Taurine balance is different in cats fed purified and commercial diets.

Ileal fluxes, urinary losses and taurine balance were determined in six taurine-replete and four taurine-depleted cats. Digesta samples collected at the terminal ileum were used to assess ileal flux of taurine. Four diets were tested: a commercial diet in two forms (heat-processed and frozen) and two purified diets containing either 1225 or 0 mg taurine/kg diet. Five-day balance trials were performed on d 3-7 with measurement of food intake and taurine in urine and ileal digesta. Substantially greater quantities of total taurine (free + bound) were found in ileal digesta from cats fed the heat-processed rather than the frozen preserved diet (205 vs. 101% of the average daily taurine intake, respectively), with calculated taurine balances of -609 vs. -212 mumol/d, respectively. The quantity of taurine in ileal digesta from taurine-replete cats fed the 1225 or 0 mg taurine/kg purified diets was not significantly different, indicating that taurine found at the terminal ileum is mostly of endogenous origin. Taurine-depleted cats had significantly lower amounts of taurine in ileal digesta, with a taurine balance of -77 mumol/d. These results demonstrate that a heat-processed diet causes substantially greater losses of taurine from the intestine than does a frozen diet. This phenomenon may explain the inability of some heat-processed diets to maintain normal plasma taurine concentrations in cats.