Utilizing an Electronic Feeder to Measure Mineral and Energy Supplement Intake in Beef Heifers Grazing Native Range

Introduction Grasslands in the Northern Plains provide the primary forage source for ruminants throughout much of the year (Schauer et al., 2004). Supplementation practices are often necessary to maintain production and offset forage nutritive decline throughout the grazing season (Schauer et al., 2004; Cline et al., 2009). Typically, to maintain a targeted production level, energy and protein supplementations are used for grazing livestock (Caton and Dhuyvetter, 1997). For developing heifers consuming low-quality forages, inclusion of energy ingredients into supplements may be beneficial for growth and reproductive performance (Schillo et al., 1992; Ciccioli et al., 2005; Cappellozza et al., 2014). In addition, the use of corn and distillers grains supplement has been compared to evaluate performance responses (Loy et al., 2007) but the influence of these strategies on intake and feeding behavior on pasture are lacking. Moreover, supplementing mineral to cattle grazing poor-quality range vegetation can improve forage utilization and animal performance (Köster et al., 1996; Caton and Dhuyvetter, 1997). An issue with providing mineral supplements to cattle, however, is the degree of variability in intake, with some cattle over consuming or under consuming supplements (Tait and Fisher, 1996; Cockwill et al., 2000; Greene, 2000). However, providing supplements to pasture-based cattle does not allow measurements of individual animal mineral and supplement intake; as a result, mineral and supplement intake is measured on a group basis. The use of electronic monitoring systems in the beef industry has been limited to systems primarily used in research settings to examine the effects on feed intake in relation to cattle growth performance (Islas et al., 2014), daily intake of salt-limited supplements (Reuter et al., 2017), health status (Wolfger et al., 2015), or animal movement in extensive pasture settings (Schauer et al., 2005). These technologies could be adapted easily for the use in beef cattle production systems to monitor activity, feeding or drinking behavior, or as tools for monitoring inventories in intensive or extensive production systems. Therefore, our objectives were to examine the relationship between mineral and energy supplementations provided via an electronic feeder on intake, liver mineral concentrations, and metabolites in heifers being managed on native range