Beef calves’ first 24

There are several primary goals for a profitable beef cow/calf herd – the majority of herd females should achieve viable pregnancies and calves are born alive and healthy.

The newborn calf’s primary requirement is colostrum. While there isn’t a lot of information on colostrum for beef cows, theres significant information about dairy cow colostrum, and it’s relatable to beeves.

“High quality colostrum is the single most important factor in keeping calves alive,” said Dr. Robert Van Saun, Penn State Extension veterinarian and professor of veterinary science. “We know it’s potentially high in fat, and higher in protein because of the immunoglobulins. It’s also high in macro minerals, and it has more trace minerals than milk.”

Colostrum is the first milk made during the last few weeks to months of gestation. As soon as the fetus signals to the cow that it’s going to be born, colostrum production stops and milk production begins.

“The longer it takes for the calf to get up and nurse the cow after birth dictates the quality of colostrum,” said Van Saun. “If the calf is weak and not standing, ideally, colostrum should be stripped from the cow to feed the calf. Gut closure happens quickly: once the calf is born, it takes 24 to 36 hours before the gut no longer absorbs proteins from colostrum.”

But milk isn’t perfect – it’s deficient in most trace elements. Fetuses absorb and concentrate minerals in their livers. “If the pregnant cow is fed correctly, mineral concentration in the liver rises,” Van Saun said. “When the calf is born and is on a trace mineral-deficient diet, stored minerals are mobilized to support its immune response.”

Feeding more minerals to late pregnancy females has long-term ramifications on calf survivability and health. In a study, calves had heavier weaning weights when cows were fed an organic mineral supplement, lower incidence of bovine respiratory disease and less treatment required. Body weight and carcass weight at slaughter was higher with organic vs. inorganic. However, Van Saun said an all-organic mineral program may not be worthwhile due to cost.

Selenium and vitamin A status are heavily correlated to the incidence of stillborn calves. Vitamin A doesn’t cross the placenta except in early pregnancy, so it’s important to provide a free-choice option for calves. Calves get vitamin A from fresh green pasture but not from dry hay or silage.

The goal of colostrum is to provide passive transfer of immunity. When a calf absorbs colostrum, there’s a big jump in immunoglobulin (IgG) concentration in its blood. These are antibodies against various diseases the cow has been exposed to or through vaccinations.

If the IgG in the calf’s blood, as a result of receiving colostrum, is above a certain level, it will be prepared to fight disease but a measure below a certain level is considered failure of passive transfer (FTP).

“In beef calves, there’s a range of between 15% and 34% failure of passive transfer based on a concentration of less than 10 mg/ml of IgG,” said Van Saun. “That’s the traditional threshold established for dairy cattle. If IgG is above 10 mg/ml, the calf has a lower risk of mortality.” Calves in the low percentage range have a much higher risk of scours and/or death from disease.

Many calf diseases occur in the first two to three weeks of age because the calf’s immune response is delayed. Exposure to disease in early life is the first time the immune system has seen disease, so it’s important to provide sufficient IgG that will allow the calf to generate antibodies to fight disease – the basic goal of passive transfer.

Van Saun referenced work out of Alberta, Canada, in which beef calves sampled between two and eight days of age had a serum IgG concentration of 30 mg/ml, or three times the low level. Calves with a concentration below 24 mg/ml had a much greater risk of being treated for illness or dying.

“This tells us that the old adage of 10 mg/ml was far too conservative. The higher, the better,” said Van Saun. “Other work with the North Carolina State University beef herd found IgG concentration in calves ranged from a low of 3 mg/ml to a high of 85 mg/ml. There’s a huge opportunity here.”

While measuring IgG is not a simple on-farm test, measuring total serum protein in blood is highly associated with IgG concentration.

Because serum total protein (STP) relates to IgG, Van Saun suggested using a Brix refractometer to measure STP in newborns’ blood. Calves should be well-hydrated prior to taking a blood sample for the measurement to avoid artificially elevated protein readings.

To use the Brix refractometer to measure STP, take a blood sample and allow it to clot. Next, take a drop of serum and place it on the refractometer to obtain a reading. About 40% of calves should be in the excellent category, 30% good and less than 10% in failure. The herd veterinarian can provide details about how to use this simple and relatively inexpensive testing method.

Excess colostrum from healthy cows can be frozen and fed to calves that need it. Colostrum should be thawed slowly in warm water – too much heat will clot the colostrum and destroy the IgG.

While colostrum replacer can be a suitable substitute for the critical first milk, theres a significant range in quality and cost among replacer products. Be sure the product is labeled “replacer” and not “supplement” (although the latter is suitable for bottle-fed calves).

Disease control for calves should be aimed at improving the immune responses, which can be done via nutrition, vaccination, genetic selection and potentially therapeutic agents. Decrease the disease challenge by providing a dry calving area with a windbreak, preferably outdoors. Biosecurity, vector control and general hygiene help reduce the challenges of disease in early life.

Ideally, cattle producers take every possible measure to achieve a large proportion of calves that survive and thrive.

by Sally Colby