Our objective was to determine if microbial (fungal) treatment of soybean meal (SBM) and dried distillers grain with solubles (DG) affected ruminal degradation and intestinal digestibility of DM and CP. In situ measurements were done using 3 mid-lactation, multiparous, ruminally-cannulated Holstein cows (BW 847 ± 96). Four feeds were evaluated: SBM, treated SBM (TSBM), DG, and treated DG (TDG). Duplicate 5 g samples in nylon bags (10 × 20 cm) were incubated in the rumen for 0, 1, 2, 4, 8, 12, 24 and 48 h. Rumen degradation constants for DM and CP were estimated using the NLIN procedures in SAS 9.3. Six additional bags of each feed were ruminally incubated for 12 h. Residues were used to determine in vitro intestinal digestibility of CP via incubation with pepsin and pancreatin solutions for 1 h and 24 h, respectively. Intestinally digestible protein (IDP), intestinally absorbable dietary protein (IADP = Rumen undegradable protein (RUP) × IDP), and total digestible protein (TDP = Rumen degradable protein (RDP) + IADP) were compared using MIXED procedures in SAS. Total CP was more in TSBM and TDG compared with original feeds. Ruminally degradable DM (RDDM) was less in TSBM and DG than in SBM, TDG. The RDP was increased in TDG versus DG and decreased in TSBM versus SBM. Effects were opposite for RUP. The IDP, IADP were less in DG and TDG compared with SBM and TSBM. The TDP was greatest in SBM and least in DG. Results indicate that microbial-treatment increased protein content of SBM and DG. Digestibility of CP was increased for TDG versus DG, but was not increased in TSBM versus SBM. Table 1.

Item	SBM	TSBM	DG	TDG	SEM
CP, % DM	49.3	59.0	29.5	42.5	—
RDDM, % of DM	67.3a	54.1b	54.3b	67.1a	1.27
RDP, % of CP	57.8b	47.2c	40.5c	69.6a	1.52
RUP, % of CP	42.2b	52.8a	59.5a	30.4c	1.52
IDP, % of RUP	89.3a	84.2b	61.4c	57.7c	0.98
IADP, % of CP	37.8ab	44.5a	36.5b	17.5c	1.52
TDP, % of CP	95.5a	91.7b	77.0d	87.2c	0.50

^a–dValues with unlike superscripts differ by P < 0.05.