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.
Keywords: alkaloid; loline; nematoda; parasites.