Sheep have a strong preference for clover in summer. One explanation for this may be the avoidance of alkaloids such as lolitrem B, ergovaline and peramine that are produced at that time of the year by endophytic fungi in ryegrass. We tested this hypothesis by exposing groups of three sheep to three food items (ryegrass with wild-type endophyte (E+), ryegrass with no endophyte (E-), and white clover (CL)), in December and in February. Each food was offered singly and in pairs, and time spent grazing on each food, short-term dry matter (DM) intake rate, and preference was measured. In February, sheep given E+ or E- ryegrass alone, grazed for 400 mins/day, compared with 370 mins/day when given a choice between them (P=0.15, SEM=14). The time spent grazing on the E+/E- choice was comprised of 280 mins/day on E- and 90 mins/day on E+ indicating a strong preference for E-. When offered ryegrass and white clover, the total grazing time (335 mins/day), and the grazing time on clover (285 mins/day) and on ryegrass (50 mins/day), were similar for E+/CL and E-/CL. Short-term dry matter intake rate of grass (3.4 g DM/min), and the strong preference for clover in this study, were unaffected by the presence of endophyte. We conclude that while sheep detect endophyte alkaloids, they avoid eating them only when doing so does not reduce daily intake or change the proportion of grass and clover in their diet.
Proceedings of the New Zealand Society of Animal Production, Volume 62, Palmerston North, 167-170, 2002
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