A comparison of two techniques used to estimate the herbage intake of lactating dairy cows in a grazing experiment

Herbage intake by grazing dairy cows can be estimated by measurements on the pasture ('t Mannetje, 1978) or by measurements on the animal (Raymond, 1969; Corbett, 1978). Of the sward sampling techniques, the difference method, based on pre- and post-grazing sampling, has the greatest potential for providing valid estimates of herbage intake, but only when grazing periods are short and stocking densities are relatively high (Pigden & Minson, 1969). Estimates of intake by measurements on the animal are made by the faecal output-indigestibility ratio technique (Raymond, 1969; Corbett, 1978). The most widely used marker for the determination of faecal output is chromic oxide (Cr2O3).