By Russ Daly
Special to the Farm Forum
If you read any articles about calving season, you’ve probably come across one stressing the importance of colostrum for a baby calf. I’m on that bandwagon too. Colostrum is likely the most important factor in ensuring the health of a calf in its first weeks of life.
What’s so great about colostrum? Well, antibodies are what’s great about colostrum. Antibodies are these miraculous molecules in an animal’s bloodstream, or body surfaces like the nose or gut, that latch onto potentially life-threatening germs, rendering them harmless. If it weren’t for antibodies, our animals would die from the most minor of infections.
Antibodies are the stars in Mother Nature’s early-life disease-protection protocol for cattle, sheep, horses, and pigs. In these animals, the antibodies from the mother don’t cross the placenta to circulate in the soon-to-be-born baby. The mother pumps these antibodies from her bloodstream into the milk she’s making, such that this first milk – colostrum – becomes loaded with them. There are some other differences between colostrum and regular milk, but antibodies are the most important.
Then, on the baby side, Mother Nature provides a 24-hour window of time after birth when those antibodies, once drank in the colostrum, can be sucked into the baby’s bloodstream right from the gut.
If both sides of this miraculous system work, we have a good start to a healthy young calf. Sometimes, however, there are problems. Malnourished or young cows may produce colostrum that’s short on antibodies or just plain scarce. Baby calves might not get up and nurse soon enough, especially if they’ve had a tough time being born or are otherwise weak or chilled. It’s difficult to tell just by looking if this antibody transfer is working. If calf health is good, it probably is. But if calf health is poor, it might not be.
Producers can turn to their veterinarians for help in determining whether poor colostrum production or consumption is a problem in a herd. While antibody levels in colostrum can be measured, it’s more efficient to determine whether sufficient antibodies got into the calf. We can do this by measuring protein levels in a blood sample.
Serum protein can be measured in a vet clinic with a refractometer. A drop of serum is placed on the instrument and the protein level determined by looking at a scale through an eyepiece. A sample could also be sent to a lab, where more sophisticated methods directly measure antibodies, but the simpler serum protein measurement works just as well.
Antibodies are proteins, so when they’re taken in through colostrum, they “top off” the normal level of protein in the calf’s blood. If total protein in a calf is down at the background level (less than 5 g/dl), we assume the calf didn’t get sufficient colostrum. If it’s above a certain level (5.5 g/dl), we’re more confident that it did. The best time to measure serum protein in a calf for this purpose is between 1 and 5 days of age. This gives the calf enough time to have absorbed what they’re going to absorb, yet is before their body starts making a lot of their own antibodies and other proteins.
Since this timing means it’s too late for a calf found with low protein to absorb more antibodies, the real use of these measurements is for the big picture, on groups of calves. Low average serum protein in a herd can spur caretakers to focus attention on baby calves’ nursing, or to tube calves right away with colostrum supplement or replacer. Longer-term, such testing can inform decisions on nutritional changes or pre-calving vaccination programs.
Serum protein levels are less useful when you’re trying to apply that information to the fate of an individual calf. A calf can be low on the scale, yet thrive and maintain its health, and a calf with good serum protein can still get sick and die. Although colostrum is important, a lot of other things affect calf health, too.
This calving season, if calf health issues crop up and persist, a good first step is to consider how well colostrum is being produced and consumed. Working with your veterinarian to test calves’ serum protein can provide some valuable information to use in ensuring healthy calves.
Russ Daly, DVM, is the Extension veterinarian at South Dakota State University. He can be reached via e-mail at [email protected] or at 605-688-5171.