Comparing the effectiveness of injectable ivermectin in combination with oral fenbendazole to injectable ivermectin with oral levamisole at reducing strongyle-type fecal egg count in weaned beef calves
Year: 2026
Type: article
Abstract: The objectives of this study were 1) evaluate combination anthelmintic therapy effect on average daily gain (ADG) in weaned beef calves on pasture, and 2) determine if injectable ivermectin + oral levamisole was noninferior to injectable ivermectin + oral fenbendazole at reducing strongyle-type fecal egg count (FEC). This study was performed in two phases using weaning-age commercial beef calves housed on pasture. Phase 1 included 74 beef calves weaned in March 2025, while phase 2 included 103 calves weaned in September 2025. In each phase, calves were allocated to 1 of 4 treatment groups based on age, body weight, and FEC at weaning (day 0). Treatment groups included injectable ivermectin (A), injectable ivermectin + oral levamisole (AP), injectable ivermectin + oral fenbendazole (AS), and no treatment (NO). On day 14 following weaning, calf body weight and FEC were collected, ADG was analyzed using linear mixed models, and non-inferiority analysis was performed using a one-tailed, two-sample t-test. In phase 1, no treatment achieved the target 99% FEC reduction, with combination treatments AP and AS achieving mean FEC reductions of 89.8% (90% C.I. 84.5-95.2%) and 77.1% (90% C.I. 65.6-88.6%), respectively, indicating the presence of multiclass anthelmintic resistance. In phase 2, treatments AP and AS achieved mean FEC reductions of 95.4% (90% C.I. 91.7-99%) and 95.9% (90% C.I. 92.8-99%), respectively. In phase 2, AP was noninferior to AS (P = 0.0264). Evidence of ivermectin resistance was present in both phases, with multiclass anthelmintic resistance apparent in phase 1.
Source: The Bovine Practitioner
DOI: 10.21423/bpj20279520
Institution: Mississippi State University
Language: English
Subfield: Parasitology
Field: Immunology and Microbiology
Domain: Life Sciences
Open Access status: diamond
OpenAlex ID: W7225455857