— are carrying organisms that are resistant to 2 or more antibiotics. “That’s a concern,” says Spire,
“because if that multidrug resis- tant bug becomes the dominant pathogen that’s going through a set of calves, we don’t have effective antibiotics for them.” But while you don’t want to over-
treat the animal so the resistant bugs will be selected out, “you don’t want to kill them with kindness, either,” he says. “In some cases we have producers that will rehandle cattle after a week or 10 days to vaccinate them again because they didn’t feel like they got vaccinated up front, or they didn’t take those vaccines.” That adds yet another stressor
to the already-stressed animals by reshuffl ing their social order and changing their intake for several days. It may also increase injury or
bruising in those animals. All these things may create a more infl am- matory environment and a potential for more issues. Stressors cause a biological re-
action that magnifi es the impact of the pathogens that are present. The stress causes the release of re- active proteins in the body called proinfl ammatory cytokines and, says Spire, “We’ve found viruses and bacteria like those in their en- vironment. It’s almost like putting them on steroids and we can see the viruses and bacteria change. They replicate, and in some cases we can see the pathogenicity change, so we actually start making a tougher bug.” The timing for additional vacci-
nations is up for debate. Spire says some research shows the ideal time for stocker calves to receive them is right up front. Other studies indicate
if the booster is delayed, there’s no difference in the number of sick or dead calves. But given the uncer- tainty, he’s in the fi rst camp, saying, “My preference is to allow that calf to start responding to our vaccines right up front when we get them, because in the majority of cases we don’t know the vaccination history in stocker calves, so we’re going to bring them into conformity with what we know works in a particu- lar operation.”
Weather, food and parasite stress Another source of stress is the
weather. Fall-weaned calves have to deal with cold nights and warm days, and if a chilly afternoon is coupled with rain, the animals can’t take in enough energy and may not respond as well to vaccines or treatment.
MORE
www.walterlasleyandsons.com
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September 2013 The Cattleman 87
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