An experiment was conducted to investigate the effect of additives on intestinal utilizable crude protein in dairy cows, and ruminal and post-ruminal nutrients disappearance of corn, alfalfa, and whole barley silages using in situ mobile bag technique. Alfalfa, whole crop corn and barley were harvested and chopped, and then treated with commercial biological and chemical additives; urea at 0.0, 10.8 and 21.6 g/kg DM in corn (CS0.0, CSU10.8 and CSU21.6, respectively) and whole barley (BS0.0, BSU10.8 and BSU21.6, respectively); Biomin® inoculant at 0.0, 800 and 9600 cfu/kg in corn (CS0.0, CSB800 and CSB9600, respectively) and at 0.0 and 800 cfu/kg in whole barley (BS0.0 and BSB800); formic acid at 0.0, 4 and 4.4 ml/kg in alfalfa (AS0.0, ASF4 and ASF4.4, respectively) and at 0.0 and 4 ml/kg (BS0.0 and BSF4) in whole barley. Urea caused the enhancement of in vitro intestinal utilizable crude protein (uCP) and its effectiveness (EuCP). in vitro intestinal utilizable crude protein was not affected by formic acid in whole barley silage, although treated alfalfa silages had higher uCP than AS0.0. Ruminal CP disappearance was higher for urea-treated corn and whole barley silages at both levels, although formic acid and Biomin® did not change it. Ruminal NDF disappearance was greater for urea-treated corn silages and BSU21.6 than CS0.0 and BS0.0. Post-ruminal disappearance of protein increased significantly in AS4.4 and reduced in urea-treated corn and whole barley silages (P<0.05). Utilizable CP at 8 h was higher for dry hays in comparison with those of silages in both alfalfa and whole barley (P<0.05). Results of the present study showed that, for the first time, silages treated with urea and formic acid had higher in vitro utilizable crude protein in dairy cow intestine compared with the untreated silages.

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