Low dietary K levels have been associated with increasing renal Ca excretion in humans, indicating a higher risk of calcium oxalate (CaOx) urolith formation. Therefore, the present study aimed to investigate whether dietary K also affects the urine composition of cats. A total of eight adult cats were fed diets containing 0·31 % native K and 0·50, 0·75 and 1·00 % K from KCl or KHCO3 and were evaluated for the effects of dietary K. High dietary K levels were found to elevate urinary K concentrations (P< 0·001). Renal Ca excretion was higher in cats fed the KCl diets than in those fed the KHCO3 diets (P= 0·026), while urinary oxalate concentrations were generally lower in cats fed the KCl diets and only dependent on dietary K levels in cats fed the KHCO3 diets (P< 0·05). Fasting urine pH increased with higher dietary K levels (P= 0·022), reaching values of 6·38 (1·00 % KCl) and 7·65 (1·00 % KHCO3). K retention was markedly negative after feeding the cats with the basal diet ( − 197 mg/d) and the 0·50 % KCl diet ( − 131 mg/d), while the cats tended to maintain their balance on being fed the highest-KCl diet ( − 23·3 mg/d). In contrast, K from KHCO3 was more efficiently retained (P= 0·018), with K retention being between − 82·5 and 52·5 mg/d. In conclusion, the dietary inclusion of KHCO3 instead of KCl as K source could be beneficial for the prevention of CaOx urolith formation in cats, since there is an association between a lower renal Ca excretion and a generally higher urine pH. The utilisation of K is distinctly influenced by the K salt, which may be especially practically relevant when using diets with low K levels.

The composition of the raw legume Phaseolus vulgaris L. var. athropurpurea (PhVa) and its effects on the metabolism of young growing rats have been evaluated. The levels of protein, unsaturated fatty acids, carbohydrate, fibre and bioactive factors present in PhVa were comparable with those in other Phaseolus vulgaris varieties. However, the lectins of PhVa were predominantly of the leucoagglutinating type, and concentrated in the albumin protein fraction. Rats fed a diet (110 g total protein, 16·0 M/g) in which PhVa meal provided about half of the protein excreted high levels of N in faeces and urine, and grew more slowly, than rats fed a high-quality control diet (ad libitum or pair-fed). Small intestine, large intestine and pancreas weights were increased (by almost 100 %, P<0·05), whilst skeletal muscle, thymus and spleen weights were reduced. Blood insulin 16·20 v. 0·50 m/, P<0·05, thyroxine, glucose, protein (60·5 v. 48·3 /, P<0·05) and LDL-cholesterol were lowered, whilst glucagon (155·3 v. 185·4 n/, P<0·05), triiodothyronine and urea were elevated, as were urinary urea, creatinine and glucose. These changes in the local (gut) and systemic metabolism of rats were probably mediated primarily by lectins in PhVa, which were concentrated in the albumin protein fraction, whereas in many other Phaseolus vulgaris lines they are distributed across the globulin and albumin fractions.