Influence of fish oil, palm oil and glycerol on milk fatty acid composition and metabolism in cows during early lactation
The aim of the study was to determine an influence of diet additives in a form of protected palm oil, protected fish oil or unprotected fish oil with glycerol in Polish Holstein-Friesian cows on milk fatty acid composition, metabolism, milk yield and milk composition. Milk production, milk fat, and milk protein did not differ statistically between the groups. A significant increase ( P<0.01) in glucose level in blood was noted after application of unprotected fish oil with glycerol. The lowest concentration of β-hydroxybutyrate and non-esterified fatty acids, with the highest cholesterol and triacylglycerol concentration was observed in protected fish oil. An increase in the content of long-chain acids was observed in milk fat of cows receiving protected fish oil when compared to the group receiving palm oil and unprotected fish oil with glycerol. Concentration of trans-vaccenic acid (TVA) was higher ( P<0.01) in protected fish oil and unprotected fish oil with glycerol when compared to palm oil group. These changes were corresponded by concentration of cis-9, trans-11 conjugated linoleic acid (CLA) (1.71, 1.68 and 0.61 g/100 g of total fatty acids, respectively). Irrespectively of the form of fish oil administration, an increase in milk eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) content was noted. The present experiment provides evidence that milk fatty acids can be manipulated via dietary fish oil or unprotected fish oil and glycerol application.