Weight loss outcomes are generally worse for dogs and cats with class II obesity, defined as > 40% overweight.

In pet dogs and cats, adiposity is most-often estimated clinically using a 9-category body condition score (BCS), with BCS 9 equating to ~ 40% overweight. Animals that are more overweight (> 40%) are seen in clinical practice but are not appropriately depicted by descriptions in the existing categories. To determine whether being > 40% overweight has clinical relevance, this study aimed to compare the outcomes of weight management in animals that were > 40% overweight with those < 40% overweight. Records of dogs and cats attending a specialist obesity care clinic, where adiposity is determined using dual-energy X-ray absorptiometry (DXA), were reviewed. Animals were assigned to two classes (class I ≤ 40% overweight: 118/398 [40%] dogs and 68/116 [59%] cats; class II, > 40% overweight: 180/398 [60%] dogs and 48/116 [41%] cats) based on DXA results, and weight loss outcomes were compared. Fewer class II dogs obesity completed weight management than class I dogs (P < 0.001), rate of weight loss was also slower (P = 0.012) and lean tissue loss greater (P < 0.001). Compared with class I, cats with class II obesity lost more weight (P = 0.048) albeit over a longer period (P = 0.043) leading to greater lean tissue loss (P = 0.004). Approximately half the pets presenting to a specialist clinic were have class II obesity (> 40% overweight), and some weight loss outcomes are worse for these animals.

The effect of obesity and subsequent weight reduction on cardiac structure and function in dogs.

BACKGROUND: In people, the cardiovascular effects of obesity include systemic hypertension, cardiac remodelling and both systolic and diastolic dysfunction, whilst weight reduction can reverse myocardial remodelling and reduce risk of subsequent cardiovascular disease. To date, variable results are reported in studies of the effect of obesity and controlled weight reduction on cardiovascular morphology and function in dogs. This prospective study aimed to assess cardiac function, heart rate variability, cardiac biomarkers and body composition before and after weight reduction in pet dogs with obesity. Twenty-four client-owned dogs referred for weight management due to obesity were recruited. To assess the cardiac effects of obesity, body composition analysis (by dual energy X-ray absorptiometry, DEXA) and cardiovascular assessment (echocardiography, Doppler blood pressure, electrocardiography, cardiac biomarkers) were performed prior to weight management. Twelve dogs completed the study and reached target weight, receiving a further cardiovascular assessment and DEXA. A Wilcoxon-signed rank test was used to compare each variable pre- and post- weight reduction. RESULTS: Median (interquartile range) duration of weight loss was 224 days (124-245 days), percentage weight loss was 23% (18-31%) of starting weight. Median change in body fat mass was -50% (-44% to -55%; P = 0.004), whilst median change in lean mass was -7% (+ 1% to -18%, P = 0.083). Before weight reduction, diastolic dysfunction (evidence of impaired relaxation in all dogs), increased left ventricular wall thickness and mildly elevated systolic blood pressure (14/24 ≥ 160 mmHg, median 165 mmHg (140-183)) were common features in dogs with obesity. However, systolic left ventricular wall dimensions were the only variables that changed after weight reduction, with a decrease in both the systolic interventricular septum (P = 0.029) and systolic left ventricular free wall (P = 0.017). There was no evidence of decreased heart rate variability in dogs with obesity (P = 0.367), and no change in cardiac biomarker concentrations with weight reduction (N-terminal proBNP, P = 0.262; cardiac troponin I P = 0.657). CONCLUSIONS: Canine obesity results in diastolic dysfunction and left ventricular hypertrophy, the latter of which improves with significant weight and fat mass reduction. Further studies are required to clarify the clinical consequences of these findings.

Maintenance energy requirements in cats following controlled weight loss: An observational study.

There is a paucity of information regarding the phenomenon of weight regain after successful weight reduction in cats. This study aimed to estimate post-weight reduction maintenance energy requirements (MER) required to maintain stable weight in a group of pet cats. Nineteen cats that had successfully completed a controlled weight reduction programme were enrolled. For inclusion, at least 2 months of follow-up had to be available for review, and the maximum change in weight during maintenance was ±2%. Post-weight-reduction MER was estimated by determining dietary energy consumption from owner diary records. The Friedman test was used to compare bodyweight and energy intake at different stages of weight management. Simple and multiple linear regression were used to identify factors associated with post-weight-reduction MER. The median (interquartile range) duration of weight maintenance was 179 days (119-408 days) and, during this time, MER was 273 ± 56.7 kJ per kg0.67 ideal bodyweight (IBW) per day. Post-weight-reduction MER was greater than metabolisable energy intake at the end (233 ± 29.5 kJ IBW per kg0.67 per day; P < 0.001) but not the start (255 ± 38.6 kJ per kg0.67 IBW per day; P = 0.148) of the weight reduction period. Using simple and multiple linear regression, the only variable that was associated with post-weight reduction MER was the mean ME intake during weight reduction (r2 = 0.349, P = 0.008). Post-weight-reduction MER at the lower limits of MER recommendations for pet cats might predispose to weight regain during the weight maintenance phase.

Digestive sensitivity varies according to size of dogs: a review.

Field observations on food tolerance have repeatedly shown that when fed an identical diet, large breed (>25 kg) dogs present softer and moister faeces than small breed ones (<15 kg). The purpose of this review is to highlight the findings of four PhD theses, carried out between 1998 and 2013, whose objectives were to investigate the anatomical and physiological peculiarities that would explain, at least in part, this observation, as well as their nutritional implication. This work showed that large breed dogs, in contrast with smaller breeds, present a highly developed caecum and colon, which could explain the relatively longer colonic transit time. A prolonged colonic transit time could explain higher colonic fermentative activity, as supported by higher faecal concentrations of fermentative by-products. This effect would be reinforced by increased intestinal permeability and reduced sodium net-absorption. Taken together, these elements could be a possible cause of higher digestive sensitivity in large breed dogs. When prescribing a diet to a small or large breed dog, several aspects of the formulation must be taken into account. For a large breed dog, the general goal is to limit any ingredient that could increase the level of fermentable undigested residues and, in fine, exacerbate colonic fermentation. Highly digestible sources of proteins and starches are therefore strongly recommended to maintain an optimal digestive tolerance. Fermentable fibre sources (i.e. beet pulp and FOS) must also be used in limited quantity in their diet. Conversely, the incorporation of non-fermentable fibre (i.e. cellulose) appears useful to increase their stool quality. For a small breed dog, the general objective is to minimize any ingredient that could excessively limit colonic fermentation and induce in fine constipation. Purified starches and cellulose are therefore not really suitable for them. In contrast, cereals flours as well as non-fermentable fibre provided by cereals are recommended.

The Effect of Moderate Dietary Protein and Phosphate Restriction on Calcium-Phosphate Homeostasis in Healthy Older Cats.

BACKGROUND: Dietary phosphate and protein restriction decreases plasma PTH and FGF-23 concentrations and improves survival time in azotemic cats, but has not been examined in cats that are not azotemic. HYPOTHESIS: Feeding a moderately protein- and phosphate-restricted diet decreases PTH and FGF-23 in healthy older cats and thereby slows progression to azotemic CKD. ANIMALS: A total of 54 healthy, client-owned cats (≥ 9 years). METHODS: Prospective double-blinded randomized placebo-controlled trial. Cats were assigned to test diet (protein 76 g/Mcal and phosphate 1.6 g/Mcal) or control diet (protein 86 g/Mcal and phosphate 2.6 g/Mcal) and monitored for 18 months. Changes in variables over time and effect of diet were assessed by linear mixed models. RESULTS: A total of 26 cats ate test diet and 28 cats ate control diet. There was a significant effect of diet on urinary fractional excretion of phosphate (P = 0.045), plasma PTH (P = 0.005), and ionized calcium concentrations (P = 0.018), but not plasma phosphate, FGF-23, or creatinine concentrations. Plasma PTH concentrations did not significantly change in cats fed the test diet (P = 0.62) but increased over time in cats fed the control diet (P = 0.001). There was no significant treatment effect of the test diet on development of azotemic CKD (3 of 26 (12%) test versus 3 of 28 (11%) control, odds ratio 1.09 (95% CI 0.13-8.94), P = 0.92). CONCLUSIONS AND CLINICAL IMPORTANCE: Feeding a moderately protein- and phosphate-restricted diet has effects on calcium-phosphate homeostasis in healthy older cats and is well tolerated. This might have an impact on renal function and could be useful in early chronic kidney disease.

Cohort Study of the Success of Controlled Weight Loss Programs for Obese Dogs.

BACKGROUND: Most weight loss studies in obese dogs assess rate and percentage of weight loss in the first 2-3 months, rather than the likelihood of successfully reaching target weight. OBJECTIVE: To determine outcome of controlled weight loss programs for obese dogs, and to determine the factors associated with successful completion. ANIMALS: 143 obese dogs undergoing a controlled weight loss program. METHODS: This was a cohort study of obese dogs attending a referral weight management clinic. Dogs were studied during their period of weight loss, and cases classified according to outcome as "completed" (reached target weight), "euthanized" (was euthanized before reaching target weight), or "stopped prematurely" (program stopped early for other reasons). Factors associated with successful completion were assessed using simple and multiple logistic regression. RESULTS: 87/143 dogs (61%) completed their weight loss program, 11 [8%] died or were euthanized, and the remaining 45 [32%] stopped prematurely. Reasons for dogs stopping prematurely included inability to contact owner, refusal to comply with weight management advice, or development of another illness. Successful weight loss was positively associated with a faster rate (P < .001), a longer duration (P < .001), and feeding a dried weight management diet (P = .010), but negatively associated with starting body fat (P < .001), and use of dirlotapide (P = .0046). CONCLUSIONS AND CLINICAL RELEVANCE: Just over half of all obese dogs on a controlled weight loss program reach their target weight. Future studies should better clarify reasons for success in individual cases, and also the role of factors such as activity and behavioral modification.

Dietary management of labrador retrievers with subclinical hepatic copper accumulation.

BACKGROUND: Genetic and environmental factors, including dietary copper intake, contribute to the pathogenesis of copper-associated hepatitis in Labrador retrievers. Clinical disease is preceded by a subclinical phase in which copper accumulates in the liver. OBJECTIVE: To investigate the effect of a low-copper, high-zinc diet on hepatic copper concentration in Labrador retrievers with increased hepatic copper concentrations. ANIMALS: Twenty-eight clinically healthy, client-owned Labrador retrievers with a mean hepatic copper concentration of 919 ± 477 mg/kg dry weight liver (dwl) that were related to dogs previously diagnosed with clinical copper-associated hepatitis. METHODS: Clinical trial in which dogs were fed a diet containing 1.3 ± 0.3 mg copper/Mcal and 64.3 ± 5.9 mg zinc/Mcal. Hepatic copper concentrations were determined in liver biopsy samples approximately every 6 months. Logistic regression was performed to investigate effects of sex, age, initial hepatic copper concentration and pedigree on the ability to normalize hepatic copper concentrations. RESULTS: In responders (15/28 dogs), hepatic copper concentrations decreased from a mean of 710 ± 216 mg/kg dwl copper to 343 ± 70 mg/kg dwl hepatic copper after a median of 7.1 months (range, 5.5-21.4 months). Dogs from a severely affected pedigree were at increased risk for inability to have their hepatic copper concentrations normalized with dietary treatment. CONCLUSIONS AND CLINICAL IMPORTANCE: Feeding a low-copper, high-zinc diet resulted in a decrease in hepatic copper concentrations in a subset of clinically normal Labrador retrievers with previous hepatic copper accumulation. A positive response to diet may be influenced by genetic background. Determination of clinical benefit requires further study.

Feeding obese dogs during weight loss is on average cost-neutral.

OBJECTIVES: The cost of feeding a purpose-formulated weight loss diet may deter owners of obese dogs from proceeding with a weight loss programme. The current study aimed to compare average food costs during weight loss with those before weight loss. MATERIALS AND METHODS: Average daily food costs, for before and during weight loss, were calculated in 22 obese dogs that had successfully completed weight management. RESULTS: The median food cost before weight loss was £0 · 52/day (£0 · 24-3 · 31/day), for main meal only, and £0 · 64/day (£0 · 26-3 · 31/day) for main meal and additional food (table scraps and treats). The median food cost during weight loss was £0 · 90/day (£0 · 26-1 · 36/day), and no additional food was given. The average daily feeding costs during weight loss did not differ from pre-weight-loss costs, either with (P = 0 · 425) or without (P = 0 · 222) the additional food included. CLINICAL SIGNIFICANCE: Knowledge that average diet costs do not significantly differ from food costs prior to weight loss may help veterinarians to persuade owners to enrol obese dogs in a weight management programme.

Plasma exogenous creatinine clearance in clinically healthy cats: comparison with urinary exogenous creatinine clearance, tentative reference intervals and indexation to bodyweight.

Glomerular filtration rate (GFR) is considered to be the best indicator of overall kidney function. The major objectives of this study were to compare plasma exogenous creatinine clearance (PECC) with a reference method, to establish reference intervals (RIs) for PECC and to assess the effects of indexation of GFR to bodyweight (BW) in cats. PECC was compared with urinary clearance of exogenous creatinine (UECC) in six clinically healthy domestic shorthair cats (experiment 1). Tentative RIs were determined according to current guidelines and the effects of indexation to BW and of covariables on GFR were assessed in 43 clinically healthy cats of various breeds (experiment 2). PECC was 15% higher than UECC (P <0.01), but the two estimates were strongly correlated (r(2)=0.97, P = 0.001). RIs for PECC were 6.4-21.3 mL/min or 1.2-4.9 mL/min/kg. The absolute (i.e. non-indexed) GFR value was not dependent on BW. Thus, indexation of GFR to BW in cats would not standardize the GFR value, but could introduce bias in clinical interpretation. Significant effects of breed, plasma protein concentration and plasma albumin concentration on GFR were demonstrated. Plasma concentrations of urea and creatinine, when assessed separately, were also weakly correlated with GFR in healthy cats. These combined findings contribute to a better understanding of renal function assessment in cats.

The effect of dietary hydroxyproline and dietary oxalate on urinary oxalate excretion in cats.

In humans and rodents, dietary hydroxyproline (hyp) and oxalate intake affect urinary oxalate (Uox) excretion. Whether Uox excretion occurs in cats was tested by feeding diets containing low oxalate (13 mg/100 g DM) with high (Hhyp-Lox), moderate (Mhyp-Lox), and low hyp (Lhyp-Lox) concentrations (3.8, 2.0, and 0.2 g/100 g DM, respectively) and low hyp with high oxalate (93 mg/100 g DM; Lhyp-Hox) to 8 adult female cats in a 48-d study using a Latin square design. Cats were randomly allocated to one of the four 12-d treatment periods and fed according to individual energy needs. Feces and urine were collected quantitatively using modified litter boxes during the final 5 d of each period. Feces were analyzed for oxalate and Ca, and urine was analyzed for specific density, pH, oxalate, Ca, P, Mg, Na, K, ammonia, citrate, urate, sulfate, and creatinine. Increasing hyp intake (0.2, 2.0, and 3.8 g/100 g DM) resulted in increased Uox excretion (Lhyp-Lox vs. Mhyp-Lox vs. Hhyp-Lox; P < 0.05), and the linear dose-response equation was Uox (mg/d) = 5.62 + 2.10 × g hyp intake/d (r(2) = 0.56; P < 0.001). Increasing oxalate intake from 13 to 93 mg/100 g DM did not affect Uox excretion but resulted in an increase in fecal oxalate output (P < 0.001) and positive oxalate balance (32.20 ± 2.06 mg/d). The results indicate that the intestinal absorption of the supplemental oxalate, and thereby its contribution to Uox, was low (5.90% ± 5.24%). Relevant increases in endogenous Uox excretion were achieved by increasing dietary hyp intake. The hyp-containing protein sources should be minimized in Ca oxalate urolith preventative diets until their effect on Uox excretion is tested. The oxalate content (up to 93 mg/100 g DM) in a diet with moderate Ca content does not contribute to Uox content.