Ruminal degradation and intestinal digestibility of dried or wet distillers grains with increasing concentrations of condensed distillers solubles.

The objective of this experiment was to determine the effect that the amount of condensed distillers solubles (CDS) added back to distillers grains (DG) and its form, wet or dried, have on nutrient digestion. Three Holstein cows with ruminal cannulas were used to evaluate in situ ruminal degradability of DM and CP and in vitro intestinal digestibility of CP. Condensed distillers solubles were added back to wet DG in the following ratios of wet DG to CDS: 100:0, 86.7:13.3, 73.3:26.7, and 60:40. One-half of each mixed feed at each ratio was dried, and the other one-half remained wet, resulting in 8 DG samples. Feeds were incubated in the rumen for 0, 3, 6, 12, 18, 24, and 48 h. Intestinal CP digestibility was measured on residue from 12-h ruminal incubation feeds by the pepsin-pancreatin method. The soluble fraction of DM and CP was greater (P \u3c 0.001) for wet compared with dried DG and increased as CDS increased in each blend (P \u3c 0.001). The potentially degradable fraction of DM and CP was greater (P \u3c 0.001) for dried compared with wet DG and decreased as CDS increased in each blend (P \u3c 0.01). The rate of DM and CP degradation was not (P \u3e 0.05) affected by form or inclusion of CDS. Rumen-degraded DM was greater (P \u3c 0.001) for wet compared with dried DG (59.7 vs. 48.6%), and as the percentage of CDS increased, it increased (P \u3c 0.001) from 49.3 to 61.2%. Rumen-degraded protein (RDP) was greater (P \u3c 0.001) for wet DG than dried DG (53.1 vs. 38.0%). In addition, RDP increased (P \u3c 0.001) from 42.0 to 50.5% as the concentration of CDS increased from 0 to 40%. Estimated intestinal digestibility of rumen-undegraded protein was greater (P = 0.003) for wet DG compared with dried DG (69.7 vs. 64.0%), but was unaffected (P = 0.11) by the addition of CDS. Intestinal absorbable dietary protein was greater (P \u3c 0.001) for dried DG (39.7%) compared with wet DG (32.7%), and decreased (P \u3c 0.001) from 39.9 to 32.0% with increasing concentrations of CDS. Total digestible protein (TDP) increased (P \u3c 0.001) from 77.7 to 85.8% for dried and wet DG, whereas different ratios of DG to CDS resulted in similar TDP. Based on this study, ruminal DM and CP degradability and intestinal protein digestibility of DG increased when the percentage of CDS increased. Although dried DG can supply more ruminal undegraded protein, wet DG can supply more TDP