Abstract

Feed and winter management options were modelled for a dairy farm and its adjoining support land in the Lake Rotorua catchment. The dairy farm grew turnips, fodder beet and oats, with non-lactating cows grazing on the dry-stock unit on pasture, kale and fodder beet. Scenarios investigated were: removing crops from the dairy farm whilst either A) reducing stocking rates by 5%; B) feeding additional palm kernel expeller (PKE); C) replacing crops, PKE and pasture silage with purchased maize grain and maize silage; or D) grazing non-lactating cows on the dairy farm and reducing stocking rates by 17%. Using a milk price of $6.00/kg MS, D was the only scenario that increased profitability of the dairy farm (7%). Compared to the base scenario, nitrate leaching on the dairy farm increased for scenario D and decreased for scenarios A, B and C. When including the dry-stock unit, total N leaching was reduced by 5, 0, 13 and 15%, for A, B, C and D, respectively, compared to the base farm. These results reiterate the importance of investigating the impact of off-farm winter grazing in nitrogen-sensitive catchments.

VT, Burggraaf, GR Rennie, P Edwards, and I Pinxterhuis

New Zealand Journal of Animal Science and Production, Volume 79, Palmerston North, 71-73, 2019