| Abstrak/Abstract |
A dual-flow, continuous-culture systemwas used to assess the effects of energysupplementation with 4 pasture forageson in vitro ruminal fermentationcharacteristics. Twelve dietary treatmentswere tested in a split-plot design:energy supplementation (no concentrate,30% ground corn, or 30% dried distilledgrains with solubles) as a whole plotand pasture forages [tall fescue (TF)without N fertilizer, TF with N fertilizer(TF+NF), TF-alfalfa mixture, andTF-birdsfoot trefoil mixture (TF+BFT)]as a subplot. Three replicated runs lasted9 d each, with 7 d for adaptation periodand 2 d for data collection. The greatesttotal VFA and propionate concentrations(P < 0.01) were detected when corn wassupplemented. Supplementing corn in theTF+BFT increased total VFA and propionateconcentration (P < 0.05). Greaterconcentrations of acetate and propionatewere found in the TF+NF (P < 0.01),but no effects were detected among otherpasture forages. Energy supplementationdecreased acetate:propionate ratio acrosspasture forages, and corn supplementationin the TF+NF resulted in the lowestratio (P < 0.01). Lower ammonia-N andmethane concentrations (P < 0.01) wereachieved due to energy supplementation,in particular when corn grain wassupplemented. Feeding the TF+NF orthe TF+BFT elicited similar ammonia-N:VFA ratios with no energy or cornsupplementation, which indicates that theTF+BFT was effectively fermented incultures, resulting in similar efficiencyof ruminal fermentation compared with the TF+NF. Data from this experimentimply that interseeding birdsfoot trefoilwith TF may be a suitable sward to establishin a grazing experiment to furtherevaluate ruminal fermentation, nutrientutilization efficiency, and performance ofgrazing cattle. |
