by Sally Colby

Dr. Billy Smith of the University of Pennsylvania School of Veterinary Medicine tells dairy farmers what they already know – colostrum is important. Well-managed dairy farms ensure newborns receive a gallon (or four liters) of colostrum shortly after birth.

“We know that if calves don’t receive colostrum early in life, they’re going to be in trouble,” said Smith. “They’ll have trouble making it through weaning, especially since the most deadly calf disease – scours – happens within the first few weeks of life.” Despite dairy farmers’ awareness of the role of colostrum, Smith said 40 percent of calves don’t receive the correct amount of high quality colostrum.

While some species acquire a degree of immunity through maternal/fetal transfer, that isn’t the case with cattle. Smith explained that the calf in the uterus is surrounded by three layers of fetal membranes, and the cow’s uterus also has three layers. “With the type of placentation a cow has, there is no way immunoglobulin protection can transfer through the cow’s blood to the calf through fetal and maternal membranes,” said Smith. “We have to rely on the newborn calf taking in specific immunoglobulins (from colostrum) transferred from the cow.”

Calves that receive top quality colostrum are protected from scours during the first few weeks and protected from respiratory disease after weaning, but is there protection later in life? Smith said the role of initial colostrum in older cattle has been unclear, but recent research shows colostrum has significant value as heifers mature. Research shows that preventing even one disease incident during calfhood can result in a significant increase in milk production in first lactation animals.

Smith said scientists compared calves that received top quality colostrum and did not have any disease incidence during pre-weaning to calves that did have disease, whether it was diarrhea with weight loss followed by lower gains or any sort of respiratory disease. “What we learned is that we can improve first and second lactation production in these calves if they started life the best possible way,” said Smith.

Research also showed that if calves receive top-quality colostrum and have no disease incidence during pre-weaning, their average daily gain (ADG) improves. If ADG is a half-pound better than another animal that’s struggling, the healthy animal will produce an average of 775 pounds more milk in a first lactation.

The definition of colostrum is the first milk produced by an animal after parturition. “Colostrum is very different from normal milk production,” said Smith. “For cattle, the main components of milk (fat, protein and lactose) are dramatically increased in colostrum versus milk. The biggest increase is protein, which is related to immunoglobulin levels in colostrum that are not present in milk.”

Immunoglobulin is the specific component of colostrum that boosts the calf’s immune system, protecting it from diseases that hamper weight gain and overall health. Colostrum also contains numerous non-specific immunity components, and although it’s unclear what the role of those components is, there’s a good chance those components prepare the calf for better response to disease challenge.

While many dairy farmers rely on the “sticky fingers” test to determine colostrum quality, Smith said that isn’t reliable. “That probably isn’t something you should live by,” he said. “Whether the color is different, a more golden yellow, or it’s more viscous, you don’t know whether the quality is related to immunoglobulin unless the colostrum is tested.”

Ideal colostrum measures 50 grams/liter or higher of immunoglobulin. “A calf should receive a total of 200 total grams of immunoglobulin in order for them to be protected,” said Smith. “That means the calf should receive four liters, or a whole gallon of colostrum.”

Well-managed dairy farms with solid SOPs assess colostrum quality with either a colostrometer or a refractor. Smith said the colostrometer is an easy option as long as the user is aware of how to use it properly. “Colostrum must be at room temperature,” he said. “If colostrum is straight out of the cow at 102 degrees, the instrument will drop lower and give a false reading.” Conversely, if colostrum is refrigerated then tested cold, the colostrometer will stay high in the sample and read as poor quality. A colostrometer costs about $30, but they’re easily broken and need to be treated carefully.

A refractometer measures sugar content in liquids, and Smith said there is sufficient research to show a refractometer has a higher correlation to actual immunoglobulin content than a colostrometer. “If you use a refractometer, a reading above 22 percent is equivalent to 50 grams/liter of immunoglobulin.” A reasonably good refractometer costs around $100.

Smith said that older cows with more than one calving tend to produce colostrum with higher immunoglobulin content. “First calf heifer colostrum generally regarded as poor,” said Smith. “However, that colostrum can provide some protection at the gut level and can be calves’ second or third feeding to extend protection in the gut against scours.” Smith recommends saving colostrum from first calf heifers and using it for subsequent feedings, especially if that colostrum has not been tested.

It’s important that calves are never fed bloody colostrum. “Bloody colostrum will kill calves,” said Smith. “The two top reasons for bloody colostrum are trauma to the gland (falls or kicked), or if there’s infection leading to vascular leakage.”

In addition to potential bacteria in bloody colostrum, there’s a lot of iron. “We know that iron is necessary in order for bacteria pathogens to multiply,” said Smith. “The more iron, the more likely pathogens will multiply. The pathogen load is tremendous in pink colostrum because bacteria have access to all that iron, multiply like crazy, and the colostrum may be coming from a mastitic cow.”

The length of the dry period influences colostrum quality. “The shorter the dry cow period, the more lactation days there are for the animal,” said Smith. “A 60-day dry period is ideal, and is sufficient time to rid the udder of alveolar cells from the just-finished lactation.” With a 60-day dry period, all that remains in the gland from the previous lactation is the major duct system, and the gland is prepared for the next lactation.

With a shorter dry period, excess material that isn’t eliminated from the udder occupies space needed by new cells. This relates directly to colostrum production in the next lactation. “The problem with shortening the dry cow period is that 30 days does not give the gland enough time to go through normal involution,” said Smith.

“The difference between a 50- and a 60-day dry period is not enough to make a difference. The point is to make the dry period as close to 60 days as possible,” he added.

Part 2 will include measures to manage colostrum quality.