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Keywords:

  • bulls;
  • grass silage;
  • daily liveweight gain;
  • mean daily return;
  • simulation model;
  • multivariate empirical variation;
  • risk

Abstract

This study focuses on the effect of grass silage energy concentration and price on the decisions about concentrate level, slaughter age and carcass weight in the finishing of young dairy bulls.

The three main steps were as follows: (i) the adaption of a daily liveweight (LW) gain simulation model to young dairy bulls of the breed Norwegian Red; (ii) the comparison of the model key output to experimental data; and (iii) model-based maximization with respect to the profitability of the finishing period, and stochastic simulations with respect to prediction error and variation as derived from the experimental data. In general, the model adequately simulated the LW gain of the bulls, but tended to overestimate the LWs of the bulls that received very high energy rations and underestimated the LWs of the bulls fed with the lowest energy diets. Model-based maximization of profit was conducted for three silage energy concentrations, expressed as feed unit beef (FUb), combined with three silage prices. Taking into account the risk associated with model prediction error and the empirical variation and correlation among key variables, we concluded that under the prevailing Norwegian economical conditions, finishing of young dairy bulls with an early harvested silage having an energy concentration of slightly above 0·90 FUb kg−1 dry matter, 10% FUb concentrate of the total FUb ration and an average daily LW gain of 1·2–1·3 kg LW d−1 will offer the highest profit.