In this study, two total mixed rations (TMR, based on dry ingredients)
consisting (per kg dry matter (DM)) of 300 or 400 g finely
chopped hay mixture of grass and alfalfa (H30 versus H40) were
compared concerning their effects on dry matter intake (DMI),
ruminal fermentation patterns and chewing activity of earlyweaned
(8 weeks milk-fed) calves. Ten ruminally cannulated male
German Holstein calves were randomly assigned to two dietary
treatments (n = 5) and observed from an age of 8–15 weeks. One
group received the H30 (11.3MJmetabolizable energy (ME)/kg DM)
and the other the H40 (10.7 MJ ME/kg DM) TMR. All calves received
grass hay (9.0 MJ ME/kg DM) separately.Water, TMR and hay were
offered ad libitum twice daily (08:00 and 16:00 h). Rumen fluid
was collected via cannula at an age of 9, 11, 13 and 15 weeks,
twice weekly just prior to as well as 1, 3, 5 and 7 h after morning
feeding. Chewing activity was recorded by a special head collar. As