating calves with an MLV when they are nursing pregnant cows. Again, use an MLV approved for that use and follow the label directions regarding vaccination of the dam. “The concern here is that calves vaccinated with an MLV may shed the vaccine virus thereby causing abortion in unvaccinated dams,” says Payne. He adds that while that risk may be low, he always encourages producers to follow the vaccine label just to be safe.

The final precaution is timing of administration prior to the breeding season. MLV labels often recommend administration no less than 30 days prior to the beginning of the breeding season. This is based on studies that have shown administering an MLV in previously unvaccinated animals at less than 30 days can have a negative impact on early pregnancy success. Even if the animals have been previously vaccinated, Payne still suggests trying to adhere to the label recommendations.

Killed Vaccines

Killed vaccines can be an attractive alternative when timing is an issue. They require fewer precautions than MLVs, yet provide good protection when used according to label directions.

He sites a 2017 Auburn University study that compared abortion rates in heifers given two does of MLV, once at weaning and again 30 days prior to breeding, then transitioned to annual vaccination with a product containing a killed BVD virus and temperature sensitive IBR virus, with those on an all MLV program. The two groups had similar abortion rates when challenged with BVD and IBR during their second pregnancy.

“While this is the only study I am aware of that has made this comparison, it suggests the strategy of using an MLV during heifer development and transitioning to a killed viral vaccine when they enter the breeding herd may be a viable alternative,” says Payne.

He again stresses the need to consult your vet when making vaccination decisions, and to always follow label directions and precautions. “There are reasons the label says what it does,” says Payne. “Know your risks and advantages of vaccine use. Then take into account the disease risk for your operation.”