Effect of dietary fat and fatty acid on fecal excretion of a calcium oleate phosphate complex

The interaction between dietary lipids and fibre in the sheep 2. Digestibility studies

Digestibility studies were carried out to establish the inter-relationship between crude fibre and total lipid digestibility in the presence of added calcium or non-ionic detergents. Three levels of calcium, corresponding to daily intakes of 2·3, 4·8 and 22·9 g per sheep, were used in a predominantly ground barley diet (65 to 73%) to which was added 8% beef tallow or maize oil. Two non-ionic detergents were used at 0·1% of the diet: nonyl phenol ethylene oxide and fatty alcohol combined with 3 molecules of ethylene oxide.

With a daily intake of 2·3 or 4·8 g calcium per sheep, supplementation with fat resulted in a reduced fibre digestibility. When the intake was increased to 22·9 g, there was a significant improvement (P<0·05) only for the maize-oil-supplemented diet. Increasing calcium intake, associated with increased calcium digestibility, significantly (P<0·05) depressed total lipid digestibility. Intake of 4·8 g calcium per day was associated with the highest calcium digestibility of 33% digestibility units and the total lipid digestibility of 94%. Maize oil was better digested than beef tallow with the lower level of calcium; the position was reversed with the higher level of calcium supplementation. No advantages were found for crude fibre and total lipid digestibility when detergents were added.

A possible mechanism by which the physical wetting of dietary lipids causes decreased digestibility of the fibre component is discussed.

Excretion of phospholipids by men on fat-free diet

The fecal excretion of phospholipids was determined in three adult males during the last 4 days of three 8- to 16-day periods on a fat-free diet. The phospholipids were isolated and identified by column and thin-layer chromatography on silicic acid. The individual phospholipids were quantitatively estimated by gas chromatographic determination of the component fatty acids, using methyl heptadecanoate as internal standard. The range of total excretion of phospholipids was 64–100 mg/day per 100 g of dry feces. In all samples the major phospholipids were tentatively identified as phosphatidyl ethanolamine, phosphatidyl glycerol, and phosphatidyl inositol. Phosphatidyl ethanolamine made up 31–41% of the total excretion. All the phospholipids contained about the same fatty acids (C14–C27), but in somewhat varying proportions. Because of the occurrence of large amounts of the odd carbon number, among both branched and long chain fatty acids, which are not commonly associated with mammalian metabolism, the presence of phospholipids in the feces was attributed to bacterial synthesis.