Abstract

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Three commercial plant tannin and a yucca extract having different secondary compound profiles were simultaneously evaluated in vitro for their effects on ruminal methane gas production and rumen fermentation patterns of wheat forage. Overall objective was to quantify in vitro, the sources of tannins and dose levels of tannins and yucca extract on rate of gas production, ruminal fermentation, foam height and foam strength from wheat forage. In vitro gas and methane production were measured from 0 to 6 h rumen incubation periods. In vitro rumen volatile fatty acids (VFA) was measured after 6 h rumen incubation. Pine bark was used as condensed tannins sources to serve as a non-extracted plant tannin source. In vitro rate of gas and potential gas production linearly decreased (P < 0.01) in a dose dependent manner for quebracho, mimosa, chestnut tannins, and pine bark addition. In the presence of quebracho (P < 0.03), mimosa (P < 0.02), chestnut (P < 0.02), yucca (P = 0.06), and pine bark (P = 0.11), methane production linearly decreased. Cumulative hourly total in vitro ruminal gas production was similar between control, yucca and pine bark at 5 mg extracts/ml after 6 h rumen fermentation. Cumulative ruminal gas production was lower for quebracho (P < 0.01), mimosa (P < 0.001), and chestnut tannins (P < 0.001) after 3-h fermentation. Total average VFA concentration was not affected by chestnut and yucca extracts treatments, but total VFA linearly decreased for quebracho (P < 0.04), mimosa (P < 0.01) and pine bark (P < 0.01) tannins treatments. Acetate and propionate (A/P ratio) molar ratios for quebracho (P <0 .01), mimosa (P < 0.01), yucca (P = 0.11), and pine bark (P = 0.001) decreased linearly in a dose dependent manner. Foam production and foam strength were lower (P < 0.01) from quebracho, mimosa, chestnut, and pine bark tannins than control treatment, but foam production and foam strength were higher (P < 0.01) for yucca extracts than for control treatment. It is concluded that addition of commercial tannins and yucca extracts changed in vitro rumen fermentations and VFA profiles. Except for chestnut tannins, addition of tannins and yucca extracts, decreased acetate/propionate (A/P) ratios, suggesting that plant tannins and yucca extracts may be nutritionally beneficial in terms of altering VFA ratios to favor improved animal growth.

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