Effect of addition of tallow and lecithin in the diet of weanling piglets on the apparent total tract and ileal digestibility of fat and fatty acids

Two experiments were performed involving a total of 54 piglets housed individually after weaning at 3 weeks of age at a mean weight of 6.5 ± 0.5 kg. Experiment I was performed on 30 piglets to evaluate the effect of incorporation of 8% tallow or 6.5% tallow plus 1.5% of lecithin, on the apparent total tract (faecal) digestibility (AFD) of major dietary components, total fat and fatty acids. Experiment II was performed on 24 piglets to evaluate the effect of mixing or spraying fat with or without addition of lecithin successively on the AFD and the apparent ileal digestibility (AID) of dietary components, total fat and individual fatty acids. Chromic oxide was used as a marker to measure AFD in Experiment I, and total collection of excreta was used to determine successively AFD then apparent ileal digestibility (AID) on the same animals in Experiment II. AID was measured on animals fitted with an ileo-rectal anastomosis. D of total fat was very low (48.9%) in non-supplemented diets; the addition of fat and fat plus lecithin increased significantly the AFD to 68.0% and 73.2% (SEM 5.4), respectively, in Experiment I. Neither the technological procedure of mixing or spraying fat nor the addition of lecithin modified the AFD of total fat or energy measured by total collection in Experiment II. AID of total fat was always higher than AFD (i.e. 82.6% (SEM 3.7) vs. 77.02% (SEM 4.5), on average). The high AFD of unsaturated fatty acids (91.3%-97.5%) contrasted with the low values for the saturated fatty acids (i.e. 38% for stearic and 89.2% for myristic acid), but AID of saturated fatty acids amounted to 74.1% whereas that of unsaturated fatty acids averaged 90.1%. The significant interaction between lecithin and the technological treatment used to incorporate fat indicated that spraying in the absence of lecithin as well as the addition of lecithin increased significantly the AID of linoleic and linolenic acids. The present results demonstrate the usefulness of the expression of ileal digestibility of fat and fatty acids, and are in favour of a total collection of faeces or ileal digesta instead of the use of a marker. The validity of the ileo-rectal anastomosis in the weaned piglet is discussed.