Effects of a diet containing dried grape pomace on blood metabolites and milk composition of dairy cows

Abstract

Background: The effect of a diet containing 15% grape pomace (GP) on the general health status and milk quality of dairy cows was assessed by plasma biochemistry and total polyphenol (TP) content, milk polyphenols, milk composition and milk protein fractions.

Results: Among the polyphenols measured by liquid chromatography-mass spectroscopy in GP, in feed containing GP (GP+) or not containing GP (GP-), gallic acid and epicatechin were present in the highest concentrations (67.58 and 19.23 µg mL^-1 , respectively). Higher amounts of TP were also detected in the blood plasma of GP+ cows (114.06 and 83.93 mg GAE L^-1 , respectively) but not in their milk (233.17 and 245.75 mg GAE L^-1 , respectively). Also a significant increase was found for lactose and β-lactoglobulin, although there was no effect on α-lactalbumin, albumin, secretory components and caseins.

Conclusion: Inclusion of 15% GP in the diets of dairy cows is beneficial for overall normal blood constituent metabolism and helps to maintain cow health. The milk of cows fed with a GP diet preserves the normal levels of fat, protein and caseins, and has increased levels of components that make this milk a versatile ingredient material for the food industry (e.g. model whey powders, stability of lactose-rich powders). © 2016 Society of Chemical Industry.

Keywords: blood metabolites; dairy cows; grape pomace; milk proteins; polyphenols.