Effects of breeding date, weaning date, and grazing season length on profitability of cow-calf production systems in southeastern Montana.

Production data from 11 southeastern Montana ranches were used to parameterize a bio-economic computer model of cow/calf range production. Effects of changes in breeding date, weaning date, and range removal date on system performance for a ranch with a fixed forage resource base (3,060 animal unit months of range forage and 744 t of hay) were simulated. Input costs were locally established in 1994. Cattle prices were determined by week from 13-yr averages. For the base scenario, breeding season was 66 d with breeding starting on June 9. Weaning, range removal, and calf sales occurred on November 3. Cows were fed stored forages from November 3 until turnout to grazing (May 1). Five replications were simulated for combinations of breeding, weaning, and range removal dates in a factorial design. Each factor was deviated from the base scenario by +/- 14 and 28 d. Production efficiency was measured by break-even steer price. Gross margin (gross revenue - variable costs) was used as a measure of profitability. Increasing calf age (and weight) at sale time, by decreasing breeding date and(or) increasing weaning date, improved ranch efficiency and profitability. Increasing range removal date improved system performance even though extending the grazing season led to decreased herd size. Compared to the base system, the best system increased gross margin by approximately 17%. Responses for gross margin reflect the dynamics of herd size, purchased feed expense, and production efficiency. Results suggest that for range-based cow-calf enterprises in the northern Great Plains, production efficiency and profitability may be improved by increasing calf weaning age and extending the grazing season, even if herd size must be reduced.