Comparison of corn gluten meal and meat meal as a protein source in dry foods formulated for cats

OBJECTIVE: To compare the nutritional value of corn gluten meal (CGM) and meat meal (MM) as a dietary source of protein in dry food formulated for adult cats. ANIMALS: 8 healthy adult cats (4 males and 4 females). PROCEDURE: Diets containing CGM or MM as the main protein source were each fed for a 3-week period in a crossover study. Digestibility and nutritional balance experiments were conducted during the last 7 days of each period. Furthermore, freshly voided urine was obtained to measure urinary pH, struvite crystals, and sediment concentrations. RESULTS: Daily food intake and dry-matter digestibility were significantly higher for the MM diet. Fecal moisture content also was higher for the MM diet. Apparent nitrogen (N) absorption and N retention were higher for the MM diet, even when values were expressed as a percentage to account for differences in N intake. Urinary pH, struvite activity product, number of struvite crystals in urine, and urinary sediment concentrations were not different between diets. Retention of calcium, phosphorus, and magnesium was lower for the CGM diet, and cats lost body calcium and magnesium when fed the CGM diet. CONCLUSIONS AND CLINICAL RELEVANCE: Meat meal was superior to CGM as a protein source in dry foods formulated for cats, because dry-matter digestibility and N utilization were higher for the MM diet. In addition, net loss of body calcium and magnesium for the CGM diet suggests that mineral requirements increase when CGM is used as a protein source.     

Association between dietary factors and calcium oxalate and magnesium ammonium phosphate urolithiasis in cats.

OBJECTIVE: To identify dietary factors associated with the increase in occurrence of calcium oxalate (CaOx) uroliths and the decrease in occurrence of magnesium ammonium phosphate (MAP) uroliths in cats. DESIGN: Case-control study. ANIMALS: 173 cats with CaOx uroliths, 290 cats with MAP uroliths, and 827 cats without any urinary tract diseases. PROCEDURE: Univariate and multivariate logistic regression were performed. RESULTS: Cats fed diets low in sodium or potassium or formulated to maximize urine acidity had an increased risk of developing CaOx uroliths but a decreased risk of developing MAP uroliths. Additionally, compared with the lowest contents, diets with the highest moisture or protein contents and with moderate magnesium, phosphorus, or calcium contents were associated with decreased risk of CaOx urolith formation. In contrast, diets with moderate fat or carbohydrate contents were associated with increased risk of CaOx urolith formation. Diets with the highest magnesium, phosphorus, calcium, chloride, or fiber contents and moderate protein content were associated with increased risk of MAP urolith formation. On the other hand, diets with the highest fat content were associated with decreased risk of MAP urolith formation. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that diets formulated to contain higher protein, sodium, potassium, moisture, calcium, phosphorus, and magnesium contents and with decreased urine acidifying potential may minimize formation of CaOx uroliths in cats. Diets formulated to contain higher fat content and lower protein and potassium contents and with increased urine acidifying potential may minimize formation of MAP uroliths.     

Evaluation of meat meal, chicken meal, and corn gluten meal as dietary sources of protein in dry cat food

The nutritional value of meat meal (MM), chicken meal (CM), and corn gluten meal (CGM) as dietary sources of protein in dry food formulated for adult cats was evaluated. Twelve healthy adult cats (11 males and 1 female) were used. Dry diets containing MM, CM, or CGM as the main protein source were given for a 3-week period in a 3 x 3 Latin-square design. Digestion and balance experiments were conducted during the last 7 d of each period. In addition, freshly voided urine was taken to determine urinary pH and number of struvite crystals. As compared with the CM diet, dry-matter digestibility was higher and lower for the MM and CGM groups, respectively. Percentages of nitrogen (N) absorption and N retention to N intake were higher in the MM group, and N utilization was not different between the CM group and the CGM group. All cats excreted alkaline urine (pH > 7). Urinary pH, struvite activity product, and number of struvite crystals in urine were lower for the CGM group. There was no difference in retention of calcium and magnesium among the groups. From the point of view of digestibility and N utilization, MM is superior to CGM, and CM is better than or equivalent to CGM as a protein source of dry foods for adult cats. However, when CM is used as a dietary protein source, some manipulation of dietary base excess may be needed to control urinary acid-base balance, because CM contains higher calcium and phosphorus.     

Feline struvite urolithiasis: factors affecting urine pH may be more important than magnesium levels in food

Eighteen male cats were fed either a canned complete diet or a commercially available dry pelleted diet or the same dry diet containing 1.6 per cent ammonium chloride. The daily food and water intake of four of these cats was measured. Urine samples were taken at random and the pH and the presence of struvite crystals in their sediment estimated. In some samples in which the pH was less than 7.0, and struvite crystals were absent, the pH was increased to 7.0 and any sediment was examined for struvite. No spontaneous struvite was seen in urine samples (pH 5.8) from cats fed the canned complete diet but when its pH was raised to 7.0, 46 per cent of these samples showed struvite. Cats fed the dry pelleted diet had urine of higher pH (7.55) and 78 per cent of the samples contained struvite crystals. Cats fed this diet supplemented with ammonium chloride had a urine pH of 5.97 and only 9 per cent contained struvite crystals but when the pH was adjusted to 7.0 all the samples showed struvite crystals. Energy intake was similar on all three diets but the intake of dry matter was greater on the dry diets. Liquid water intake was greater on the dry diets but total water intake was greatest on the canned complete diet. The intake of magnesium, calcium and phosphate was greater on the dry diets. It is concluded that urine pH is a more important controller of struvite precipitation than mineral intake.     

Substitution of dietary calcium chloride for calcium carbonate reduces urinary ph and urinary phosphorus excretion in adult cats

Summary

In a 4×4‐vvk cross‐over study, eight adult cats were given four moist diets containing identical amounts of calcium (13.9 mmol/MJ) but with different ratios of calcium carbonate to calcium chloride, the calcium salts providing half of the total dietary calcium. Increasing amounts of calcium chloride were substituted for equimolar amounts of calcium carbonate. Higher intakes of calcium chloride caused significantly lower pH values in postprandial and 24‐h urine samples. The urinary excretion of ammonium and titratable acid rose with increasing calcium chloride intake. The urinary concentrations of calcium and magnesium were not affected by the type of calcium salt, but the urinary excretion and concentration of phosphorus were significantly depressed when the amount of calcium chloride in the diet was increased. The results are discussed in the context of dietary prevention of and therapy for struvite urolithiasis in cats.     

Associations between dry dietary factors and canine calcium oxalate uroliths

OBJECTIVE: To identify factors in dry diets associated with the occurrence of calcium oxalate (CaOx) uroliths in dogs. ANIMALS: 600 dogs with CaOx uroliths and 898 dogs without urinary tract diseases. PROCEDURE: Univariate and multivariate logistic regression were performed. RESULTS: Compared with diets with the highest concentrations of sodium, dry diets with the lowest concentrations of sodium, phosphorus, calcium, chloride, protein, magnesium, or potassium were linearly associated with increased risk of CaOx urolith formation. Significant nonlinear associations between increased occurrence of CaOx uroliths and urine acidifying potential and low moisture content were observed. Significant nonlinear associations between decreased occurrence of CaOx uroliths and carbohydrate and fiber contents were observed. A significant association between the occurrence of CaOx uroliths and dietary fat was not observed. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that dry diets formulated to contain high concentrations of protein, calcium, phosphorus, magnesium, sodium, potassium, and chloride may minimize formation of CaOx uroliths. In addition, comparison of risk and protective factors of various diet ingredients fed to dogs with CaOx uroliths suggests that although similar findings were observed in canned and dry formulations, in general, greater risk is associated with dry formulations. However, before these hypotheses about dietary modifications are adopted by food manufacturers, they must be investigated by use of appropriately designed clinical studies of dogs with CaOx urolithiasis.     

Associations between dietary factors in canned food and formation of calcium oxalate uroliths in dogs

OBJECTIVE: To identify dietary factors in commercially available canned foods associated with the development of calcium oxalate (CaOx) uroliths in dogs. ANIMALS: 117 dogs with CaOx uroliths and 174 dogs without urinary tract disease. PROCEDURE: Case dogs were those that developed CaOx uroliths submitted to the Minnesota Urolith Center for quantitative analysis between 1990 and 1992 while fed a commercially available canned diet. Control dogs were those without urinary tract disease evaluated at the same veterinary hospital just prior to or immediately after each case dog. A content-validated multiple-choice questionnaire was mailed to each owner of case and control dogs with the permission of the primary care veterinarian. Univariate and multivariate logistic regressions for each dietary component were performed to test the hypothesis that a given factor was associated with CaOx urolith formation. RESULTS: Canned foods with the highest amount of protein, fat, calcium, phosphorus, magnesium, sodium, potassium, chloride, or moisture were associated with a decreased risk of CaOx urolith formation, compared with diets with the lowest amounts. In contrast, canned diets with the highest amount of carbohydrate were associated with an increased risk of CaOx urolith formation. CONCLUSIONS AND CLINICAL RELEVANCE: Feeding canned diets formulated to contain high amounts of protein, fat, calcium, phosphorus, magnesium, sodium, potassium, chloride, and moisture and a low amount of carbohydrate may minimize the risk of CaOx urolith formation in dogs.     

Effects of a high-protein diet versus dietary supplementation with ammonium chloride on struvite crystal formation in urine of clinically normal cats

OBJECTIVE: To evaluate the effects of a high-protein diet versus dietary supplementation with ammonium chloride (NH4Cl) on struvite crystal formation in the urine of clinically normal cats by measuring the urine concentration of hydrochloric acid (HCl)-insoluble sediment, urine pH, struvite activity product (SAP), number of struvite crystals in urine, and urine volume. ANIMALS: 23 healthy adult cats. PROCEDURE: Urine was fractionated by centrifugation with subsequent extraction of the sediment with 1 N HCl (study 1). Diets containing either 29% crude protein or 55% crude protein were fed to cats in a crossover trial of 3 weeks/period (study 2). Diets supplemented with either sodium chloride (NaCl) or NH4Cl were fed, by use of a 3 x 3 Latin-square design with 3 wk/period (study 3). In studies 2 and 3, urine samples were collected for the last 7 days of each period. RESULTS: The HCl-insoluble sediment contained Tamm-Horsfall glycoprotein (THP; study 1). The high-protein diet (study 2) and dietary supplementation with NH4Cl (study 3) resulted in a decrease in urine pH, SAP, and the number of struvite crystals in urine. However, the high-protein diet decreased urine concentrations of HCl-insoluble sediment containing THP (study 2), in contrast to the NH4Cl supplementation that increased urine volume without a significant effect on the urine concentration of the HCl-insoluble sediment (study 3). CONCLUSIONS AND CLINICAL RELEVANCE: Our results indicate that compared with dietary supplementation with NH4Cl, the high-protein diet is preferable as a urine acidifier for the prevention of struvite crystal formation in clinically normal cats.     

The effect of urine acidification on calcium oxalate relative supersaturation in cats

There is an apparent reciprocal relationship between magnesium ammonium phosphate (MAP, struvite) and calcium oxalate (CaOx) urolithiasis incidence rate in cats. The number of struvite uroliths submitted for analysis over the past 35 years has been decreasing, with an increase in CaOx urolith submissions. Commercial diets aimed to dissolve struvite uroliths are typically acidified, and it has been suggested that dietary acidification increases urinary calcium excretion and the risk of CaOx crystallization. The objective of this study was to assess the effect of urine acidification on the relative supersaturation (RSS) of CaOx in cats, as a representation of crystallization risk. Four diets were extruded to contain identical nutrient contents, but with gradual acidification (0, 0.6, 1.3 and 1.9% sodium bisulphate substituted sodium chloride in diets A, B, C and D respectively). Thirteen adult cats were fed each diet sequentially for a minimum of 10 days. Average urine pH was 6.4, 6.2, 6.0 and 5.9 on diets A, B, C and D respectively (p < 0.0001). Struvite RSS decreased on diets inducing more acidic urine pH (p < 0.0001). Urinary calcium excretion and concentration increased with diets inducing lower urine pH (p < 0.0001), but oxalate excretion and concentration decreased (p < 0.001). CaOx RSS was not different between diets (p = 0.63). These results suggest that a lower diet base excess and resulting urine pH to support struvite dissolution do not increase the risk for CaOx crystallization in the range of urine pH representative of most commercial feline diets. Long-term studies are needed to confirm this.     

Effect of diet on struvite activity product in feline urine

Groups of male specific-pathogen-free cats were fed a basal, purified diet (A), with or without 0.45% added magnesium (MgCl2, diet B; MgO, diet C) or 1 of 2 commercial diets (D,E). Urine samples collected for 48 hours after 2 weeks of feeding were analyzed for calcium, magnesium, sodium, potassium, ammonium, sulfate, phosphate, oxalate, and citrate content. Concentrations were used to calculate the negative logarithm of the struvite activity product (pSAP), using a microcomputer-based program for calculation of supersaturation of the urine with crystal solutes. The pSAP value for all samples also was hand-calculated by use of an equation. Consumption of diet B caused a significant (P less than 0.05) increase in urine calcium concentration. Total urine phosphate concentration was lower in urine from cats fed diets A, B, or C than in urine from cats fed diets D or E. For the various diets, urine PO4(-3) was: 5.3 microM for diet A; 6.3 microM for diet C; 0.9 microM for diet E; 36 nM for diet D, and 0.5 nM for diet B. Consumption of diets B and C caused significant increases in urine magnesium concentration (53.1 nM and 49.1 mM, respectively). Ammonium ion concentration was highest in urine from cats fed diets B and D, 116.2 mM and 100.3 mM, respectively. When the pSAP, hand-calculated assuming ionic strength u = 0.2, was regressed on that calculated by use of the microcomputer program, the coefficient of determination was 0.96 (P less than or equal to 0.01).     

Medical dissolution of feline struvite urocystoliths

The efficacy of a diet designed to facilitate dissolution of feline magnesium ammonium phosphate (struvite) uroliths was evaluated in 30 cases of urolithiasis, sterile struvite uroliths dissolved in a mean of 36 days after initiation of dietary treatment. In 5 cases of urolithiasis, struvite urocystoliths associated with urease-negative bacterial urinary tract infection dissolved in a mean of 23 days after initiation of dietary and antimicrobial treatment. In 3 cases of urolithiasis, struvite urocystoliths associated with urease-positive staphylococcal urinary tract infection dissolved in a mean of 79 days after initiation of dietary and antimicrobial treatment. Dissolution of uroliths in cats fed the treatment diet was associated with concomitant remission of dysuria, hematuria, and pyuria, and reduction in urine pH and struvite crystalluria. In one case, a urocystolith composed of 100% ammonium urate, and in another case, a urolith composed of 60% calcium phosphate, 20% calcium oxalate, and 20% magnesium ammonium phosphate did not dissolve.     

Feline struvite crystalluria: a comparison of some commercially available dry cat diets in New Zealand

Thirteen adult cats were each fed consecutively five test diets: firstly a complete canned diet, and then four commercially available dry cat diets (New Formula Biscats, Cat Chow, Go-Cat and Whiskettes) for 7,13, 5, 4 and 4 weeks respectively. Urine samples were tested for pH and presence of struvite crystals. Body weight was recorded weekly. Urine pH was ranked from acid to alkaline as follows: Whiskettes (pH 5.8), canned diet (pH 5.9), Biscats (pH 6.1), Cat Chow (pH 6.45) and Go-Cat (pH 6.5). The pH of urine when cats were fed Whiskettes, Biscats and canned diet was not significantly different. Biscats produced a urine pH significantly higher than Whiskettes but, in each case, these three diets produced a significantly lower urine pH than Cat Chow and Go-Cat. Struvite crystals occurred spontaneously in 9% of urine samples from cats when fed Whiskettes and Biscats, 71% when fed Cat Chow and 38% when fed Go-Cat: spontaneous struvite was not seen in any cat fed CX9. Haematuria was seen in 2.9% (2/69) urine samples from cats fed Cat Chow. One tom cat had a blocked urethra after 24 days on Go-Cat. No abnormalities were observed in any cat when fed canned diet, Biscats or Whiskettes. It was concluded that of the four dry cat diets tested only Biscats and Whiskettes produce urine with an acceptably low rate of spontaneous struvite crystalluria.     

Effect of dietary phosphoric acid supplementation on acid-base balance and mineral and bone metabolism in adult cats.

Experimental evidence indicates that maintenance of urinary pH < or = 6.4 is the single most effective means of preventing feline struvite crystalluria or urolithiasis of noninfectious causes. This may be accomplished by dietary acidification, but must be moderated to avoid potential adverse effects of excessive acidification, including bone demineralization, negative calcium balance, potassium depletion, and renal disease. Effects of chronic dietary phosphoric acid supplementation on acid-base balance and on mineral and bone metabolism were investigated in adult, domestic cats. One group of 6 cats was fed a basal, naturally acidifying diet without added acidifiers, and another group of 6 cats was fed 1.7% dietary phosphoric acid. Changes observed during 12 months of study included development of noncompensated metabolic acidosis, increased urinary calcium excretion, and lower but positive calcium balance in cats of both groups. Urinary pH decreased in cats of both groups, but was significantly (P < 0.05) and consistently maintained < or = 6.4 in cats given dietary phosphoric acid. Urinary phosphorus excretion increased in cats of both groups, but was significantly (P < 0.05) greater in phosphoric acid-supplemented cats, leading to lower overall phosphorus balance as well. Potassium balance decreased in cats of both groups, but was only transiently negative in the phosphoric acid-supplemented cats midway through the study, and normalized at positive values thereafter. Plasma taurine concentration was not affected by dietary acidification, and remained well within the acceptable reference range for taurine metabolism. Double labeling of bone in vivo with fluorescent markers was followed by bone biopsy and histomorphometric measurement of several static and dynamic variables of bone formation. Overall indices of bone formation decreased in cats of both groups with age and confinement, but were not affected by dietary phosphoric acid supplementation. Dietary supplementation with phosphoric acid used as the principal inorganic P source to achieve moderate and stable degree of urinary acidification, did not appear over the course of 1 year, to have induced adverse effects on mineral, bone, or taurine balance in these adult domestic cats.     

Effects of dietary fat and energy on body weight and composition after gonadectomy in cats

OBJECTIVE: To evaluate the effect of dietary fat and energy density on body weight gain, body composition, and total energy expenditure (TEE) in neutered and sexually intact cats. ANIMALS: 12 male and 12 female cats PROCEDURE: Male cats were castrated (castrated male [CM]) or underwent no surgical procedure (sexually intact male [IM]). Female cats underwent ovariectomy (spayed female [SF]) or laparotomy and ligation of both uterine tubes without ovary removal (sexually intact female [IF]). Cats were fed either the low-fat (LF) or high-fat (HF) diet for 26 weeks, with the final allocation consisting of 8 groups: IF-LF IF-HE SF-LF, SF-HF IM-LF, IM-HF, CM-LF, and CM-HF. Mean food intake for each group was recorded daily, and body weight was monitored weekly throughout the study. Body composition and TEE were measured before surgery in week 0 and at the end of the study (week 26) by isotope dilution (double-labelled water). RESULTS: N eutered cats gained significantly more body fat and body weight (53.80+/-5.79%) than sexually intact cats (27.11+/-5.79%) during the study. Body weight gain of neutered cats fed the HF diet was greater than those fed the LF diet. Following correction for body composition, TEE was similar in all groups and no pattern towards increased food intake was evident. CONCLUSIONS AND CLINICAL RELEVANCE: Weight gain in neutered cats was decreased by feeding an LF, low energy-dense diet. To prevent weight gain in cats after neutering, a suitable LF diet should be fed in carefully controlled meals rather than ad libitum.     

Phenothiazine toxicity

Thirteen adult cats were each fed consecutively five test diets: firstly a complete canned diet, and then four commercially available dry cat diets (New Formula Biscats, Cat Chow, Go-Cat and Whiskettes) for 7,13, 5, 4 and 4 weeks respectively. Urine samples were tested for pH and presence of struvite crystals. Body weight was recorded weekly.

Urine pH was ranked from acid to alkaline as follows: Whiskettes (pH 5.8), canned diet (pH 5.9), Biscats (pH 6.1), Cat Chow (pH 6.45) and Go-Cat (pH 6.5). The pH of urine when cats were fed Whiskettes, Biscats and canned diet was not significantly different. Biscats produced a urine pH significantly higher than Whiskettes but, in each case, these three diets produced a significantly lower urine pH than Cat Chow and Go-Cat. Struvite crystals occurred spontaneously in 9% of urine samples from cats when fed Whiskettes and Biscats, 71% when fed Cat Chow and 38% when fed Go-Cat: spontaneous struvite was not seen in any cat fed CX9. Haematuria was seen in 2.9% (2/69) urine samples from cats fed Cat Chow. One tom cat had a blocked urethra after 24 days on Go-Cat. No abnormalities were observed in any cat when fed canned diet, Biscats or Whiskettes.

It was concluded that of the four dry cat diets tested only Biscats and Whiskettes produce urine with an acceptably low rate of spontaneous struvite crystalluria.     

Effects of high carbohydrate and high fat diet on plasma metabolite levels and on i.v. glucose tolerance test in intact and neutered male cats

To elucidate the impact of dietary influence on carbohydrate and lipid metabolism and on the development of diabetes mellitus in the carnivorous cat, a 3 weeks feeding trial was carried out on six sexually intact and six neutered adult male cats. The effects of two isonitrogenic diets, differing in carbohydrate and fat content, were investigated on plasma metabolite levels in a 24-h blood sampling trial. Plasma leptin concentrations were also determined at the beginning and at the end of the 24-h trial. Glucose and insulin response was measured in an i.v. glucose tolerance test. A 5 days long digestion trial was also performed, which revealed a high digestion capacity of both fat and carbohydrates in cats. The high fat diet induced a significant rise in the plasma triglyceride, FFA, beta-hydroxybutyrate and cholesterol concentration, while the elevation in the glucose level did not reach significance. In the glucose tolerance test no significant difference was found between the neutered and intact cats. However, independently of the sexual state, the cats on the high fat diet showed a slightly elongated glucose clearance and reduced acute insulin response to glucose administration. This is indicative of diminished pancreatic insulin secretion and/or beta-cell responsiveness to glucose. The results of this preliminary study may be the impetus for a long-term study to find out whether it is rather the fat rich ration than carbohydrate rich diet that is expected to impair glucose tolerance and thus might contribute to the development of diabetes mellitus in cats. Whether the alteration in glucose metabolism is due to altered leptin levels remains to be determined.     

Nutrient digestibility,but not mineral absorption,is age‐dependent in cats

Availability of nutrients is influenced by extremes of age, and a better characterization of this influence is necessary for appropriate development of foods and nutritional management throughout life stages of cats. This study investigated nutrient digestibility, mineral absorption, faeces and urine production in three groups of six young, mature and old cats fed two diets containing different energy densities. Apparent digestibility and mineral absorption were calculated by total collection method and values were tested with anova and regression analysis. A quadratic relationship was detected between age and digestibility of dry matter, organic matter, crude protein, acid‐hydrolysed fat and starch in the low‐energy diet. Starch digestibility showed the same response in the high‐energy diet. Young adult cats had intermediate digestibility, mature cats the highest and old cats the lowest. Mineral absorption (calcium, phosphorus, magnesium, sodium, potassium and chloride) and urinary pH were not different among groups. These findings confirm previous studies that found low digestibility of nutrients in some old cats, and support evidence that this trend is even more important in less digestible dry foods. On the contrary, data suggest that mineral formulations do not need to be varied in diets for adult cats of different ages.     

Characterization of magnesium-induced urinary disease in the cat and comparison with feline urologic syndrome

Aggregates of struvite crystals caused urethral obstruction in a high percentage of cats fed moist and dry diets supplemented with Mg oxide. Some of the diets were associated with cystolith formation as well. The percentage of Mg in the experimental diets was a misleading indicator of Mg intake because of differences between moist and dry diets in their caloric density. Magnesium homeostasis was maintained in cats ingesting large quantities of Mg. Tissue (kidney, muscle, and rib) concentrations of Mg were the same in cats fed high Mg and control diets. Plasma Mg concentration was increased only in cats ingesting the largest amount of Mg. Magnesium homeostasis was maintained by a marked increase in urine Mg excretion. However, urine Mg concentration was not directly related to Mg intake, apparently because of differences between diets in intestinal absorption of Mg. Urethral obstruction of experimental cats was not associated with a transient increase in Mg intake, nor did obstructing cats have higher urine Mg concentrations than did nonobstructing cats fed the same diet. This observation indicates that factor(s) other than urine Mg concentration are important in urethral obstruction. Cats with urethral obstruction due to naturally occurring disease, feline urological syndrome (FUS), had markedly lower urine Mg concentrations than cats fed high Mg diets. This finding refutes the theory that cats develop FUS because of primary Mg hyperabsorptive phenomena or because of a primary urinary leak of Mg. It also indicates that factors other than urine Mg concentration are involved in the genesis of naturally occurring urethral obstruction. Another difference between the natural and the induced disease was related to the character of the urinary precipitates. Experimental diets higher in Mg concentration caused urolith formation, which is uncommon with FUS. Lower Mg diets caused obstruction with aggregates of crystals, but mucus was not observed. However, in the experimental disease induced in the present study, urinary precipitates were predominantly or exclusively struvite, as has been reported in the natural disease. Many similarities were seen between the diet-induced disease and FUS, but factors in addition to Mg intake are involved in the natural disease. The importance of Mg, compared with the undefined factors, remains to be established.     

Effects of dietary potassium citrate supplementation on urine pH and urinary relative supersaturation of calcium oxalate and struvite in healthy dogs

OBJECTIVE: To assess the effect of dietary potassium citrate supplementation on the urinary pH, relative supersaturation of calcium oxalate and struvite (defined as the activity product/solubility product of the substance), and concentrations of magnesium, ammonium, phosphate, citrate, calcium, and oxalate in dogs. ANIMALS: 12 healthy adult dogs. PROCEDURE: Canned dog food was fed to dogs for 37 days. Dogs were randomly allocated to 3 groups and fed test diets for a period of 8 days. Study periods were separated by 6-day intervals. During each study period the dogs were fed either standard diet solus (control) or standard diet plus 1 of 2 types of potassium citrate supplements (150 mg potassium citrate/kg of body weight/d) twice daily. Urinary pH, volume and specific gravity, relative supersaturation of calcium oxalate and struvite, and concentrations of magnesium, ammonium, phosphate, calcium, oxalate, and citrate were assessed for each treatment. RESULTS: Mean urine pH was not significantly affected by dietary potassium citrate supplementation, although urine pH did increase by 0.2 pH units with supplementation. Diets containing potassium citrate maintained a higher urine pH for a longer part of the day than control diet. Three Miniature Schnauzers had a significantly lower urinary relative calcium oxalate supersaturation when fed a diet supplemented with potassium citrate, compared with control diet. CONCLUSIONS AND CLINICAL RELEVANCE: Dietary potassium citrate supplementation has limited effects on urinary variables in most healthy dogs, although supplementation results in maintenance of a higher urine pH later in the day. Consequently, if supplementation is introduced, dogs should be fed twice daily and potassium citrate should be given with both meals or with the evening meal only.     

Absorption of carbohydrate-derived nutrients in sows as influenced by types and contents of dietary fiber

The current investigation was undertaken to study the absorption and plasma concentration of carbohydrate-derived nutrients [glucose, short-chain fatty acids (SCFA), and lactate] and the apparent insulin production in sows fed diets containing contrasting types and contents of dietary fiber. Six sows were fed 3 experimental diets, low fiber (LF; 177 g of dietary fiber and 44 g of soluble fiber/kg of DM), high soluble fiber (HF-S; 429 g of dietary fiber and 111 g of soluble fiber/kg of DM), and high insoluble fiber (HF-I; 455 g of dietary fiber and 74 g of soluble fiber/kg of DM), in a repeated crossover design. Variations in dietary concentration and solubility of dietary fiber were obtained by substituting starch-rich wheat and barley in the LF diet with dietary fiber-rich co-products (sugar beet pulp, potato pulp, pectin residue, brewers spent grain, pea hulls, and seed residue, which have distinct physicochemical properties). The main carbohydrate component of the LF diet was starch and nonstarch polysaccharides (cellulose and noncellulosic polysaccharides) for the 2 high dietary fiber diets. Consumption of the LF diet resulted in increased and rapid glucose absorption at 0 to 4 h postfeeding. With the HF-I diet, the glucose absorption pattern was similar but at a decreased rate, whereas it was decreased and delayed with the HF-S diet (diet, P < 0.001; time, P < 0.001). These differences were also reflected in the insulin response. The quantitative absorption of SCFA at 0 to 10 h postfeeding was greater when feeding the HF-S diet compared with the LF diet (P < 0.001) and intermediate when feeding the HF-I diet (P < 0.001). The study showed that feeding the high dietary fiber diets resulted in a increased and more uniform uptake of SCFA than when feeding the LF control. Moreover, the HF-S diet reduced diurnal variation in glucose and insulin concentrations.