The use of redberry juniper (Juniperus pinchotii) to reduce Haemonchus contortus fecal egg counts and increase ivermectin efficacy.

Objectives of this study were to determine if a redberry juniper-based diet can reduce fecal egg counts (FEC) and increase ivermectin (IVM) efficacy in IVM-resistant Haemonchus contortus. Predominant genera present were Haemonchus (range 45-100%) and Trichostrongylus (range 0-47%). The FEC reduction for IVM in the ewe flock was 25% (95% confidence intervals 79% to -162%) and confirmed IVM resistance. After natural infection was established, Barbados Blackbelly and St. Croix lambs (n=64, 6 months old) were randomly assigned to pens and fed a pelleted treatment diet (4 pens/treatment and 8 lambs/pen) consisting of traditional feed ingredients mixed with either 30% hay (CNTL) or 30% ground juniper leaves and stems (JUN). Lambs were fed during two periods: Period 1 (days 0-28) and Period 2 (days 28-42). On day 28, half of the lambs from each treatment and pen were treated with IVM orally (0.2 mg/kg), creating four treatment groups: lambs fed CNTL or JUN and either not treated (CNTLn, JUNn) or treated (CNTLi, JUNi) with IVM. During Period 1, lambs fed CNTL had greater (P<0.001) average daily gain than lambs fed JUN, which was probably caused by the CNTL diet having greater protein and less acid detergent fiber, lignin, and condensed tannins than the JUN diet. Lambs had similar (P>0.46) FEC on days 0 and 28, but lambs fed JUN had 69.1% lower (P<0.001) FEC on day 15 as compared to lambs fed CNTL. During Period 2, CNTLi lambs had greater (P<0.05) average daily gain than JUNn and JUNi lambs. Lambs fed JUN and treated with IVM (JUNi) had 66%, 65%, and 61% lower (P<0.05) FEC as compared to CNTLn, CNTLi, and JUNn lambs, respectively. Results suggest that feeding lambs a diet containing 30% redberry juniper reduced FEC and increased IVM efficacy by 65% (JUNi vs. CNTLi). Specific mechanisms involved in increasing IVM efficacy by feeding diets containing bioactive compounds warrants further investigation.