Alternatives to traditional anthelmintics to control gastrointestinal nematodes in grazing meat goats
Abstract
Studies were conducted to determine the efficacy of a commercial herbal dewormer (HDC, Studies 1 and 2) and a tanniferous perennial legume (Study 3) to reduce fecal egg counts (FEC) in grazing goats (Capra hircus). Goats grazed Festuca arundinacea (Study 1), Lolium multiflorum L. (Study 2), and Lespedeza cuneata or Tripsacum dactyloides (Study 3). In study 1, the eggs per gram (EPG) of feces from goats orally-drenched weekly with HDC decreased from 1,006 to 758 by Day 33, then stabilized at a mean of 740 EPG until the end of the trial (Day 103). Conversely, FEC of goats drenched with ivomectin (IVO) decreased from 935 EPG to 163 EPG by Day 26, then steadily increased to 646 by Day 103. The EPG differed between IVO and HDC on Day 12, 19, 26, 33, 40 (P <0.0001), 47 (P <0.007), 54 (P <0.07), 61 (P<0.002), 68 (P <0.04) and 89 (P<0.09). In Study 2, neither oral fenbendazole nor one or two weekly doses of HDC had an effect on FEC, an indication of resistance to fenbendazole by gastrointestinal nematodes. In Study 3, FEC of goats grazing L. cuneata and T. dactyloides for 5 wk had decreased from 860 to 500 EPG for the former and increased from 1630 to 2310 EPG for the latter (P <0.06). Thereafter, FEC of goats switched from T. dactyloides to L. cuneata decreased to 1595, 1120 and 410 during the following 3 wk, whereas FEC of goats switched from L. cuneata to T. dactyloides still decreased to 220, 195, and 70 EPG (P <0.007, P <0.02, and P <.09, respectively). Within the confines of studies 1 and 2, HDC showed some or no effectiveness in reducing FEC in goats grazing infected pastures, whereas there was a significant reduction in FEC of goats grazing L. cuneata.