Effect of diet supplement in dairy cow with grape pomace on quality of milk and cheese

The aim of the study was to evaluate the effect of dairy cow diet supplement with grape pomace (GP) on quality of milk and cheese derived. The GP, a biomass deriving from winery and distillery industries, is a source of polyphenols and unsaturated fatty acids. Twelve lactating Holstein Friesan cows were randomly divided in two homogenous groups for parity, milk yield and days in milk. Cows were fed during 60 days with conventional ration in the control group (CG) and with GP (10% on daily dry matter intake) as supplement of conventional ration in the experimental one (EG). Samples of both diet were collected for chemical analyses. Milk production was monitored during the trial and individual milk samples were collected at the end of the experiment for both groups. Milk samples were analyzed to evaluate quality parameters (protein, casein, lactose, lipids, fatty acids profile, urea and somatic cells). Milk produced the last day of the experimental period was collected for both groups and used to produce cheese. Cheese was sampled at 1 (T1) and 30 (T30) days over ripening and fatty acids profile and lipid oxidation (TBARs test) were assessed. Statistical analysis was carried out using GLM procedure of SAS. Chemical analyses performed on diets highlighted a higher content of linoleic acid in EG diet compared with the CG one (46.73 vs 40.11%, respectively). Milk yield did not differ between two groups during the experimental time (16.58 vs 15.29 kg/d, CG and EG group respectively). Vaccenic (0.95 vs 1.45%), rumenic (0.55 vs 0.91%) and linoleic (2.05 vs 2.60%) acids were significantly higher in EG milk compared to CG one. Fatty acids composition of cheese, in particular vaccenic, rumenic and linoleic acids, were higher in EG group. Malondialdehyde did not differ at T1 between groups while it resulted almost three times lower in EG cheese after 30 days of ripening (0.117 vs 0.043 μg MDA/g). Results indicate that GP diet supplement in dairy cows may enhance milk and cheese fatty acids composition. The lowest lipid oxidation observed in treated cheese may be related to antioxidant properties of the higher concentration of polyphenols in grape pomace