While calves are born with a functional immune system, they have no immunity. However, they can make antibodies.
“It's a cow essentially lending her immunity to her calf, while it builds some of its own. The major points of this are that we have to have healthy, well-fed cows that are in good body condition,” says Brian Vander Ley, veterinary epidemiologist at University of Nebraska-Lincoln. “That's the one parameter that we can measure well that's tied to adequate colostral transfer. That give birth to healthy calves in an uncomplicated way.”
After four hours, a calf’s ability to absorb the passive transfer declines. That’s why it pays to make sure calves get colostrum when calving assistance is needed.
“The most important ones are the ones that we actually assist anyway. The ones that we're already there, it's a huge missed opportunity for us to not deliver or guarantee that calf received colostrum, if we assist it. It's kind of, we brought a live calf into the world, it's kind of a letdown to turn that calf loose without making sure that it got its colostrum meal,” Vander Ley says.
Allowing it to nurse is better than tubing, which deposits the replacer fluids into the rumen or forestomach, where it pools and is harder to absorb.
“What happens when a calf nurses is there's a reflex, there's a response and then a muscle response in their forestomach, in the rumen, omasum, abomasum, that basically creates a straight shot from the esophagus to the small intestines. If they nurse, that closes and it takes that colostrum and deposits it basically directly into their small intestine. If we tube, that doesn't happen,” he says.
As Vander Ley says, “Don’t let perfect be the enemy of good.” Sometimes a calf just isn’t up for nursing on its own.
“There's actually two common mistakes. One is tubing a calf that's laying on its side. You want them sitting up with their chest touching the ground, not on their side. The next part is we often stretch their necks out, so when you stretch a calf's neck out, we actually make it much easier to get into the trachea with the tube,” Vander Ley continues. “If you put the tube in with the calves head at about a 90 degree angle to their neck, it's much less likely that that tube will go into the trachea. Instead, it'll kind of bounce over the opening to the trachea and go behind it into the esophagus, which is exactly what we want to happen.”
You want to make sure calves get the full dose. A boost won’t do any good. You want to guarantee it gets as many antibodies as possible.
“It's complicated, but the management's simple; keep those cows fed well through the winter. Start early if they're thin, and have a plan in place before you start calving, because your window closes quickly when those calves are born,” he says.