Mineral Intake, Feeding Behavior, and Growth Performance of Cow-Calf Pairs Grazing Native Range

Crossbred Angus cow-calf pairs (n = 28 pairs) at the Central Grasslands Research and Extension Center (Streeter, ND) were used to evaluate an electronic feeder to monitor mineral intake and feeding behavior, and their relationship with growth performance and concentrations of mineral in liver. Cows and calves were fitted with RFID ear tags that allowed access to an electronic feeder (SmartFeed system; C-Lock Inc., Rapid City, SD) containing mineral (Purina Wind and Rain Storm, Land O’Lakes, Inc., Arden Hills, MN). Mineral intake, number of visits, time of visits, and duration at the feeder were recorded over a 95d monitoring period while pairs were grazing native range. Liver biopsies were conducted on cows on the final day of monitoring and analyzed for mineral concentrations. Data were analyzed in SAS with mineral intake and feeding behavior compared among cows and calves with the GLM procedure, correlations calculated among cow feeding behavior and calf intake and growth performance with the CORR procedure, and a comparison of liver mineral concentrations among cows of HIGH (>90 g/d) and LOW (<90 g/d) mineral intake with the GLM procedure. Mineral intake was greater (P < 0.01) in cows (81.1 ± 8.2 g/d) than in calves (44.2 ± 8.6 g/d) but both classes of cattle attended the mineral feeders a similar (P = 0.71) proportion of the days during the experiment (overall mean of only 20%, or once every 5 d). Interestingly, the daily mineral feeding recommendation (113.4 g) was exceeded by calves on days they visited the feeders (222.3 ± 27.3 g/d), and calves had reduced (P < 0.01) intake on feeding days compared with cows (356.2 ± 26.2 g). Over the grazing period calves gained 1.17 ± 0.02 kg/d whereas cows lost 0.35± 0.02 kg/d, but cow mineral intake and feeding behavior were not correlated (P ≥ 0.12) with calf intake, feeding behavior, or ADG. Cows with HIGH mineral intake had greater (P < 0.01) concentrations of Se (2.92 vs 2.41 ug/g), Cu (247.04 vs. 115.57 ug/g), and Co (0.506 vs. 0.266 ug/g) compared with LOW mineral intake cows, but liver concentrations of Fe, Zn, Mb, and Mn did not differ (P ≥ 0.22). We were able to successfully monitor mineral intake and feeding behavior with the electronic feeder evaluated, and the divergence in mineral intake observed with the feeder was corroborated by concentrations of mineral in the liver.