Keys to sustainable grazing : economic and environmental consequences of grazing strategies for dairy farms

In order to maintain grazing at highly productive dairy farms (i.e. farms with a high stocking density on the available grazing area), farmers start to change from traditional continuous and rotational grazing systems to compartmented continuous grazing (CCG) and strip grazing (SG). Unlike the traditional grazing systems, CCG and SG are grazing systems in which cows receive a new grazing area each day. A complete overview of the interlinked effects of grazing strategies, grassland utilization and cow productivity on the economic and environmental performance of highly productive farms was missing. The aim of this thesis, therefore, was to quantify the technical performance of improved grazing strategies, such as CCG and SG, in order to determine the economic and environmental consequences for dairy farms. In a grazing experiment we showed that, overall, CCG and SG can support fresh grass intake of high yielding dairy cows at high stocking densities, without compromising on milk production. Results showed furthermore that increasing fresh grass intake of dairy cows can improve the economic performance of dairy farms, at various levels of milk production, and that reducing grazing losses can improve both the economic and the environmental performance of dairy farms. To improve fresh grass intake, the right amount of fresh grass has to be allocated to the herd, which requires a reliable estimate of the fresh grass allowance. To improve such estimates, we first showed that one region-specific calibration equation to estimate fresh grass allowance can be used across grazing systems. Second, we showed the importance of correcting the fresh grass allowance for the formation of rejected patches surrounding dung. Third, we found a more labour-friendly method to quantify fresh grass allowance, which can take into account rejected patches, using drone technology.