Abstract
Effect of stocking rate on herbage utilization were studied in lactating Holstein cows. Cows (average BW=594kg, days in milk=47.2) were divided into two stocking rates; L=five cows/ha, and H=seven cows/ha. Cows were allowed to graze 5 hours daily from May to October of 1993 and 1994 at Experimental Farm, Hokkaido University, under time-restricted grazing system. Total numbers of cows grazed in 1993 and 1994 were: L=825 and 828, and H=1062 and 1153, respectively. In 1993, daily herbage utilization was almost equal in both groups (51 to 53kgDM/ha), but the annual herbage utilization of H was lower than L (7.9 vs. 9.1tDM/ha). Higher stocking rate in 1993 reduced sward height (8 to 17cm). This might be due to the shorter grazing cycle for H during spring of 1993 (4 to 8 days) compared to L (12 to 22 days). Also, total number of grazing days was shorter for H compared to L (156 vs. 171 days). However, there was no difference between annual herbage utilization of H and L (9.9 vs. 9.6tDM/ha) in 1994, when herbage was utilized in proportion to the seasonal changes of daily herbage production.
