Exogenous creatinine clearance rate was determined in 8 partially (approx 75%) nephrectomized dogs fed 2 concentrations of dietary sodium, beginning 9 weeks after partial nephrectomy was performed. In a double crossover design, dogs were then fed low-sodium diet (0.18% sodium on a dry-weight basis) or high-sodium diet (1.3% sodium on a dry-weight basis) in 2 sequences (L/H/L or H/L/H) for 3 consecutive 4-week observation periods. Glomerular filtration rate (GFR) was measured by exogenous creatinine clearance before and after partial nephrectomy, and every 2 weeks during the experimental diet periods. Initial mean +/- SD GFR (3.76 +/- 0.78 ml/min/kg of body weight) decreased precipitously after nephrectomy (1.25 +/- 0.45 ml/min/kg); however, during the postnephrectomy and experimental diet periods, GFR gradually increased in all dogs to nearly half the prenephrectomy values (1.87 +/- 0.22 ml/min/kg). Significant differences in GFR were not observed when dogs were fed the IM or the H/L/H sequence. Therefore, it was concluded that abrupt change from high dietary sodium (1.3%) to restricted dietary sodium (0.18%), or vice versa, does not cause deterioration of renal function in dogs with moderate renal impairment. However, caution should be used in extrapolating these findings to dogs with clinically evident (azotemia, isosthenuria) renal failure.

Four diets were formulated to contain: 16% protein and 0.4% phosphorus-diet 1; 16% protein and 1.4% phosphorus-diet 2; 32% protein and 0.4% phosphorus-diet 3; and 32% protein and 1.4% phosphorus-diet 4. Forty-eight dogs were fed diet 1 for 3 months after surgical reduction of renal mass, then were allotted to 4 groups of 12 dogs each, with equal mean values for glomerular filtration rate (GFR). Dog of groups 1-4 were fed diets 1-4, respectively, for 24 months. Data collected from the dogs during and at termination of the study were analyzed statistically for effects of dietary protein, phosphorus (P), time, and interactions between these factors. During the 24 months of study, 24 dogs developed uremia and were euthanatized for necropsy. Necropsy also was performed on the remaining 24 dogs after they were euthanatized at the end of the study. Dog survival was significantly enhanced by 0.4% P diets (vs 1.4% P diets), but survival was not significantly influenced by amount of dietary protein. The 0.4% P diets (vs 1.4% P diets) significantly increased the period that GFR remained stable before it decreased, but dietary protein did not have significant effect. Significant blood biochemical changes attributed to P, protein, and time were identified during the study. Terminally, plasma parathyroid hormone concentration was significantly increased from prediet values in all groups of dogs. Urine protein excretion was not significantly affected by dietary amount of either protein or P, when measured by either timed urine collection or urine protein-to-creatinine ratio. A tendency was seen for increased protein excretion with passage of time. Histologic and mineral analyses of kidneys removed at necropsy revealed some significant difference attributable to diet, but differences were more marked when diet was ignored, and the 24 surviving dogs were compared with the 24 that developed uremia. Overall, amount of dietary P was more important than amount of dietary protein for preventing adverse responses. However, because renal damage specifically attributable to either dietary component was not obvious, it is possible that the effects of P were manifested by extrarenal mechanisms.

Serum lipoprotein concentrations, routine serum biochemical values, and morphologic changes of the liver were evaluated in cats undergoing weight loss. Food was withheld from 6 obese and 6 control cats for 3 days (days 0 to 2), followed by feeding 50% of previous food intake for 26 days (days 3 to 28). Percutaneous liver biopsy specimens were obtained from all cats on days 0, 7, 14, and 28. Blood samples for serum biochemical analysis and lipoprotein profiles were obtained on days 0, 3, 7, 14, and 28. All cats lost weight throughout the study, and none developed signs of chemical illness, including those of idiopathic hepatic lipidosis syndrome. Serum total cholesterol concentrations decreased initially in all cats, but rapidly returned to normal after day 3 in obese cats, suggesting altered cholesterol metabolism during dietary restriction. Low-density lipoprotein concentrations decreased throughout the study in control cats, but were unchanged in obese cats. Examination of liver biopsy specimens from each cat revealed minimal lipid accumulation in all specimens, although some specimens contained hydropic degeneration.

The effect of a high insoluble-fiber (IF) diet containing 15% cellulose in dry matter, high soluble-fiber (SF) diet containing 15% pectin in dry matter, and low-fiber (LF) diet on glycemic control in 6 dogs with alloxan-induced insulin-dependent diabetes mellitus was evaluated. Each diet contained > 50% digestible carbohydrate in dry matter. A crossover study was used with each dog randomly assigned to a predetermined diet sequence. Each dog was fed each diet for 56 days. Caloric intake was adjusted weekly as needed to maintain each dog within 1.5 kg of its body weight measured prior to induction of diabetes mellitus. All dogs were given pork lente insulin and half of their daily caloric intake at 12-hour intervals. Mean (+/- SEM) daily caloric intake was significantly (P < 0.05) less when dogs consumed the IF diet vs the SF and LF diets (66 +/- 3 kcal/kg, 81 +/- 5 kcal/kg, and 79 +/- 4 kcal/kg, respectively). Serum alkaline phosphatase activity was significantly (P < 0.05) higher when dogs consumed the LF diet vs the iF and SF diets (182 +/- 37 IU/L, 131 +/- 24 IU/L, and 143 +/- 24 IU/L, respectively). Mean postprandial plasma glucose concentration measured every 2 hours for 24 hours, beginning at the time of the morning insulin injection, was significantly (P < 0.05) lower at most blood sampling times in dogs fed IF and SF diets, compared with dogs fed the LF diet. As a result, 24-hour mean plasma concentration of glucose (IF, 165 +/- 17 mg/ dl; SF, 169 +/- 19 mg/dl; LF, 218 +/- 29 mg/dl), 24-hour mean plasma-glucose fluctuation (IF, 49 +/- 2 mg/dl; SF, 47 +/- 4 mg/dl; LF, 63 +/- 7 mg/dl), and 24-hour urine-glucose excretion (IF, 31 +/- 10 g/d; SF, 42 +/- 16 g/d; LF, 67 +/- 13 g/d) were significantly (P < 0.05) lower in dogs fed IF and SF diets, compared with dogs fed the LF diet. These variables were not significantly different between dogs fed IF and SF diets. Mean glycosylated hemoglobin concentration also was significantly (P < 0.05) lower when dogs consumed the IF diet, compared with the LF diet (4.3 0.4% vs 5.2 +/- 0.4%, respectively). In dogs with alloxan-induced insulin-dependent diabetes mellitus, consumption of diets containing 15% cellulose or 15% pectin and > 50% digestible carbohydrate on a dry-matter basis resulted in improvement in glycemic control, compared with consumption of a diet containing > 50% digestible complex carbohydrate without added fiber.

The main objective of the study reported here was to determine whether signs typical of exocrine pancreatic insufficiency (EPI) are alleviated when affected dogs are fed a diet with low fat content, compared with feeding ordinary commercial dog food or food prepared by the owner. The most cost-effective amount of enzyme supplement also was estimated. The study consisted of 6 test periods. Duration of the first and third periods was 4 weeks, and that of the others was 2 weeks. During the first 2 periods, the dogs were fed their original diet. The amount of enzyme supplement was reduced by half between the first and the second period. During the last 4 periods, the dogs were fed only the low-fat diet, and amount of the enzyme supplement was reduced stepwise. During the entire study, owners were asked to assess daily the severity of 9 signs typical of EPI. A new index was established by adding the daily scores of each individual EPI sign. This index was designated the EPI index and was used as a measure of the general well-being of the dog. When the mean EPI indexes of the original diet periods were compared with those of the corresponding low-fat diet periods, there were no statistically significant differences by use of Turkeys test or the paired t-test. There was considerable variability between dogs, however. The fat content of the original diet did not correlate with the difference in EPI signs when the dogs were fed the low-fat diet. According to our study, feeding a low-fat diet to dogs with EPI did not significantly alleviate clinical signs of the disease. Decreasing the enzyme supplementation by 50% of the recommended of dose did not significantly increase severity of the cumulative EPI score. Decreasing the enzyme supplement by three-fourths of the recommended dose was excessive, and the severity of the clinical signs increased significantly (P < 0.05) The cost of the low-fat diet, compared with that of the original diet, was high.

To determine the effects of long-term dietary protein restriction in cats with chronic renal failure (CRF), 4 healthy adult cats and 7 cats with surgically induced CRF were fed a high-protein (HP, 51.7% protein) diet and 4 healthy adult cats and 7 cats with surgically induced CRF were fed a low-protein (LP, 27.6% protein) diet for 1 year. Cats with induced CRF that were fed the LP diet had reduced serum urea nitrogen concentrations, despite lower glomerular filtration rates, compared with cats with CRF fed the HP diet. Despite five-sixths reduction in renal mass, reduced glomerular filtration rate, and azotemia, 13 of the 14 cats with induced CRF retained the ability to concentrate urine and produced urine with a specific gravity > 1.035. Cats fed the HP diet consumed significantly more calories than did cats fed the Lp diet, presumably because the HP diet was more palatable. As a result of the lower caloric intake in cats fed the LP diet, these cats were protein and calorie restricted, compared with cats fed the HP diet. Cats fed the HP diet weighed significantly more than did cats fed the LP diet. Mean hematocrit and mean serum albumin concentration ere significantly lower in control cats and in cats with CRF fed the LP diet, compared with control cats and cats with CRF fed the HP diet. Hypokalemia developed in 4 of 7 cats with CRF fed the HP diet (containing 0.3% potassium); hypokalemia did not develop in control cats fed the same diet or in cats with CRF fed the LP diet containing 0.4% potassium. Excessive kaliuresis, hypomagnesemia, and metabolic acidosis did not appear to contribute to the hypokalemia. Subsequent supplementation of the HP diet with potassium gluconate prevented hypokalemia in cats with CRF.

Amino acid profiles and serum albumin and serum total protein concentrations were evaluated in dogs with renal disease. Nine dogs ranging in age from 1 to 15 years were identified as having mild to moderate chronic renal failure (CRF; exogenous creatinine clearance, 0.5 to 2.13 ml/kg of body weight/min). These dogs and a group of 10 clinically normal control dogs were fed a diet containing 31% protein for 8 weeks, at which time serum and urine amino acid assays and clearance studies were performed. All dogs then were fed a diet containing 16% protein for 8 weeks and then reevaluated. Chronic renal failure was associated with mild abnormalities in serum concentrations of amino acids. When fed the higher protein diet, dogs with CRF had lower serum concentrations of glutamine, leucine, proline, and serine and higher serum concentrations of cystathionine and 3-methylhistidine than clinically normal control dogs. When fed the low protein diet, dogs with CRF had lower serum serine concentrations and higher serum concentrations of cystathionine, phenylalanine, and 3-methylhistidine. Urine excretion of amino acids in all dogs on both diets was low, and dogs with CRF had lower renal clearances of 3-methylhistidine than control dogs. There were no significant differences in concentrations of serum albumin and total solids between either group, regardless of diet. We concluded that dogs with mild to moderately severe CRF have mild abnormalities of serum free amino acid concentrations, but renal conservation of essential amino acids is not impaired.

Exogenous creatinine clearance, urinary electrolyte excretions, calcium and phosphorus balance, serum cholesterol concentration, arterial blood pressure, and body weight were evaluated in dogs with chronic renal failure that were fed 2 commercial diets. Nine dogs ranging in age from 1 to 15 years were identified as having mild to moderate chronic renal failure (CRF, exogenous creatinine clearance = 0.5 to 2.13 ml/kg of body weight/min). These dogs and a group of 10 clinically normal controls were fed a diet containing 31% protein for 8 weeks at which time hematologic and biochemical evaluations and clearance studies were performed. All dogs then were fed a phosphorus-restricted diet containing 16% protein and then reevaluated after 8 weeks. The dogs in this study had hematologic and biochemical abnormalities typical of CRF. Urine absolute and fractional excretion of electrolytes was higher in dogs with CRF than in controls and was affected by diet. Serum cholesterol concentration was higher in dogs with CRF and increased in those dogs after feeding the low protein diet. Changes in dietary sodium intake did not affect arterial blood pressure. The phosphorus-restricted diet did not affect serum amino terminal parathyroid hormone concentration in either group. Control dogs lost body weight, whereas dogs with CRF gained weight when fed the low protein diet. We concluded that dogs with mild to moderately severe CRF have the same biochemical abnormalities and response to dietary restriction of protein and phosphorus as has been previously reported in dogs with experimentally induced CRF. Restriction of dietary sodium may not decrease arterial blood pressure in some dogs with CRF. Dogs with CRF may be predisposed to hypercholesterolemia when fed restricted protein commercial diets, and reduction of dietary phosphorus intake may be inadequate to control renal secondary hyperparathyroidism in dogs with CRF.

Casein has been used as a protein source in diets designed to dissolve canine ammonium urate uroliths and to prevent their recurrence, because it contains fewer purine precursors than do many other sources of protein. However, an important question is whether reduced quantities of dietary casein have any benefit in modifying saturation of urine with urates. To answer this question, activity product ratios of uric acid, sodium urate, and ammonium urate were determined in 24-hour urine samples produced by 6 healthy Beagles during periods of consumption of a 10.4% protein, casein-based (10.4% casein) diet and a 20.8% protein, casein-based (20.8% casein) diet. Significantly lower activity product ratios of uric acid, sodium urate, and ammonium urate were observed when dogs consumed the 10.4% casein diet. Significantly lower 24-hour urinary excretions of ammonia and phosphorus were observed when dogs consumed the 10.4% casein diet. Twenty-four-hour urinary excretions of magnesium and 24-hour urine pH values were significantly higher when dogs were fed the 10.4% casein diet. These results suggest that use of the 10.4% casein diet in protocols designed for dissolution and prevention of uric acid, sodium urate, and ammonium urate uroliths in dogs may be beneficial.

Effects of increased dietary chloride and reduced sodium and potassium ion concentrations on coxofemoral joint conformation, as assessed by radiography, were examined in growing dogs. Dietary electrolyte balance was quantified by dietary anion gap (DAG), defined as Na+ + K+ - Cl- in milliequivalents per 100 g of food. Diets had anion gap ranging from 8 to 41 mEq/100 g of food. One hundred sixty-seven pups from 27 litters representing 5 breeds were studied during the period of rapid growth. The extent of subluxation of the femoral head was measured on radiographs, using the method of Norberg. On average, less subluxation of the femoral head (P < 0.05) was observed when diets with lower DAG were fed. Differences in DAG balance did not result in different rates of weight gain; therefore, the reduction in coxofemoral joint subluxation attributable to low DAG was unrelated to weight gain. Norberg angles measured at 30 weeks of age were highly correlated with coxofemoral joint status at 2 years of age, as measured by the Swedish diagnostic system and the scoring system of the Orthopedic Foundation for Animals (/r/ greater than or equal to 0.70, P < 0.0002, n = 24). This diet-related improvement in coxofemoral joint sub-luxation would be expected, on average, to delay or mitigate the characteristic clinical and radiographic signs of hip dysplasia in growing dogs.