Production responses following strategic parasite control in a beef cow/calf herd.

Strategic parasite control has been reported to improve performance in a beef cow/calf herd that does not demonstrate clinical parasitism. This study was conducted to determine if strategic anthelmintic treatment at turnout and at midsummer would improve growth and reproduction. Two cow/calf groups of similar composition were grazed on separate, but equivalent pastures in the spring, and at midsummer, they were moved to new pastures. The treated group was given fenbendazole at tumout (cows) and at midsummer (cows and calves). The control group was not treated. The study was repeated in the following year. Across both years of the study, parasite egg counts were substantially reduced in both the treated cows (P < 0.005) and treated calves (P < 0.0001). The calves in the treated group significantly (P < 0.0001) outgained the control calves in both years of the study by 19.3 kg and 13.2 kg, respectively. Average daily gain (ADG) after adjusting for birth weight and birth date for treated calves was 0.13 kg greater than for control calves (0.83 vs 0.70) for the 2-year study (P < 0.0001) There was also a significant (P = 0.0357) increase in the reproductive performance of the cows. The pregnancy rate averaged across years was 94% for the treated cows compared to 82% for the control animals.