Two experiments were carried out using healthy cats to examine the effects of feeding pattern and crude protein (CP) content of dry cat foods on urination frequency (the number of urination in a day) and the diurnal variation of urine pH. The effect of feeding pattern was examined in Experiment 1 (n=7), in which a commercial dry cat food containing 30% CP on DM basis was used. Although urine volume did not change, the urination frequency decreased when cats were allowed to consume the dry food only for three hours in a day. The restricted feeding time resulted in a marked increase in urine pH after meals, but urine pH was comparatively stable and higher when cats were allowed free access to the food. The effect of CP content of dry cat foods was examined in Experiment 2 (n=12). When cats were given free access to dry foods containing 29%,50% and 71%CP on DM basis, both urine volume and urination frequency increased with an increase in CP content of foods. However, the increase in dietary CP content resulted in a decrease in urine pH, which was relatively lower all day when cats were allowed free access to the food containing 71% CP. Present results suggest that free access to high-protein foods is effective for the prevention of struvite uroliths in healthy young adult cats through urine acidification as well as an increase in urination frequency.

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To confirm whether or not plasma concentrations of free amino acids are useful as a criterion to estimate amino acid requirements in adult dogs, three experiments were conducted using seven adult male Beagles per experiment. In Experiment 1, we examined the changes over time in plasma concentrations of free amino acids after feeding a diet containing 23% CP. Plasma concentration of all free amino acids except Met and Cys increased until about 4 h after feeding, and then gradually decreased to the levels before the morning feeding. In Experiment 2, the dietary CP levels were changed from 27 to 24% to examine the quickness and the stability of responses of plasma concentrations of free amino acids, and urea to the abrupt change in dietary CP levels. Plasma concentrations of Arg, Ile, Leu, Lys, Val, Tau decreased, whereas that of Ala increased until 3 d and these changes were kept for 8 d after the dietary CP levels were lowered. In Experiment 3, dietary CP levels were gradually increased from 15 to 35% to examine the response of plasma concentrations of free amino acids, and urea to the graded increase in dietary CP levels. Plasma concentrations of Arg, Asp, Lys, Thr, Val, and urea increased with an increase in dietary CP levels over 15%, whereas those of Glu, His, Ile, Leu, Phe, and Tyr increased with increasing dietary CP levels over 20%. Conversely, plasma concentrations of Pro, Ser, Trp, and Tau rapidly reached the highest values and thereafter remained constant. Plasma concentration of Met, Cys, and 3-methyl His were not affected by the dietary CP levels, and those of Ala and Gly decreased with increasing dietary CP levels. These results suggested that the requirements of essential amino acids of which plasma concentrations responded linearly with an increase in the CP intake could be obtained by using their concentrations in the plasma as an index.

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