Simulating Beef Cattle Herd Productivity with Varying Cow Liveweight and Fixed Feed Supply

The liveweight of New Zealand beef cows has increased in recent decades due to selection for higher growth rates. Published data suggest that the efficiency cow production decreases with increasing liveweight. Changes herd size, feed demand, production, and cash operating surplus (COS) were simulated average mature varied 450, 500, 550, 600 kg. With total annual demand fixed at same level, all scenarios numbers weaned calves decreased When model was run consistent calf across liveweights (scenario A), heavier more profitable. However, using published (scenarios B C), herds less likely most realistic scenario hill country farms B) had COS decrease from Dollars (NZD) 456/ha a 450 kg NZD 424/ha cows. Reductions relatively small, which may not deter farmers breeding results this analysis combined indirect potential economic impacts heaviest be optimal conditions.