Range of quality characteristics of New Zealand forages and implications for reducing the nitrogen leaching risk from grazing dairy cows

The New Zealand Government's National Policy Statement on Fresh Water Management has resulted in increased scrutiny of New Zealand grazing systems with regards to their environmental impact. With this has been greater interest in nitrogen (N) loss mitigation options, including identifying crops with high nutritive value but low protein content. New Zealand data have been collated with key data fields: publication, experiment, site and, crop details and chemical analysis. This paper discusses these data with respect to the range of nutritive values observed in these New Zealand crops and feed supplements, including the implications for reducing N leaching risk. Feeds most likely to result in less urinary nitrogen (UN) excretion, and thus less nitrate (NO3-) leaching, include fodder beet, swedes, turnips, barley and wheat grain. The high soluble sugar and starch content of these feeds will support high animal production but may increase the risk of nutritional disorders.