Dose titration of sericea lespedeza leaf meal on Haemonchus contortus infection in crossbred lambs

Gastrointestinal nematode (GIN) parasitism is a problem for small ruminant producers. Haemonchus contortus is the most detrimental because of substantial economic losses. Over the past decades, chemical anthelmintics have been used to control GINs. Recently, GINs have developed resistance to most anthelmintics, and now reliance on anthelmintics is not possible. Alternative control methods are needed. Also, the use of fewer chemicals in agricultural products has called for alternative methods to be less synthetic and more organic. One promising alternative method is the feeding of condensed tannin (CT) containing forages as either fresh forage or dried products such as hay, ground hay, and pellets. Studies have shown that grazing or feeding sericea lespedeza (SL), a forage plant high in CTs, as whole plant resulted in some level of controlling H. contortus infection. The leaf has the highest CT content; so this study was conducted to determine which percentage of SL leaf meal was the most effective at controlling H. contortus infection in lambs and to determine any effect on reducing GIN larval development in the feces. Thirty-two cross bred lambs were randomly allocated into 4 groups with 8 animals each for a 5 week confinement trial. One group served as the control and received no SL. The other 3 groups received diets containing 25, 50, and 75% SL. Each week, feces and blood were collected to monitor infection level based on fecal egg count (FEC), blood packed cell volume (PCV), and enumeration and identification of larvae from fecal cultures. Fecal egg count decreased significantly (P \u3c 0.05) over time for all 4 groups; however, there were no significant differences between groups. There was a trend on regression analysis for the control group FEC to be significantly (P \u3c 0.001) greater during the trial. Reduction in FEC for the 3 treatment groups was 37.44-67.28% subsequent to week 1. There was no effect on PCV or nematode larvae population distribution and viability in feces. The antiparasitic effect of SL fed as leaf meal was not conclusive in this trial, but there was some evidence that suggested further evaluation is warranted