Tall fescue (Lolium arundinaceum (Schreb.) Darbysh) is a valuable perennial pasture species, the productivity of which is increased by infection with endophytic fungi. However, toxins produced by the endophyte can cause fescue toxicoses, which are potentially detrimental to animal growth and health. It is desirable therefore, to develop non-ergot alkaloid producing endophytes which are not harmful to livestock. The purpose of this study was to compare cultivars of tall fescue with or without novel endophytes for their effect on lamb growth and productivity. Five tall fescue cultivar or endophyte treatments were sown into a randomised block design including three replicates. The treatments were Martin 2 (Mart; no endophyte, acting as a positive control), Kentucky-31 (KY-31; containing wild endophyte and acting as a negative control), Martin 2 with novel endophyte Protek™ (Mart Protek™), Tower with endophyte Protek™ (TowerProtek™) and DuraMax fescue with endophyte Series 9 (DuraMax 9). When established, composite lambs were allocated to the 15 plots and grazed the irrigated pastures in two successive periods of 42 (n = 150 lambs; summer) or 65 days (n = 150 lambs; autumn) between January and May 2012. Herbage quality was similar between treatments. Ergovaline was detected at low levels (
