The prediction of grass silage intake by beef cattle receiving barley-based supplements

Data on the intake by beef cattle of 11 silages either unsupplemented or su pplemented with barley-based concentrates were provided from six studies ca rried out at the Institute. An empirical model was developed from these dat a which described an exponential decrease in silage intake as concentrate i ntake was increased, with y-axis intercepts corresponding to unsupplemented silage intakes and a common x-axis intercept of 73.3 (S.E. = 2.00) g/kg W- 0.75 corresponding to concentrate intake when offered as a sole feed. The m odel curvature (r parameter) was also shown to be constant for all silages (1.025 (S.E. = 0.0038)). When the model was validated against external data (11 published studies), the relationship between actual and predicted sila ge DMI gave an R-2 of 0.89 with an intercept and slope not significantly di fferent from 0 and 1, respectively. Seventy-six percent of silage DMIs pred icted using the developed model were within 0.5 kg DM of the observed intak es in the validation data. The developed model showed an improvement over a previously published model, as indicated by a significant reduction in the mean squared prediction error. (C) 2001 Elsevier Science B.V. All rights r eserved.