5.4. Postnatal changes in serum lipid and fatty acid composition

The concentration of serum lipids was low in the newborn reindeer (<8 h) but the total lipids and cholesterol increased significantly during the first few days and PLs increased during the first week after birth (III). The principal serum lipid in the newborn reindeer was PLs whereas in the older calves the principal serum lipid was total cholesterol followed by PLs and TAGs.

The fatty acid composition of serum CEs of the newborn calves was significantly different from that of their mothers, especially the proportion of C18-PUFAs. The proportion of CE-18:2 in the newborn reindeer was only one fifth of the proportion in their mothers (11 vs. 49 %), and the proportion of 18:3n-3 was one sixth (0.4 vs. 2.3 %). The proportions of both of these principal PUFAs increased rapidly and significantly during the first few days of life: the proportion of CE-18:2 increased from 11 to 34 %, and the proportion of CE-18:3n-3 from 0.4 to 1.3 % during the same time (III). By the age of two weeks, the proportions of CE-18:2 and CE-18:3n-3 in the calves were at the same level as in the mothers.

The proportions of 18:2 and 18:3n-3 in serum PLs were also significantly lower in the newborn reindeer than the mothers. In addition, the proportions of long-chain PUFAs, 20:4n-6 and docosapentaenoic acid (22:5n-3), were significantly lower in the calves than in the mothers, but the proportion of docosahexaneoic acid (22:6n-3) was higher. The proportion of the principal C18-PUFAs increased significantly in serum PLs of the calves during the first few days after birth. The fatty acid composition of serum TAGs in the newborn reindeer resembled that of the milk TAGs. The proportions of oleic acid (18:1) and palmitic acid (16:0) were the dominant fatty acids in both. The proportion of 18:2 was 3 % of all TAG fatty acids of the milk and 2 % of its energy content. There were significant positive correlations between all serum lipids and milk TAGs.