Endophyte and dairy production in New Zealand: experience at the Dairying Research Corporation

Abstract

Sixteen short term tests of the effects of ryegrass (Lolium perenne L.) endophyte on milk production from dairy cows were carried out at Dairying Research Corporation (DRC) sites in Taranaki (1992/93) and Waikato (1993-1999). Increasing contamination of endophyte-free areas with volunteer endophyte-infected ryegrass could have modified milk production responses to endophyte in the first of two trials in the Waikato (1993- 1996). Test periods were in spring, summer and autumn. Significant effects of endophyte on milk production were detected on only 4 occasions. Small (<6%) reductions due to endophyte occurred in spring 1994, summer 1995/96 and spring 1997, and in autumn 1998 cows grazing pastures with high (H) levels of endophyte produced more milk than those grazing pastures with low (L) endophyte levels. Herbage levels of lolitrem B and ergovaline were low in spring 1994 and spring 1997 (<0.4 μg/ g DM) compared with peak levels in summer of 1.2 to 3.1 μg/g DM. Ryegrass staggers occurred in cows grazing H pastures in summer 1993/94 and summer/autumn 1994/95, but not when there was an endophyte effect in summer 1995/96. Herbage ergovaline levels and ambient temperatures were generally below critical levels for development of clinical heat stress in cattle, and cow rectal temperatures were unaffected by treatments. Overall effects of endophyte on milk production were considered to be small and inconsistent. Keywords: alkaloids, contamination, dairy cows, endophyte, ergovaline, lolitrem B, Lolium perenne, milk production, Neotyphodium lolii, perennial ryegrass, somatic cell counts