Effect of grazing method on grass quality change during a 24- hour period

Changes in grass quality during day and night can be relevant for both research and practice. In research a representative sample of the provided grass is essential for reliable results, and for practice it can affect management decisions. In a zero-grazing system, grass is brought to the barn two to three times a day and afterwards fed in small portions which might lead to a decay of grass quality. In a pasture, fresh grass quality can change during the day and night under the influence of sunlight and selection by the cows.In a grazing trial on the Dairy Campus, it was examined how grass quality was affected over time. In the zero-grazing system, a sample was taken on 7 occasions during a 24-h period to assess the quality. In the 24-h grazing system, fresh grass samples were taken from the same plot around 8 am and 6 pm. The samples were analysed on feed quality. It appeared that mowing fresh grass twice a day and providing it in small portions over the day did not result in a significant change in feed quality. During grazing, it was found that in the evening the sugar content was higher and the crude protein content lower. There was no significant difference in the other components. These results show that time of sampling fresh grass in pasture needs to be taken into account in grazing research.