Studies of the nutritive value of New Zealand dairy pastures

Abstract

Results are reported of digestibility trials with fresh pasture herbage fed at two levels to non-lactating twin cattle. Data are available from 16 consecutive weekly trials under full feeding, and 24 trials under restricted feeding. Feed/faeces ratios were calculated from feed O.M., feed energy, and faecal O.M. These were related by regression analysis to faecal nitrogen and energy contents. Prediction errors were higher under full than under restricted feeding, although similar regression coefficients applied to each level. Use of faecal energy content resulted in lower errors than when nitrogen content was used. Deviations from intake factor regressions were associated with level of faecal output. Direct estimation of intakes from faecal output and nitrogen or energy content was therefore examined and problems associated with the use of these equations in field intake studies have been discussed.