Estimation of the digestibility of low-quality hays by cattle from measurements made with sheep

Seventeen sets of apparent digestibility data derived from 10 experiments, in which both cattle and sheep had been fed on the same hays, were examined. The study was restricted to low-quality hays of less than 60% apparent digestibility of dry matter. On average, digestibility was higher for cattle than for sheep, and the difference was greatest with the samples of lowest digestibility. A linear equation found to describe best the relationship between the digestibility of hays by cattle and sheep was:

$\text{y = 0.673 x + 20.3}$

where y = digestibility of hay to cattle (%) and x = digestibility to sheep (%) (r = 0.843; S_y.x, ± 3.41; standard error of the slope, ± 0.111). This equation may be used to correct apparent digestibility values of 60% or less measured with sheep, or estimated in vitro with the use of sheep standards, if the digestibility data are to be applied to cattle.