Effect of anthelmintic and selenium drenching on live-weight gain in young beef cattle

Abstract

Over 5 years the live-weight gain responses obtained from drenching 6- to 7-month-old weaner beef steer and heifer calves were examined in eight trials covering three localities in South Canterbury. In six trials, calves were drenched with thiabendazole at monthly and 2-monthly intervals between April and September. Undrenched cattle were used as controls. Three drenches at 2-montbly intervals increased live weight by 12.2 kg (range 8.2 kg to 21.1 kg) and five monthly drenches by 15.7 kg above controls (range 8.1 kg to 29.0 kg). Therefore, three drenches achieved 80% of the response obtained from five drenches. In two further trials, three drenches at 2-monthly intervals increased live weight by 0.5 kg and 22.4 kg; the addition of selenium to the drench gave live-weight gains of 12.4 kg and 29.3 kg respectively. Worm burdens were generally low (faecal counts up to 165 eggs/g), few calves had clinical signs of worm infestation such as scouring, and no control calves required drenching at any time during the experimental period. After allowing for partial compensation of live-weight differences during subsequent growth, it is concluded that, although the responses are economic at current prices, the overall effect tends to be small compared with the live-weight gains possible when nutrition is adequate.