A new generation ryegrass endophyte - the first results from dairy cows fed AR37

Abstract

The AR37 endophyte strain in ryegrass produces epoxyjanthitrems but no peramine, lolitrem B or ergovaline, associated with the wild-type (HE) endophyte. An experiment commenced in 2005 to measure dairy cow health and production responses to AR37 in ryegrass. Four herds of 15 cows grazed on each of three endophyte treatments (AR37, AR1, HE and endophytefree (Nil) control) for 12 days in spring 2005 and autumn 2006, and in summer 2006 four groups of 10 cows were fed indoors to accurately assess cow dry matter and alkaloid intakes. Milk yields (kg/cow/day) were similar in spring but in autumn were lower (P<0.001) for cows fed ryegrass containing HE (11.8) than for those fed AR37 (14.1), AR1 (14.9), and Nil endophyte (14.2) ryegrass. Mild clinical signs of ryegrass staggers were noted in 67% of cows fed HE ryegrass in autumn. In summer, ryegrass staggers occurred in all cows fed HE ryegrass and average milk production was lower from these cows (10.9 kg/cow/day) than from those fed AR1 (12.9) and nil (13.5), but not significantly different from cows fed AR37-infected ryegrass (11.6 kg/cow/ day). No deleterious effects of AR37 on animal health were observed in any season. This experiment is ongoing and a more definitive evaluation of the AR37 endophyte is anticipated. Keywords: novel endophytes, milk production, cow health, cow intake, season