| Popis: |
The objective was to determine if lactate adaption in cannulated steers affected fermentation characteristics in an ex vivo model of ruminal acidosis. Eighteen cannulated steers (790 ± 68 kg) were assigned to 1 of 2 treatments: 500 mL of H2O (CON) or 1 mM DL-Lactic acid solution per kg steer BW (LAC). After treatments were dosed prior to feeding for 6 d, rumen fluid was collected for an ex vivo study. Three flasks for each steer contained 7.5 g DM of substrate (70% corn, 15% DDG, and 15% silage) and 160 mL of inoculum with rumen fluid and McDougall’s buffer (4:1 ratio). Sample aliquots (1.7 mL) were collected every 4 h from the flask for 36 h fermentation for later analysis. At 12 h, 90 mM of neutralized DL-Lactic acid was added to each flask to further evaluate lactate utilization over time. Data were analyzed using the MIXED procedure of SAS 9.4 with a repeated measures analysis. A treatment by hour interaction was not detected (P = 0.19) for pH. However, steers on LAC tended (P = 0.06) to have a greater pH than CON. No treatment by hour interaction or treatment effect was observed (P ≥ 0.44) for molar proportion of acetate, propionate, butyrate, and ammonia. A treatment by hour interaction tended (P = 0.07) to be observed for total VFA; CON was greater than LAC at hour 8, 13, 16, and 20. Control steers had a greater (P = 0.03) in vitro dry matter disappearance compared with LAC (63.6 vs. 54.0%, respectively). Although results indicated that rumen fluid from lactate-adapted steers had a greater pH in an acidosis model, rumen fluid from CON steers had improved IVDMD and total VFA concentrations. |
