Effectiveness of Different Anthelmintic Classes on the Texas A&m University-commerce Goat Herd


Lauren Parker

Document Type


Degree Name

Master of Science (MS)


Agricultural Sciences

Date of Award

Summer 2018


Helminth overloads are one of the main causes of economic losses in livestock operations due to decreased animal health, inefficiency, and death. Nematodes that commonly affect sheep and goats are Bunostomum (hook worms), Haemonchus (stomach worms), and Trichostrongylus (hair worms). Three classes of anthelmintics are available to control helminths in sheep and goats: Macrocyclic lactones, benzimidazoles, and tetrahydropyrimidines. Overuse and limited availability of dewormers for sheep and goats has caused global anthelmintic resistance. Levels of resistance vary from farm to farm due to differences in management practices. Anthelmintic resistance in the Texas A&M University-Commerce (TAMU-C) goat herd (N = 14) was determined by comparing 2 different classes of dewormers, fenbendazole (benzimidazole) and moxidectin (macrocyclic lactone). Using a Latin square design (see Table 1 in the appendix), animals were randomly assigned to moxidectin (n = 7; 0.2 mg/kg of body weight) or fenbendazole (n = 7; 5 mg/kg of body weight) treatments in period A and switched in period B. Data were collected for 4 weeks in both periods with 7 weeks rest between periods. Body weights were taken and treatments were orally administered on day 0 for both periods. Fecal samples and Faffa Malan Chart (FAMACHA) scores were collected on weeks 1, 2, 3, and 4 for both periods to estimate eggs per gram (EPG), fecal egg count reduction test (FECRT), and degree of anemia. EPG, FECRT, and FAMACHA scores were analyzed by period using the PROC MIXED procedure of SAS (version 9.3; Cary NC). Treatment, week, treatment x week interaction, and status (pregnant vs. open) were included as fixed effects; animal was included as a random effect, and age was included as a covariate. Significance was determined at p < .05. In period A, EPG and FAMACHA scores were lower (p < .0131) after deworming in weeks 2, and 4 and weeks 3 and 4 compared to week 1, respectively. Pregnant animals had lower (p = .0002) FAMACHA scores in period A compared to open animals; however, pregnant animals had higher (p = .0372) EPG counts in period B. Age was significant for EPG, FECRT, and FAMACHA scores in period A but not in period B. In conclusion, no differences between dewormers were observed in either period, although numerically moxidectin appeared to be more effective. Other variables, including dosage rate and pasture management, may have important roles in parasite control and need to be investigated further.


Douglas Eborn

Subject Categories

Agriculture | Life Sciences