Simulating use of terminal sires in a self-replacing beef suckler herd with varying weaning rate, calf sale policies, and price premiums

Abstract

New Zealand farmers can choose to breed a proportion of their beef cow breeding herd with terminal breed sires to produce heavier offspring to sell for higher per head prices. However, the heavier weights of terminal offspring also increase their feed demand which may necessitate cow herd size reductions in a system with a fixed feed supply. This study used a bio-economic, system dynamics model to simulate cattle numbers, production, and beef enterprise cash operating surplus (COS) for a self-replacing beef suckler herd of Angus breed cows bred with only Angus sires to produce purebred offspring or a proportion of cows bred with European breed terminal sires (such as Charolais or Simmental). The herd was also modelled with varying calf weaning rates (84 or 90%), with offspring sales occurring either at weaning or at 27 months of age, and in a secondary analysis, with or without price premiums for sales of cattle of at least 75% Angus breed. Total annual beef feed demand was maintained at 40% of total farm feed supply (total farm area of 530 ha) in all scenarios, with the remainder consumed by the on-farm sheep flock. Beef enterprise COS was therefore divided by the beef herd proportion of farm area (212 ha) to derive a per ha COS value. Herd replacement rate was first modelled at 22% allowing for 43% of cows to be bred with terminal sires with a weaning rate of 84%. With a weaning rate of 90% the replacement rate was 18% allowing 60% of cows to be bred with terminal sires. The base scenario with a herd weaning rate of 84% using only Angus sires had a COS of NZD 255 /ha. Relative to the base scenario, use of terminal sires increased COS by the largest amount (COS = NZD 317 /ha), Angus premiums increased COS by a lower amount (COS = NZD 307 /ha), and the higher weaning rate of 90% increased COS by a slightly lesser amount (COS = NZD 302 /ha). Alternatively, these strategies could be implemented concurrently, which was predicted to have the highest COS at NZD 381/ha. These results can inform farmer decision making and farmers can consider the relative profitability potential and practicality of the explored strategies for their breeding herd.