Helminthiasis control in Calves Raised in the Tropical Semiarid Region

This study aimed to characterize the helminthiasis and anthelminthic effectiveness in calf herds raised in a hot semi-arid area. Sixty (60) cattle farms from the northern area of Minas Gerais, Brazilian sertao, were categorized by semi-structured questionnaires. It was also performed the fecal egg counts (FEC) reduction test to analyze the profile of anthelminthic resistance in eight herds. The study selected groups of at least 10 homogeneous calves with FEC ≥ 150 per treatment. After 12 h of fast, calf groups were treated with albendazole, levamisole, ivermectin, doramectin or abamectin, except the control groups (untreated). It was collected feces before treatments and 14 d later larvae genera of nematodes were identified after coproculture. Extensive grazing was the predominant creation system for beef calves, worming was employed every 6 mo in 64 % of the farms and macrocyclic lactones was the most frequently used anthelminthic group. The anthelminthic efficacy varied from 62 to 98.9 %. The resistance profile to ivermectin, levaminosole, albendazole and (or) doramectin verified in this research is alarming as the genus Haemonchus was the most frequent one before and after the treatments. It was detected variations in the creation systems, in control practices and in anthelminthic susceptibility profiles between herds. Therefore, this work emphasize the importance of using strategic control with FEC reduction test for choice of anthelminthic and the encouragement of practices of alternative control.