DIETARY ANTIBIOTICS DECREASE TAURINE LOSS IN CATS FED A CANNED HEAT-PROCESSED DIET

In a crossover design, cats were fed a canned heat-processed diet (18 g dry matter/kg initial body wt) either with (+) or without (-) antibi otics [a mixture of penicillin G, procaine (25 mg/18 g diet) and tetra cycline (50 mg/18 g diet)]. The (-/+) group received no antibiotics du ring the first 5-wk period and received antibiotics during the second 5-wk period; the (+/-) group received the reverse. Plasma, whole blood , urinary and fecal concentrations of taurine, fecal bile acid excreti on and cholyltaurine hydrolase activities were measured. Consumption o f antibiotics for 5 wk resulted in a lower rate of depletion of plasma taurine. Taurine concentrations decreased more over the first 5 wk in cats in the (-/+) group than in cats in the (+/-) group [from 116 +/- 26 to 26 +/- 6 mu mol/L (-/+) and from 109 +/- 6 to 77 +/- 7 mu mol/L (+/-) for plasma, and from 546 +/- 8 to 292 +/- 29 mu mol/L (-/+) and from 560 +/- 11 to 431 +/- 20 mu mol/L (+/-) for whole blood]. Urinar y total taurine excretions during the 5th week were 54 mu mol/d for th e (-/+) group and 135 mu mol/d for the (+/-) group (pooled SEM +/- 13) , Fecal total taurine excretions during the 5th week were 184 and 53 m u mol/ d for the (-/+) and (+/-) groups, respectively, (pooled SEM +/- 9). Most of the fecal taurine was unconjugated (free). Fecal bile aci d excretions during the 5th week were 235 +/- 18 and 106 +/- 11 mu mol /d for the (-/+) and (+/-) groups, respectively. Dietary antibiotics s uppressed fecal cholyltaurine hydrolase activity of cats. Fecal cholyl taurine hydrolase activities during the 5th week were 279 +/- 54 and 4 2 +/- 10 nmol cholic acid released . min(-1). g dry feces(-1) in the ( -/+) and (+/-) groups, respectively. After the crossover, mean values for the groups were reversed, showing that the observed changes were d ue to the antibiotic treatment. These results support the hypothesis t hat the dietary taurine requirement of cats is largely determined by t he extent of microbial degradation of taurine in the gastrointestinal tract.