Combining the optimal management of grazing and the performances of dairy cows : issue and tools

Abstract

Utilisation of grazed grass should form the basis of sustainable dairy systems in the future. Grazed grass is the cheapest feed available for dairy cows and may also help to reduce the environmental impact of the most intensive systems while giving a natural image of farming. Efficient exploitation of grass by grazing will require the development of grazing systems designed to maximise daily herbage intake per cow while maintaining a greater quantity of high quality pasture over the grazing season. This paper discusses the conditions for efficient exploitation of grass and outlines the possibilities for future advances. There are opportunities to consume more grass by extending the grazing season in early spring and late autumn or by intentionally deferring grazing from a period of grass surplus in the spring to a period of grass shortage in the summer. The introduction of legumes in grass-based swards should also be seriously considered as an alternative option to pure grass swards in order to maximise cow performance. There are also opportunities to manage seasonal production of grass by plant selection, improved N fertilisation strategies and better grazing management. The opportunity to increase cow perfor-mance by decreasing stocking rates is rather limited because this practise is constrained by the necessity to maintain high quality swards over the grazing season, unless alternative strategies are adopted. Increasing leaf blade mass at the base of the sward by appropriate gra-zing management in the early spring may play a major role in increasing herbage intake. This will result in a low residual sward height thus making grazing management easier. This requires a greater knowledge of the carryover effects of early season grazing management on mid-season pasture quality and the implication for milk output per hectare. In the future, development of reliable decision support methods and tools for short term rationing of grass at the paddock level and long term budgeting of grass at the farm level will give far-mers more confidence in grazing and will undoubtedly contribute to optimising the proportion of grazed grass in the annual diet of the dairy cow.