PS5-22. Using an Ex-situ Model to Assess the Effects Saccharomyces Cerevisiae on Beef Cattle Ruminal Fermentation Gas Profile.

Abstract The effects of live yeast on ruminal gas and methane productions using an ex-situ model were evaluated. Ruminally cannulated beef steers (n = 8; body weight = 550 ± 20 kg]) were used in a duplicated 4 × 4 Latin Square design following a 2 × 2 factorial arrangement of treatments: A) presence of live yeast (Saccharomyces cerevisiae [CNCM I-1077], at 1 × 1010 CFUּ/animal-daily); and B) diet type (steam-flaked corn-based grower or finisher diets) that were offered to ad libitum intake. Live yeast was delivered with gel-capsules (0.25 g, as is) twice daily via ruminal-cannula throughout four-35 d periods. On d 19 of each collection period, ruminal fluid was collected from each steer (approximately 1,000 mL) at 4 h after-feeding by filtering the ruminal contents through four layers of cheesecloth. Thermos used for the individual collections were pre-heated with warm water (39 °C) prior to the contact with the ruminal inoculum. Thermoses were transported to the laboratory in an insulated container within 25 min of collection. Upon arrival at the Ruminant Nutrition Laboratory, contents were individually homogenized for 60 s while also flushed with CO2 of high-purity, and subsequent aliquots (triplicate) of 50 mL representing each steer were placed into 160 mL pre-warmed serum glass vials. Vials were flushed with CO2 for 15 s prior to sealing with a rubber stopper and aluminum ring. Serum vials were incubated at 39 °C for 24 h within a constant agitation (125 rpm) dry incubator for a period of 24 h. Fermentation process was stopped by colling-down vials in iced-water for 15 min. After vials achieved room temperature, total gas production was quantified by using a water displacement technique (inverted burette). Gas chromatography procedures were used to quantify methane concentration in the headspace gas remaining within the serum vials. Upon incubation, the ruminal specimen dry matter and ash contents were analyzed. The GLIMMIX procedure of SAS was used with animals as the experimental unit, the fixed effects (diet, period, interaction), and the random effects of animal ID within square, square, and period. No effect live yeast × diet interaction (P ≥ 0.73) was observed. Live yeast did not affect (P ≥ 0.34) the ex-situ model total gas or methane production. Regardless of live yeast, the ruminal inoculum from steers consuming a grower diet induced greater (P < 0.01) gas and methane (P < 0.01) production per unit of total volume or dry matter and organic matter of the ruminal fluid. Not adjusted methane concentration (% of total gases) was not affected (P = 0.17) by treatments. The model replicated expected results between grower and finisher diets. The current live yeast inclusion did not raise methane production on either beef cattle grower or finisher diet.