Loline Alkaloid Effects on Gastrointestinal Nematodes

SIMPLE SUMMARY: Many plants contain natural secondary compounds that can exert medicinal effects. Parasitism in sheep is an animal welfare issue and affects performance. Much is unknown about natural plant compounds and how they could potentially serve as an alternative to traditional dewormers. Therefore, a series of preliminary studies conducted in the lab and in lambs were used to determine potential anti-parasitic effects of loline. Loline is an alkaloid found naturally in many fescue-type grasses and is considered non-toxic to mammals. Results from the studies were mixed. Despite potential promising results in the lab, there was limited evidence to support an anti-parasitic effect of loline in lambs. Discrepancies between lab and lamb studies were potentially a result of loline contact time with parasite larvae, mode of ingestion or the forms of loline present. ABSTRACT: Loline, an alkaloid with several derivatives, has suggested antimicrobial and anthelmintic properties. Therefore, loline was investigated as a natural anthelmintic against Trichostrongylus colubriformis, Teladorsagia circumcincta, and Haemonchus contortus. Preliminary in vitro studies had reduced L3 T. circumcincta establishment but no effect on L3 T. colubriformis larvae migration or H. contortus establishment. While loline-treated lambs had lower establishment of L4 and adult T. circumcincta and L4 T. colubriformis, L4 and adult H. contortus appeared unaffected. Following preliminary study, an in vivo experiment examined lambs infected with a mix of L4 T. circumcincta, T. colubriformis, and adult H. contortus. These lambs were treated with either a loline seed extract (LOL, n = 7), nothing (CON, n = 7), or a non-loline seed extract (NIL, n = 2). There were no differences in worm burdens, fecal egg counts, weight gain, or feed intake between treatments. However, an average growth efficiency (kg LWG/kg DM intake) was detected (p = 0.01) in CON (0.18) which was less than LOL (0.24) or NIL (0.23). There was limited evidence to support an in vivo anti-parasitic effect of loline despite in vitro studies indicating potential benefits. Discrepancies between in vivo and in vitro studies results were potentially a result of loline contact time with larvae, mode of ingestion or the forms of loline present.