Estimating forage mass of tall fescue pastures and dry matter intake and digestibility of fescue forage by beef steers

A series of three experiments were conducted to evaluate different methods of estimating forage mass of tall fescue pastures, and dry matter intake and digestibility in beef steers under indoor and grazing conditions. Forage mass was estimated with the herbage cutting method (HCM) and three indirect methods; the pasture capacitance meter (PCM), the plate meter (PPM), and the visual estimation (VE). The coefficients of determination from the calibration equations were 0.686, 0.751, and 0.862 for the PCM, PPM, and VE, respectively. There were differences in forage mass estimates due to sampling method, sampling date, and their interaction. The second experiment was a digestion trial conducted with confined animals to determine the recovery rate of chromic oxide and alkanes from controlled release capsules and to evaluate the accuracy of the concurrent estimations of intake and digestibility. No difference was found in the recovery rate of either alkanes or chromic oxide during the 7 d of the collection period. Likewise, actual fecal output, dry matter intake, and digestibility were not different from the estimated values. However, estimated values had to be adjusted for the respective recovery rate. The third experiment was conducted under grazing conditions to evaluate the chromic oxide controlled release capsule technique in estimating intake and digestibilty. In this trial, although the recovery rate of the marker was extremely high (avg. = 1.89), the actual and estimated values of dry matter fecal output, intake, and digestibility were not different. Again the recovery rate had to be used as a correction factor.