Effect of Dietary Fat Source on the Apparent Digestibility of Fat and the Composition of Fecal Lipids of the Young Pig

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Abstract
Two experiments, each of 5 weeks' duration, were conducted with 18-day-old weanling pigs to determine the effect of dietary fat source and age of animal on apparent fat digestion and absorption. In each experiment two males and two females were fed diets that contained 10% coconut oil, rapeseed oil, lard or tallow. Fecal collections were made for 5 consecutive days beginning at 21 and 49 days of age. The petroleum ether-soluble lipids of the diets and of acidified (HCl-ethanol) lyophilized feces were extracted and fractionated into free fatty acids (FFA), fatty acids of glyceryl esters (FAGE) and nonsaponifiables using a 0.05 n KOH-60% ethanol system. None of the differences in average percent digestibility of the dietary fat, which varied from 63.8 to 78.4 at 21 days of age and from 69.6 to 82.2 at 49 days of age, was related to fat source, sex of animals or age of the animals. Partition of the fecal lipids revealed that the FFA fraction accounted for 74 to 85%, and the FAGE fraction, 4 to 8%, of the total lipids excreted by the pig, irrespective of fat source or age of the animal, which suggests that digestion (that is, hydrolysis) of the dietary fat was essentially complete at both 21 and 49 days of age. Gas-liquid chromatographic analyses indicated that dietary fatty acid composition influenced the fatty acid patterns of the fecal lipids, although there were notable qualitative and quantitative differences. Total saturated fatty acids constituted a higher proportion of the FFA fraction than of the dietary lipid fraction or of the FAGE fraction for groups fed rapeseed oil, lard or tallow. Apparent digestibilities of palmitic and stearic acids were lower than those of the unsaturated or medium-chain saturated fatty acids.