Abstract
It is important that herbage intakes by grazing cows are estimated accurately. Here we compare use of a rising plate meter (RPM) and measurement of body weights to determine whether cows received sufficient total digestible nutrients (TDN). Additionally we measured changes in glucagon and the thyroid hormones triiodothyronine (T3), and thyroxine (T4) in blood. Eight Holstein cows were grazed all day on meadow fescue pasture. Cows were given formula feed and silage in the cowshed before milking. TDN satisfied by using a RPM were 82〜251%. Body weights were measured ①in the morning, ②in the morning after feeding milking,③ in the evening, and④in the evening after feeding milking. It was most reality method in estimate herbage intake by a body weight difference, (③in the evening weight)-(②in the morning after feeding milking weight)-(evening milk yield weight). There were no significant changes in T3, and T4levels over the experimental period although there was a significant rise in glucagon. In the period increasing glucagon the cows received lower than 100 % TDN suggesting that glucagon in grazing cows may indicate the levels of TDN.
