Abstract
The hypothesis tested was, that in ruminating goats on positive energy balance the dietary intake of polyunsaturated fatty acids would be reflected in the fatty acid composition of erythrocytes. Eight goats were fed a diet rich in olive oil, supplying 34% the energy requirement for maintenance (NE
l). Four animals were given diets containing either olive or corn oil at an energy level of 1.5 times the requirement for maintenance. Each feeding period lasted 21 days. On the last day of each period, plasma and erythrocytes were collected. Feeding of the diet containing corn oil, which is rich in linoleic acid, resulted in a significant increase in the level of linoleic acid in both plasma lipids and erythrocytes. Likewise, feeding of the diet containing olive oil, while the goats were in positive energy balance, produced higher levels of oleic acid in plasma lipids and erythrocytes. The fatty acid composition of plasma lipids was influenced more strongly by dietary unsaturated fatty acids than that of erythrocytes. The concentrations of plasma lipids, including total cholesterol, did not respond to the type of fat during the experimental periods. When the goats were in negative energy balance, they had significantly higher plasma levels of non-esterified fatty acids. The present study demonstrates that dietary unsaturated fatty acids are incorporated into plasma total lipids and erythrocytes, suggesting a partial escape of dietary unsaturated fatty acids from ruminal biohydrogenation. The escape from hydrogenation may ensure the provision to the goat tissues of essential, polyunsaturated fatty acids. It further implies that the composition of ruminant milk and meat can be influenced by the intake of polyunsaturated fatty acids.