Effects of loline-alkaloid-containing seeds or seed extract on in vitro gas production and apparent dry matter digestibility

Abstract

Loline alkaloids produced by Epichloë endophytes in pastoral grass species have suggested potential antimicrobial and anthelmintic properties. Loline is considered nontoxic, but the known effects of loline and derivatives on ruminal fermentation are limited. Negative effects could outweigh potential pharmacological benefits in vivo. Therefore, loline’s effect on ruminal fermentation was assessed using an in vitro gas production technique. Two experiments with 24-h in vitro gas production were conducted using an ANKOM gas production system. In Exp. 1, treatments were Festuca pratensis seeds either with loline (LS, 330 µg/mL) or without loline (NLS) as the sole substrate. In Exp. 2, treatments were Lolium perenne (perennial ryegrass) only (RGS), ryegrass with loline-containing seed extract (RGL, 330 µg/mL), or ryegrass with non-loline-containing seed extract (RGN). Cumulative gas production was measured over 24 h, and apparent DM digestibility and pH were collected at the end. Data were analyzed using a linear mixed effect regression in Exp. 1, and in Exp. 2 data were fitted to Ørskov’s nonlinear model to determine rate and extent of gas production. At 24 h, NLS had a 9% greater ( P < 0.01) gas yield than LS with similar apparent DM digestibility. Potential gas production was similar among ryegrass treatments. However, the fractional rate (%/h) was greatest ( P < 0.05) for RGN at 0.112 ± 0.02 and lowest for RGS at 0.093 ± 0.02, with RGL (0.109 ± 0.02) being intermediate and different than RGN and RGS. Apparent DM digestibility (73.2 ± 0.07, 63.3 ± 0.06, and 60.7 ± 0.06%) was greater ( P < 0.05) for RGS compared with RGL and RGN. Loline had little antimicrobial effect on ruminal microbes and fermentation, but the fermentation kinetics were altered. Loline needs further study as a potential pharmaceutical to be used on gut-dwelling organisms without negatively affecting rumen fermentation.