PSIII-1 - Impact of Low Levels of Tannin Supplementation on Enteric Methane Emissions and Performance in Organic Dairy Heifers

Abstract: Condensed tannins are theorized to reduce enteric methane emissions by enhancing protein efficiency and decreasing ruminal fiber fermentation in ruminant animals. The objective of this study was to assess the viability of supplemented condensed tannins fed at increasing levels: 0% (CON), 0.075% (LOW), 0.15% (MED), and 0.30% (HIG) of dry matter intake (DMI). The study acclimation utilized 24 organic Holstein heifers, one GreenFeed emission measurement system, two SmartFeed Pro systems (C-Lock Inc., Rapid City, SD), and individual animal feeding stanchions. Twenty organic Holstein heifers (BW = 218.75 ± 16.78 kg) were selected based on acclimation and were stratified into treatment groups based on initial body weight and acclimation status. A 7-d covariate gas analysis was performed prior to the study to account for individual animal emission differences. Daily, heifers were offered 1 kg of starter calf feed and tannin in the individual feeding stanchions for 45-d and fed a basal TMR diet through the SmartFeed Pro systems. Statistical analysis was conducted in R with the fixed effect of treatment and pre-trial emission rate as a covariate. Daily methane production ranged from 141 to 152 g methane (CH₄)/day between treatments. No significant difference was observed between treatments for daily methane production (P=0.53), methane yield (g CH₄/ kg DMI; P=0.82), or emission intensity (g CH₄/kg of body weight gain; P=0.62). Similarly, a treatment effect was not observed for DMI (P=0.95), average daily gain (ADG) (P=0.50), or feed efficiency (P=0.36). However, DMI and ADG continued to increase throughout the study, suggesting that the supplemental tannin did not negatively impact animal performance. The results of this study would not indicate that low levels of tannin supplementation alter CH₄ emissions in organic Holstein heifers.