Scours prevention begins during the dry period

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Pregnancy checking time represents an opportunity for producers to perform other procedures at the same time. For some producers, vaccinating cows is on this list of tasks. But just because it’s handy for us, will it work for the cow?  

There are two main reasons most producers vaccinate cows. One of them is for infectious reproductive pathogens that can cause harm to the developing fetus.  The other is that of the calf scours complex, which includes vaccinations against neonatal diarrhea pathogens such as rotavirus, coronavirus, clostridial organisms and E. coli strains. 

Vaccination programs against calf scours have a unique goal. Here we are attempting to raise the level of antibodies in the cow’s bloodstream so that when she starts manufacturing colostrum for her calf, a high concentration of those antibodies will be there in the colostrum when the calf nurses in those first hours of life. It’s an indirect way of providing immunity to the calf. 

Is preg-check time the best time to stimulate this immune response in a cow? We know that a cow begins the process of moving antibodies from the bloodstream to the mammary tissue no sooner than about 5 weeks before she calves. Her blood antibody level at that late stage of gestation is the determining factor in how much antibody is present in the colostrum. 

There are a wide variety of calf scours vaccines on the market, and each of them has different recommendations for vaccine timing. Some are labeled to be given as early as 16 weeks prior to the expected calving date; others may require administration closer to calving. Vaccine manufacturers base these recommendations on their product’s ability to show increased levels of antibody in colostrum when cows are vaccinated at those particular stages of gestation. 

There’s a great temptation by some producers to use these vaccines at pregnancy checking to take advantage of the obvious labor savings, but some basic immunology should be kept in mind. If it takes 1-2 weeks for the cow’s body to show a peak response to the vaccine, this means the best time to stimulate this immunity would be no sooner than about 7 weeks prior to calving.  Later is better (up to a point) when using scours vaccines.

Does this mean that a scours vaccine given to cows too far ahead of calving is worthless? No, not really. But we would expect that, when compared to cows vaccinated later, those early-vaccinated animals would have a waning immune response by the time they start making colostrum, and therefore a lower concentration of antibodies for the calf. 

Calf scours is a disease complex that results from many factors, including overwhelming exposure to germs, environmental conditions, and poor colostrum uptake by calves. It’s entirely possible that herds could vaccinate cows at a less-than-optimal time (or even not at all!) and still breeze through calving with no scouring calves. These are likely to be herds that have a good handle on those other factors (low dystocia levels, clean calving areas, etc.). But for other herds, tweaking the timing of scours vaccination may help alleviate some of these problems. Consult with your veterinarian about how best to use tools such as scours vaccines as part of a calf scours-prevention plan.

Source: Russ Daly, South Dakota State University Extension



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