Abstract
Five imported grass hays (oat, sudan grass, tall fescue, bermudagrass and timothy) were evaluated by palatability test with dry cows, feeding trials with lactating cows, in vitro digestibility with rumen fluid and counting the numbers of chewing in lactating cows. The daily intakes of hay dry matter were 7.6^<abcd>, 7.0^<cd>, 6.8^d, 8.1^b and 9.0^a kg per cow, and the daily milk yields were 26.5, 25.7, 25.0, 25.2 and 25.5kg per cow on the oat, sudan grass, tall fescue, bermudagrass and timothy respectively (a, b, c, d different superscripts are siginificantly different, p<0.05). The following equations ware obtained for hay dry matter intake (HDMI) from in vitro digetion data: HDMI=0.707×CW digestion rate (%)-1.64×lag time (hr)+8.0 (R^2=0.91), and HDMI=0.26×12hr digestibility (%)-1.2×lag time (hr)+7.9 (R^2=0.98).
