Abstract

Lambs grazing ryegrass infected with endophyte (Acremonium lolii) may exhibit staggers or diarrhoea or both, with little correlation between these two conditions. Associated mycotoxins/toxins other than the staggers-inducing lolitrems are likely to be responsible for metabolic changes causing reduced intake, elevated temperature and diarrhoea. These mycotoxins are not necessarily confined to the base of the leaf sheath and stem as is the case for lolitrems. The distribution of mycotoxins to proximal portions of vegetative ryegrass and the effect of these plant components on grazing animals was investigated. Following experimental confirmation in 1991 of nil correlation between staggers and diarrhoea, groups of lambs were grazed in autumn 1992 on 100% endophyte-infected hybrid ryegrass cv. Grasslands Marsden (Lollium boucheanum Kunth.), using a leader-follower system. Upper and lower leaves, and pseudostem were progressively removed by four groups of lambs on three day breaks, replicated twice. Liveweight gain ranged from 164 g/day in lambs having first offer, to 28 g/day in those grazing the base of the plants (P<0.01). Rectal temperature averaged 40.2 C being slightly above normal in all treatments. Faecal moisture was high; ranging from 79-87% throughout the experiment with no significant differences due to treatment. Observed faecal soiling was greatest in lambs receiving high leaf component (P<0.05). Clinical staggers, barely detectable in lambs grazing leaf, became severe as the proportion of pseudostem in the diet increased (P<0.01). In contrast to the clear association between endophyte and staggers in lambs grazing the base of infected ryegrass, consistently high faecal moisture, and consequent faecal soiling occurred regardless of the part of the plant consumed, but tended to be greatest in lambs grazing leaf. Analysis of plant components suggested that peramines may be associated with this problem.

MD, Bown, JB Clayton, and ML Bigham

Proceedings of the New Zealand Society of Animal Production, Volume 52, , 293-296, 1992