Effects of Ryegrass Endophyte and Different White Clover Levels in Pasture on Milk Production from Dairy Cows
New Zealand dairy cows are grazed all year round on pastures dominated by perennial ryegrass (Lolium perenne L.). The ryegrass is usually infected with the endophyte Acremonium lolii Latch, Christensen and Samuels. The endophyte produces alkaloids (e.g. peramine) which protect the host plant from insect attack, but animals consuming the forage may be adversely affected and show clinical symptoms of ryegrass staggers and heat stress associated with the alkaloids lolitrem B and ergovaline, respectively. There has been little New Zealand research on the effects of ryegrass endophyte on milk production, so pastures were established with perennial ryegrass containing high (H, 85%) or nil (L, 0%) infection with the “wild type,” or common New Zealand endophyte. Previous work measured milk production on pure ryegrass but since most New Zealand dairy pastures also contain white clover (Trifolium repens L.), the ryegrass treatments were established with (+C) or without (−C) white clover.
KeywordsHeat Stress Milk Production White Clover Perennial Ryegrass Lolium Perenne
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