Effect of forage condensed tannins on gastro-intestinal parasite infection in grazing wether goats

B. R. Min¹, W. Pomroy², S. P. Hart¹, and T. Sahlu¹

¹E (Kika) de la Garza Institute for Goat Research, Langston University, Langston, OK
²Veterinary and Biomedical Science, Massey University, Palmerston North, New Zealand

The objective of this study was to evaluate effects of dietary condensed tannins (CT) in Sericea lespedeza (SL; Lespedeza cuneata; 4.6% extractable CT/kg DM) on total fecal egg output (TFEO; eggs/d) and stage of larvae development compared with non-CT-containing forage (rye/crabgrass (RC); 0.6 g extractable CT/kg DM) in grazing wether goats. A grazing trial (cross over) involving 11 naturally parasite-infected (>1,200 eggs/g) goats (47 ± 3.3 BW) were randomly selected 1 mo after Ivermectin treatment (0.2 mg/kg BW) failure. Larval culture of pre-treatment feces showed that 86-97% of larvae were Haemoncus, with the remainder being Trichostrognylus and Ostertagia. Periods lasted 15 d, with fecal samples taken on d 0, 5, and 15. The number of eggs/g feces were determined by a modification of the McMaster technique. Larvae were cultured for 10 d at 27^oC by placing 20 g of fresh feces inside a small glass container within a larger container holding free water (20 ml) to maximize humidity. Larvae were collected using a modified Baermann's procedure and counted. Mean fecal egg counts (2,722 vs 1,162 eggs/g) and TFEO (173 vs 45 x 10⁴ eggs/d) were lower (P < 0.01) for RC vs SL. Larvae development from eggs to infective stage of larvae (L3) by 15 d was 88% (3,432 vs 421 larvael/20 g feces; P < 0.001) lower for RC vs SL. In conclusion, CT in forages such as SL may reduce pasture contamination with infective larvae and be a valuable tool for parasite control.