title: Efficacy and productive performance of moxidectin in feedlot calves infected with nematodes resistant to ivermectin.
abstract: Anthelmintic resistance (AR) of gastrointestinal nematodes to macrocyclic lactones is an increasingly common worldwide phenomenon limiting cattle production. This has motivated the search for alternatives, such as new active compounds, added drug synergisms, different doses, and alternate administration routes. The aim of this study was the assessment of moxidectin (MXD) performance in feedlot calves with a history of AR to ivermectin (IVM). Crossbred female calves aged 6-7 months and weighing 163kg (SD=34kg) were divided into 3 groups of 35 animals each. They were assigned to the following antiparasitic treatment groups: IVM group (0.2mg/kg IVM); MXD group (0.2mg/kg MXD), and ricobendazole+levamisole (RBZ+LEV) group (7.5mg/kg RBZ+8mg/kg LEV). On days 0, 26, and 47, fecal samples were taken and the weight of each animal was registered. Anthelmintic efficacy (by fecal egg count reduction), total weight gain (TWG) and average daily weight gain (AWG) were compared between the groups. A mixed SAS procedure was used for statistical analysis. Fecal egg count reduction 26 days post-treatment (PT) was calculated at 28% for the IVM group, 85% for the MXD group, and 99% for the RBZ+LEV group. AWGs (Standard Error) of 1.095g (56), 1.264g (49), and 1.340g (52) were registered for the IVM, MXD, and RBZ+LEV groups, respectively (p<0.05). Coprocultures revealed that MXD more effectively reduced Haemonchus spp. and Cooperia spp. egg counts than IVM. This resulted in higher AWGs and TWGs for this group; similar results were seen for the RBZ+LEV group as well. In this study, animals treated with MXD gained about 160 more g/day than animals treated with IVM. This represents a gain of 16 USD per animal over the 47 day trial.
authors.affiliation: Facultad de Ciencias Veterinarias, Universidad Nacional de La Plata (UNLP), 60 y 118, 1900 La Plata, Argentina. Electronic address: fazzio@fcv.unlp.edu.ar.
authors.forename: L E
authors.initials: LE
authors.lastname: Fazzio
authors.affiliation: Facultad de Ciencias Veterinarias, Universidad Nacional de La Plata (UNLP), 60 y 118, 1900 La Plata, Argentina.
authors.forename: N
authors.initials: N
authors.lastname: Streitenberger
authors.affiliation: Facultad de Ciencias Veterinarias, Universidad Nacional de La Plata (UNLP), 60 y 118, 1900 La Plata, Argentina.
authors.forename: W R
authors.initials: WR
authors.lastname: Galvan
authors.affiliation: Laboratorio Mesopotámico de Diagnóstico Veterinario, Ramírez 72, 3200 Concordia, Argentina.
authors.forename: R O
authors.initials: RO
authors.lastname: Sánchez
authors.affiliation: Facultad de Ciencias Veterinarias, Universidad Nacional de La Plata (UNLP), 60 y 118, 1900 La Plata, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.
authors.forename: E J
authors.initials: EJ
authors.lastname: Gimeno
authors.affiliation: Facultad de Ciencias Veterinarias, Universidad Nacional de La Plata (UNLP), 60 y 118, 1900 La Plata, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.
authors.forename: R E F
authors.initials: RE
authors.lastname: Sanabria
mesh_terms: D015766:Albendazole / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000627:therapeutic use; D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy / Q000469:parasitology*; D004351:Drug Resistance; D005260:Female; D007559:Ivermectin / Q000494:pharmacology*; D007978:Levamisole / Q000008:administration & dosage / Q000627:therapeutic use; D018942:Macrolides / Q000627:therapeutic use*; D009348:Nematoda / Q000187:drug effects*; D009349:Nematode Infections / Q000188:drug therapy / Q000469:parasitology / Q000662:veterinary*
chemical_list: D018942:Macrolides; D007978:Levamisole; D007559:Ivermectin; D015766:Albendazole; C027186:albendazole sulfoxide; C027837:moxidectin
keywords: Average weight gain; Cattle; Cooperia; Haemonchus; Macrocyclic lactones