放牧牛の生理・生態に関する研究(II-8) : Indicator methodによる放牧和牛の消化率と採食量の推定について

The indicator methods by the use of chromogen and <Cr>_2O_3 as indicators were applied on grazing cows, for determining digestibility and intake of pasture forage. Four Japanese Black Breed of Cattle were used in this trial.
During 7 days adjustment period and 5 days fecal sampling period, 15 g of <Cr>_2O_3 were administered for each cow at 8 a.m. once daily. During 5 days sampling period, fecal grab sameles were taken rectally at 8 a.m. and 4 p.m.. These samples were analyzed and determined their chromogen and <Cr>_2O_3 contents.
The estimated coefficients of dry matter digestibility of pasture forage by grazing cows were ranged from 65.6 to 68.8%, and the estimated forage intakes were 30.3 to 45.3kg/day in fresh weight. The forage intakes were higher in two milking cows. The chromogen levels of forage samples from pasture had large variations and the chromogen and <Cr>_2O_3 contents of fecal grab samples also largely variated day by day.
From these results, it is suggestted that the reliability of estimated, values of digestibility and forage intake would be affected by the sampling of pasture forage, representative of the one consumed by cows, and by the period of fecal sampling.