Effect of ruminal administration of the lactate-utilizing strain Megasphaera elsdenii (Me) NCIMB 41125 on abrupt or gradual transition from forage to concentrate diets

The objective in Trial 1 was to study feed intake and ruminal acidosis when the diet is rapidly transitioned from forage to concentrate and Megasphaera elsdenii (Me) NCIMB 41125 (strain CH4) is administered into the rumen. The objective in Trial 2 in addition was to investigate whether drenched CH4 can be measured in the rumen and will promote a viable lactate-utilizing population during transition. In Trial 1, 24 rumen-cannulated lambs were used and in Trial 2, 12 rumen-cannulated steers. The lambs were randomly allocated to one of four treatments in a 2 × 2 factorial design: drenched with either CH4 or a placebo, and fed forage ad lib. or restricted to 200 g/day. On day 1 of the trial, the lambs in addition to the forage were fed a concentrate mixture at 09:00 and 15:00, and dosed 1011 cfus at 12:00. Intake and lamb weight were measured for 50 days until slaughter to obtain dressing %. Rumen pH and lactic acid concentration were measured between days −1 and +14. In Trial 2, four treatments of three steers each received one of four dosages intra-ruminally: a placebo (Control), 109 cfus (low), 1010 cfus (medium) and 1011 cfus (high). The transition from forage to concentrate was in five steps, i.e. more gradual than in the lamb trial. Feed intake and weight gain were measured for 37 days. Rumen fluid was sampled for determination of pH, lactic acid concentration, VFAs and qrt-PCR analysis for Me presence between days −4 and +35. Lambs drenched with strain CH4 consumed more concentrate than Control (P<0.006), but less forage (P<0.049). Total feed intake was also higher and it fluctuated less (P<0.023). Lamb ADG and dressing % did not differ. Rumen pH declined less in CH4 than Control lambs (P<0.001) and lactic acid accumulated less (P<0.001) during days +2 and +3. In Trial 2, feed intake and ADG were higher in CH4 treatments than Control. The low, medium and high CH4 treatments did not differ in any parameter. qrt-PCR results reflect higher Me concentrations during days +2 and +3 (P<0.06) in CH4 treatments than in Control, coinciding with lower lactic acid concentrations (P<0.13). Rumen pH in Control approached pH = 5 between days +9 and +17, whereas pH in the CH4 treatments remained above 5.5. Total VFAs were similar in all treatments, but the proportional distribution shifted towards butyric acid in the CH4 treatments. It is concluded that strain CH4 should control ruminal acidosis during transition from forage to concentrate.