Achieving high dry-matter intake from pasture with grazing dairy cows

Abstract

Due to economic, environmental and animal-welfare constraints, it is envisaged that in the future a larger proportion of the milk produced in temperate regions will be produced from grazed pasture. However, with the selection of modern higher-production dairy cows, increased emphasis on product quality and issues associated with nitrogen leaching, soil compaction, greenhouse-gas emissions and animal welfare, pasture-based systems will also require higher per-animal productivity in the future. This will necessitate the development of grazing systems designed to maximize daily herbage intake per cow, while at the same time maintain a high-quality pasture over the entire grazing season. Daily grass DM intake will be maximized by adhering to important sward characteristics such as maintaining a high proportion of green leaf within the grazing horizon while allocating an adequate daily herbage allowance. Increasing the green-leaf proportion at the base of the sward through appropriate grazing management in early spring may play an important role in increasing herbage intake and making grazing management easier. This requires knowledge of the carryover effect of early-season grazing management on midseason pasture quality and the implication for milk output per hectare. The present plant selection and evaluation systems target improved grass DM yields rather than parameters that influence animal performance. There is a clear requirement for an increased selection emphasis on characteristics that influence animal performance, i.e., herbage intake. This can be best achieved by adopting an interdisciplinary approach with plant physiologists, nutritionists, breeders and evaluators sharing knowledge and resources. Likewise, in the future the cow genotype must be compatible with the system of milk production, and prediction of the phenotypic performance of dairy cattle must be based on knowledge of the cows’ genotype as well as the environment in which they are managed. The development of reliable, easy to use decision support tools that facilitate increased reliance on grazed grass, to be used by farmers and extension services, will contribute to optimize animal performance from grazed pasture