Responsible

Duration

Description

Dairy farming at present under Danish conditions is based on high animal performance, and in the summer period grazing at short-lasting grass/clover areas with a high herbage production and moderate applications of N. Time for milking and feeding of supplement are the limited factor for herbage intake and not the amount of herbage available.

The N-surplus under these conditions with continuously grazed grass/clover pastures during the whole season can be as much as 429 kg N ha-1 y-1 under Danish conditions. The present management systems used appear to cause a higher N-surplus than necessary. When grazing time is not restricted the N-excretion on pasture will be relatively high compared to the N-intake by the cows. The protein content in herbage is high in the present pastures both due to a low herbage mass and to a high content of clover. A better management could optimise the protein/high digestible carbohydrate ratio in the herbage. The N-utilization by cows is lower during grazing than during winter but there seems to be considerable possibilities for improving N utilization both through an even ruminal energy supply and a better synchronization of ruminal degradation of protein and energy.

We expect that grazing also in the future will play an important part in dairy farming management due to the aspects of animal welfare and economy, as grazing still will be a cheap way to provide fodder. We also expect that the pastures will remain as high-production short-duration grass/clover with white clover and that the management still will be a cutting/grazing system. However, the size of dairy farms and herds will increase rapidly during the next decade. This means that the distance from stable to pastures may increase, and the potential area per cow for grazing may decrease. Further, will an increasing number of automatic milking systems (AMS) mean that the cows rather than the farmer are managing the milking time. Based on these facts it will be necessary to improve the grazing system towards a lower N-surplus and to adjust to large-scale farming systems and AMS without compromising milk production per cow.

The main objective of this project is to find new knowledge and create tools that will reduce N-surplus at dairy cow grazing both at cow-level and grazing-system level. We will use a combination of experiments, modelling and system development at commercial farms in order to find systems for grassland management that can combine productivity of herd and grassland, with environmental concern and the future changes in farming systems in general.

In a grazing experiment with high yielding dairy cows the effect of varieties of perennial ryegrass, herbage allowance, time in the season and supplementation of energy and protein concentrates will be examined. Models will be made for climate-depended content of crude protein and water-soluble carbohydrates in pastures in spring, and management-depended content of crude protein during the grazing season. Grazing systems involve a number of biological and production system factors, which means that the behaviour of the system and the individual processes are difficult to estimate from experiments. The objectives of the farmer and the limits of the production system are important aspects, which together with the results from the experiment and the ‘model pasture’ will be used in development of grazing system with restricted grazing time at a number of commercial study farms. The expected results will include decision support systems for grazing management concerning prognosis for spring herbage quality and tools for operative managing herbage protein content. Tools will be made for improved management at restricted grazing-time in daytime including supplementation, grassland species, herbage allowance and the farming system.