The effects of molybdenum water concentration on feedlot performance, tissue mineral concentrations, and carcass quality of feedlot steers

Thirty cross-bred steers (initial BW 452.0 +/- 12.1 kg) were used to investigate the effects of Mo water concentration on performance, carcass characteristics, and mineral status of feedlot steers. The experimental design was a randomized complete block design. Steers were blocked by weight and then divided into 2 weight blocks each consisting of 15 steers. Steers were randomly assigned within block to one of 5 treatments (3 steers/treatment per block). Water treatments consisted of: 1) 0.0 mu g/L, 2) 160 mu g/L, 3) 320 mu g/L, 4) 480 mu g/L, and 5) 960 mu g/L of supplemental Mo added as Na2MoO4 to the drinking water. Steers were housed in individual pens (steer = experimental unit) that contained individual 265 L water tanks for monitoring water intake. Steers were fed a growing diet for 28 d and then transitioned to a finishing diet. Block 1 steers were fed for a total of 151 d and block 2 steers were fed for a total of 112 d. Daily water intake was recorded for each steer. Steers were individually weighed on 2 consecutive days at the beginning and end of the experiment and interim weights and jugular blood samples were obtained every 28 d. Liver biopsies were obtained on d 0 and 84 from each steer within each block. Steers were transported to a commercial abattoir, slaughtered, and individual carcass data and liver samples were collected. Initial BW was used as a covariate for statistical analysis of data and significance was determined at P = 0.05. No differences were observed for final BW (P > 0.98). Overall ADG (P > 0.91), DMI (P > 0.92), feed efficiency (P > 0.94), water intake (P > 0.40), hot carcass weight (P > 0.98), dressing percentage (P > 0.98), yield grade (P > 0.91), and marbling score (P > 0.29) did not differ across treatments. Lastly, no treatment differences were observed for liver concentrations of Cu (P > 0.93), Mo (P > 0.90) and Zn (P > 0.86) or plasma concentrations of Cu (P > 0.42), Mo (P > 0.43) and Zn (P > 0.62). These data indicate that water Mo concentration, within the range studied, had no impact on performance, mineral status, water intake, and carcass characteristics in feedlot steers.