Nutritional care for aging cats and dogs.

Veterinarians need to be prepared to provide nutritional advice for healthy pets as well as for pets that are ill. Before instituting a dietary change in any patient, especially an older dog or cat, a nutritional evaluation should be completed. This should include an evaluation of the patient, the current diet, and feeding management. Diets should be appropriate to the unique needs of the individual patient. Many diseases in senior pets are "diet-sensitive" meaning that diet can play a role in managing the effects of the disease. Common examples discussed include cognitive dysfunction of aging, osteoarthritis, and obesity.

Companion Animals Symposium: Obesity in dogs and cats: What is wrong with being fat?

Few diseases in modern pets are diet induced. One possible exception to this is obesity, which is ultimately caused by consuming more calories than needed by the dog or cat. Although fat is the most concentrated and efficiently stored source of calories, and protein least so, an excess of calories from any source will contribute to adiposity. Obesity is an excess of body fat sufficient to result in impairment of health or body function. In people, this is generally recognized as 20 to 25% above ideal BW. This degree of excess is important in dogs as well. A lifelong study in dogs showed that even moderately overweight dogs were at greater risk for earlier morbidity; these dogs required medication for chronic health problems sooner than their lean-fed siblings. The average difference in BW between groups was approximately 25%. Obese cats also face increased health risks, including an increased risk of arthritis, diabetes mellitus, hepatic lipidosis, and early mortality. The risk for development of diabetes increases about 2-fold in overweight cats and about 4-fold [corrected] in obese cats. Altered adipokine secretion appears to be an important mechanism for the link between excess BW and many diseases. Once considered to be physiologically inert, adipose tissue is an active producer of hormones, such as leptin and resistin, and cytokines, including many inflammatory cytokines such as tumor necrosis factor-α, IL-1ß and IL-6, and C-reactive protein. The persistent, low-grade inflammation secondary to obesity is thought to play a causal role in chronic diseases such as osteoarthritis, cardiovascular disease, diabetes mellitus, and others. For example, tumor necrosis factor-α alters insulin sensitivity by blocking activation of insulin receptors. In addition, obesity is associated with increased oxidative stress, which also may contribute to obesity-related diseases. Management of obesity involves nutritional modification as well as behavioral modification. Increased protein intake combined with reduced calorie intake facilitates loss of body fat while minimizing loss of lean body mass. Limiting treats to 10% of calorie intake and increasing exercise both aid in successful BW management.

Effect of diets differing in fat content on chronic diarrhea in cats.

BACKGROUND: Fat-restricted diets have been advocated for dogs with diarrhea for many years. Recommendations for cats with diarrhea have varied between low-fat and high-fat diets, but there have been no published studies to support either recommendation. OBJECTIVES: The objective of this study was to compare the clinical responses of cats with chronic diarrhea to dietary management using either a high fat or a low fat, highly digestible diet. ANIMALS: Sixty pet cats with chronic diarrhea were recruited; 55 cats completed the study. METHODS: Randomized, double-blinded, controlled clinical trial. Upon completion of baseline measures, cats were fed 1 of 2 diets for 6 weeks, during which the owners recorded fecal scores daily using an illustrated fecal score chart ranging from 0 (very watery) to 100 (firm and dry). After 6 weeks, cats were reevaluated by the attending veterinarians. RESULTS: Fecal scores improved significantly, with 78.2% of cats improving by at least 25 points on the 100-point scale or having a final fecal score of at least 66. Over one third of the cats developed normal stools. There were no differences in clinical responses between the diets. Clinical improvement was noted within the 1st week, and maximized within 3 weeks. CONCLUSIONS AND CLINICAL IMPORTANCE: These results show that dietary management can be helpful in cats with chronic diarrhea, but dietary fat content does not appear to affect the outcome. Cats that do not respond within 3 weeks should be evaluated further.

Pet food safety: dietary protein.

The goal of this article was to review the evidence surrounding the risks posed by insufficient or excessive dietary protein. Dietary protein is required to provide essential amino acids and replenish protein reserves. When intake is deficient, protein turnover slows and lean body mass is gradually depleted. These changes lead to increased morbidity and mortality. Dogs can maintain nitrogen balance (typically used to define minimum requirements in adults), yet be in a protein-depleted state due to physiologic adaptations. Preservation of protein turnover and lean body mass requires about threefold more protein than nitrogen balance. The ability of excess dietary protein to induce renal pathology was studied in both dogs with chronic kidney failure and older dogs without kidney failure. Numerous studies have confirmed that protein does not adversely affect the kidneys. However, phosphorus- and protein-restricted diets are clinically beneficial in dogs with existing chronic kidney failure. Protein restriction for healthy older dogs is not only unnecessary, it can be detrimental. Protein requirements actually increase by about 50% in older dogs, while their energy requirements tend to decrease. When insufficient protein is provided, it can aggravate the age-associated loss of lean body mass and may contribute to earlier mortality. Older dogs should receive at least 25% of their calories from protein, typically provided by diets containing at least 7 g protein/100 Kcal ME.

Effect of diet on markers of intestinal health in dogs.

The effects of two popular commercial pet foods on faecal markers of microbial metabolism were investigated. Adult dogs were fed a dry, extruded diet and a moist, canned diet in a randomly assigned crossover design. Fresh faecal samples were collected for chemical and enzyme activity assays. Relative to the canned diet, the dry food resulted in decreased faecal pH and faecal indole, sulphide and ammonia concentrations and increased total short-chain fatty acid, acetic and propionic acid concentrations. Faecal beta-glucosidase, beta-glucuronidase, beta-galactosidase and nitroreductase activities were decreased in dogs fed the dry diet. These changes in microbial metabolic activity are consistent with beneficial effects of the dry diet on colonic health.

Determining metabolizable energy content in commercial pet foods.

This study was conducted to assess the suitability of several equations for the estimation of metabolizable energy (ME) of pet foods. Sixteen canned and 31 dry cat foods and 24 dry dog foods representing the range of energy densities found in commercial adult, growth or all life stage products were evaluated in four separate experiments. In vivo ME was compared with estimates of ME generated by several previously published equations. The results indicated that the equation recommended by Association of American Feed Control Officials provided reasonable estimates of in vivo ME for both canned cat foods and dry dog foods, but proved unsuitable for dry cat foods. Better estimates were generated in each case using other published equations. Of the equations tested, the most accurate equations for estimating ME (kJ/g) without feeding trials were: for canned cat foods: [(16.32 x protein) + (32.22 x fat) + (12.55 x NFE)]; for dry cat foods: [((GE x 1.209) - 1.911) x 4.184] or [((0.075 x g fat) + 2.766) x 4.184] for dry dog foods: [GE=(24 x g protein) + (38 x g fat) + (17 x g NFE), then percentage energy digestibility=91.2 - (1.43 x percentage crude fibre in dry matter), then ME=(GE x percentage energy digestibility) - (4.34 x g protein)]. With the exception of high-fibre weight-management diets, the simple equation [((GE x 1.209)-1.911) x 4.184] also reliably predicted ME in dry dog foods.

Influence of diet on urinary pH, urine and serum biochemical variables, and blood-ionized calcium concentrations in healthy dogs.

Urolithiasis is a common cause of lower urinary tract disease in dogs. Diet influences urine composition, and dietary change is often incorporated into medical management of uroliths. The purpose of this study was to determine the influence of four diets on urine pH in healthy dogs. Sixteen adult dogs of various breeds, ages, and weights were fed four diets in Latin Square design: a diet formulated for adult dogs at maintenance (Diet A; ProPlan Canine Chicken and Rice Adult [dry], Ralston Purina Co, St. Louis, MO); a diet formulated to aid in management of fiber-responsive diseases (Diet B; CNM Canine DCO [dry], Ralston Purina Co, St. Louis, MO); a diet formulated to aid in management of chronic renal failure (Diet C; CNM Canine NF [dry], Ralston Purina Co, St. Louis, MO); and a diet designed to aid in prevention of struvite urolithiasis (Diet D; Prescription Diet Canine c/d [dry], Hill's Pet Nutrition Inc, Topeka, KS). Diets were fed for 21 days. On day 21, blood and urine samples were collected before feeding one-half of daily caloric requirements, and urine was collected 4 and 8 hours later. A biochemical analysis and ionized-calcium test were conducted on blood samples, and a complete urinalysis and urine pH determined by a pH-electrode were conducted on urine samples. Thirteen dogs completed the study. Serum phosphorous concentrations were significantly lower and urine pH was significantly higher when dogs consumed Diet C when compared with the other three diets. A postprandial effect on urine pH was not demonstrated when dogs consumed any diet. Other urinalysis parameters were not different between dogs or diets. Diet does influence urine pH in healthy dogs; however, healthy dogs produced urine with an acidic pH except while consuming a diet specifically formulated to produce alkaluria. Furthermore, crystalluria was commonly found in these healthy dogs regardless of the diet.

Comparison of dual-energy x-ray absorptiometry and measurement of total body water content by deuterium oxide dilution for estimating body composition in dogs.

OBJECTIVE: To compare percentage of body fat (%BF) estimates from dual-energy x-ray absorptiometry (DEXA) with those derived from total body water (TBW) determination by deuterium oxide (D2O) dilution. ANIMALS: 31 healthy, adult, purebred dogs of various ages and breeds (body weight, 15 to 39 kg). PROCEDURE: The TBW was measured by D2O dilution and subsequent analysis via nuclear magnetic resonance (NMR). Blood was collected before and 2 hours after IV administration of 275 mg of D2O/kg of body weight. Plasma was separated and stored at -30 C until analysis by deuterium NMR. The DEXA scans were obtained immediately after blood collection from dogs under general anesthesia. RESULTS: Measurements of %BF by DEXA averaged 15.8% higher than calculated estimates of TBW content by D2O dilution. The linear regression of %BF by TBW content on %BF by DEXA had a slope of 1.04 and a correlation coefficient of 0.84, indicating excellent relative agreement between methods despite the significant difference in absolute agreement between the 2 methods. The average difference between methods did not differ by breed, sex, body condition score, body weight, or %BF, as measured by DEXA. CONCLUSION: Comparability of our data with those of previous studies suggest that DEXA is useful for in vivo estimation of body composition in healthy dogs. Body fat estimated by D2O dilution will be less than that determined by DEXA, despite excellent relative agreement between methods.

Evaluation of weight loss protocols for dogs.

Several canine weight loss protocols were evaluated to determine their relative safety and efficacy. Dogs were fed 100%, 75%, 60%, or 50% of maintenance energy requirements (MERs) using the dogs' target body weights. No indications of adverse health effects were observed with any weight loss protocol. Triiodothyronine (T3) levels and apparent MERs decreased in dogs restricted to 50% to 60% of their MERs. The rate of weight loss was correlated linearly with degree of calorie restriction, although there was considerable individual variation. Percent overweight by the end of the test was not different between protocol groups for dogs fed 50%, 60%, or 75% of MERs. Therefore, any of the protocols tested in this study may be used in the management of overweight dogs; however, individual responses will be expected to vary, and severe calorie restriction may predispose dogs to weight rebound.

Surgical creation of portacaval shunts during temporary intestinal arterial and venous occlusion in dogs.

OBJECTIVE: To surgically create complete portacaval shunts in dogs during temporary arrest of intestinal arterial and portal venous blood flow. DESIGN: Complete portacaval anastomoses were surgically created, and liver function was evaluated for 14 to 18 weeks after surgery. ANIMALS: 32 adult mixed-breed dogs of either sex. PROCEDURE: Administration of deferoxamine and temporary intestinal arterial occlusion were used to minimize the intestinal cellular damage resulting from the complete, temporary arrest of portal venous blood flow during creation of the portacaval anastomosis. Side-to-side, appositional anastomoses ( > 2 cm diameter) were formed between the portal vein and caudal vena cava. Dogs were observed daily for signs of hepatic encephalopathy, and food intake was recorded. Body weight was recorded weekly. Preprandial plasma ammonia, serum urea nitrogen, and glucose concentrations and sulfobromophthalein retention were measured monthly. The dogs were euthanatized, and necropsy was performed 14 to 18 weeks after surgery. RESULTS: 30 of 32 dogs recovered without complications. Complete portosystemic shunting was documented by increased plasma ammonia concentration, decreased serum urea nitrogen and glucose concentrations, prolonged sulfobromophthalein retention (P < 0.01), and inspection at necropsy. CONCLUSION: This method of providing temporary, complete arrest of portal venous blood flow was helpful in allowing accurate, appositional portacaval anastomoses to be created that remained patent for 14 to 18 weeks. CLINICAL RELEVANCE: This method of providing temporary, complete arrest of portal venous blood flow may prove useful in clinical surgery when temporary arrest of portal blood flow is desired.

Microcytosis and iron status in dogs with surgically induced portosystemic shunts.

Microcytosis is common in dogs with congenital portosystemic shunts (PSS) and acquired liver disease. The objective of this study was to determine if microcytosis could be induced in normal dogs by surgical creation of PSS, and to characterize the changes in hematology and iron status. Hematocrit, mean cell volume, mean cell hemoglobin, and mean cell hemoglobin concentration decreased linearly from 45.5%, 69.1 fL, 22.8 g/dL and 33.1% to 39.5%, 55.9 fL, 17.8 g/dL and 31.9%, respectively, 18 weeks after creation of PSS. The erythrocyte count did not change, but red cell distribution widths indicated a shift to a heterogenous population with decreased volume. Mean cell volume and mean cell hemoglobin decreased rapidly after induction of PSS and were significantly (P < .05) different from presurgery values within 2 weeks. Serum iron and copper concentrations and total iron binding capacity were decreased in dogs with PSS. Liver iron concentration doubled after creation of PSS, with the majority of stainable iron located in Kupffer cells. The changes in erythrocyte indices and measures of iron status in dogs with surgically induced PSS were similar to those in dogs with congenital PSS. Microcystosis developed rapidly in dogs after induction of PSS. These results indicate that iron deficiency was not the cause of microcytosis in these dogs.

Apparent dietary protein requirement of dogs with portosystemic shunt.

Current medical management of dogs with portosystemic shunt (PSS) includes dietary protein restriction. After establishment of baseline values, 32 dogs underwent portosystemic anastomosis to induce PSS. They were assigned to 1 of 4 dietary treatments, and given 11 or 24% crude protein (CP); 20% of the protein was derived from branched chain or aromatic amino acids. The apparent digestibility of CP and of total digestible energy were not affected by PSS. The apparent digestibility of fat decreased from 92% to 85% in dogs with PSS (P < 0.01). Across all diets, the apparent dietary protein requirement (ADPR) was 2.07 g of CP/kg of body weight/d in clinically normal dogs and 2.11 g of CP/kg/d after PSS. Dietary amino acid composition had no effect on ADPR. The ADPR for dogs fed the 11% protein diets was 1.69 g of CP/kg/d in clinically normal dogs and 1.62 g of CP/kg/d after PSS, whereas the ADPR in dogs fed the 24% protein diets was 3.94 g of CP/kg/d before PSS and 3.31 g of CP/kg/d after PSS. Serum total protein, urea nitrogen, and albumin concentrations were lower in dogs with PSS fed the 11% protein diets, compared with those fed the 24% protein diets. We conclude that there is no difference in ADPR in dogs with PSS; however, the low protein intake of 1.62 g of CP/kg/d appeared inadequate to maintain normal protein stores. Dietary protein that provides at least 2.1 g of CP/kg/d is recommended for dogs with PSS.

Comparison of procedures for assessing adequacy of dog foods.

Dog foods with similar claims for nutritional adequacy were tested by chemical analysis and the American Association of Feed Control Officials' growth trial. All foods tested were similar chemically, however, dogs given one regionally marketed food had lower growth rate and food efficiency as well as suboptimal PCV and hemoglobin values during the growth trial. Pups fed this diet also had clinical signs typical of zinc and copper deficiencies. We concluded that American Association of Feed Control Officials' approved feeding tests provide valid assessment of pet food quality, and procedures involving only chemical analysis or calculated values may not.

A simplified technique for chronic cerebrospinal fluid collection in the awake dog.

A modified design for a guide tube to facilitate collection of cerebrospinal fluid from the lateral ventricle of awake dogs was developed. The modifications allowed for rapid, inexpensive and secure implantation. The tested guide tubes remained in place and patent for 20 weeks.

Effects of various known and potential cyanide antagonists and a glutathione depletor on acute toxicity of cyanide in mice.

To compare the protective potencies of a large number of known and potential cyanide antagonists in one stock of mice, groups (N = 10) of male CF-1 Swiss-Webster mice were given a single maximal or near-maximal intraperitoneal injection of each substance. Ethyl maleate, a glutathione (GSH) depletor and potential enhancer of cyanide toxicity, was given to other groups. Thirty min later, the mice were given subcutaneous injections of graded doses of KCN. In untreated control mice, the 24-hr median lethal dose (LD50) of KCN was 11 mg/kg of body weight (potency ratio, PR = 1.0). In comparison, protective effects of traditional antagonists thiosulfate and nitrite produced PR values of 1.48 and 2.95, respectively. Tetrathionate, sulfate, dithionite, methionine, hydroxocobalamin, ascorbate, pyridoxal phosphate, alpha-ketoglutarate, alpha-ketobutyrate, GSH, GSH disulfide (GSSG) and selenite were similar in efficacy to thiosulfate (P less than 0.05; PR values 1.35-1.59). Cysteine, diethyldithiocarbamate (DEDC), and cobaltous chloride were more effective than thiosulfate (PR values 1.68, 1.69, and 1.85, respectively). Phentolamine and dicobalt EDTA were ineffective, whereas papaverine enhanced toxicity (PR 0.72). Agents with significant PR values (greater than or equal to 1.14) but which were less effective than thiosulfate included sulfite, dimercaptosuccinic acid, pyruvate, citrate, alpha-ketovalerate, naloxone, and corn oil. Ethyl maleate in corn oil markedly enhanced KCN lethality (PR 0.57 compared to corn oil alone), and caused prolonged illness in several mice. Vitamin E in corn oil had no effect. Dual mixtures of thiosulfate with other selected substances were also tested.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute intraperitoneal cholecalciferol (vitamin D3) toxicosis in mice: its nature and treatment with diverse substances.

To study the overt toxicosis of intraperitoneally (IP)-administered single doses of cholecalciferol (D3), groups of male CF-1 mice (N = 12) were given graded doses of D3 in corn oil and observed for 21 days. There was a 2- to 4-day onset of signs, including ocular squinting, reluctance to move, lethargy, weakness, anorexia, hunched posture, rough haircoat, and dehydration. This was followed by tremors, coma, and death (large doses) or gradual recovery. Deaths occurred 3 days (larger doses) to 21 days after D3 injection. The linear regression of mortality probits on log10 dose was Y = 7.332X-10.653. The median lethal dose (LD50) of D3 and 95% confidence limits were 135.4 mg/kg (112.2-157.4 mg/kg). To screen potential antidotes against acute D3 toxicosis, groups of mice (N = 12) were given subcutaneous (SC) injections of various substances beginning 2 days after IP injection of a large dose of D3 (300 mg/kg). Substances were given once or twice daily in constant volumes of saline solution (66.8 ml/kg) for 7 days. Two control groups were given D3 but no treatment. They both had 91.7% mortality; their mean (+/- SD) survival time (MST: censored to 21 days observation) was 6.8 +/- 4.7 days and 10.3 +/- 7.0 days. Mortality and MST were not affected significantly (P greater than 0.05) by once-daily injection of saline solution, saline containing dexamethasone (DEX), or saline containing the following substances with or without DEX: ascorbate; citrate; dimercaptosuccinic acid; oxytetracycline; ZnSO4; or MgCl2.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of low to normal dietary phosphorus levels on zinc metabolism and tissue distribution in calves.

Sixteen 10-wk-old, phosphorus (P)-depleted Holstein bull calves were fed for 6 wk a control diet containing .08% P or P-supplemented diets containing .14, .20 or .32% P with supplemental P from two sources (CDP and Dynafos). The diets contained .45, .56, .66 and .87% Ca. After 5 wk of the experiment, the calves were dosed orally with 65Zn, and daily total fecal collections were initiated. At the end of the experimental period, the calves were killed and tissue samples were taken for total Zn and 65Zn analyses. Growth, feed intake and feed efficiency improved with increasing dietary P levels. Level of dietary P and Ca had little or no effect (P greater than .05) on total Zn content of rib, tibia, liver, heart, kidney, muscle or blood. Likewise, 65Zn absorption and content in most tissues were not affected (P greater than .05). The results do not preclude the possibility of some minor effects of P levels on Zn metabolism. However, it is apparent that when adequate Zn is fed, any effects are likely to be of little or no practical importance.