Phosphorus is present in diets as naturally occurring P from raw materials or added as an inorganic salt. However, little is known about postprandial kinetics of P absorption in cats. Here, we describe several studies quantifying postprandial kinetics following the ingestion of diets of varying composition. Briefly, cats were fed a meal consisting of 50 % of their metabolic energy requirement in a randomised crossover design. A pre-meal baseline blood sample was taken via cephalic catheter and repeated measurements taken regularly up to 6 h post-meal to assess the whole blood ionised Ca, plasma P and parathyroid hormone concentrations. A diet containing 4·8 g total P/4184 kJ (1000 kcal), 3·5 g P from sodium dihydrogen phosphate (NaH2PO4)/4184 kJ (1000 kcal) and Ca:P 0·6 caused a marked increase in plasma P from baseline to a peak of 1·976 (95% CI 1·724, 2·266) mmol/l (P <0·001), whereas a diet containing 3·38 g total P/4184 kJ (1000 kcal), no added inorganic P and Ca:P 1·55 resulted in a postprandial decrease in plasma P (P = 0·008). Subsequent data indicate that added inorganic P salts in the diet above 0·5 g P/4184 kJ (1000 kcal) cause an increase in plasma P in cats, while diets below this do not. The data presented here demonstrate that sources of added inorganic P salts cause a temporary postprandial increase in plasma P in a dose-dependent manner, prolonged in diets with Ca:P <1·0. Dietary P derived from natural food ingredients (e.g. meat or vegetable matter) does not appear to have any effect on postprandial plasma P.

To understand the effects of neutering on food intake, body weight (BW) and body composition in kittens, data from an unrelated study were subjected to post hoc analysis. A total of twelve pairs of 11-week-old female littermates were randomly assigned to either a neutered group (neutered at 19 weeks old) or an entire group (kept entire) and offered free access to a dry diet until the age of 1 year. Neutered kittens exhibited increased food intake and increased BW after neutering (both P, 0·00 001). Food intake (per kg BW) peaked 10 weeks after neutering; the mean intake of neutered kittens was 17 (95 % CI 8, 27) % more than entire littermates (P¼ 0·00 014). The intake was then reduced until there was no significant difference between the groups 18 weeks post-neutering. By 52 weeks of age, the neutered kittens were 24 (95 % CI 11, 39) % heavier than entire littermates (P, 0·0001) with a body condition score (BCS) 16·6 (95 % CI 0·9, 34·8) % higher (P¼0·0028). Neutered kittens continued to grow significantly fatter after neutering (all P, 0·0014), while entire kittens showed no significant change after 18 weeks of age. As neutered kittens consumed similar amounts of energy to their entire littermates from 18 weeks post-neutering, while their BW, BCS and percentage fat continued to increase, we suggest that neutered kittens have a reduced metabolisable energy requirement, and should therefore be fed to maintain an ideal BCS rather than ad libitum. Moreover, to maintain an ideal BCS, entire kittens consumed 93 (95 % CI 87, 100) % of their theoretical intake at 26 weeks of age, and 79 (95 % CI 72, 87) % at 52 weeks of age, suggesting that the current energy recommendation is inappropriate for these kittens.Key words: Cats: Kittens: Neutering: Food intake: Energy requirements: Body composition Throughout the developed world, cat obesity rates are rising, with approximately 30 -40 % of cats in the USA being obese or overweight (1) . Although obesity can occur in both neutered and intact cats, data suggest that neutered cats are more likely to become obese than sexually intact cats (1) . Neutering rates for both pet male and female cats are high in the developed world and many cats are neutered before 1 year of age (2,3) . Furthermore, in an effort to control the stray and pet cat populations, early neutering is recommended as the most appropriate surgical choice (4) . Long-term studies (5) have not identified early neutering (before puberty) as a risk factor for increased obesity v. traditional age neutering (7 months of age) and neutering studies carried out in pre-pubertal v. sexually mature kittens have not identified any differences in body weight (BW) and body condition score (BCS) in adulthood (6,7) , and the effects on individual feeding behaviour have also not been measured.The food intake in ad libitum-fed cats increases after neutering, and it has been shown that intake needs to be reduced by 20 -30 % to prevent BW gain (8,9) , and one study has suggested that neutered female cats have a peak in food i...

27Phosphorus (P) is present in diets either as naturally occurring P from raw materials or added 28 as an inorganic salt, however little is known about postprandial kinetics of P absorption in cats. 29Here we describe several studies quantifying postprandial kinetics following the ingestion of 30 diets of varying composition. Briefly, cats were fed a meal consisting of 50% of their metabolic 31 energy requirement in a randomized crossover design. A pre-meal baseline blood sample was 32 taken via cephalic catheter and repeated measurements taken regularly up to 6h post meal to 33 assess whole blood ionized calcium, plasma P and parathyroid hormone (PTH) concentrations. 34A diet containing total P 4.8g/1000kcal, sodium dihydrogen phosphate (SDHP, NaH2PO4) 35 3.5g/1000kcal, Ca:P 0.54 caused a marked increase in plasma P from baseline to a peak of 36 1.976 mmol/L with 95% confidence interval (1.724, 2.266), p<0.001, whereas a diet containing 37 total P 3.38g/1000kcal, no added inorganic P, Ca:P 1.55 resulted in a postprandial decrease in 38 plasma P (p=0.008). Subsequent data indicate that added inorganic P in the diet (above 39 0.5g/1000kcal) causes an increase in plasma P in cats while diets with low added inorganic P

Methionine, an essential sulphur-containing amino acid (SAA), plays an integral role in many metabolic processes. Evidence for the methionine requirements of adult dogs is limited, and we employed the indicator amino acid oxidation (IAAO) method to estimate dietary methionine requirements in Labrador retrievers (n 21). Using semi-purified diets, the mean requirement was 0·55 (95 % CI 0·41, 0·71) g/4184 kJ. In a subsequent parallel design study, three groups of adult Labrador retrievers (n 52) were fed semi-purified diets with 0·55 g/4184 kJ (test diet 1), 0·71 g/4184 kJ (test diet 2) or 1·37 g/4184 kJ (control diet) of methionine for 32 weeks to assess the long-term consequences of feeding. The total SAA content (2·68 g/4184 kJ) was maintained through dietary supplementation of cystine. Plasma methionine did not decrease in test group and increased significantly on test diet 1 in weeks 8 and 16 compared with control. Reducing dietary methionine did not have a significant effect on whole blood, plasma or urinary taurine or plasma N-terminal pro B-type natriuretic peptide. Significant effects in both test diets were observed for cholesterol, betaine and dimethylglycine. In conclusion, feeding methionine at the IAAO-estimated mean was sufficient to maintain plasma methionine over 32 weeks when total SAA was maintained. However, choline oxidation may have increased to support plasma methionine and have additional consequences for lipid metabolism. While the IAAO can be employed to assess essential amino acid requirements, such as methionine in the dog using semi-purified diets, further work is required to establish safe levels for commercial diet formats.

Dogs suffer from skin associated issues with a disproportionate frequency, with consequent interest in providing nutrition to optimize their skin's natural defences. Linoleic acid (LA) is known as an essential nutrient in dogs and plays a critical part in the lipid component of skin barrier formation. Minimum requirements have been defined, primarily based on eliminating signs of deficiencies such as dry, flaky skin and inflammation. Zn has been shown as an important nutrient for maintaining epidermal health. This pilot study investigated whether there are skin barrier benefits from feeding both linoleic acid and Zn at levels significantly in excess of published minimum requirements. Eight Labrador retrievers were fed a diet containing 3.8 g/Mcal LA, 21 mg/Mcal Zn for 12 weeks to establish baseline conditions for all dogs (basal diet). After this period, for a further 12 weeks, the dogs were switched onto a diet containing 7.9 g/Mcal LA and 50 mg/Mcal Zn (test diet). Transepidermal water loss (TEWL measurements) were used as a measure of skin quality and integrity and were taken at the end of the initial feeding period, and at 6 and 12 weeks of the test feeding period. TEWL was reduced by 8.11 g/m2/h (P < 0.001) six weeks after instigation of the test diet, and by 7.52 g/m2/h (P < 0.005) at 12 weeks, compared to the levels (14.73 g/m2/h) at the end of the basal feeding trial period. The results showed evidence of improved barrier properties as TEWL when feeding higher levels of LA and Zn for six and 12 weeks.