Perennial ryegrass (Lolium perenne L.) pastures in New Zealand contain the fungal endophyte (Acremonium lolii). This association produces a range of toxins; some, such as lolitrem B and ergovaline have been associated with ryegrass staggers, decreased serum prolactin, heat stress and decreased milk yield. Grazing trials with lactating cows have given equivocal results in terms of milksolids yield. Two experiments examined the effects on autumn milk production of supplementing cows grazing pasture with grass and grass/clover silages containing different endophyte concentrations on autumn milk production. Forty cows were used in a 2 x 2 factorial experiment with low (L) and high (H) levels of endophyte in both pasture and silage. In Experiment 1 (28 March - 6 April 1995) cows were grazing clover free pastures and supplemented with either L or H endophyte grass silage. In Experiment 2 (7-12 April 1995) cows were grazing pastures containing about 17-25% white clover and supplemented with either L or H endophyte grass/clover silage. At the first milk sampling three days after treatments started in Experiment 1, milk yield from cows given L pastures was 6.9% higher than from those grazing H endophyte pastures (P=0.006), and 4.1% more when L rather than H endophyte silages were given (P=0.10). These effects were additive so the cows fed L endophyte silage and L endophyte pasture produced 11.3% more than those fed H silage and H pasture (P=0.002). The effect of pasture endophyte on milk yield was still evident after seven and ten days of treatment, with 10.3% more milk from L than from H endophyte pastures (P=0.01). Milk protein yields paralleled milk yields after seven and ten days but there was an endophyte x silage interaction (P=0.05) for milkfat yield and protein and fat yields were not effected by treatment. In Experiment 2 when clover was included in the diet there were no significant effects from either pasture or silage endophyte status on any milk yield components. A comparison of milksolids yield from Experiment 1 and Experiment 2 shows that changing to diets containing white clover increased milksolids by 6.4, 13.9 and 21.9% for the L/L, L/H and H/L pasture/silage combinations, respectively, but only increased milksolids by 2.7% for the H/H pasture/silage combination. We conclude that endophyte in both pasture and pasture silage can have a transitory effect on milk and protein yield during the autumn and the nutritional benefits of white clover for increasing milksolids was much reduced by endophyte in both pasture and silage diets.

DA, Clark, ER Thom, and CD Waugh

Proceedings of the New Zealand Society of Animal Production, Volume 56, , 292-296, 1996
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