Part 2: Clean colostrum and feeding goals
by Sally Colby
The long-term goal of a colostrum management program on any farm should be raising healthy and well-grown heifers that calve between 22 and 24 months of age and at 85% of mature body weight.
Achieving that goal begins with colostrum, but more importantly, through successful transfer of passive immunity. “With improved levels of passive transfer, we see improved rate of gain and feed efficiency,” said Dr. Sandra Godden of the Veterinary Population Medicine at the University of Minnesota. “If we grow them faster, we can breed them at an earlier age and decrease the age at first calving, which is a huge economic benefit.”
The gold standard for measuring passive transfer of IgG is to obtain a blood sample and measure serum IgG. While that isn’t practical, measuring serum total protein is. “It’s a refractometer measurement that in the first week or so of life is positively correlated with serum IgG,” said Godden. “Serum total protein is a cheap, simple test that can be done on farm or at the local vet clinic.”
To achieve a passing serum IgG value of 10 or greater, the corresponding total serum protein value would be 5.0 to 5.2 grams/deciliter. To determine this level, the herdsman or veterinarian collects blood from 12 or more clinically normal (not sick) calves between one and seven days old.
Godden said the goal is a 90% pass rate, which means at least 90% of the calves tested will be at or above 5.2 on the serum total protein scale. “This goal of 90% passing is somewhat of an old goal,” said Godden. “The corresponding goal if we’re using a Brix refractometer for the serum is for 90% of calves to be at or above 8.4% on the Brix scale.”
Calves fed shortly after birth will peak with a higher IgG concentration of around 25 grams/liter in the blood. Calves that receive a first feeding between six and 24 hours after birth peak at a much lower IgG level due to less efficient absorption.
Colostrum should be clean to afford the best protection. “If bacteria are pathogenic, they can cause disease in calves,” said Godden. “Examples would be E. coli, salmonella and mycobacterium avium ss paratuberculosis (the agent that causes Johne’s) that could be shed in colostrum. The other reason we want to feed clean colostrum is that we’ve learned over the years that high bacterial levels in colostrum are associated with impaired absorption of IgG. The higher the coliform levels, the lower the IgG levels.”
One contamination source is the cow. She may be subclinically infected and shedding bacteria in colostrum, or may have fecal material caked onto her teats. Another source is dirty equipment used to collect, store or feed colostrum. Bacterial growth in stored colostrum is also a source of contamination.
The first step in avoiding contamination is prepping the cow properly prior to colostrum collection. “We don’t let the calf suckle the cow,” said Godden. “If a cow is subclinically infected, don’t feed colostrum from a positive cow.”
Avoid pooling raw colostrum to avoid exposing multiple calves. Godden suggested using the “one cow to one calf rule” for feeding raw colostrum.
Colostrum should immediately be refrigerated after collection. Alternatively, colostrum can be frozen, and should be good for up to one year. Potassium sorbate is a suitable preservative for delaying bacterial growth in fresh colostrum.
One additional management strategy, something Godden said everyone should have on hand, is colostrum replacer. “Some of these products are colostrum-derived,” she said. “They come from spray-dried colostrum. In other products, the IgG is serum- or plasma-derived. You’re going to get better IgG absorption out of colostrum-derived product than from a serum-derived product.”
With such products, the dose is important – one dose barely achieves the 10 grams/liter minimum. Feeding two doses is preferable, but it quickly becomes expensive to feed multiple doses. In the case of high-value calves, Godden said it’s worth feeding more than one dose.
Heat treating colostrum is an acceptable way to preserve it. Fresh colostrum is heated at 140º F for 60 minutes, then transferred to a clean receptacle, refrigerated or frozen. The treated product is warmed prior to feeding. Heat treating can be done in a batch pasteurizer or in individual bags. Godden said while heat treating isn’t widely adopted, it’s becoming more common in larger herds. One study showed that calves fed heat-treated colostrum had a significant reduction in scours and in overall treatment rate.
“Colostrum management is the cornerstone of a successful calf or young stock program,” said Godden. “While we’ve made improvements as an industry, there’s still an opportunity for a lot of producers to improve. The take home message is to feed clean colostrum.”