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SIOUX FALLS, S.D. - A newborn calf is a delicate creature. Veterinarian Dr. R.M. Thornsberry compares raising a dairy calf specifically to raising a fawn deer - they are fragile.
For this reason, Thornsberry gave a presentation on relatively new research on basic calf immunology and how it relates to calf growth and performance, during the Central Plains Dairy Expo, March 26-27 in Sioux Falls, S.D.
To get a calf off to a good start, Thornsberry referenced a process that takes place in a calf - in the first few hours after birth, the calf can absorb antibodies from the mother's colostrum and absorb them into it's own bloodstream.
"It's a mechanism known as survival of the fittest," Thornsberry said. "Beef cattle function in this capacity as a wild animal. The calf is supposed to get up, suck out the colostrum that it needs and follow it's mother."
Through the years, this trait - survival of the fittest - has been selected out of the qualities in dairy cows. A newborn dairy calf has to consume four quarts (for a Holstein or three quarts for a Jersey) of colostrum to get the amount of antibodies it needs to be healthy.
"Often, the calf will get up, take a swallow or two and then go over and lay down," Thornsberry said. "The mechanism of absorbing colostrum is an all or none mechanism for the calf - and it begins to shutdown after 2-3 hours. We need to get it all in as quick as possible after birth."
Thornsberry stressed the importance of operating within these parameters - the process cannot be changed because of inconvenience. Thornsberry worked with a dairy that was experiencing a 50 percent death loss in newborn calves. The dairy had 300-400 heifers ready to calve in a paddock. Every day, calves were picked up at 5 p.m. - whether they had sucked from a cow or not. Thornsberry worked with the dairy to set up a new schedule of picking up calves every two hours and bringing them back to the farm to administer colostrum. The dairy's death loss dropped to 6 percent in two weeks.
From a recent study by the University of Missouri, Thornsberry explained the changes the cow's udder undergoes from the time of birth to the hours following. Two hours after giving birth, colostrum in the cow's udder is already becoming colostrum diluted with milk. It is a change that takes place when the cow begins to secrete the hormone prolactin to start lactation.
"Absorption of antibodies is directly related to the concentration," Thornsberry said. "When you dilute them down, the calf won't absorb as many antibodies as it would have if it had colostrum immediately."
Thornsberry said if the calf is given adequate amounts of colostrum immediately after birth and it absorbs those antibodies in its blood, the antibodies don't stay in the blood. The calf utilizes the antibodies to fight off disease, whether the disease is present or not.
A calf's continued health and performance is contingent upon the timing of when all the antibodies the calf has taken in from the colostrum are gone and when administered vaccinations take affect.
"Tests of a calf's intestinal tract reveals that about one to four grams of antibody is absorbed every day. Out of four quarts of colostrum, a calf will absorb about 25 to 35 grams of antibodies," Thornsberry said. "Divide 35 by four grams per day and that gives you one week. When that calf is 1 to 2 weeks of age, all the antibodies the calf has taken in from colostrum are gone. If I vaccinate that calf the day it's born, I am looking at three to four weeks before I can get that calf's immune system kicked into gear to produce enough antibodies."
This, Thornsberry said, leaves a large gap of vulnerability for the calf - between 10 days old to 3 weeks old - where it has no antibody protection.
"That time period can be significant and is when we often have calves crash," Thornsberry said. "Some of it has to do with the incubation period of the organisms that cause disease but a big part is because of the huge gap of unprotected time we have to deal with."
Thornsberry has established a dairy calf vaccination protocol beginning at birth to help stimulate production of interferon - antiviral against antibodies. The primary reason for doing this is to get some antiviral immunity against some of the more common viruses that cause diarrhea, rotovirus and others. Thornsberry suggests vaccinating the calf the day it is born. Antibodies will still not be measurable for 3-4 weeks, but given latest research on calf immunology, Thornsberry said a calf's immune system is there - not fully mature - but is more than capable of responding to vaccination.
"We now know calves will respond to the vaccine but we have to be very cautious on the vaccines we are using," Thornsberry said. "Most of them will say do not vaccinate a calf until it is 250-350 pounds and do not vaccinate calves that are not healthy. So be very cautious on which vaccines you utilize. Calves will respond but they don't deal well with a lot of stress."
Thornsberry's recommendations are based on experience. He suggests utilizing an oil-based vaccine called Virashield 6 which is an inactivated vaccine. It is slowly absorbed and does not cause the calf to get sick.
"We can get an effect out of the inactivated vaccine if we can bombard the immune system with the vaccine over several days of time," Thornsberry said. "Which is exactly what an oil-based vaccine does."
Thornsberry's protocol includes giving a nasal vaccine at birth to get the interferon, a half dose of Virashield 6 and a half dose of an 8-way like Covexin 8. At three weeks old, the calf receives another half dose of these vaccines - to act as a booster of what it was given at birth. At either one week before weaning or one week after weaning, the calf is given a full dose of vaccines.
"Don't use any modified live vaccines in these calves other than the nasal until the calf is about 300 pounds," Thornsberry said.
Thornsberry stressed the importance of following the label on vaccines and to always discuss your vaccination protocol with your veterinarian.
"I have around 500,000 calves around the country on this protocol (see sidebar)," Thornsberry said. "It's one that works."
Thornsberry also suggested not administering a modified vaccine for BVD in any form.
"BVD is like the AIDS virus in humans," Thornsberry said. "It represses the immune system and you don't want to do that in calves while they're developing immune function."
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