Genetic variability of fatty acids in bovine milk

For a long time, the perception of consumers about fat from animal origin was linked to the increased risk of cardiovascular diseases, especially due to the large amounts of saturated fatty acids. The dairy products provide 15 to 25% of fat consumed by humans and 25 to 35% of saturated fat (Chilliard et al., 2001). This statement of cognizance, even if the potential effects of saturated fatty acids are more nuanced (Chilliard et al., 2001), has forced the dairy industry to consider new options to produce and promote healthy milk. A way of doing this, is to modify the milk fat composition to improve the nutritional quality of dairy products. Bovine milk fat, with a percentage varying between 3 and 5% (Jensen et al., 1990), is emulsified in the aqueous phase of milk. Milk fat globule is protected by a membrane partially derived from the plasma membrane of the lactating cell (Jensen et al., 1990; Danthine et al., 2000). The centre of this droplet is essentially composed by the lipids. The latter are complex both with the respect to lipids classes and to fatty acid components (Jensen et al., 1988). Triglycerides compose 98% of lipids present in bovine milk. The last 2% include small amounts of free fatty acids, monoand diglycerides, phospholipids, sterols and hydrocarbons (Jenness, 1988). The analysis of fatty acids is difficult due to the volatile trend of short chain fatty acids and the large amounts of fatty acids present in milk (Jensen et al., 1988). Currently, 406 fatty acids are listed (Debry, 2001). However, few fatty acids represent the majority of fat present in bovine milk. Table 1 shows the contents of the principal fatty acids present in bovine milk based on the results obtained by Collomb et al. (2000). The 16 major fatty acids represented approximately 79% of milk fat content (Table 1). The fatty acids with the highest contents were C16:0 and C18:1 9-cis (Table 1). Typical milk fat from dairy cows contains 70% of saturated, 25% of monounsaturated and 5% of Genetic variability of fatty acids in bovine milk