On 6 of a set of 12 self-contained experimental farmlets, improved pasture cultivars 'Ellett' ryegrass, 'Grasslands Wana' cocksfoot, 'Grasslands Tahora' white clover, Whatawhata Early Flowering' white clover, 'Mount Barker' sub clover, 'Tallarook sub clover, 'Grasslands Mama prairie grass, 'Grasslands Pitau white clover and 'Grasslands Pawera' red clover were successfully established in 1986. Measurements began May 1987. Results presented to May 1989 include pasture production, animal production and financial returns. Matua prairie grass failed to persist beyond spring 1988 but clovers including Pawera and Pitau in these pastures increased summer production in 1989. In summer 1989 the improved steep pastures produced 8 kg DM/ha/day more feed than the resident pastures, with most of this increase owing to Wana cocksfoot. Lamb numbers and lamb weight gains were greater with improved pastures. Bulls were priority finishing animals and their weights were insensitive to pasture treatment. Current returns from this experiment show little to justify the investment made in introducing new cultivars into existing developed hill pastures. Keywords pasture cultivars, hill country, finishing systems, pasture improvement

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'Grasslands Matua' prairie grass was direct drilled into easy hill county at Whatawhata Research Centre. Establishment was excellent, but persistence was poor in most paddocks after 2 years. Site conditions associated with a range of Matua populations were surveyed. Matua population decline was greatest during spring. Spring soil nitrogen levels were associated with persistence, implying that nitrogen application in late winter may enhance persistence. In a trial to assess the effect of spring management on tillering patterns, seed production and seedling vigour, October closing resulted in the highest seed production, seed vigour and highest tiller density after herbage removal. It is proposed that a springsummer hay making policy will enhance the vigour of the existing population and provide adequate reseeding for new plant recruitment. Keywords Matua, persistence, soil survey, nitrogen, tiller density, closing date

Levels of treading damage were measured for a range of cattle feeding regimes and grazing managements which were compared during winter and spring. These paddock- and systems-based results provide a context within which component research on soil and plants can be interpreted. Soil surface damage was higher in farmlets with heavier cattle (390 kg vs. 200 kg steers) and on paddocks where feeding was restricted through the use of a slow rotation (100-120 days vs. 35-45 days). Where cattle grazed under wet conditions, with a pre- and post- grazing herbage mass of 2400 and 650 kg DM/ha respectively, damage levels reached 60-70% of the soil surface. Under these conditions, 300-350 kg DM/ha of initial forage on offer was pushed onto or into the surface soil; and pasture growth rates during early-mid spring would be reduced by 10 kg DM/ha/day. In practice the objective of grazing plans and management should be to minimise these negative impacts within the constraints of the required feeding regimes. Recommendations are made for the alignment of stock class and enterprise with land capabilities and the feed allocation processes of a winter rotation. Keywords: cattle grazing systems, forage supply treading damage

A dynamic model for nematode parasites in lambs which links their adult worm burden with decrease in liveweight gain has recently been developed. This model allows for individual lamb variability in response to parasite infection. We use this model to track the liveweight performance of a mob of weaned lambs under six different grazing rotation length scenarios. In all scenarios, lambs with a low worm burden were weaned onto parasite-free pasture. Post-weaning, lambs were either grazed in a 12-week, 8-week, 6-week, 4-week or 2-week grazing rotation, or set stocked. Scenarios were run for 24 weeks with no anthelmintic intervention. The 12-week and 8-week grazing rotation scenarios provided lower worm burdens, higher liveweight gains and lower variation between individual lambs than the other scenarios due to the delay in grazing self-contaminated pastures. For systems that use little or no anthelmintics, being able to provide 8 weeks or more of parasite-free pasture to weaned lambs is likely to provide substantial benefits in the form of higher liveweight gains with less variation between individuals. Keywords: grazing, lambs, liveweight, modelling, parasites