Trans fatty acids. 4. Effects on fatty acid composition of colostrum and milk.

trans Isometric fatty acids of partially hydrogenated fish oil (PHFO) consist of trans 20:1 and trans 22:1 in addition to the trans isomers of 18:1, which are abundant in hydrogenated vegetable oils, such as in partially hydrogenated soybean oil (PHSBO). The effects of dietary trans fatty acids in PHFO and PHSBO on the fatty acid composition of milk were studied at 0 (colostrum) and 21 days postpartum in sows. The dietary fats were PHFO (28% trans), or PHSBO (36% trans) and lard. Sunflower seed oil (4%) was added to each diet. The fats were fed from three weeks of age throughout the lactation period of Experiment 1. In Experiment 2 PHFO or "fully" hydrogenated fish oil (HFO) (19% trans), in comparison with coconut oil (CF) (0% trans), was fed with two levels of dietary linoleic acid, 1 and 2.7%, from conception throughout the lactation period. Feeding trans-containing fats led to secretion of trans fatty acids in the milk lipids. Levels of trans 18:1 and trans 20:1 in milk lipids, as percentages of total cis + trans 18:1 and cis + trans 20:1, respectively, were about 60% of that of the dietary fats, with no significant differences between PHFO and PHSBO. The levels were similar for colostrum and milk. Feeding HFO gave relatively less trans 18:1 and trans 20:1 fatty acids in milk lipids than did PHFO and PHSBO. Only low levels of cis + trans 22:1 were found in milk lipids.(ABSTRACT TRUNCATED AT 250 WORDS)