Six Wagyu (Japanese Black) steers fitted with a ruminal cannula were used in a split‐plot design experiment comprising a 3 × 3 Latin square design (whole plot) and a randomized blocks design (subplot) to determine the effect of the treatment of potato pulp (PP) with urea and the effect of inclusion levels of PP silage in feed supplement on digestibility, ruminal in situ degradation and ruminal fermentation. The whole plot consisted of 20%, 50% and 80% PP silage (dry matter (DM) basis), with PP silage replacing formula feed. The subplot included untreated or 0.5% (on an as‐fed basis) urea‐treated PP. The treatment of PP with urea showed no effect on DM intake and digestibility. The percentage of the rapidly degradable DM fraction of the urea‐treated PP silage was higher (P < 0.01) and the percentage of its slowly degradable DM fraction was lower (P < 0.01) than for the untreated PP silage. Ruminal ammonia concentration was greater (P < 0.01) for steers fed urea‐treated PP silage than that for steers fed the untreated PP silage. The treatment of PP with urea caused a decrease in the molar proportion of acetate and an increase in the proportion of propionate in ruminal fluid after feeding. The rate of DM degradations in hay (linear, P < 0.01) and in PP silage decreased (linear, P < 0.01) as the inclusion level of PP silage increased. Increasing the inclusion level of PP silage in supplement decreased the effective degradability of DM in hay (linear, P < 0.05) and in PP silage (linear, P < 0.05). An increase in the amount of PP silage increased the molar proportion of acetate (linear, P < 0.01) and decreased the butyrate proportion (linear, P < 0.05) in ruminal fluid. The results suggest that urea treatment of PP facilitates microbial access to starch of PP silage in the rumen and that surplus level of PP silage in supplement have adverse effect on ruminal digestion.

Six Japanese Black (Wagyu) steers (average initial weight 467 Ϯ 45 kg) fitted with a ruminal cannula were used in a split-plot design experiment comprising a 3 ¥ 3 Latin square design (whole-plot) and a randomized block design (subplot). The whole-plot treatments were three different feeding levels of urea-treated potato pulp (PP) silage-based concentrate: 1.00%, 1.75% and 2.50% of body weight (BW) (on a dry matter (DM) basis). The subplot treatments consisted of the concentrate formulated to contain either soybean meal (SBM) as a rapidly rumen-degraded protein source or corn gluten meal (CGM) as a slowly degraded protein source. Dry matter intake tended to be lower (P = 0.071) for CGM (8.9 kg/day) than for SBM (9.4 kg/day). Protein sources had no significant effect on digestibility and in situ degradation. Ruminal ammonia nitrogen (NH3-N) was lower (P = 0.033) for CGM (7.5 mg/dL) than for SBM (9.5 mg/dL). Protein sources did not affect ruminal pH and the total volatile fatty acids (VFA) concentrations. The molar proportions of ruminal acetate and valerate were higher (P = 0.032) for CGM than for SBM. The maximum daily intake of the PP silage-based concentrate expressed as a percentage of BW was approximately 1.4% of BW. Dry matter intake was higher (P = 0.046) for steers fed at 1.0% of BW of the PP silage-based concentrate than for steers fed at 1.75% or 2.5% of BW of the concentrate. The feeding levels of the PP silage-based concentrate had no effect on DM and nutrients digestibility, except for crude protein (CP) digestibility. CP digestibility tended to be lower (P = 0.071) for steers fed at 1.75% of BW of the PP silage-based concentrate than for steers fed at 1.0% or 2.5% of BW of the concentrate. The feeding levels of the PP silage-based concentrate also did not affect the in situ degradation parameter of hay and PP silage. The feeding levels of the PP silage-based concentrate did not affect ruminal pH, NH3-N and total VFA concentrations. The molar proportion of acetate was highest for steers fed at 1.0% of BW of the concentrate. In conclusion, in the urea-treated PP silage-based concentrate, CGM seems to be more effective than SBM for stabilizing the ruminal NH3-N concentration and to be advantageous for fiber digestion in the rumen. The feeding levels of the PP silage-based concentrate did not change the amount of VFA production in the rumen and the DM digestibility. Science †Potato pulp was ensiled for 6 months with urea (0.5%, as fed-basis) and beet pulp (9%, as-fed basis) before it was fed to the steers. M. SUGIMOTO et al.Animal Science Journal (2008) 79, 443-452 †Potato pulp silage was ensiled for 6 months with urea (0.5%, as fed-basis) and beet pulp (9%, as-fed basis) before it was fed to the steers. PROTEIN SOURCES WITH UREA-TREATED POTATO PULP 445No supplementation level ¥ diet interactions were detected (P Ն 0.05). ADF, acid detergent fiber; CGM, corn gluten meal; CP crude protein; DM, dry matter; EE, ether extract; NDF, neutral detergent fiber; OM, organic matter; SBM, soybean meal; s.e., standar...