Case Study: Irrigation and stocking rate influences on northern Michigan beef cow-calf and forage production

Although the Great Lakes Region has abundant fresh water, the area can be dry, especially during the summer growing season. Beef producers are considering use of irrigation because of this combined with diminished access to grazing land. Our objective was to investigate the combination of irrigation, genotype, and stocking rate on northern Michigan cow-calf production systems. Treatments were a combination of 2 irrigation levels, 2 breeds of cattle of contrasting body size, and 3 stocking rates expressed in animal unit equivalents (AU/ha). Sixty-four Red cow-calf pairs in total were assigned to 1 of 4 treatments: (1) 3 small Angus cow-calf pairs without irrigation (3SWO; 2.1 AU/ha); (2) 3 small Angus cow-calf pairs with irrigation (3SW; 2.1 AU/ha); (3) 5 small Angus cow-calf pairs with irrigation (5SW; 3.5 AU/ha); and (4) 5 large Simmental cow-calf pairs with irrigation (5LW; 4.4 AU/ha). Both animal and forage performance were monitored from May to August 2011. Irrigation aided forage growth with 17.8 and 16.0% greater pregrazing forage biomass in August compared with May in the 5SW and 5LW treatments, respectively. The greater stocked treatments returned more performance per hectare; 5SW had twice the overall cow and calf BW gain/ha in July to August when compared with 3SW. Overall, irrigation may sustain greater stocking rates and herbage production later in the grazing season and may be a viable tool for Midwest beef producers. This study was limited to 1 yr, so more long-term studies are needed to address the effect of variable precipitation and climatic conditions in Midwest beef systems.