Abstract

A study at the Taranaki Agricultural Research Station investigated possible limitations to dairy production due to recently released ryegrass cultivars. Dairy animals grazed pure swards of either Yatsyn-1, Embassy, Vedette or Pacific in a series of three trials from February 1992 to April 1993. Three ryegrass cultivars (Yatsyn-1, Embassy and Vedette) were infected with the endophyte Acremonium lolii. Pacific was infected with an Acremonium endophyte, strain 187B. In trial 1 (autumn 1992) liveweight gain of dairy calves grazing the respective cultivars over eleven weeks were monitored. Trial 2 (spring 1992) and trial 3 (summer/autumn 1993) were each conducted over 3 consecutive 8 day periods using dairy cows. Liveweight gain and ryegrass staggers were monitored in trial 1, and milk volume and composition in trials 2 & 3. Herbage mass before and after grazing, dry matter disappearance, botanical composition, lolitrem b, in-vitro digestibility and crude protein levels were measured on each occasion, and ergovaline levels in trial 3. Ryegrass cultivar had no effect on calf liveweight gain. Ryegrass staggers were encountered in calves grazing Yatsyn-1, Embassy and Vedette but not in Pacific. In spring and in February and March of the summer/autumn trials, ryegrass cultivar had no effect on milk production or composition. Milksolids production from Yatsyn-1 was lower (P<0.05) than from Vedette and Pacific in April. Lolitrem content of Pacific was lower (0.14 ug/g grass) and ergovaline content higher (0.99 ug/g grass) in comparison to the other ryegrasses. There was no difference between cultivars in pasture utilisation, botanical composition, digestibility or crude protein levels. It is concluded that ryegrass cultivar or endophyte strain had little effect on dairy animal performance.

DA, McCallum, and NA Thomson

Proceedings of the New Zealand Society of Animal Production, Volume 54, , 87-90, 1994