Nitrogen balance, blood metabolites and milk fatty acid composition of dairy cows fed pomegranate-peel extract

An experiment was carried out to determine the effect of pomegranate peel extract (PPE) on nitrogen balance, blood parameters and the milk fatty acid profile of dairy cows. Four Holstein cows were used in a 4×4 Latin square design with 28-d periods and 4 treatments: PPE0 (no extract), PPE400 (400 ml PPE/cow/d), PPE800 (800 ml PPE/cow/d) and PPE1200 (1200 ml PE/cow/d). Nitrogen balance, blood parameters and the milk fatty acid profile were measured. Determination of secondary metabolites showed its high content of aqueous fraction, total phenolics and total tannin with reasonable content of saponins. Outputs of N in milk were quadratically increased (P=0.044) by inclusion of PPE at 400 and 800 ml PPE/cow/d in the diet. Blood cholesterol (quadratic effect, P=0.043), blood urea nitrogen (linear effect, P=0.047) and milk urea nitrogen (quadratic effect, P=0.0008) concentrations decreased with adding PPE. Supplementation with PPE quadratically lowered total saturated fatty acid (P=0.005), proportions of C12:0 (linear effect=0.040), C16:1c9 (quadratic effect, P=0.011), C18:0 (linear effect, P=0.083, quadratic effect, P=0.011) and ω6/ω3 (quadratic effect, P=0.007). Amount of C18:3c (n-3) (linear effect, P=0.046), DHA (C22:6) (quadratic effect, P=0.009) and EPA (C20:5) (quadratic effect, P=0.012) were increased by inclusion of PPE. Adding PPE lowered blood cholesterol, blood urea nitrogen and milk urea nitrogen. Milk from cows fed PE had significantly lower total saturated fatty acid, desirable ω6/ω3 ratio and higher content of EPA and DHA.