Consumption of feeds containing tannins might lead to lower absorption of nutrients such as glucose and amino acids into the blood. Polyethylene glycol (PEG) reacts preferentially with condensed tannins and prevents the formation of tannin-protein complexes, therefore could be increase absorption of nutrients into the blood. In this study, 9 multiparous dairy goats after the peak of lactation were used in a 3 × 3 Latin square design with 21-d periods, including 14 d of adaptation followed by 7 d of sampling. The individual animals randomly distributed into metabolic cages to evaluate the effect pistachio hull (PH, source of tannin) and PEG (source of tannin binding) on the blood biochemical parameters. Three treatments were formulated: T1) Control, without PH, T2) 30% PH (DM basis) that provided 18.1 g condense tannin per kg DM of diet and T3) 30% PH + 1% PEG (DM basis). In T2 and T3, PH was replaced with alfalfa hay. Blood samples were taken from the jugular vein before and 3 h after morning feeding. Data were analyzed as a repeated measurement design using PROC MIXED of SAS (P < 0.05). BUN (Blood Urinary Nitrogen) was significantly decreased at T2 and was compensated by addition of PEG in T3. Plasma concentration of triglycerides in T2 and T3 was higher than control, although significantly in T3. There were no differences between plasma concentrations of glucose, total protein, albumin, and cholesterol. Liver enzymes such as alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were stable. In conclusion, the negative effect of tannins on nitrogen metabolism can be covered by PEG supplementation.

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