| Popis: |
Gastrointestinal nematodes are the major obstacle to sheep farming, and their rational control depends on reliable parameters that guarantee both productivity and animal health. Thus, the objective of this study was to evaluate a method of targeted selective treatment (TST) of Morada Nova lambs, using the average daily weight gain (DWG). For this, 114 lambs in the rainy and 102 in the dry season were randomized into three treatments: Control (CT), Routine (RT - treated every 42 days), and Targeted Selective (TST - treated according to DWG). Packed cell volume (PCV) and eggs per gram of feces (EPG) tests were performed. Intending to investigate the resistance of parasites to anthelmintic, the EPG count reduction test (FECRT), RESISTA-Test© and molecular test (detection of a 63 bp indel in the acr-8 gene in Haemonchus contortus) were performed. For CT, RT and TST groups, the following results were obtained: mean EPG were 4665.1, 3063.5 and 3462.1 in the rainy season and 4475.1, 1341.7 and 2863.4 in the dry season, respectively; mean PCV were 32.1, 33.4 and 32.3% in the rainy season and 33.9, 36.0 and 35.1% in the dry season; mean DWG were 0.087, 0.101 and 0.094 kg in the rainy season and 0.102, 0.113 and 0.112 kg in the dry season; efficacies of levamisole in FECRT were 66.4, 24.1 and 76.4% in the rainy and 90.7, 12.4 and 64.8% in the dry season, respectively; in the RESISTA-Test© LC50 were 0.482, 1.926 and 0.117 µg.mL-1 in the rainy and 0.437, 0.851 and 0.045 µg.mL-1 in the dry season, respectively; in the molecular test, the frequencies of the homozygous resistant genotype were 57.1, 71.4 and 40.0% in the rainy season and 47.8, 55.9 and 41.9% in the dry season. In conclusion, TST allowed less resistance development through refugia maintenance, without productive losses, contributing to the sustainability of the sheep chain. |
