53. Using a High-quality Fibrous Co-product to Apprise the Effects of Saccharomyces Cerevisiae and beef Cattle Diet Type on Ruminal Degradability Kinetics

Abstract The effects of ruminal degradability kinetics using a high-quality co-product substrate (wet corn gluten feed, WCGF) of Saccharomyces cerevisiae and types of beef cattle diets were evaluated. Eight ruminally cannulated beef steers were utilized in a duplicated 4 × 4 Latin square design within a 2 × 2 factorial arrangement of treatments, as follows: A) presence of live yeast (Saccharomyces cerevisiae [CNCM I-1077], at 1 × 1010 CFU/animal-daily); and B) diet type (steam-flaked corn-based grower or finisher diets [ad libitum intake]). Live yeast was placed in gel capsules (0.25g, as-is) twice daily via the ruminal cannula. Pre-dehydrated (55 °C for 72 h) WCGF was ground (2mm) and placed into 10 × 20 cm (28μm) nylon nags (8g, as-is). Substrate bags were placed within a nylon mesh into the rumen and reversely removed at 0, 2, 4, 8, 12, 20, 32, 48, 64, 72, and 96h after incubation. Bags were rinsed, dehydrated for 72 h at 55 °C and organized by steer, period, and incubation time, and used to fit a first-order kinetics model using the NLIN procedure of SAS (animal as the experimental unit). No interaction (P ≥ 0.26 diet × yeast was observed for degradability variables, except for a tendency (P = 0.15) for yeast to increase the WCGF substrate dry matter (DM) and hemicellulose rate of degradation (kd, %/h) for steers consuming finisher diets, while either not affecting the kd within the grower diet or decreasing it, respectively. Regardless of diet type, the present of live yeast increased (P < 0.01) the WCGF substrate kd of DM and tended (P = 0.14) to increase for the OM fraction; and tended (P = 0.14) to decrease the lag time (h) for hemicellulose degradation. Live yeast did not affect (P ≥ 0.24) other remaining ruminal degradability variables. Regardless of live yeast inclusion, steers offered the grower diet had greater (P ≤ 0.05) WCGF substrate potentially degradable (B) fraction, effective degradable (ED) fraction (kp at 4, 5,or 6%/h), and lesser (P < 0.01) undegradable (C) fraction for DM, organic matter (OM), NDF, ADF, and hemicellulose; tended (P ≤ 0.12) for a greater lag time for ADF and hemicellulose; and tended (P = 0.10) to show a subtle difference for the soluble fraction (A) of ADF, compared to steers offered the finisher diet. Treatments did not affect (P ≥ 0.24) substrate lag time and soluble fraction (A) of the DM, OM, and NDF. The model replicated expected results between grower and finisher diets when using a high-quality co-product substrate. Live yeast improved the ruminal rate of degradation of DM of wet corn gluten feed, while tending to show more of such an effect on a beef cattle finisher diet rather than on a grower diet.