CASE STUDY: In Vitro Ruminal Fermentation Characteristics of Birdsfoot Trefoil (Lotus corniculatus L.) Hay in Continuous Cultures1

A dual-flow continuous culture system was used in a 3 x 3 Latin square design to evaluate the effects of ruminal fermentation in mixed microbial cultures when replacing alfalfa hay (Medicago sativa L.) with birdsfoot trefoil hay (Lotus corniculatus L.). Ruminal fluid was collected from 2 ruminally cannulated, lactating dairy cows fed a TMR diet. Treatments consisted of 1) 100% alfalfa hay (AH; 0.06% tannins), 2) 50% AH and 50% birdsfoot trefoil hay (DM basis; AHBFTH; 0.32% tannins), and 3) 100% birdsfoot trefoil hay (BFTH; 0.97% tannins). Three replicated periods lasted 8 d each, with the first 5 d allowed for microbial adaptation to the diets, and 3 d for sampling. Culture pH decreased when the BFTH was fed compared with the AH and the AHBFTH. Methane production and total VFA profiles were not affected by the dietary treatments except that molar proportion of isobutyrate tended to decrease (P = 0.09) by feeding the AHB-FTH. In addition, NDF digestibility was not affected by the dietary treatments. However, NH3-N concentration and flow were reduced when replacing the AH with the BFTH. It was concluded that feeding a tannin-containing forage hay diet (BFTH) increased in vitro N utilization without reducing in vitro methane production, and that a possible cause was the action of plant tannins.