Decreasing the level of saturated fatty acids (SFA) and increasing monounsaturated FA (MUFA) and polyunsaturated FA (PUFA) content in ruminant’s milk would be beneficial for human health and would be of commercial interest. It is also recognized that tannins affect rumen biohydrogenation therefore increase the MUFA and PUFA content of milk and meat. We aimed to evaluate the effects of feeding pistachio hull (PH, source of tannin) and PEG supplementation on milk fatty acids composition in Saanen dairy goats. Nine Saanen dairy goats were used in a 3 × 3 Latin square design. Treatments were T1) Control, without PH, T2) 30% PH (DM basis) that provided 18.1 g tannin per kg DM of diet, and T3) 30% PH + 1% PEG (DM basis). In T2 and T3, PH replaced alfalfa hay. Milk fatty acids were analyzed on a Gas Chromatography with a flameionization detector and column. Statistical analysis was performed using the MIXED procedure of SAS (P < 0.05). Concentration of UFA, MUFA, and PUFA in treatments including of tannin (with PH) were significantly higher than control (without PH). Conversely, concentration of SFA and medium-chain FA (MCFA) in T2 were significantly lower than the control and with addition of PEG in T3 were significantly increased relative to T2. Concentration of short-chain FA (SCFA) in T2 and T3 was significantly lower than the control. Long-chain FA (LCFA) in T2 was significantly higher than the control and with addition of PEG in T3 was significantly decreased relative to T2. In conclusion, tannin has the ability to reduce SFA and to increase UFA. PEG will reverse this effect but not to the control levels.

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