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Breeding for Worm Resistant Animals

We started a program in 2007 to try and develop our herd into a more worm resistant breed. We are very excited about the progress we have seen as we enter 2013.  Our program was basically to understand which animals needed more de-worming throughout the year and which ones needed little or no de-worming. We started out doing a monthly maintenance check at the beginning of each month and document our findings according to our Monthly Management program.  We started identifying animals that seemed like they never needed worming and others that seem to have a worm problem more than others. We started culling the animals that needed more de-worming. Animals needing less de-worming are the genetics that we want to keep. We often see the offspring from those animals are more worm resistant also.

After a few years, we no longer do our monthly program every month. We can now tell if there are some changes in the animals and if we don’t see any changes, we may bypass the program if no vaccines are needed at the time. It is clear to tell that we are de-worming far fewer animals now than we did back in 2007. We also follow the refugia program now. The basic focus is to ensure we have animals in the pastures that have not had much de-worming and animals that have had some de-worming. When the worm larvae from each type of animal is ingested, some worms will be less resistant and some more resistant to the larvae. Those larvae will breed and result in worm eggs that are not as resistant to the worms. This keeps the average worms in the herd to be less resistant.