The importance of nutrient balance, cropping strategy and quality of dairy cow diets in sustainable organic systems

This paper reviews some of the key factors that influence the sustainability and performance of organic dairy farms. These include the efficient utilisation of on-farm nutrients to maintain soil fertility and optimal crop production, minimising the importation of nutrients via purchased feeds and organic fertilisers, and the production of high-quality milk products. The system requires the growing of a range of crops to produce diets with a minimum content of 60% forage and an adequate feed energy concentration, with the growing of high-energy forages being limited on some farms by local climatic conditions. The compatibility between the genetic merit of the cow and the type of organic system depends on the quality of the forages produced on the farm and the level of concentrates fed annually. A failure to feed diets with sufficient energy, particularly during the early lactation period, leads to lower production, an increased risk of metabolic disorders and reduced reproductive efficiency. While purchasing concentrate feeds increases the stocking density, milk output and income per unit area of land, and also increases the flexibility to meet the annual feed requirements, the sustainability of the system is markedly reduced.