The Gastrointestinal Digestion of Fat in Dogs Fed Triglycerides, Partial Glycerides and Free Fatty Acids

Abstract

Dogs were fed cottonseed oil triglycerides and 4 lipid mixtures, the composition of which represented various stages in the hydrolysis of triolein in vitro. The composition of lipid recovered from the various parts of the small intestine of dogs fed these test meals closely resembled that obtained during the hydrolysis of triolein in vitro. Triglycerides may be hydrolyzed, therefore, in much the same manner in vivo as in vitro. Although the composition of the dietary lipids was quite different, there was a tendency for a common lipid system to be formed in the proximal portion of the small intestine (free fatty acids, 27%; monoglycerides, 9%; di- and triglycerides, 64%) of dogs fed these test meals. Hydrolytic reactions predominated in the duodenum of dogs fed lipids which contained a high proportion of glycerides to free fatty acids. The percentages of free fatty acids and monoglycerides decreased and the percentage of combined diglycerides and triglycerides increased in lipid recovered from the duodenum of dogs fed lipid containing a high proportion of free fatty acids to glycerides. This suggested that a synthesis of higher glycerides occurred in the duodenum of these dogs. Hydrolytic reactions predominated in the jejunum and ileum of dogs fed the various test meals. The composition of lipids recovered from the jejunum (free fatty acids, 36%; monoglycerides, 13%; di- and triglycerides, 51%) was very similar regardless of the lipid fed. The same was true for lipid recovered from the ileum (free fatty acids, 43%; monoglycerides, 16%; di- and triglycerides, 41%).