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

Apparent digestibility and calcium and phosphorus in urine after feeding different combinations of calcium and phosphorus sources to adult dogs

The present study aimed to investigate the effect of the combination of a water-soluble calcium (Ca) source (CaCl2) with a water-soluble phosphorus (P) source (NaH2PO4*2H2O, diet soluble, SOL) in comparison to a water-insoluble P source (CaHPO4*2H2O, diet insoluble, INS) on apparent digestibility and renal excretion of Ca and P in dogs. The Ca intake was 226 mg/kg bodyweight (bw), the Ca/P ratio 1.9/1 in SOL and 2.0/1 in INS. The percentage of Ca from CaCl2 was 60% in SOL and 33% in INS. Eight adult Foxhound-crossbred dogs FBI, (3-5 years, bw 24-32 kg) were available. Standard digestion trials were carried out (10 days adaptation, 5 days total faecal collection). Spontaneously excreted urine was collected pre- and postprandially. In vitro water solubility of P in the mineral premixes was determined. The Ca digestibility was negative in both trials without significant differences between the groups. Apparent P digestibility was increased in group SOL (26% vs. 20% in INS). In both groups, P content in urine was higher pre- compared to postprandial, with higher concentrations in group SOL. The same was true for the P/Crea ratio. The water solubility of P in the mineral premixes used in the trials showed considerable differences: The P in premix INS was insoluble in water after 1 and after 90 min. By contrast, the P in the premix SOL was highly soluble (98%) after 1 minute. After 90 min, however, the P solubility decreased to 43%, suggesting the formation of insoluble CaP salts, presumably from CaCl2 and NaH2PO4*2H2O. In conclusion, in the present study, apparent Ca digestibility in dogs was not affected by the solubility of Ca and P, while P digestibility and renal P excretion increased.

Starch to protein ratio and food moisture content influence water balance and urine supersaturation in cats

Two starch to protein ratios (high starch [HS], 25% starch and 36% protein; high protein [HP], 15% starch and 53% protein on DM basis) and two moisture contents (5%, dry kibbles; 80%, wet food) were compared in a 2 x 2 factorial arrangement totaling 4 diets. Each diet was evaluated in 9 cats, with 8 d of total collection of urine and feces. Results were subjected to an analysis of variance of the effects of starch to protein ratio, moisture content and their interactions (P<0.05). Urine density was lower and volume was higher in cats fed wet foods (P<0.01). Calcium (Ca) urine concentration was higher for dry and HP diets (P<0.05). The oxalate urine concentration was 60% higher for cats fed both HS formulations (dry and wet; P<0.05). The relative supersaturation (RSS) of urine for calcium oxalate was higher for dry foods and HS formulations (P<0.01), and for struvite, it was lower for both wet foods, and among the dry diets, it was lower for the HS than for the HP formulation (P<0.01). Foods with a high protein-to-starch ratio reduced urine oxalate and RSS for calcium oxalate in wet and dry diets, and wet foods reduced RSS for calcium oxalate and struvite.

A Meta-Analysis on Quantitative Calcium, Phosphorus and Magnesium Metabolism in Horses and Ponies

The aims of the present meta-analysis were (i) to re-evaluate the factorially calculated Ca, P and Mg requirements to replace endogenous faecal losses, taking new data into account, (ii) to identify potential differences between horses and ponies regarding requirements, apparent digestibility, serum levels and renal excretion of Ca, P and Mg and (iii) to investigate the influence of mineral sources, i.e., "inorganic" sources from added mineral salts and "organic" sources from feed plants. For P, the water solubility of "inorganic" sources was taken into consideration. Data on the aforementioned parameters from 42 studies were plotted against intake, similar to the Lucas test for true digestibility and faecal endogenous losses. Within specific intake ranges, data were compared using t-tests and an ANOVA, followed by Holm-Sidak post hoc tests. Ponies had lower endogenous faecal Mg losses than horses. Consequently, apparent Mg digestibility was higher in ponies. Factorial calculations of Mg requirements to replace faecal losses showed that ponies needed approximately half of the current recommended amount, while horses required 1.9 times the amount currently recommended by Kienzle and Burger. The overall mean matched previous recommendations. For Ca, there was no discernible difference between ponies and horses. True Ca digestibility calculated by the Lucas test was higher and endogenous losses were lower when "organic" Ca was fed as opposed to when "inorganic" sources were used. The resulting factorial calculations of the requirements to replace faecal losses were close to current recommendations for "organic" Ca. For "inorganic" sources, however, the new calculations were below the recommended level. For P, there were no discernible differences between horses and ponies. There were also no clear effects of "inorganic" or "organic" P sources. The water solubility of "inorganic" sources was the key factor determining P metabolism. Water-soluble P sources exhibited higher true and apparent digestibility. The intake of these P sources led to hyperphosphatemia and hyperphosphaturia, even at low intakes. In other species, this has been shown to pose a health risk. Therefore, it is recommended to avoid the use of highly water-soluble "inorganic" P sources in horses and ponies. Given the lower digestibility of insoluble P sources, the factorially calculated P requirements for such sources are higher than the current recommendations.

Phosphocalcic metabolism and its potential association with biomarkers of kidney disease in dogs with spontaneous hyperadrenocorticism

The pathogenesis of increased serum phosphate concentration and proteinuria in dogs with spontaneous hyperadrenocorticism (HAC) is unclear. A potential link between proteinuria and calcium/phosphate metabolism has never been studied in dogs with HAC. The aims of the study were: (1) To evaluate calcium/phosphate metabolism in dogs with spontaneous HAC and compare to healthy dogs as well as to dogs with non-HAC illness; (2) to look for associations between markers of calcium/phosphate metabolism and biomarkers of kidney disease in dogs with HAC. Fifty-four dogs were included in the study, classified as HAC (n=27), non-HAC disease (n=17), and healthy (n=10). Serum calcium, phosphate, 25(OH)Vitamin D, 1,25(OH)2Vitamin D, plasma intact parathyroid hormone concentration (iPTH), FGF23, and urinary fractional excretion of calcium and phosphate were evaluated in all dogs at diagnosis and compared between each group. The correlation between these variables and urine protein-to-creatinine ratio (UPC) and urinary N-acetylglucosaminidase-to-creatinine ratio (uNAG/C) was evaluated in the HAC group. Medians [range] of serum phosphate concentration, urinary fractional excretion of calcium (FE(Ca)), and iPTH were significantly higher in dogs with HAC than in dogs with non-HAC illness (P<0.01) and healthy dogs (P<0.01). Increased 1,25(OH)2Vitamin D/25(OH)Vitamin D was also observed (P<0.001). In HAC group, UPC was significantly negatively correlated with 25(OH)Vitamin D (r(s): -0.54; P<0.01). Urinary NAG/C was significantly positively correlated with serum phosphate (r(s): 0.46; P=0.019). Increased serum phosphate, urinary excretion of calcium, and hyperparathyroidism were observed in dogs with HAC. Vitamin D metabolism may be shifted towards increased 1-alpha hydroxylation.

In vitro digestibility and solubility of phosphorus of three plant-based meat analogues

Interest in plant-based meat analogues has increased and can be expected to be applied to pet foods, which necessitates the understanding of the nutrient supply in those foods. Our primary aim was to advance our understanding of the digestive properties of sterilized plant-based meat analogues. The impact of the preparatory processing steps on the solubility of meat analogues was studied. Meat analogues were made by mixing water, salt, and wheat gluten with soy protein isolate, pea protein isolate, or faba bean concentrate. Mixed materials were processed into model meat analogues using shear cell technology. Products were canned in water or gravy and sterilized. An animal-based canned pet food was made as a reference. Products sampled at the processing steps (mixing, shearing, sterilization) were digested in vitro. Samples of digestate were taken at the gastric phase (0 and 120 min) and small intestinal phase (120, 200, 280, and 360 min) for analysis of protein hydrolysis. The extent digestion of nitrogen and dry matter was determined at the end of incubation. Total phosphorus, soluble phosphorus after acid treatment, and after acid and enzymatic treatment were determined. The degree of hydrolysis after gastric digestion was low but increased immediately in the small intestinal phase; products based on pea had the highest values (56%). Nitrogen digestibility was above 90% for all materials at each processing step, indicating that bioactive compounds were absent or inactivated in the protein isolates and concentrate. Phytate seemed to play a minor role in meat analogues, but phosphorus solubility was influenced by processing. Shearing decreased soluble phosphorus, but this effect was partly reversed by sterilization. Nutrient digestibility as well as phosphorus solubility in plant-based products was higher than or comparable with the reference pet food. These findings show that the digestive properties of the tested plant-based meat analogues do not limit the supply of amino acids and phosphorus.

Mineral and heavy metal content in dry dog foods with different main animal components

Dog caregivers, mainly for economic reasons and easy availability, choose dry, over the counter diets (OTC). The mineral composition of OTC foods depends primarily on the components used in the production of the pet food. Regardless of the main component of the food, it must meet the recommended minimum mineral content, established by nutritional guidelines. Therefore, the aim of this study was to determine the mineral (Ca, K, Mg, Na, Fe, Mn, Zn, Cu, Mo) and heavy metal content (Pb, Co, Cd, Cr, Ni) using the methods of colorimetry and mass spectrometry, of OTC dry dog foods and to compare with the FEDIAF and AAFCO nutritional guidelines. Dry foods pose no risk to dogs in terms of heavy metal content. The worst results in terms of mineral content were obtained in mixed foods, therefore it is worth considering feeding the dog a mono-protein food. The PCA analysis disproved our hypothesis and revealed that the main animal source did not statistically significantly affect the levels of minerals and their ratios. However, the analysis of contrasts confirms the differentiation of the content of individual minerals between the groups of foods. For the first time, we proved that pet food with a mineral composition similar to the MIN-RL may be characterized by unfavorable mineral ratios.

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.