TANNIN BLEND EFFECTS DAIRY COW METHANE EMISSIONS-Supplemental.docx

The objective of this study was to determine if a commercial feed additive blend composed of quebracho and chestnut tannins and saponins (<b>TAN</b>; SilvaFeed® BX) could reduce enteric GHG and ammonia (<b>NH</b>_{<strong>3</strong>}) emissions without negatively impacting the productive performance of dairy cows. Twenty mid-lactation Holstein dairy cows were blocked by DIM and parity in a randomized complete block design, and were assigned to one of two treatments: TAN (n=10) or control with no TAN (<b>CON</b>; n=10). The treatments were administered as a top dress at each of two daily feedings with TAN supplemented at a rate of 0.07% of dietary DM. Cow blocks were sampled for enteric gaseous emissions in head chambers (<b>HC</b>) for a 12-h period on their respective treatment days 0, 16, 32, and 48. After the enteric emission sampling period concluded, collected urine and manure were combined into a manure slurry at 1:1.7 (urine wt:feces wt) per cow. Manure slurry methane (<b>CH</b>_{<strong>4</strong>}), carbon dioxide (<b>CO</b>_{<strong>2</strong>}), nitrous oxide (<b>N</b>_{<strong>2</strong>}<b>O</b>), and NH₃ emissions were measured for 24-h. Supplemental TAN decreased enteric production (g/HC period or mg/HC period gas) of CH₄, CO₂, and N₂O over the trial period, and tended to increase NH₃ production in TAN-supplemented cows. Gaseous emission yield (g or mg gas/kg HC DM intake) did not differ between TAN- and CON-supplemented cows for CH₄, CO_2, or N₂O, though TAN-supplemented cows had greater NH₃ yield. Methane, CO₂, N₂O, and NH₃ intensity (g or mg gas/kg PM energy-corrected milk) were not affected by TAN-supplementation. Supplemental TAN did not impact slurry GHG emissions, though it increased NH₃ emissions. No differences in energy-corrected milk, milk fat yield, milk protein yield, and DMI in TAN- vs. CON-supplemented cows were noted.