| Abstrakt: |
Gastrointestinal nematodes (GIN) parasitism is the greatest threat to economic sheep and goat production in the southern USA, and there is widespread prevalence of GIN resistance to broad-spectrum anthelmintics in this region. A natural alternative for controlling GIN in small ruminants is feeding hay of sericea lespedeza [SL, Lespedeza cuneata (Dum.-Cours., G. Don)], a perennial warm-season legume high in condensed tannins. To determine the level of SL needed to reduce GIN infection, a confinement study was completed with 32 Spanish/Boer/Kiko cross yearling bucks offered one of four diets with 75% hay and 25% concentrate (n=8, 2 pens/treatment, 4 goats/pen). The hay portion of each diet consisted of a combination of ground SL (0%, 25%, 50%, and 75% of the diet) and bermudagrass [BG, Cynodon dactylon (L.) Pers.; 75%, 50%, 25%, and 0% of the diet]. The bucks were allowed to acquire a natural GIN infection on pasture prior to moving to the pens. After a 3-week adjustment period in the pens, the goats were stratified by fecal egg count (FEC) and packed cell volume (PCV), randomly assigned to treatments and pens, and then fed the treatment diets for six weeks. During the experimental period, fecal and blood samples were collected from individual animals weekly to determine FEC and PCV, respectively. Adult worms from abomasum and small intestines were collected for counting and identification of species at slaughter. Goats fed SL hay at 25%, 50%, and 75% of the diet had 45.3% (P=0.2048), 66.3% (P=0.0134), and 74.5% (P=0.0077) lower FEC than control animals (75% BG hay) after 21 days. The 50% and 75% SL goats had 84.6% (P=0.0625) and 91.9% (P=0.0340) lower FEC than controls by day 42. The 75% SL-fed goats tended to have higher (P=0.0624) PCV and had fewer (P=0.035) abomasal worms than control animals, while PCV and adult worm numbers of the 50% and 25% SL goats were not different from controls. The optimum level of SL hay in the diet for reducing worm numbers of small ruminants appears to be 75%, whereas 50-75% SL reduces FEC, which could lead to reduced larval infection on pasture. |
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