Ruminal Degradation Kinetics of Beef Steers Fed Annual or Perennial Grass-hay with or Without Supplementation

Abstract

Abstract The effects of dried distillers grains plus solubles (DDGS) supplementation on ruminal degradation kinetics of steers fed annual [‘Tiffany’Eragrostis tef (Zucc.) Trotter; TEFF] or perennial [‘WW-B Dahl’ Old World bluestem, Bothriochloa bladhii (Retz).T. Blake; OWB] grass hay were evaluated. Ruminally cannulated crossbred-Angus steers (n = 6; BW = 304 ± 11 kg) were assigned to a 4 × 6 unbalanced Latin square design with 4 treatments. Treatments were arranged as a 2 × 2 factorial, with factors being hay type (OWB or TEFF) and DDGS supplementation [0 or 0.5% BW (DM basis)]. Steers had ad libitum access to hay and received 110 g of a mineral/vitamin packet daily. Periods consisted of a 14-d adaptation followed by 7 d of collection. Hay types were reverse-incubated at 0, 3, 6, 12, 24, 36, 48, 72, and 96 h post-feeding. Residues from the in situ incubations were fitted to a first-order kinetics model using the non-linear procedure of SAS. The GLIMMIX procedures of SAS were used for the statistical analysis. A hay type × DDGS interaction was observed (P ≤ 0.05) for the estimation of substrate effective degradable fraction of OM, NDF, ADF, and hemicellulose; however, after adjusting with Tukey’s, there were no treatment mean differences (P ≥ 0.08). The rate of digestion, soluble fraction, and the potentially degradable fraction of OM, NDF, ADF, and hemicellulose increased (P ≤ 0.05), while the undegradable fraction decreased (P ≤ 0.01) when steers were fed TEFF, regardless of DDGS supplementation. Ruminal degradation lag-time increased (P ≤ 0.02) by 1.5, 1.45, and 2.6 h for DM, OM, and ADF, respectively in steers fed OWB, regardless of DDGS supplementation. Ruminal degradation kinetics were not (P ≥ 0.17) independently affected by DDGS supplementation. Future investigations should elucidate the interaction between supplementation and forage quality.