Potential for improving fiber digestion in the rumen of cattle ( Bos taurus ) through microbial inoculation from bison ( Bison bison ): In situ fiber degradation.

The objective of this experiment was to determine if partial replacement of cattle rumen contents with those from bison would increase in situ ruminal fiber degradation of various forages. The second objective was to examine individual variation among cattle in their ability to degrade forage and their responses to inoculation. In situ degradation of barley straw, canola straw, alfalfa hay, and timothy hay was measured in 16 ruminally cannulated heifers fed a barley straw-based diet before and after inoculation with combined rumen contents from 32 bison (performed twice, 14 d apart). Each feed was incubated in the rumen of each heifer for 0, 4, 8, 12, 24, 48, 96, and 120 h, and the degradation parameters were determined as washout fraction (), potentially degradable fraction (), rate of digestion of fraction (), and total potentially degradable fraction (). The of barley straw decreased ( = 0.04) after inoculation, whereas fraction of NDF increased ( = 0.03) and fraction of NDF and ADF decreased ( ≤ 0.02) by inoculation. In contrast, of alfalfa hay NDF and ADF decreased ( = 0.002) after inoculation, but fraction of NDF and ADF ( ≤ 0.02) increased. There were no major effects ( > 0.06) of inoculation on the fiber degradation of timothy hay or canola straw. The differential response between barley straw and alfalfa hay may have occurred because the cattle were previously adapted to a barley straw diet, whereas the bison were fed barley silage and oats. Some animals consistently ranked higher or lower for or across at least 3 of the 4 feeds incubated, but the rankings changed after inoculation. In conclusion, inoculation of cattle with bison rumen contents failed to improve degradation of fiber from barley straw, canola straw, or timothy hay in cattle well adapted to a barley straw diet, although there were small improvements in the extent of degradation of fiber from alfalfa hay. Cattle varied both in their ability to degrade various forages and in their responses to inoculation with bison rumen contents.