Evaluation of parasite resistance to commonly used commercial anthelmintics in meat goats on humid subtropical pasture

Abstract

Anthelmintic-resistant gastrointestinal nematode parasites are a threat to small ruminant industry sustainability. Meat goat does were administered one of four anthelmintics orally (ivermectin (n=18), moxidectin (n=18), levamisole hydrochloride (n=17), or albendazole (n=19)) or water (n=18). Fecal samples were collected pretreatment and 12days post-treatment. Fecal egg counts (FEC) were determined by the modified McMaster technique. The FEC reduction percentages (FECR%) were calculated using three equations. Log transformed FEC means were analyzed by treatment, sire breed of doe, and doe age. Sire breed affected (P<0.05) pretreatment FEC, but not post-treatment FEC (P=0.12). Pretreatment FEC did not differ (P=0.21) by treatment group. Posttreatment FEC varied (P<0.05) by treatment. Anthelmintic resistance determinations were based on FECR% falling below 90% or 80%, dependent on equation applied. Resistance was detected to all four anthelmintics using each equation. These results suggest the need for alternative methods of internal parasite control in goats.