Extending grazing by changing calving date in the Nebraska Sandhills: Production and economic comparisons. Stalker, Aaron^*,1, Adams, Don ¹, Clark, Richard¹, Klopfenstein, Terry, ¹ University of Nebraska-Lincoln, Lincoln, NE

ABSTRACT- Calving date for 120 cows in the Nebraska Sandhills was delayed from March until June to extend grazing by better matching nutrient requirements for lactation with nutrient content of grazed forages. Half of the June calving cows were bred on subirrigated meadow regrowth while the remaining half and all March calving cows (75) were bred on upland range. Economic and financial costs were estimated by production phase on steer calves for four calf crops from both calving groups. Fed hay was reduced by 1.69 metric tons per cow for June calving cows compared to March by increasing days grazing from 233 days in March calving to 357 days in June calving cows. Pregnancy rates were similar (P > 0.10) for March calving (94.8%) and June calving cows bred on meadow (92.1%) and range (91.7). Weaning rate was similar (P > 0.10) among all treatments. Weaning weight was greater (220 versus 189 kg; P < 0.05) in March-born steers; however, gross value of a weaned March-born steer was only $11 greater ($439 versus $428) due to increased seasonal prices in January compared to October and price slide for lighter weights. Costs to produce a weaned steer were $76 less in the June calving system ($176 versus $252, without land and management costs) due to decreased feeding of harvested forage and labor inputs. Net returns per steer were $65 greater in the June calving system ($252 versus $187). Delaying calving until June did not change reproductive performance but reduced production costs and increased economic and financial net returns in the Nebraska Sandhills. Date of calving as a means to extend grazing will vary with geographic location and forage resources.

KEY WORDS: Extended grazing, Calving date, Production systems