EFFECTS OF DIETARY SAPONINS ON FECAL BILE-ACIDS AND NEUTRAL STEROLS, AND AVAILABILITY OF VITAMIN-A AND VITAMIN-E IN THE CHICK

Saponins are a heterogenous group of triterpene or steroidal glycosides that are widely distributed among food plants. They have been implicated in reduced animal growth, interference with the absorption of cholesterol and bile acids, and with fat digestibility, but also have shown potential in the reduction of blood cholesterol levels. This study investigated whether these effects of saponins affect the availability of the fat-soluble vitamin A and vitamin E. Chicks fed gypsophila and quillaja (triterpenoid) saponins, at 0.9% of diet, had reduced weight gains, feed intake, digestibility of lipid, marked increases in cholesterol excretion, but no changes in excretion of coprostanol or bile acids. Blood total cholesterol and high density lipoprotein cholesterol were unaffected. Both saponins appeared to interfere with the absorption of vitamin A and vitamin E, as indicated by reduced concentrations of plasma retinol and vitamin E, and liver retinol, vitamin A palmitate, and vitamin E. Feeding a steroidal saponin (sarsaponin) had virtually no effect on any of the parameters measured. Further studies will be needed to determine if saponins have specific or general inhibitory effects on nutrient availability and how much these effects contribute to reduced animal performance.