Cobalt is an essential trace mineral required for ruminal vitamin B₁₂ synthesis, but sources differ in ruminal microbial utilization, i.e., cobalt carbonate is poorly water soluble, whereas acetate and lactate forms are water soluble. Reports comparing organic cobalt lactate to other cobalt salts are lacking. The study objective was to determine if feeding cobalt lactate at two inclusion rates resulted in similar growth performance and tissue cobalt concentrations as the carbonate and acetate forms used in feeds. One hundred Angus cross bred steers weighing 385 ± 20 kg were randomly assigned to one of five treatments. Cattle were fed a basal diet plus: 1) cobalt carbonate to supply cobalt at 30 mg/steer/d, 2) cobalt acetate to supply cobalt at 30 mg/steer/d, 3) cobalt acetate to supply cobalt at 60 mg/steer/d, 4) cobalt lactate to supply cobalt at 30 mg/steer/d, and 5) cobalt lactate to supply cobalt at 60 mg/steer/d. Cattle were fed according to industry standards until body fat deposition was visually deemed to grade USDA Choice, which was 92 and 117 d for each of the 2 blocks, respectively. Steers were harvested and carcass measurements recorded along with sampling of adipose, heart, kidney, liver, and muscle for tissue cobalt concentrations. Three statistical contrasts consisted of: 1: inorganic (cobalt carbonate) vs. organic (cobalt acetate and lactate); 2: cobalt acetate vs. cobalt lactate; and 3: feeding rate of 30 vs. 60 mg/steer/d cobalt. Body weight gains, average daily gains, dry matter intake, and feed conversions were similar (P > 0.10) for steers fed all cobalt sources and feeding rates. Hot carcass weight, yield grade, back fat thickness, and ribeye area were similar (P > 0.10) among steers fed all cobalt sources and inclusion rates. Liver, kidney, muscle, and adipose cobalt concentrations were similar (P > 0.08) for steers fed inorganic vs. organic cobalt sources. Feeding cobalt lactate compared with cobalt acetate did not affect (P > 0.10) liver, kidney, heart, muscle, and adipose tissue cobalt concentrations. Feeding 60 mg/steer/d cobalt compared with 30 mg/steer/d increased (P < 0.01) liver, kidney, heart, and adipose tissue cobalt concentrations, while muscle was a tendency (P < 0.06). The study demonstrated that feeding soluble cobalt lactate, a new cobalt source, resulted in similar growth performance, carcass characteristics, and tissue cobalt concentrations when compared with cobalt acetate and carbonate.

Rachel Raths

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