Replacing Alfalfa with Panicled-Tick Clover or Sericea Lespedeza in a Dairy Diet Decreases Ruminal Methane but not Total Gas Production

Abstract Text:    Enteric methane (CH₄) emissions by ruminants represent a decrease in gross-energy intake by the animal. Biologically active forage plant polyphenols, condensed tannins (CT), are known to suppress enteric CH₄ production in ruminants that consume them. However, consumption of these forages alone, or in too great of quantities could result in antinutritional effects, negatively impacting ruminant efficiency and growth. The objective of this study was to determine the effects of replacing the forage component of a traditional dairy diet (50% corn grain, 50% alfalfa; CRN:ALF) with that of forages containing CT on enteric methane and total gas production. Desmodium paniculatum (panicled-tick clover; PTC) and Lespedeza cuneata (sericea lespedeza; SL) were evaluated as an alfalfa replacement at levels of 15%, 30% and 45%. Methane production was determined using an in vitro gas production technique. In a randomized complete block design, replications consisted of two fermentation events, 06/25/2012 and 09/16/2012, where each diet was fermented in each of two fermentation chambers. Fermentation chamber was considered a random variable, whereas fermentation flasks within each fermentation chamber were considered random factors. Two ruminally-cannulated steers not adapted to forage containing CT were used for rumen fluid collection. Forages were individually fermented anaerobically in rumen fluid for 48h. Methane concentrations were determined by gas chromatography following fermentation. LS-means were determined and a value of P < 0.05 was considered significant. There was no difference in CH₄ production among PTC 15%, SL 15% and CRN:ALF (130.5, 132.2 and110.8 g/kg fermentable-organic matter; FOM, respectively). Fermentation of PTC 30% and SL 30% produced 85.5 and 89.7 g CH₄/kg FOM, respectively, which did not differ from CRN:ALF. However, fermentation of PTC 45% resulted in the least amount of CH₄ produced (38.1 g/kg FOM), which was 54% less than that of SL 45% (84.0 g/kg FOM; P = 0.0022) and 65% less than that of CRN:ALF (P < 0.0001). Total gas production did not differ among treatments compared to the CRN:ALF control. Results from this study suggest that 45% replacement of alfalfa with PTC or SL will suppress ruminal CH₄ with no compromise in total gas production (i.e. FOM). 

Keywords: Condensed tannin, legume, ruminal fermentation