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Two bioeconomic computer models were used to evaluate calving seasons in combination with calf marketing strategies for a range-based cow-calf enterprise in the Northern Great Plains. Calving seasons studied were spring (SP, calving beginning March 15 and weaning October 31), spring with calf mortality increased by 5% (SP-IM), summer (SU, calving beginning May 15 and weaning December 31), summer with early weaning (SU-EW, calving beginning May 15 and weaning October 31), and fall (FA, calving beginning August 15 and weaning February 1). Marketing scenarios for steer calves and nonreplacement heifer calves were as follows: sold after weaning (WS), backgrounded in Montana and sold as feeder cattle (WBS), backgrounded in Montana and then fed to slaughter BW in Nebraska (WBFS), and shipped to Nebraska at weaning and fed to slaughter BW (WFS). Quarterly inflation-adjusted cattle and feedstuff prices were representative of the 1990s cattle cycle. Cumulative gross margin (CGM), the sum of ranch gross margin and net return from retained ownership was used to compare systems. At the peak of the cattle cycle, all forms of retained ownership (WBS, WBFS, WFS) were profitable for all calving seasons, but during the descending phase, only WBS increased CGM markedly over WS for SU-EW. At the cycle valley, retained ownership was not profitable for SP and SP-IM, whereas WBFS and WFS were profitable for SU and SU-EW, and all forms of retained ownership were profitable for FA. During the ascending phase, retained ownership was profitable for all calving season-marketing combinations. Systems with the greatest CGM at each phase of the cattle cycle were FA-WFS, SP-WBS, FA-WFS, and FA-WFS at the peak, descending, valley, and ascending phases, respectively. In beef enterprises representative of the Northern Great Plains, with a restricted grazing season and limited access to low-cost, good-quality grazeable forage, no single calving season and no single combination of calving season and calf marketing is expected to be superior throughout the cattle cycle. Fall calving systems most often benefit from retained ownership through slaughter. [ABSTRACT FROM AUTHOR]

Cattle grazing wheat pasture in the southern Great Plains are sometimes fed an energy supplement; however, the benefits of supplementation on nutrient balance, energy metabolism, and greenhouse gas emissions have not been elucidated. Therefore, we used 10 British crossbred steers (206 ± 10.7 kg initial BW) in a respiration calorimetry study to evaluate the effects of energy supplementation on energy losses, N balance, and nutrient digestibility of steers fed green-chopped wheat forage. The study design was an incomplete replicated 4 × 4 Latin square with treatments in a 2 × 2 factorial arrangement. Steers (n = 8) were assigned to 1 of 2 BW blocks (4 steers per block) with dietary factors consisting of 1) no supplementation (CON) or supplemented with a steam-flaked corn-based energy supplement (that also contained monensin sodium) at 0.5% of BW daily (SUP) and 2) NEm intakes of 1 times (1x) or 1.5 times (1.5x) maintenance. Wheat forage was harvested daily and continuously fed as green-chop to steers during the 56-d study. There were no differences (P ≥ 0.32) between CON and SUP for OM (78.3 vs. 80.7%, respectively) or NDF (68.3 vs. 64.8%, respectively) digestibility. At the 1.5x level of intake, there was no difference (P ≥ 0.16) in energy lost in feces (4.27 vs. 3.92 Mcal/d) or urine (0.58 vs. 0.55 Mcal/d), heat production (8.69 vs. 8.44 Mcal/d), or retained energy (3.10 vs. 3.46 Mcal/d) between supplementation treatments. Oxygen consumption (1,777 vs. 1,731 L/d; P = 0.67) and CO2 production (1,704 vs. 1,627 L/d; P = 0.56) of CON and SUP steers, respectively, were not different; however, SUP steers tended to have (P = 0.06) lower CH4 production (115 vs 130 L/d) than CON steers. Methane, as a proportion of GE intake, was similar for CON (6.87%) and SUP (6.07%; P = 0.18), as was the ME:DE ratio (P = 0.24; 86.3% for CON and 87.9% for SUP). Fractional N excretion in urine and feces, as a proportion of total N excreted (P ≥ 0.84) or N intake (P ≥ 0.63), was not different between treatments. Calculated NEm and NEg values for CON were 1.76 and 1.37 Mcal/kg DM, respectively, whereas the NEm and NEg values for the SUP treatment were 2.32 and 1.61 Mcal/kg DM, respectively. Calculated NE values for steers fed additional energy were approximately 17.5% greater than the expected difference in energy content. This was probably the result of the inconsistent response at the 1x DMI level. Under these circumstances, energy supplementation did appear to enhance NEm and NEg value of the supplemented wheat forage diet. [ABSTRACT FROM AUTHOR]

A bioeconomic computer model was used to evaluate alternate calving seasons in a cow-calf enterprise under range conditions representative of the Northern Great Plains. The simulated ranch utilized a rotational breeding system based on Hereford and Angus and had a fixed forage base (4,500 animal unit months of native range, 520 t of grass hay, and 183 t of alfalfa hay). Calving seasons studied were spring (SP, beginning March 15), summer (SU, beginning May 15), and fall (FA, beginning August 15). Weaning dates were October 31, December 15, and February 1, for SP, SU, and FA. The SP system was also simulated with a 5% increase in calf mortality (SP-IM), and SU with early weaning on October 31 (SU-EW). Herd size for the fixed resource was 509, 523, 519, 560, and 609 cows exposed per year for SP, SP-IM, SU, SU-EW, and FA, respectively. Corresponding values for weight weaned per cow exposed were 206, 186, 193, 153, and 145 kg. Steer calves, nonreplacement heifer calves, and cull cows were sold at the time of weaning. Quarterly cattle and feed prices used were representative of the peak, descending, valley, and ascending phases of the 1990s cattle cycle adjusted for inflation. Estimates of ranch gross margin (gross returns minus variable costs) were greatest for SP, followed by SP-IM, SU, SU-EW, and FA, and the ranks were consistent across phases of the cattle cycle. Differences between ranch gross margin for SP-IM and SU were small. In beef enterprises representative of the Northern Great Plains, with a restricted grazing season, limited access to low-cost, high-quality grazeable forage, and with calves sold at weaning, switching from early spring to a summer or fall calving date is not expected to improve profitability. If delaying calving improves calf survival, then calving in early summer may be a competitive choice. [ABSTRACT FROM AUTHOR]