Antioxidant status of blood and liver of turkeys fed diets enriched with polyunsaturated fatty acids and fruit pomaces as a source of polyphenols

It was hypothesized that dietary polyphenol-rich fruit pomaces can improve the antioxidant status of both diets and the tissues of turkeys fed such diets. Turkeys were fed diets containing a cellulose preparation (C) or 5% dried apple pomace (AP), blackcurrant pomace (BCP), strawberry pomace (SP) and seedless strawberry pomace (SSP). Blood and liver biochemical parameters were determined in 7 birds from each experimental group slaughtered at 15 weeks of age, after 5 weeks of feeding diets containing soybean oil and linseed oil (approx. 1:1 ratio). Dietary linseed oil added to diets at 2.5% lowered the n-6/n-3 PUFA ratio from approx. 7:1 to below 2:1, thus reducing the antioxidant properties of diets measured using DPPH, ABTS and photo-chemiluminescence assays, compared with diets containing only soybean oil and administered to birds in the first phase of feeding. Fruit pomaces, in particular SSP with the highest polyphenol content (32.81 g/kg) and the highest antioxidant activity (256.4 μM Trolox/g), increased the antioxidant capacity of turkey diets. In comparison with the control group, the dietary treatments with fruit pomaces improved blood antioxidant parameters, including catalase activity (groups AP and BCP), the total antioxidant capacity of hydrophilic (group AP) and lipophilic (groups AP, SP, and SSP) compounds, peroxide levels (groups AP and SSP) and antioxidant capacity measured by the FRAP (ferric reducing antioxidant power of plasma) assay (groups AP, BCP and SSP). Significantly lower concentrations of both vitamin E and thiobarbituric acid reactive substances (TBARS) were noted in the livers of turkeys fed all diets with dried fruit pomaces.