A stochastic, individual based systems simulation model describing U.S. beef cow-calf production was developed. Accounting for genetics, nutrition, reproduction, growth, health, and economics, allows analysis of various scenario outcomes encompassing different genetic, management, and marketing strategies. The model’s stochastic nature enables consideration of biological variation and probabilistic risk, while the systems design accounts for time delays and complex, prolonged feedback structure, all inherent to beef production. Any number of production years and iterations can be simulated. These capabilities make it ideal for decision analysis and assessment of long-run outcomes regarding a multitude of metrics simultaneously.
Parameterizing the model to match Kansas Flint Hills production and economic conditions for the years 1995 through 2018, 32 breeding systems with different genetic combinations for mature cow weight and peak lactation potential were simulated 100 iterations each. Sire mature cow weight genetics ranged from 454 kg to 771 kg in 45 to 46 kg increments. Sire peak lactation genetics were considered at 6.8, 9, 11.3, and 13.6 kg/d for all eight mature cow weights. Retaining replacement females, the breeding herd size goal was 100 animals. Model decision rules aimed to meet individual animal nutrient requirements.
Utilizing model results for the years 2000-2018, three different validation procedures were applied. A six person panel with combined expertise spanning veterinary medicine, animal breeding and genetics, ruminant nutrition, agricultural economics, and beef production modeling reviewed model output in both absolute and comparative scenario terms. Separately, raw model results were assessed against actual historical cow-calf production data. Finally, exploratory factor analysis was applied to interpret the underlying factor scores of model output relative to real-world cow-calf production data.
In cow-calf production, biological and economic efficiency are not perfectly synonymous. Research simultaneously assessing both the biological and economic efficiency of different mature cow weight and peak lactation combinations for twenty-first century cow-calf production is scarce to non-existent. Aggregating simulation results for the 2000 through 2018 production years, under the specific parameters previously described, larger, heavier milking cows exceled in kilograms weaned per cow exposed, while kilograms weaned per net energy for maintenance (kg/Mcal*100) favored smaller, heavier milking cows. Assuming no price differentiation between weaned calves from different breeding systems, 454 and 499 kg mature cow weight with 13.6 kg/d peak lactation had the highest median annual enterprise return on investment (fed ration, pasture, replacement, and interest expenses) at 8.9 and 7.4 percent, respectively. Applying the assumptions that herds comprised of 454 and 499 kg mature cow weight with 13.6 kg/d peak lactation do not exist and that all weaned calves from 454 kg mature cow weight breeding systems receive a small frame price discount, the 544 kg mature cow weight-13.6 kg/d peak lactation combination generated the greatest median annual return on investment at 7.0 percent. Several combinations of 499, 544, 590, and 635 kg mature cow weights with 11.3 or 13.6 kg/d peak lactation produced a median annual return on investment between 4.1 percent and 5.4 percent.
