Page 385 - Small Animal Clinical Nutrition 5th Edition

Feeding Mature Adult Cats 395

intake of 0.2% of the food DM, or almost threefold the mini-
VetBooks.ir mum recommended allowance (2007). Some commercial moist
foods exceed 1.0% DM sodium or almost 15 times the mini-
mum recommended allowance. Sodium intake at this level is
markedly above that needed for optimal health. The recom-
mended range for dietary sodium for mature adult cats is 0.2 to
0.4% DM.
Chloride is now recognized as a co-determinant in salt-sen-
sitive hypertension; thus, control of dietary excess is also impor-
tant (Kurtz et al, 1987; Kotchen et al, 1987) (Chapter 36).
Unfortunately, little information is available about the chloride
requirement of cats. The minimum recommended allowance
for dietary chloride is 0.096% DM (NRC, 2006); however,
more typically, chloride values are approximately 1.5 times the
concentration of sodium.
Figure 21-2. Relative frequency of feline lower urinary tract disease
Potassium
(LUTD), struvite (magnesium ammonium phosphate, MAP) urolithia-
The potassium requirement for older cats is thought to be sis and calcium oxalate (CO) urolithiasis in cats of varying age. Note
greater than that for young adult cats. This impression comes that LUTD is most common in adult cats, struvite urolithiasis is most
from anecdotal reports of low serum potassium levels and common in adult cats less than six years old and calcium oxalate
improved attitude, appetite, muscle strength and renal function urolithiasis is most common in cats over six years old. (Adapted
from Bartges JW. Lower urinary tract disease in older cats: What’s
following oral potassium supplementation in older cats.
common, what’s not. Veterinary Clinical Nutrition 1996; 3: 57-62.
However, the potassium requirement of healthy older cats has Thumchai R, Lulich JP, Osborne CA, et al. Epizootiologic evaluation
not been determined and an increased need remains specula- of urolithiasis in cats: 3498 cases (1982-1992). Journal of the
tive. Nevertheless, factors common in mature adult cats that American Veterinary Medical Association 1996; 208: 547-551.)
support the need for increased dietary potassium include: 1)
kaliuresis as a result of kidney disease, high dietary protein or
high metabolic and/or dietary acid load, 2) reduced food intake ance for foods for adult cats is 0.04% DM (NRC, 2006).
and 3) increased intestinal loss. Mature adult cats with normal
appetite and renal function probably do not benefit significant- Urinary pH
ly from increased dietary potassium levels. However, hypoka- Older cats frequently have clinical or subclinical renal disease
lemia can cause signs ranging from mild lethargy to marked that may impair their ability to compensate for acid-base alter-
polymyopathy and nephropathy. Thus, increasing dietary po- ations resulting from metabolic and dietary influences. In a
tassium to support moderate losses may benefit some older cats. study in which cats were fed a food with higher urinary acidi-
Levels as low as 0.3% resulted in hypokalemia when provided fying potential (pH 6.39 vs. 6.6 in the control food), older cats
in high-protein or acidified foods (DiBartola et al, 1993). The lost more weight, had lower red cell counts and had greater sys-
minimum recommended allowance for potassium in foods for temic acid loads than younger cats (Lawler and Ballam, 1995).
adult cats is 0.52% DM (NRC, 2006). Dietary potassium lev- This observation, combined with the reduced risk of struvite
els for foods for mature adult cats should be at least 0.6% DM. urolithiasis, increased risk of calcium oxalate urolithiasis and
high frequency of kidney disease in older cats, supports the the-
Magnesium ory that foods fed to older cats should have a lower urine acid-
Increased losses of magnesium, similar to those seen with ifying potential (i.e., higher published urinary pH averages)
potassium, may affect magnesium balance in older cats. than foods for young adult cats. A safe range of measured uri-
Hypomagnesemia has also been associated with refractory nary pH values in mature adult cats is between 6.4 and 6.6.
hypokalemia, particularly in cats with diabetes mellitus The acidifying potential of commercial foods for older cats is
(Dhupa, 1995). The benefit of limiting dietary magnesium in not typically tested despite the fact that older cats generate a
cats is a reduced risk of struvite-mediated lower urinary tract significantly lower urinary pH than younger cats fed the same
disease. However, the risk of struvite-mediated disease is low in foods (Smith et al, 1997). To achieve a normal urinary pH, the
older cats (Figure 21-2) (Bartges, 1996). Furthermore, foods acidifying potential of foods for mature adult cats should be
containing very low levels of magnesium have been associated lower than that of foods for young adult cats. Published urinary
with the development of calcium oxalate uroliths in an epi- pH averages should be greater for foods for older cats than for
demiologic survey of cats (Thumchai et al, 1996) and deficien- foods for young adults, unless the foods have been specifically
cy increases risk of urolith formation in rats (Su et al, 1991). tested in old or very old cats and found to be safe. Providing
Therefore, magnesium should be provided at moderate levels food with less acidifying potential helps avoid metabolic acido-
(0.05 to 0.1% DM) and severe magnesium restriction should be sis and its complications in older cats (Thumchai et al, 1996;
avoided (<0.04% DM). The minimum recommended allow- Kirk et al, 1995).