The objective of this study was to determine if supplemental polyethylene glycol (PEG) and urea affected feed intake and milk production by dairy cows fed a diet containing tannin. Eight multiparous Holstein dairy cows averaging 61 ± 23 DIM and 38 ± 3.6 kg of milk production were used in a 4 × 4 replicating Latin square design. Fresh pistachio by-products (PB)averaging 32% dry matter (DM) were supplemented with PEG and Urea at 1% and 0.5% of DM, respectively and then ensiled for 60 days. Experimental treatments were as follows: 1) corn silage (15% of diet DM) as a control, substitution of corn silage with: 2) Pistachio-by products silage, 3) Pistachio-by products silage supplemented with urea, 4) Pistachio-by products silage supplemented with PEG. Feed intake was similar among treatments with the average of 26.63 kilogram per day. Milk production (35.5 Kg/d), milk fat (3.76% ), milk protein (3.23% ), and milk lactose (4.92% ) remained unchanged between dietary treatments. Results of this study show that under our experimental conditions, pistachio by-products silage can be substituted with corn silage up to 15% of diet DM in dairy cows ration.

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