With spring approaching, cow-calf and stocker operators need to begin planning their control programs for internal parasites. During the recent Cattle Industry Convention in San Antonio, Merck Animal Health veterinarian Harold Newcomb discussed parasite-control strategies and methods to prevent development of drug resistance in parasite populations.

Newcomb notes that in stocker cattle, owners often do not have access to past records and do not know which deworming products the animals have received in the past. Increasingly, he says, stocker operators use a dual treatment prior to turnout to reduce parasite infections to near zero as cattle move onto pastures.

In a recent trial, researchers treated over 600 stocker steers with a combination of Safe-Guard (fenbendazole) and generic ivermectin prior to turnout on Mississippi pastures and achieved greater than 99 percent reduction in parasites shed by the cattle. The broad control achieved with the combination treatment helps prevent the possibility of introducing resistant parasites to the pasture.

At days 28 and 56 of the grazing season, the researchers followed up with treatments using convenient Safe-Guard range cubes, which kept parasite numbers well below threshold numbers throughout the grazing season. At a treatment cost of $5.40 per head, the program resulted in about 23 pounds per head greater weight gains and $53 per head higher returns compared with cattle treated with a competing product.

In this trial, the researchers used fecal egg counts to monitor the quantity of parasite cattle were shedding , and a polymerase chain reaction (PCR) diagnostic test to determine which parasites were present. These tools are valuable for research, but also for cow-calf and stocker producers. Newcomb says that with the help of a veterinarian, producers can implement a regular program of testing and monitoring as a means of evaluating the success of their parasite-control programs. Results can help them fine-tune those programs, adjusting product selection, timing of treatment and other management practices to improve control and optimize cattle performance.

Newcomb notes that even in arid Western regions, ranchers can see a 20-pound gain in average weaning weights by implementing an appropriate deworming program. He also says producers increasingly recognize the benefits of parasite control, with industry-wide U.S. sales of deworming products continuing to grow in recent years in spite of lower cattle populations.