Comparative analysis of pancreatic amylase activity in laboratory rodents.

Alpha-amylase is the main enzyme for starch digestion in the mammalian gastrointestinal tract. There are species differences in the enzymatic activity of pancreatic amylase that are related to the digestive strategy and natural diet of a species. This aspect is well investigated in pet and farm animals, while in common laboratory animal rodents, information is scarce. In the context of the 3R concept, detailed knowledge of the digestive physiology should be the basis of adequate nutrition, experimental planning and data interpretation. The present study aimed to obtain reference data on amylase activity in pancreatic tissue and duodenal digesta in laboratory mice, rats and hamsters. In addition, digesta was stained with Lugol's iodine to visualize starch in the process of degradation throughout the gastrointestinal tract. Amylase activity in pancreatic tissue and duodenal digesta was significantly lower in hamsters than rats and mice. The Lugol staining showed intense starch degradation in the hamsters' forestomachs, presumably by microbial fermentation. A possible explanation is that the prae-duodenal microbial starch fermentation enhances digestibility and reduces the need for pancreatic amylase in hamsters. Rats and mice may rely more on pancreatic amylase for prae-caecal starch digestion, while the microbial fermentation is mainly located in the caecum. The results clearly show species differences in the digestive capacity for starch in mice, rats and hamsters that need to be considered in the feeding of these species in the laboratory setting as well as in the use of rodents as translational animal models.

True mineral digestibility in C57Bl/6J mice.

Data on mineral digestibility is key to understand mineral homeostasis and refine the recommendations for the dietary intake of these nutrients. In farm animals and pets, there is plenty of data on mineral digestibility and influencing factors. In laboratory mice, however, there is a lack of information on mineral digestibility under maintenance conditions, although this should be the basis for studies on mineral homeostasis under experimental conditions. The aim of the present study was to analyse data on intake, faecal excretion, and apparent digestibility of calcium, phosphorus, sodium, potassium, and magnesium in C57BL/6J mice fed different maintenance diets with varying voluntary dry matter intake. Lucas-tests were used to quantify true digestibility and describe correlations between dietary intake and excretion/absorption of the nutrients. Calcium, phosphorus, and magnesium showed a linear correlation between intake and faecal excretion (R2: 0.77, 0.93 and 0.91, respectively). Intake and apparently digested amounts of sodium and potassium were correlated linearly (R2: 0.86 and 0.98, respectively). These data show that intake is the major determinant of absorption in the minerals listed above. Faecal calcium and phosphorus excretion were correlated as well (R2 = 0.75).

High Intake of Sodium Chloride for 28 Days Causes No Effect on Serum FGF23 Concentrations in Cats.

BACKGROUND: FGF23 is an acknowledged parameter to assess kidney health. As chronic kidney failure is one of the most common diseases in aging cats, dietary influences on renal health warrant investigation. The purpose of this study was therefore to investigate potential correlations between dietary sodium chloride and FGF23. METHODS: In a total of two trials, 11 cats were included. In the first trial, the cats were fed a complete and balanced control diet; in the second trial, sodium chloride was added (8 g/kg/DM)). Blood, urinary, feed, and faecal samples were analysed for major minerals. FGF23 and creatinine were measured in blood and urine samples. RESULTS: Serum phosphate and FGF23 were unaffected by high sodium chloride intake, thus showing no correlation between serum FGF23 and sodium concentrations. Apparent phosphorus digestibility was significantly increased, however, by high sodium chloride intake, whereas apparent digestibility of calcium was unaffected. The present study confirms differences in FGF23 and sodium chloride interaction in cats compared with other species. Further research regarding the correlation between sodium chloride and phosphate homeostasis is warranted.

Morphometrics of Xenopus laevis Kept as Laboratory Animals.

Morphometric data that provide information on body conditions can be used to monitor the health and well-being of animals. In laboratory animals, they can help to evaluate the stress due to experiments or treatments, following the 3R principles. The aim of the present study was to obtain morphometric data of male and female African clawed frogs, Xenopus laevis, as the bases for body condition evaluations. Adult frogs (n = 198) were weighed and standardized photographs were taken. The photographs were used to determine several measurements (length, cranial width, caudal width, thigh width). In addition, a triangle was drawn to outline each frog's simplified body form, and the triangle surface was calculated. In conclusion, the triangle surface drawn on the dorsal plane of each frog correlated with the body weight of the females. There were significant differences between the body weights and sizes of male and female frogs, with males being smaller (p < 0.001). Based on the morphometric data, females could be assigned to five groups in which an assessment of the animal's well-being is feasible.

Faecal dry matter excretion per se affects faecal calcium and phosphorus losses in dogs.

The study aimed to investigate the effect of faecal dry matter (DM) excretion on faecal losses of calcium (Ca) and phosphorus (P) without potentially confounding factors. Dogs were fed two levels of the same basal diet (cooked pork, rice, gelatine; 8.5 ± 0.7 and 12.6 ± 1.2 g DM/kg BW). Mineral supplements were added separately for identical Ca and P supply independent of DM intake (Ca 226 and P ~170 mg/kg BW). Digestion trials (10 days adaptation, 5 days quantitative faecal collection) were carried out. Digestibility of DM averaged 87% in both trials. Faecal DM and mineral excretion increased highly significant (DM 1.1 ± 0.3 to 1.7 ± 0.2 g/kg BW, p = 0.00005; Ca 185 ± 34 and 233 ± 22 mg/kg BW, p = 0.00119; P 99 ± 23 to 127 ± 12 mg/kg BW, p = 0.00212), revealing a highly significant correlation. Apparent digestibility of Ca was positive in the first trial and negative in the second leading to a slightly negative Ca retention in the latter one. The results suggest that in dogs (i) factors influencing Ca and P absorption can only be compared if faecal DM excretion is identical and (ii) Ca requirements may be affected by DM intake and digestibility.

Chemical composition of snakes.

The present study was carried out to provide insight into the body composition of snakes, which is an important basis for determination of nutrient requirement and physiological processes. Carcasses of 86 captive snakes (31 pythons, 32 colubrids and 23 boas) were available for analysis. Skins and vertebrae bones of 11 snakes and livers of 64 snakes were analysed separately from the carcasses. Crude nutrients, major minerals and trace elements were investigated. The content of crude nutrients of the whole body was similar to those of mammals and birds. Relatively high contents of copper, zinc and especially of iron (up to 23,973 mg/kg dry matter) were found in the body, particularly in the liver. There was an increase of the iron content of the whole body over age.

Morphology of Starch Particles along the Passage through the Gastrointestinal Tract in Laboratory Mice Fed Extruded and Pelleted Diets.

Diet processing impacts on starch properties, such as the degree of starch gelatinization. This affects digestibility, as shown in laboratory mice fed either a pelleted or an extruded diet. In the present study, the morphology of starch particles throughout the digestive tract of mice was visualized. Thirty-two female C57BL/6J mice were used for a feeding trial. They were fed a commercial maintenance diet for laboratory mice, which was available in pelleted and extruded form, for seven weeks. The mice were sacrificed after the feeding period, and chyme samples were collected from five sites (stomach, anterior and posterior small intestine, caecum, colon). Samples of diets, chyme and faeces were analyzed via stereomicroscopy (stained with Lugol's iodine) and scanning electron microscopy (SEM). The starch granules appeared more compact in the pelleted diet, showing first signs of degradation only in the small intestine. The caecum content of both diets group was intensively stained, particles as well as fluid phase, indicating that it contained mainly starch. The SEM pictures of caecum content showed abundant bacteria near starch particles. This suggests selective retention of prae-caecally undigested starch in the murine caecum, likely the site of microbial fermentation.

A pilot study on dietary and faecal calcium/phosphorus ratios in different types of captive ruminating herbivores.

Quantitative differences in calcium and phosphorus metabolism between domestic species exist and can be visualised using data on calcium and phosphorus intake and faecal excretion. The parameter for analysing the results was defined as Δ = dietary calcium/phosphorus (Ca/P) ratio - faecal Ca/P ratio. In previous studies, hindgut fermenters had significantly higher Δ values than ruminants (sheep, cattle, goats), which was explained by the high calcium digestibilities in hindgut fermenters in contrast to highly efficient phosphorus recycling in ruminants. The first hypothesis of the present study was that different types of ruminants (grazer, browser, intermediate feeder) would show differences in Δ as a proxy for quantitative calcium and phosphorus metabolism. The second hypothesis was that camelids as functional, but not taxonomic ruminants would show Δ values similar to ruminants. We used herbivorous zoo animals (17 species, hindgut and foregut fermenters), which were kept on their regular diet without variation for 1 week. Then, faecal samples were obtained from the individual animals. Feed items and faecal samples were analysed for calcium and phosphorus, and dietary and faecal Ca/P ratios as well as Δ were calculated. A comparison of the species groups (one-way ANOVA on ranks, p < 0.05) showed that zoo hindgut fermenters had significantly higher Δ values (0.67 ± 0.34) than camelids and zoo ruminants (-1.07 ± 0.35 and -1.87 ± 1.56). There was no significant difference between camelids, grazers (-1.49 ± 1.31), browsers (-1.63 ± 0.88) and intermediate feeders (-2.11 ± 1.76). The ruminant species from this study had markedly lower Δ than domestic ruminants from literature data. Especially intermediate feeders had low Δ, possibly due to more efficient phosphorus recycling than the domestic ruminants.

The Source Matters-Effects of High Phosphate Intake from Eight Different Sources in Dogs.

Elevated serum phosphate concentrations are an established risk factor for cardiovascular disease and mortality in chronic kidney disease in various species. Independent associations of other parameters of phosphorus metabolism, such as phosphorus intake from different sources and serum concentrations of phosphorus, as well as parameters involved in the regulation, such as parathyroid hormone (PTH) or markers of bone turnover, have been studied in less detail. Therefore, the serum kinetics of phosphate, PTH, and the bone resorption marker bone-specific alkaline phosphatase (BAP) were investigated after 18 days of feeding a control diet and diets supplemented with eight different organic and inorganic phosphate sources aiming at 1.8% phosphorus per dry matter and calcium to phosphorus ratio between 1.3 and 1.7 to 1. Eight healthy beagle dogs (f/m, 2-4 years, 12.9 ± 1.4 kg body weight) were available for the trial. Highly significant differences in the serum kinetics of phosphorus, PTH, and BAP with the highest postprandial levels after feeding highly water-soluble sodium and potassium phosphates were found. We conclude that the use of certain inorganic phosphates in pet food is potentially harmful and should be restricted.

Influence of Strain and Diet on Urinary pH in Laboratory Mice.

Acid base homeostasis and urine pH is influenced by the dietary cation anion balance (DCAB) in many species. Here, a negative DCAB acidifies the urine, while higher DCABs alkalize the urine. The dimension of the DCAB effect can be species-specific, because of differences in urine buffer systems. The aim of the present study was to describe the response of laboratory mice to diets with different DCAB. We used 8-week-old wildtype male mice of the C57Bl/6J inbred strain and CD1 outbred stock. Three groups (n = 15 animals/group) were formed and fed standard diet A for adaptation. For the 7-week feeding trial, mice were either kept on diet A (DCAB -7 mmol/kg dry matter (DM) or switched to diet B (246 mmol/kg DM) or C (-257 mmol/kg DM). Urine pH was measured weekly from a pooled sample per cage. There was a significant difference in the basal urine pH on diet A between C57Bl6/J and CD1 mice. The shift in urine pH was also significantly different between the two groups investigated.

Processing Matters in Nutrient-Matched Laboratory Diets for Mice-Microbiome.

The composition of the microbiome is subject to the host's diet. In commercial laboratory mouse diets, different physical forms of the same diets are available, containing-according to their labels-identical ingredients and nutrient compositions. However, variations in nutrient composition and starch gelatinization due to production processes and their impact on digestibility have been described. In this study, a total of 48 C57BL/J6 mice were assigned to two equal groups and were fed diets (produced with different processes-extruded vs. pelleted) for eight weeks in two biological replicates. At the end of the experiment, samples were collected from five different gastrointestinal regions, including the stomach, small intestine, cecum, large intestine, and an extracorporeal region (feces), and the microbiome was analyzed with 16S rRNA gene amplicon sequencing. The replicates in both experiments differed significantly in their relative abundances of Muribaculaceae species. Furthermore, the gastrointestinal content of pellet-fed mice contained larger numbers of Lactobacillus species. These results indicate that starch gelatinization and ingredient composition significantly influence microbial makeup. In conclusion, different feed processing methods may affect fundamental digestive and metabolic processes, impacting animal experiments and biasing microbiome data.

Processing Matters in Nutrient-Matched Laboratory Diets for Mice-Energy and Nutrient Digestibility.

Starch gelatinization is a major determinant of carbohydrate digestibility and varies with diet processing. Laboratory rodent diets are often marketed as identical, but are sold in different forms, regardless of the markedly higher starch gelatinization in extruded than in pelleted diets. Our hypothesis was that this would impact energy and nutrient digestibility in mice fed pellets or extrudate, respectively. Trial 1 showed that feeding C57BL/6 mice a standard maintenance diet in extruded form results in a significantly higher digestibility of organic matter, energy, and carbohydrates than the identical diet in pelleted form. The replication of the experiment, however, revealed a variation between batches of the same pelleted diet regarding starch and total dietary fiber contents. Given the significant differences in diet digestibility and the potential impacts of digestibility on nutrient utilization, the intestinal microbiome, and intermediary metabolism, trials performed with differently processed diets are not comparable. This might partly explain failures to reproduce results, especially in gastrointestinal or microbiome research. Considering this impact on experimental animals, the degree of starch gelatinization should be declared in the diet information for laboratory animal diets. The differences between batches of laboratory animal diets as observed in the pellets are not acceptable.

The effect of crude protein content of the diet on renal energy losses in horses.

Renal energy losses of horses are high in comparison with other species. In the present study, more data were obtained on this parameter to improve predictive equations for renal energy losses. Four adult ponies (247-344 kg body weight [BW]) were fed with eight different diets based on first cut hay, second cut hay, early first cut fresh grass, late cut herbs-grass mix, early cut clover-grass mix, sugar beet pulp, rice bran and straw. Feed intake was measured, and urine and faeces were quantitatively collected for 3 × 12 hr at daytime and afterwards 3 × 12 hr at nighttime. Feed was analysed for crude nutrients, gross energy, amino acids and neutral-detergent-insoluble crude protein (NDICP); faeces were analysed for crude nutrients and gross energy; and urine was analysed for nitrogen (N) and gross energy. Renal energy losses per gram dry matter (DM) intake (y; kJ/g DM) were strictly correlated to protein content in DM (x; g/kg DM): y = 0.325 + 0.00431x; r2  = .81; n = 38; p < .001. The data suggest that the intercept represents energy losses by detoxification products such as hippuric acid and the regression coefficient by protein metabolites such as urea.

Metabolisable energy intake and growth of privately owned growing dogs in comparison with official recommendations on the growth curve and energy supply.

The correct assumption of metabolisable energy (ME) requirement is essential for the nutrition consultation and diet formulation. In young dogs, too high energy supply can accelerate growth and thus lead to developmental orthopaedic diseases. The aim of the present study was to collect the data on ME intake and body weight (BW) development in privately owned growing dogs in order to compare these data with the current recommendations. Our hypothesis was that the actual ME intake of healthy young dogs would be lower than the actual recommendation. The data of 493 privately owned puppies (median age at first consultation 21 weeks, the median expected mature BW 30 kg) on ME intake, actual and expected mature BW were collected and compared with recommendations of the Society of Nutrition Physiology (GfE, Meyer and Zentek and NRC). In 243 dogs, there was a follow-up. The actual BW did not deviate systematically from the calculated expected BW (R2  = .929). The ME intake significantly decreased with age (p < .05) and significantly increased with expected mature BW (p < .05). There was no significant interaction between these two parameters (p > .05). Sex had no effect on the ME intake (p > .05). The ME intake of young dogs with a history of skeletal problems or of food allergy did not differ systematically from healthy dogs of similar age and expected mature BW. The ME intake was considerably below NRC recommendations, especially in younger puppies (>8-17 weeks: 78%, >17-26 weeks: 83% of NRC recommendation). A predictive linear equation for ME intake was developed: ME intake (MJ) = (1.063 - 0.565 × [actual BW/expected mature BW]) × actual BW0.75 .

[A simple indicator for ruling out inadequate phosphorus digestibility in growing pigs]. / Eine einfache Methode zum Ausschluss unzureichender Phosphorverdaulichkeit bei wachsenden Schweinen.

OBJECTIVE: Species differences in calcium and phosphorus metabolism can be expressed via dietary and faecal calcium/phosphorus ratios. The aim of the present meta-analysis was to use faecal Ca/P ratios as an indicator of phosphorus digestibility in growing pigs as a simple diagnostic tool. This tool can be useful in cases of suspected phosphorus deficiency but adequate dietary calcium and phosphorus contents. MATERIAL AND METHODS: Studies (n = 34) with phytase-supplemented (PHYT; n = 110) and non-supplemented control (CON; n = 106) diets were analysed for dietary intake, faecal excretion and apparent digestibility of calcium and phosphorus. A modified Lucas-test was used for both minerals plotting intake against faecal excretion (mg/kg body weight0.75). RESULTS: For calcium, there was no significant difference between PHYT and CON (p = 0.29) while in accordance with literature, the relative faecal phosphorus excretion was significantly lower in PHYT than CON (p < 0.01). Faecal calcium/phosphorus ratios were calculated and grouped according to the animals' body weight and apparent phosphorus digestibility (body weight ≤ 30 kg: apparent phosphorus digestibility ≤ 60 % and > 60 %; body weight > 30 kg: apparent phosphorus digestibility ≤ 40 % and > 40 %). CONCLUSION: Data distribution as displayed in a box plot shows that - given a dietary Ca/P ratio of > 1.2 - faecal Ca/P ratios of > 1.5 in pigs with a body weight of ≤ 30 kg and of > 1.2 in pigs with a body weight of > 30 kg indicate a high apparent digestibility of phosphorus of > 60 % and > 40 %, respectively. CLINICAL RELEVANCE: When faecal samples reveal a Ca/P ratio above the indicated thresholds, a low phosphorus digestibility is unlikely. No conclusion regarding the apparent phosphorus digestibility can be drawn from faecal Ca/P ratios below this threshold.

Remarkable frequency of a history of liver disease in dogs fed homemade diets with buckwheat.

OBJECTIVE: In our nutrition consultation service we observed liver disease in 2 dogs of one owner who was feeding buckwheat. This led to the hypothesis that buckwheat may cause problems. The present retrospective study in a German and a Russian nutrition consultation service was carried out to see whether there is an increased incidence of liver disease in dogs fed buckwheat. MATERIALS AND METHODS: A retrospective study was carried out on the nutrition consultation cases of the Chair of Animal Nutrition and Dietetics, LMU Munich and a Russian nutrition consultant. All cases of dogs with buckwheat in their nutritional history were evaluated and compared with randomly selected dogs that had not been fed buckwheat from the same case set. Two German and 1 Russian buckwheat samples were compared (appearance, nutrient content, starch gelatinization, flavonoids, fagopyrin) as well as cooking methods. RESULTS: In the years 2007-2017, 34 cases of dogs fed buckwheat were identified in Germany and 57 in Russia. Eighty-five control cases in Germany and 48 in Russia were evaluated. In Germany, the incidence of liver disease in dogs fed buckwheat was 32 %, while that of the control group was 3.5 %. However, in Russia there was no significant difference between dogs fed buckwheat and control dogs. The appearance of the German and Russian buckwheat differed, with smaller seeds and more greenish colour in the German specimens while the Russian buckwheat presented larger and more brownish seeds. There was no difference in the analyses of the 3 buckwheat samples in crude nutrient and rutin content. Quercetin, quercitrin and fagopyrin were not detectable in all three samples. The degree of starch gelatinization in the Russian sample was higher than in the German. In Russia it is recommended to remove the reddish scum during boiling whereas this is rarely mentioned in Germany. CONCLUSION AND CLINICAL SIGNIFICANCE: German buckwheat may represent a risk in canine diets. With the difference remaining unclear, it is recommended to refrain from feeding buckwheat to dogs. In dogs fed homemade diets and suffering from liver disease, buckwheat should be considered in the nutrition history.

Factorial calculation of calcium and phosphorus requirements of growing dogs.

Calcium and phosphorus requirements for growing dogs can be calculated by different methods. The current standard feeding recommendations are based on experimental data derived from young giant breed puppies. In order to determine the absolute requirement, an extrapolation via metabolisable energy requirement is recommended. Another approach is to calculate the requirement factorially, taking into account the endogenous losses and the amount of calcium and phosphorus retained due to tissue accretion during growth as well as the expected availability of these nutrients. The working hypothesis was that both methods are valid and lead to comparable results in young puppies of a high mature body weight (BW). Yet, deviations for other age and mature BW groups were expected. Thus, the aim of the present study was to compare the results of both methods using exemplary puppies of different age and mature BW groups. The hypotheses could be verified for calcium. The extrapolated requirements overestimate the factorial requirements by up to 59.7% for puppies <60kg mature BW and/or >6 months of age. In case of phosphorus requirement, the deviations between both methods are overall very high in all stages. Taking into account the potentially harmful effects of calcium and phosphorus excess, the feeding recommendations based on the extrapolation should be reconsidered.

Canine symmetrical lupoid onychomadesis in bearded collies.

BACKGROUND: Symmetrical lupoid onychomadesis (SLO) is a disease not infrequently seen in bearded collie dogs in Germany. OBJECTIVES: The aim of this study was to compare historical and clinical data, as well as the mineral content of the hair and claws of bearded collies with SLO with that of normal control dogs. ANIMALS: Twenty-eight affected bearded collie dogs and 39 control dogs. METHODS AND MATERIALS: Owners completed an extensive questionnaire regarding upbringing, environmental conditions and diets. Claw specimens were obtained by claw trimming or gathering lost claws; hairs were obtained by plucking samples from several areas of the body; samples were converted to ash and evaluated in an atomic absorption spectrophotometer. RESULTS: Clinical signs in affected dogs eventually involved all claws on all paws. In twelve dogs recurrence of onychomadesis was observed. There was no relevant association between gender, housing, diet and health management, physical stress and the development of SLO with exception of the age at which more intense exercise began. The most commonly used treatment combination was fatty acids, pentoxifylline and tetracycline; improvement occurred in 17 animals. Calcium, sodium and phosphorus concentrations were higher in the claws of affected dogs, whereas zinc concentrations were lower. The mineral content of hair samples of the affected dogs was not significantly different than controls. CONCLUSION AND CLINICAL IMPORTANCE: Symmetrical lupoid onychomadesis in bearded collies is clinically similar to what has been described in other breeds with regard to clinical signs and response to treatment. Early strenuous activity may increase the risk for disease occurrence in this breed.

A pilot study on in vitro solubility of phosphorus from mineral sources, feed ingredients and compound feed for pigs, poultry, dogs and cats.

Excess phosphorus (P) as seen in cat foods can have a negative effect on health (Dobenecker, Webel, Reese, & Kienzle, ; Pastoor, Klooster, Mathot, & Beynen, ). P surpluses may affect the environment, and economics in food producing animals, whereas marginal supply may impair performance and health. P can only be absorbed if it is soluble. Solubility of feed P in water and weak acid solution-as a precondition for absorption-was investigated in feed for dogs, cats, pigs and poultry. Different P containing mineral compounds (Ca(H2 PO4 )2 , CaHPO4 •2H2 O, Ca4 Na(PO4 )3 , KH2 PO4 , K4 P2 O7 , NaH2 PO4 , Na5 P3 O10 (29 samples), as well as eight different ingredients such as wheat or meat, 64 compound feeds for pig and poultry, eight complete dry and 13 complete moist dog foods, 25 complete moist cat foods and 29 experimental diets were analysed for P solubility. Finely ground feeds were soaked in water or hydrochloric acid (0.4%) for 1 and 90 min. The samples were centrifuged and the supernatant was analysed for P (photometric vanadate molybdate method after wet ashing). The solubility of P from inorganic sources reflected the solubility of the main compound of the feed grade material. "organic" ingredients, such as fish meal or meat, showed a lower P solubility than inorganic sources. Most ingredients from animal origin (exception fish meal) had a higher P solubility than those from plant origin. When inorganic and "organic" P sources were mixed, the P solubility of the mixture reflected the P solubility and percentages of its compounds. In chicken, turkey and pig compound feed the percentage of acid soluble P increased with increasing P content. Pet moist food showed high percentages of water-soluble P. The results show that the method is suitable to obtain data on water and acid solubility of P in feed and ingredients.

Renal phosphorus excretion in adult healthy cats after the intake of high phosphorus diets with either calcium monophosphate or sodium monophosphate.

Renal and faecal phosphorus excretion of adult healthy European shorthaired cats after the intake of high phosphorus diets (meat/rice based) with either calcium monophosphate (HP-CaP) or sodium monophosphate (HP-NaP) as main phosphorus source was compared. The control diets (CON-CaP and CON-NaP, respectively) did not contain any added phosphorus. Calcium/phosphorus ratio was adjusted to 1.3/1 by adding calcium carbonate. Twenty-three cats were available for the trials. All cats were fed the control diets for 29 days; then, the HP diets were tested for 29 days against controls in a crossover design. Faeces and urine were collected in the last 10 days of each trial. Phosphorus in food, faeces and urine was measured by photometry after wet digestion. Phosphorus intake amounted to 84 ± 10 mg/kg body weight (BW) in CON-NaP (n = 13) and to 74 ± 7 in CON-CaP (n = 12). In the HP groups, the intake was 255 ± 34 mg/kg BW (HP-NaP; n = 13) and 216 ± 20 mg/kg BW (HP-CaP; n = 12). The sodium monophosphate in group HP-NaP led to a higher renal phosphorus excretion (83 ± 15 mg/kg BW) than the calcium monophosphate (25 ± 5 mg/kg BW; p < 0.05), even though the apparent phosphorus digestibility was higher in HP-CaP than in HP-NaP (p < 0.05). Faecal calcium excretion was strictly correlated to faecal phosphorus excretion (r2  = 0.98). The same was true for calcium and phosphorus balance (r2  = 0.89). In group HP-NaP, seven of 13 cats showed glucosuria. By contrast, in HP-CaP glucosuria was not observed. Highly water-soluble inorganic phosphorus sources such as sodium phosphate are likely to lead to phosphaturia and may present a risk for renal health of cats.