Using genetics to control cattle parasites-the Rockhampton experience.

Ever since their accidental introduction, cattle ticks, gastrointestinal nematodes and buffalo flies have been major parasites of cattle in northern Australia. Enormous effort and resources have been directed at chemical control of these parasites but the problem persists in undiminished form. The principal control measure remains the use of breeds that have some degree of parasite resistance. No breed is completely resistant and all are at times adversely affected by parasites. Complete resistance is the ultimate solution but has been generally ignored as a commercial reality. Studies at Rockhampton have demonstrated that completely resistant lines can be developed by genetic means within a commercially acceptable timeframe from even the most parasite-susceptible breeds. Genetic changes in tick and worm resistance over 15 years in response to selection for increased tick resistance in the Belmont Adaptaur (Bos taurus) line are reported. Costs and benefits of achieving increased tick resistance are examined and the applicability of the results to other breeds is discussed. Breed differences in resistance to buffalo flies and their effects on live weight are also reported and the possibility of selecting for increased buffalo fly resistance is explored.