The effect of pasture species on lamb performance in dryland systems

Abstract

The effects of two contrasting forage supply options on forage and sheep production were evaluated on unirrigated farmlet systems at Winchmore, Mid-Canterbury. One option was based on perennial ryegrass pastures (Control), and the other (Improved) on hybrid ryegrass, tall fescue, and chicory pastures. All pasture types grew at similar low rates during winter but chicory grew more rapidly than the grasses during the summer droughts. The Control conserved more but required less conserved feed than the Improved system. Both had a feed deficit which averaged 23 and 42 kg DM/ewe respectively over the 2 years. The lambs on the Improved pastures grew more rapidly than the Controls throughout, exceeding the rate of the Controls by 142 and 165 g/head/day post-weaning in years 1 and 2 respectively. This resulted in considerably more lambs reaching target drafting weights on the Improved system, 92 vs. 53 and 97 vs. 58%, in years 1 and 2 respectively. This increased the income from lambs by $104 and $94/ ha in these years. Ewe liveweights were similar during pregnancy but differed during lactation and post-weaning at the end of which, ewes on Improved pastures were 6 and 4 kg heavier than the Controls in years 1 and 2 respectively. They consequently produced fleeces that were 10 and 12% heavier. The superior animal performance associated with the Improved system reflects higher pasture quality due to less endophyte and dead matter, and an increase in the proportion of the more nutritious components, legumes and chicory. Keywords: dryland, lamb production, pasture production, pasture quality, pasture species