STRATEGIC DEWORMING Production research relevant to you CALVES by Josh Davy, UC Livestock Advisor, Tehama, Glenn, Colusa; Larry Forero, UC Livestock Advisor, Shasta, Trinity; and Gabriele Maier, DVM, UC Beef Herd Health Veterinarian Does deworming calves at branding time offer significant benefits? As the diet of young calves consists of a high proportion of milk, the thought is they may have limited exposure to parasites on grass pastures. However, this leaves a long period between branding and preconditioning when calves start consuming more forage and parasite loads may increase. One idea to prevent loss of calf weight gain during this period is the use of an extendedrelease (ER) dewormer (LongRange® Boehringer Ingelheim Animal Health USA Inc.; 1 ml/110 lbs). The product label claims parasite control of 100150 days depending on parasite species, which, if given to calves at branding, would provide efficacy in reducing intestinal parasites well into the period prior to weaning. One enticing aspect of this treatment is that the cost of deworming young calves is much less than for adult cattle due to body weight differences. Product cost is approximately $1.37 per ml, which translates to $17.43 a head for a 1,400-lb. cow, but is only $2.49 per head for a 200-lb calf. With the lower treatment cost for calves, this cost amount is a minimal investment if additional weight gain can be attained. To test the hypothesis that an ER dewormer can benefit calves at branding, 127 springcalving pairs (all were either first or second calf dams) were broken into three treatment groups, which included LongRange® ER dewormer, Dectomax® injectable conventional dewormer (Zoetis; 1 ml/110 lbs), and a saline control. The pairs were stratified by calf weight, calf sex and dam parity for each treatment, but were all 18 California Cattleman December 2023
grazed through the season in the same pasture. Cattle grazed irrigated pasture throughout the trial at the UC Sierra Foothill Research and Extension Center. Dams received the same treatments as their calves. Fecal samples were collected from all cattle at trial initiation this spring on May 14, midseason on July 28, and at trial end on October 6 for a total trial length of 145 days. At each sampling, all cattle were weighed, fecal egg counts were performed, and cows were body condition scored by two scorers who were unaware of the treatment assignments. Fecal egg counts data was collected 14 days after treatment to evaluate dewormer efficacy in the calves. Bulls had been turned out at the beginning of the trial and cows were pregnancy tested mid-season by ultrasound to estimate the age of the fetus. The only factor that affected calf weight gain was cow parity, with calves from secondcalf dams gaining 0.11 more lbs per day than those from first-calf dams. On average, all calves gained roughly 1.9 lbs. per day. Weight gain was significantly higher in the second half of the season when compared to the first half. None of the deworming treatments had an effect on calf weight gain. Based on these results, it does not appear cost effective to deworm suckling calves at branding. In other studies, deworming light weight calves has had economic return, but in those trials all the calves were weaned. Unlike the calves, the cows did show a dewormer treatment difference in weight gain. Cows receiving the LongRange® ER treatment