Long-term research has provided information regarding the importance of colostrum for newborn calves, and science continues to uncover more subtleties.

“Despite decades of research and advances in colostrum management, there’s still a lot to learn,” said veterinarian Dr. Sandra Godden, Department of Veterinary Population Medicine, University of Minnesota. “There’s a lot to managing heifers, including maximizing immunity, which includes colostrum, the milk and nutrition program, minimizing stressors and vaccinations. We’ve been getting better but there are opportunities to improve.”

Colostrum quality refers to the concentration of IgG in the colostrum. “Experts have suggested quality should be 50 grams/liter or higher,” said Godden. “The higher the quality fed, the higher the serum IgG level reached in the calf. More grams fed equals more grams absorbed … into the calf’s circulation.”

Ideally, dairy farmers would have access to an on-farm test for serum total protein (STP) to accurately assess calves’ IgG levels. Although such a test doesn’t exist, laboratory analysis is an option.

“On the farm, we use indirect tests such as serum Brix or serum total protein,” said Godden. “In the first week of life, we know serum total protein will be positively correlated with serum IgG. If we’re looking for a serum IgG of 10 or greater, an STP between 5.0 and 5.2 grams/deciliter most accurately predicts an IgG value of 10.”

A USDA/NAHMS researcher assembled a group of calf experts and looked at data from over 2,000 calves from 103 farms. The morbidity risk was highest in calves with serum IgG of less than 10 g/L, and the study showed further morbidity reduction when serum IgG was greater than 25 g/L.

Farmers know colostrum provides maternal immunoglobulins (IgG) via passive absorption, especially in the first feeding, but colostrum also provides value in subsequent feedings. The failure of passive transfer in one calf is estimated to cost $70, which Godden said is an underestimate because it only considers calfhood.

“We know the calf needs these passively absorbed antibodies to mount a protective immune response during its first days, weeks and even months of life while building its own acquired immune system and producing its own antibodies,” said Godden. “We tend to focus on colostrum when we’re doing research on colostrum management; however, colostrum isn’t just about antibodies. There are multitudes of other bioactive compounds – immune factors, growth hormones, leucocytes and especially nutrients that benefit calf health and growth.”

Holstein tank milk contains about 12.5% total solids. In contrast, colostrum is about 24% total solids, with high levels of fat, dietary protein, vitamins and minerals. “With colostrum it’s about the whole package,” Godden said. “We default back to measuring passive absorption of serum immunoglobulin, especially serum IgG, as a way of monitoring passive transfer.”

Farmers who do a good job with colostrum see successful transfer of passive immunity and reduced disease mortality rates, especially in the first few months of life. “It doesn’t stop there,” said Godden. “There are other intermediate benefits of successful passive transfer. We see improved growth rate and feed efficiency, which means animals reach breeding stature sooner.”

Although colostrum quality varies widely among cows, management steps can help improve its quality. “Look at dry cow vaccinations that cause her to produce more antigen-specific antibodies against scours pathogens such as E. coli, rotavirus and coronavirus,” said Godden. “If you adopt a cow scours vaccination program in dry cows, you won’t see a dramatic bump in colostrum quality as measured through Brix or colostrometer – it’s more subtle.”

Dry cows should receive a balanced dry cow ration with adequate vitamins, minerals, energy and protein. Dry matter intake is also crucial for good colostrum in fresh cows.

Godden suggested avoiding stressors such as overcrowding, frequent transports and heat stress during the dry period. “We do these things anyway for the cow’s benefit, but it also benefits colostrum quality,” she said. “Avoid excessively short dry periods – with less than 21 days dry, she won’t produce the quality or volume.”

Milk cows as soon as possible after calving, ideally within one to two hours of calving, for higher quality colostrum. Smaller herds that don’t monitor cows through the night should milk fresh cows as soon as possible in the morning.

Prior to making major changes in herd management to improve colostrum quality, Godden suggested monitoring colostrum. While many farmers still use a glass colostrometer to measure colostrum quality, it isn’t the most ideal tool. “It isn’t perfectly accurate,” she said. “It’s impacted by colostrum temperature and there’s glass in the barn.”

More recent colostrum research involved studies with the Brix refractometer, which measures total solids and provides results that are positively correlated with high IgG. Godden said it’s reasonably accurate and better than the colostrometer.

“A reading of 19% to 22% indicates an IgG of 50 grams/liter or higher,” said Godden. “If you’re doing herd-level testing on every cow that calves, my goal would be for at least 90% of samples tested have a Brix reading of 22% or higher. If samples are under 22%, go back to management.”

by Sally Colby