The Quantities of Herbage Eaten by Grazing Dairy Cows

The herbage dry matter intake of grazing animals may be estimated by chemical marker and faecal analysis methods (Raymond, 1954) or by pasture sampling methods.Pasture sampling methods generally involve two main difficulties. The first is the low precision resulting from the variability of pasture yields. When intake is estimated from the difference between the yields of herbage on a given area sampled before and after the grazing period, the estimate bears the error variances of both the sample means. The second difficulty lies in ensuring that the estimated difference in yields is the true difference due to consumption. The samples must be cut below the level to which the animal can graze, and the amount of herbage growth during the grazing period must be estimated and allowed for. Growth can be estimated from the difference between the yield of herbage before grazing and the yield of protected herbage at the end of the grazing period.