Pasture management strategies for high yielding dairy cows

Grazed grass is the cheapest feed available to dairy cows, yet milk yield from grass on many dairy herds has either been static or declined over the last decade. This is partly explained by reduced intakes of grazed grass compared with the increase in silage based total mixed rations. High-yielding cows are unlikely to achieve their nutritional requirements from grazing alone and this has led many high output dairy farms to house their cows over the summer period as they can feed a more consistent total mixed ration thus maintaining milk yield. Reducing access to pasture is increasingly being perceived by the public as unnatural and cause for welfare concern as proved by the recent public debate relating to the proposed Nocton development. Indoor housing may also be associated with higher levels of mastitis as well as higher incidences of hoof disorders and lameness compared to cows kept at pasture. Appropriate supplementation of dairy cows at grass offers the opportunity to maintain animal performance, increase the yield from grass and potentially provide a higher welfare environment. However, the majority of research carried out to date investigates the effect of supplementation or buffer feeding of dairy cows at pasture using cows with moderate to low milk yields. There is a research requirement to optimise the use of grazed pasture in the diet of high yielding dairy cows through supplementation and grazing management. In recent studies from Harper Adams University College have demonstrated that cows with an previous experience of grazing spent 71% more time at pasture but offering the total mixed ration at pasture did not appear to alter their milk production or preference for grazing. Additionally, cows are prepared to work harder (i.e. walk further) for access to pasture at night than during the day, suggesting that using pasture for lying down at night is more important than grazing during the day. Research at SAC relating to continuously housed dairy cattle has shown that cows may be motivated to go outside even if this is only to a concreted loafing area, although this is strongly influenced by weather condition. There is therefore a strong research requirement to establish the importance of grazed grass to the welfare of high yielding, high genetic merit dairy cows and to determine how this is influenced by factors such as grazing allowance and previous exposure to grazing.

Aims & Objectives:

• To determine factors which influence the behaviour and performance of high yielding dairy cows at grass and to optimise their intake of pasture.
• To determine the effects of timing of pasture access and how this interacts with a buffer-fed TMR on the performance of dairy cows.
• To determine if the age at which dairy cattle are first exposed to pasture (either in their first or second year of age) has any effect on their subsequent motivation to access pasture.
• To provide information on the effects of different supplementation strategies on the performance of grazing cows.