Livestock Management RANCHING
The calf’s
immune system is not fully
functional until well after 8
months of age.
goes beyond the antibodies passed along by its mother. Spire says the fi rst milk also contains other chemi- cals and proteins that prime the immune system, so by the end of the fi rst week to 10 days of life the calf is ready to start defending itself against disease. “A (newborn) calf is basically
totally naive to any disease organ- ism,” he says. “That’s why we see such a tremendous health risk in that fi rst 28 days after a calf’s born.” Among the other key ingredients
in the colostrum are white cells, na- ture’s defense against the system’s invaders. Spire says the mother’s white cells essentially spell out to the still-primitive white cells of the calf how they should behave to de- fend the system. There are also chemicals that
Spire says act as “triggers” that fl ip the switches needed to activate the calf’s bodily functions. He says, “It’s like turning on a
succession of generators and the lights get brighter and brighter — that’s exactly what happens here. By the time we see the chemicals come into the body they’ll turn the
56 The Cattleman May 2014
system on, and it takes about a full week. Then it takes about another 6 weeks before we get the cell popula- tion that the calf has to have to get up to its functional level.”
Booster the calves’ vaccines The calf’s immune system is not
fully functional until well after 8 months of age. This means that to compensate for the loss of maternal antibodies a vaccination program has to take into account the calves’ rising exposure risk to different pathogens at different times in its life. And some of the calves are susceptible shortly after they enter the world. Studies show about 10 percent of beef calves do not get the antibody protection they need from colostrum. So population dy- namics fi gure into the vaccination scheme. A few of the animals are already more susceptible to illness, and more and more of them become susceptible over time. “What we have to think about
are those calves that can respond directly to a vaccine as we give it, and those calves that we defi nitely need to booster up,” says Spire. “The
younger a set of calves is, the more likely it is that we need to booster them sooner than what the calen- dar tells us that we need to do it. A lot of times that may fall 2 to 4 months after that initial vaccina- tion, so vaccine delivery becomes a population dynamic. “While dealing with a set of
6-month-old calves I consider the fi rst time they get vaccinated as their primary vaccination. Depend- ing on the particular vaccine, those delivered at 6 months of age may need to be boostered at some point past that.” Producers should also plan vac-
cinations based on seasonal aspects. Three of the most common patho- gens that affect calves in the sum- mertime are bovine respiratory syn- cytial virus (BRSV), Histophilus somni, and Pasteurella multocida. Since calves are going to be de-
pleted of colostrum antibodies by the time they’re about 2 to 3 months of age, initial vaccination programs for those diseases should start at about that point in time. Spire says many ranches work calves through branding at 2 to 3
thecattlemanmagazine.com
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