Weaning stress; cold, changing weather; and tight quarters leave the door wide open for the opportunistic, pound-robbing coccidia protozoa.
"Severe outbreaks of coccidiosis are common around weaning and shortly after very cold weather,1 which can lead to increased death loss, decreased growth rate and poor feed conversion,"2 says Joe Dedrickson, DVM, Merial.
While some may consider coccidiosis a feedyard disease, all weaned calves 6 months and older are at risk, even those on pasture.1 An unusually wet summer in the western Plains states had coccidiosis cases showing up in grazing cow/calf pairs, says Steve Paisley, PhD, University of Wyoming Extension beef cattle specialist. "Typically, coccidiosis doesn"t show up until weaning, when the combination of stress, tighter quarters and poor sanitation in confinement lots or weaning pastures put cattle at greater risk,"2 Paisley says.
Add cold weather to the mix and the risk level goes up, according to a coccidiosis study comparing sheltered and unsheltered calves. The study found that in the control groups, which were not artificially inoculated with coccidia, the unsheltered calves developed mild coccidiosis, indicating cold may increase a host"s susceptibility to clinical coccidiosis.1
"Coccidia are very common and often show up in 100% of tested calves,"1 Dedrickson says. While an animal with clinical coccidiosis is relatively easy to spot, Dedrickson says 95% of coccidiosis cases are subclinical, causing few if any outward signs.3 However, subclinical coccidiosis can result in damage to the lining of the intestine, impacting nutrient absorption and, ultimately, reducing weight gain.3
One study found that weaned calves on a preventive coccidiosis program gained 0.5 lb more per day than the control group, which was classified as being only mildly to moderately infected.4 These subclinical cases, where cattle experience weight loss and decreased weight gains, are responsible for most of the losses attributed to coccidiosis.3,4
"Besides weight loss, calves also are more likely to be weak, which can lead to secondary diseases, such as pneumonia and other respiratory diseases," Paisley says.
Once calves develop clinical coccidiosis, one in five is likely to die.2 And, Dedrickson says, clinical signs appear only when the disease has reached its final stages and most of the damage has already occurred.2
"The level of infection is different every year, but the cost of prevention is so cheap it"s worth doing every year," Paisley says. "Producers should make sure to include a preventive coccidiostat as part of any weaning or receiving program."
Producers also can reduce risk by reducing fecal contamination in feed and water.2
While prevention is the most economical route, Dedrickson notes that calves can be saved through treatment, too. "It"s important to treat as soon as signs of the disease, such as watery feces and general discomfort, appear," he says. "Producers should use a coccidiostat approved for both prevention and treatment of coccidiosis and that comes in multiple formulations so they can adapt it to their unique situation."
1Niilo L. Experimental Winter Coccidiosis in Sheltered and Unsheltered Calves. Can J Comp Med 1970;34(1):20-25. Accessed September 15, 2009.
2Kvasnicka B. Coccidiosis in Beef Cattle. Western Beef Resource Committee Cattle Producer"s Library CL685. PDF file. Accessed September 15, 2009.
3Quigley J. Calf Note #17 – A Review of Coccidiosis in Calves. PDf file. Accessed October 8, 2009.
4Maas J. Fact Sheet No. 10: Bovine Coccidiosis. UCCE Livestock Health Fact Sheet No. 10.