Enrichment of cattle rumen with bison rumen contents improves N digestion

Abstract Text:  This study investigated if the transfer of rumen contents from bison to cattle enhances cattle total tract fiber digestion. The experiment was a repeated measures design with two rumen transfers using 16 rumen cannulated Angus × Hereford cross beef heifers (461 ± 21 kg BW). Heifers were adapted to barley straw diet (70/30% of DM; forage/concentrate) for 28 d prior to the experiment. After 46 d, 70% of rumen contents were removed from each heifer and replaced with mixed rumen contents collected after slaughter from 36 bison. This procedure was repeated 14 d later. Intake, chewing activity, apparent total tract digestion, ruminal passage rate, VFA, ammonia-N and protozoa counts were measured before the first transfer and 2 wk after the second transfer. The DMI increased (P = 0.04) from 1.39% to 1.50% of BW after the rumen transfers. Total chewing time did not change (P = 0.74; 13.9 h/d) but the chewing time per kg DM and NDF intake was reduced (P < 0.001) after rumen transfers. The DM, OM, NDF and ADF digestibility were not affected (P ≥ 0.44) by rumen transfers, but the total N digestibility was improved (P < 0.001; 68.3% vs. 70.4%). Microbial N flow (g/d) increased (P = 0.03); however, the efficiency of microbial N synthesis (g/kg of digested OM) was not improved (P = 0.77). No differences (P > 0.14) were observed for the ruminal rate of passage of fluids and solids. Ruminal ammonia-N (mM) was not affected (P = 0.77) before feeding by rumen transfers but was greater (P = 0.05) 6 h after feeding. Total VFA (mM) and the proportion of butyrate increased (P < 0.001); however, acetate and the C2:C3 ratio decreased (P ≤ 0.02) before and 6 h after feeding as a result of rumen transfers. As a result of rumen transfer, total protozoa counts and the proportion of Ostracodinium increased (P < 0.001) whereas Entodinium decreased (P < 0.001) before and at 6 h after feeding. Overall, cattle rumen inoculation with bison rumen contents improved diet protein digestion; however, DM and NDF digestibility were not affected.

Keywords: bison, digestibility, rumen inoculum