Modelling the role of dairy-origin cattle for young beef production in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Manawatu, New Zealand

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Approximately 42% of calves produced annually in the New Zealand dairy industry are slaughtered by 2-weeks of age. This is seen as a wasted economic opportunity and has perceived welfare and ethical issues which could potentially affect both the dairy and beef trade. Young beef cattle production has been proposed to finish these calves for beef at 8 to 12-months of age. This study employed mathematical models to: 1) predict hind-leg muscle weight from young beef as an indirect indicator of saleable meat yield, 2) understand feed utilization and financial effects and 3) acceptance level of young beef cattle within the existing New Zealand beef cattle production systems. A univariate analysis using carcass weight explained 61% of variations in hind-leg muscle weight. This was improved by 6% in multivariate regression analysis using carcass weight, wither height and eye muscle area. Identifying additional traits in young beef cattle would improve the prediction accuracy and efficiency of the equations. A profit optimization model developed in this study identified selling strategies of beef cattle and sheep activities to increase farm profitability and pasture utilization on beef cattle and sheep farms. Including young beef cattle in the existing beef cattle and sheep farms increased the number of beef cattle processed per hectare, farm carcass output and pasture utilization. However, the farm earnings per hectare was lower than the optimized farm when carcasses from young beef cattle were processed under manufacturer beef price (i.e., NZ$ 4.50). Bulls (mainly Holstein-Friesian and Holstein-Frisian-Jersey cross breeds) accounted more than 50% of the total dairy-origin beef cattle processed in agent-based modelling (ABM). The uptake of Jersey breed for beef finishing was lower than 5% of the total dairy-origin beef cattle. Young beef cattle finishing under NZ$ 4.50 per kg carcass was not competitive with the traditional beef finishing systems. A 10% increase in value per kg carcass for young beef allowed them to contribute 6% of the total processed dairy-origin beef cattle. Incorporating consumers perspectives and other decision alternatives for the finisher could improve decision making on the use of young beef cattle in New Zealand.
Beef cattle, Dual-purpose cattle, Economic aspects, New Zealand, Mathematical models