Effects of a Proprietary Kelp Blend Product on Enteric Methane Production and Tissue Residues in Cattle

Three experiments were performed investigating bovine enteric methane (CH₄) production inhibition using a proprietary kelp blend product (PKBP) containing a halogenated methane analog (i.e., bromoform). Calves were fed a corn-silage basal diet top-dressed with the assigned treatment, with rations provided at 1.5 × NE_m in Experiments 1 and 2 (<i>n</i> = 12 and 6 steers, respectively) and ad libitum in Experiment 3 (<i>n</i> = 9 steers). In Experiment 1, we evaluated bromoform's potency in decreasing CH₄. Dry matter intake (DMI) was not affected by treatment (<i>p</i> ≥ 0.11; 0 vs. 52.5 ± 10.5 ppm bromoform), whereas bromoform supplementation decreased CH₄ (<i>p</i> < 0.01). In Experiments 2 and 3, treatments were 0, 9.5 ± 1.5, or 20 ± 3 ppm bromoform. In Experiment 2, we examined CH₄ recovery following bromoform removal from the ration. Bromoform treatments were fed on d1, but not the subsequent 8 d, to investigate residual effects. On d1, CH₄ was below limits of detection for 20 ppm bromoform inclusion. Across days, a cubic response (<i>p</i> < 0.01) was observed with 20 ppm bromoform inclusion, but not with 0 and 9.5 ppm inclusion levels. Experiment 3 (30 d finishing trial) tested bromoform effects on feeder calves. DMI (<i>p</i> = 0.53), average daily gain (<i>p</i> = 0.55), and gain:feed (<i>p</i> = 0.82) were not influenced by bromoform inclusion. Bromoform residues were undetectable in liver, kidney, adipose, and muscle samples collected at harvest. These experiments demonstrated that cattle fed PKBP experience short-term reductions in CH₄ without tissue accumulation of bromoform and without evidence of effects on animal growth or feed consumption.