A comparison of two methods for the estimation of herbage intake by lactating dairy cows

Extract

The herbage Intake of grazing dairy cows can be estimated either directly from measurements made through the animal or alternatively from sward measurements. Of the animal-based techniques, the most widely adopted method used to estimate herbage intake is the faecal output-indigestlbillty ratio technique. More recently, animal energy requirements have been used as a basis to predict herbage Intake. The objective of the present study was to compare the two animal-based techniques for estimating herbage intake.

Two experiments were carried out during 1984 and 1985. In Experiment 1 a total of 42 lactacing British Friesian cows were allocated to three grazing treatments. Herbage Intakes were estimated over three twelve-day periods during the experiment. In Experiment 2, 40 cows were allocated to three grazing treatments and Intakes were again estimated over three twelve-day periods. Two methods were used to estimate the herbage Intake of the cows. Method 1 involved the estimation of herbage intake from animal energy requirements using both observed liveweight changes (Method 1a) and liveweight changes calculated from a regression analysis of llvewelghts over the experitmental period (Method 1b). With Method 2 intakes were estimated by the faecal output-indigestibllity ratio technique.