Methane emissions and rumen microbial changes in steers fed condensed tannin containing diets under western Canadian conditions
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A study was conducted to determine if sainfoin, a condensed tannin (CT) containing legume, fed to beef cattle as hay or silage during a western Canadian winter would result in a reduction in methane (CH4) emissions without compromising animal performance. Forty yearling beef steers were fed four diets in a factorial design consisting of two legume forage species (sainfoin or alfalfa) and two preservation methods (silage or hay) over 15 weeks (wks). For each sample wk, animal weight, 24-h CH4 expiration and rumen fluid samples were obtained. Rumen methanogens were characterized using terminal restriction fragment length polymorphisms analysis. Specific bacteria were quantified with real-time polymerase chain reaction analysis. Sainfoin silage (SS) and sainfoin hay (SH) contained 11.9 and 10.5 mg g-1 of CT respectively and supported an acceptable growth rate for backgrounding steers. A decline (P < 0.05) in enteric CH4 formation could only be detected from SH-fed animals compared to alfalfa hay (AH) fed animals when CH4 was expressed as L d-1 or L kg BW-1. The rumen archaeal community structure of experimental animals remained stable regardless of diet type or sample wk. Structural carbohydrate-fermenting bacteria were suppressed in silage diets. Methanogens were less abundant in the rumen fluid samples of steers fed SS but not SH.