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.
Berumen et al. (Wed,) studied this question.