Page 765 - Small Animal Clinical Nutrition 5th Edition

Chronic Kidney Disease 793

minimize damage by ROS including several nutritional antiox- food DM in older dogs improved immune function (Hayes et
VetBooks.ir idants: vitamins E and C and carotenoids (Brown, 2008). al, 1969; Hall et al, 2003; Meydani et al, 1998). Based on the
above studies, foods for canine CKD patients should contain at
Supplementation of foods with these antioxidants has been
least 400 IU vitamin E/kg DM and higher levels are probably
evaluated in dogs and cats with naturally occurring CKD. In a
canine study, 10 patients with CKD (IRIS stage 2 to 3) and 10 better. In one report, dietary supplementation of food for dogs
healthy dogs were evaluated to determine effects of supplemen- with induced CKD, 5 IU/kg body weight was effective; this
tation of vitamins E (1,200 IU/kg DM) and C (150 mg/kg amount translates to approximately 450 IU/kg food DM
DM), and β-carotene (1.6 mg/kg DM) in a dry veterinary (Brown, 2008).
therapeutic renal food (Yu et al, 2006). Levels of vitamins E The minimum recommended allowance of vitamin E in
and C and β-carotene in the control food were not reported. foods for healthy adult cats is 38 IU/kg DM (NRC, 2006). No
The antioxidant supplementation reduced oxidative stress as safe upper limit has been established for cats. One antioxidant
measured by significantly reduced plasma malondialdehyde biomarker study suggested that cat foods should contain 600
concentration. The antioxidant-supplemented renal food sig- IU/kg DM for improved antioxidant function (Jewell et al,
nificantly reduced serum creatinine concentration and resulted 2000). A study in aged cats showed that increasing dietary
in increased body weight and activity (eight of 10 dogs) in the intake of vitamin E to 272 and 552 IU/kg of food DM
CKD dogs compared with dogs receiving the unsupplemented improved immune function (Hayes et al, 1969; Hall et al,
commercial maintenance-type food (Yu et al, 2006). 2003). Based on these data and studies in cats with CKD dis-
Similarly, effects of antioxidants on renal oxidative stress cussed above, foods for cats with CKD should contain at least
were studied in 10 cats with CKD compared with healthy cats 500 IU/kg DM and, as with dogs, higher levels are probably
(Yu and Paetau-Robinson, 2006). Supplementation of vitamins better. Foods high in polyunsaturated fatty acids (e.g., those
E (742 mg/kg DM) and C (84 mg/kg DM) and β-carotene containing fish oils), may require increased amounts of vitamin
(2.1 mg/kg DM), compared with the control food containing E (four or more times levels in typical foods) to prevent steati-
166 mg/kg DM vitamin E, less than 5 mg/kg DM vitamin C tis (NRC, 2006).
and 1.4 mg/kg DM β-carotene, resulted in reduced markers of Healthy dogs can synthesize required amounts of vitamin C
oxidative injury. Antioxidant supplementation significantly for normal maintenance conditions (Innes, 1931; Naismith,
reduced DNA damage in cats with CKD as evidenced by 1958; Chatterjee et al, 1975) and they can rapidly absorb sup-
reduced serum 8-hydroxy-2’-deoxyguanosine (8-OHdG) and plemental vitamin C (Wang et al, 2001). However, in vitro
comet assay parameters (Yu and Paetau-Robinson, 2006). studies indicate that dogs and cats have from one-quarter to
Based on these studies, supplementation with vitamins E and one-tenth the ability to synthesize vitamin C as other mam-
C and β-carotene as antioxidants may benefit dogs and cats mals (Chatterjee et al, 1975). Foods for canine and feline CKD
with CKD. patients should contain at least 100 and 100 to 200 mg vitamin
Dietary supplementation with antioxidants in combination C/kg DM, respectively. This recommendation is based on the
with increased omega-3 fatty acids (discussed above) reduces aforementioned vitamin E levels in foods for dogs and cats with
renal oxidant injury. Supplementation with vitamin E sup- CKD and data indicating that vitamin C regenerates vitamin E
pressed renal oxidative stress in rats with 5/6 nephrectomy at about a 1:1 molar ratio (Barclay et al, 1985).This range is not
(Tain et al,2007).Also,as mentioned above in dogs with a rem- a risk factor for urinary oxalate production in cats (Yu and
nant kidney model of CKD, dietary omega-3 fatty acid supple- Gross, 2005).
mentation reduced proteinuria, prevented glomerular hyper-
tension and decreased production of proinflammatory eicos- Other Nutritional Factors
anoids (Brown et al, 1998, 2000). In other studies in dogs with β-carotene
a remnant kidney model of CKD, dietary supplementation β-carotene is a carotenoid like lutein and lycopene. As men-
with omega-3 fatty acids and antioxidants (vitamin E, tioned above, the carotenoids have antioxidant properties. β-
carotenoids and lutein) both independently were renoprotective carotene can be absorbed by dogs and cats. β-carotene is also a
and their effects were additive when used together (Brown, precursor for vitamin A. Dogs, but not cats, are able to convert
2008). In this model, addition of antioxidants reduced protein- β-carotene to vitamin A. β-carotene can be pro-oxidant at high
uria, glomerulosclerosis and interstitial fibrosis independent of levels in people and laboratory animals (Alpha-Tocopherol,
the ratio of dietary omega-6 polyunsaturated fatty acids to Beta-Carotene Cancer Prevention Study Group, 1994). β-
omega-3 polyunsaturated fatty acids (Brown, 2008). carotene values in foods typically are difficult to obtain from
The DM requirement of vitamin E in foods for adult dogs is manufacturers. For these reasons, at this time, β-carotene is not
30 IU/kg (NRC, 2006). An upper limit of 1,000 to 2,000 considered a key nutritional factor for foods for dogs or cats
IU/kg food DM has been suggested for dogs (AAFCO, 2007). with CKD.
One antioxidant biomarker study in dogs indicated that for
improved antioxidant performance, foods should contain at Acidifiers and Buffers
least 500 IU vitamin E/kg DM (Jewell et al, 2000). Besides Metabolic acidosis is a common finding in patients with
helping to prevent chronic diseases associated with oxidative CKD. Decreased venous blood pH and plasma bicarbonate or
stress,increasing dietary intake of vitamin E,up to 2,010 mg/kg total CO concentrations are common, particularly in cats
2