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

• Four anthelmintics were tested for resistance in an institutional meat goat herd.
• Pre-treatment fecal egg counts were affected by sire breed of doe.
• Post-treatment fecal egg counts were affected by anthelmintic type.
• Anthelmintic resistance was found to all four anthelmintics tested.
• Each anthelmintic except levamisol was significantly more effective than water.

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 12 days 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.