Balancing multiple objectives in Southland, New Zealand: performance of dairy cow wintering systems.

Practices used to overwinter dairy cows by grazing them on forage crops in New Zealand are coming under increased scrutiny from the populace at large due to potential environmental and animal welfare issues. Farmers in the southern South Island are seeking wintering options that improve the physical and environmental performance of their farms. However, they need to balance a range of objectives for their farms including profitability, labour requirements, effects on the environment, feed supply and quality, animal health and welfare. This paper describes a project involving six commercial dairy farms, each using a different approach to dairy cow wintering: direct-grazed pasture and silage, direct grazing of brassica crops with supplementary feed offered in the paddock, stand-off pads, loose housing with slatted or woodchip flooring and a free stall (cubicle) barn. A range of performance indicators were identified and monitored over a three-year period on each farm. Pasture, supplement and crop yields and quality were assessed and milksolids (MS) production and reproductive performance recorded. Nitrogen (N) losses were estimated using the OVERSEER® nutrient budgeting model. Animal welfare was assessed by body condition scoring (BCS) cows and measuring lying times in the winters of 2011 and 2012. Profitability was assessed by comparing weekly costs per cow during winter. A whole-farm system approach was chosen to assess positive and negative consequences of choices made, and to develop options to improve system performance. Radar charts were used to demonstrate the performance of each farm system against a range of objectives. These charts can be useful when discussing how to balance multiple objectives, helping to avoid unintended negative consequences when changes are based on only one aspect of a system. The monitoring resulted in the development of a wintering risk assessment tool for use by other farmers in the region to benchmark the performance of their wintering system and identify areas for improvement.