Feeding and grazing management for dairy cattle: opportunities for improved production

An adequate feed intake is an important prerequisite to realize high milk production in dairy cows, especially during grazing. The analysis of feed intake behaviour can assist in understanding variation in daily intake and in improving its prediction. Indeed, our results indicated that differences in feed intake behaviour were more pronounced when varying the type of roughage than when varying the type of concentrate. Dry matter intake (DMI) was reduced when a ration high in grass silage was fed, but milk production was only numericaly affected. Grazing management might result in increased herbage intake and higher intake of nutrients from herbage by improved nutritional composition of herbage. In the first grazing experiment, herbage DMI was indeed increased when allocating cows daily (1Da) to a new grazing plot compared to every four days (4D) allocation, but only when pasture mass on offer and sward surface height (SSH) were high. Grazing time increased numerically and ruminating time decreased between days in the 4D treatment, coinciding with differences in rumen fermentation characteristics and milk composition. Milk yield was greater in 1Da than in 4D, but milk fatty acid (FA) composition, potentially influencing human health, showed hardly any difference. In a subsequent experiment, herbage DMI was again greater when allocating twice daily (2D) compared to once daily (1Db), especially when SSH was high. Grazing behaviour was more equally distributed in 1Db than in 2D and milk yield was increased in 2D compared to 1Db at high SSH, but as before milk FA composition hardly differed between treatment. The last grazing experiment aimed to take advantage of the higher sugar contents of grass in the afternoon than in the morning. It showed that grazing behaviour and herbage intake were similar between morning (MA) and afternoon allocation (AA), but cows receiving a fresh plot in the afternoon had a longer evening meal than cows receiving a fresh plot in the morning. This, in combination with differences in diurnal chemical composition of the grass between treatments probably caused higher intake of sugars in AA, resulting in a higher milk fat content. However, milk production remained unaffected. In conclusion, the results of this thesis indicate that short-term feed intake behaviour is related to DMI and therefore may be a helpful tool in optimizing DMI and milk production in high-production dairy cows. Increased pasture allocation frequency improves intake and milk yield in grazing dairy cows, especially when offered SSH is high enough. In intensive stripgrazing systems, reallocation of dairy cows following afternoon milking instead of morning milking has no added value.