The objective of this study was to determine if a commercial feed additive blend composed of quebracho, chestnut tannins, and saponins (TAN; Silvafeed BX) could reduce enteric GHG and ammonia (NH₃) emissions without negatively effecting 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 1 of 2 treatments: TAN (n = 10) or control with no TAN (CON; n = 10). The treatments were administered as a top dress at each of 2 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 (HC) for a 12 h period on their respective treatment d 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 (CH₄), carbon dioxide (CO₂), nitrous oxide (N₂O), 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, although TAN-supplemented cows had greater NH₃ yield. Methane, CO₂, N₂O, and NH₃ intensity (g or mg gas/kg PM ECM) were not affected by TAN supplementation. Supplemental TAN did not effect slurry GHG emissions, although it increased NH₃ emissions. No differences in ECM, milk fat yield, milk protein yield, and DMI in TAN-supplemented cows versus CON-supplemented cows were noted.

Manure management emits large quantities of greenhouse gases (GHG) in California. Eminex^®, a manure additive, previously demonstrated significant GHG reductions in slurry. However, it has not been tested in lagoon wastewater. The aim of the present study was to investigate the effects of Eminex^® on GHG, ammonia (NH₃), and ethanol (EtOH) emissions from fresh dairy slurry and dairy lagoon wastewater. Both manures received the following treatments: high (1.0 kg Eminex^®/m³ manure), low (0.5 kg Eminex^®/m³ manure). Experiments were conducted in four replicates with an untreated manure control. The physical characteristics of the manure were determined during the monitoring periods of emissions: 7 days for slurry and 28 days for lagoon wastewater. All slurry emissions, except for N₂O, declined over time (p < 0.05). Lagoon wastewater total N increased with treatment (p < 0.05) possibly due to the urea provided by Eminex^®. Most lagoon wastewater emissions also decreased over time (p < 0.05). However, Eminex^®, compared to control, increased lagoon wastewater NH₃ volatilization (p < 0.05). With improvements to manure composition through increasing N content, as well as reductions in emissions, Eminex^® is a promising tool to mitigate the negative environmental impacts of manure management.