Nutrient utilization in rats and pigs fed enzyme resistant starch

The influence of 6% dietary raw or retrograded high-amylose corn starch on protein, fat, carbohydrate, energy and mineral utilization was studied in rats and ileum-cannulated pigs fed the same conventional diets. Ileal nitrogen digestibility tended to decrease and faecal nitrogen excretion to increase in pigs fed one of the tested enzyme resistant starch (RS) sources. In rats, the effect from RS intake on faecal nitrogen excretion was more pronounced (P < 0.05). These effects were paralleled by a shift of the nitrogen excretion from the renal to the faecal output. As a result, no significant effects from RS on nitrogen retention could be established in pigs and rats. RS consumption tended to lower apparent faecal fat digestibility in rats as well as apparent ileal and faecal fat digestibility in pigs. This effect on faecal fat digestibility was significant in pigs fed retrograded high-amylose corn starch. Faecal starch digestibility was significantly decreased in rats fed RS. Similar effects were found at the terminal ileum in pigs, but not at the anal level possibly due to more intensive fermentation in the large intestine of these animals. Apparent faecal digestible and metabolizable energy values were significantly lower in rats receiving RS. These effects were less pronounced in pigs, although RS intake significantly lowered apparent ileal energy digestibility when retrograded high-amylose corn starch was fed. In vivo determination of the RS concentrations in both test diets using ileum-cannulated pigs revealed values of 2.9% raw and 5.7% retrograded high-amylose corn starch instead of the 6% RS as measured in vitro, indicating that the tested retrograded starch behaved more like RS in the small intestine as compared with the raw starch. RS did not significantly affect apparent faecal absorption or retention of Ca, P, Mg and Zn in rats and pigs. In pigs, RS intake tended to decrease ileal absorption of the minerals, but these effects appeared to be neutralized in the large intestine. Despite the moderate dietary RS content, increases in faecal water content and bulking were found in rats and pigs. In conclusion, the investigated effects from RS ingestion were in general qualitatively similar in both species. Retrograded high-amylose corn starch, as compared with raw high-amylose corn starch, often exerted more pronounced effects, but the differences were not always significant.