The histamine content of commercial pet foods

The histamine contents of a range of North American commercial pet foods and pet food ingredients were determined by a spectrofluorometric technique. The change in histamine content of open cans of pet food stored in a refrigerator or at room temperature was also investigated. The histamine content of the pet foods examined ranged from a low of 0.16 𝛍g/g in a liquid critical care diet to a high of 65.5 𝛍g/g in a canned fish diet. The amount of histamine in the foods tested was insufficient to cause histamine toxicosis but it cannot be excluded that some of the foods contained sufficient histamine to cause idiosyncratic reactions in histamine-sensitive cats. Storage of opened cans of pet food, either under refrigeration or at room temperature, did not significantly increase the histamine content of most pet foods.     

Determination of bisphenol A in canned pet foods

Bisphenol A (BPA) contamination of canned foods for human use has been studied, but there are no reports concerning BPA contamination of canned pet foods. The purpose of this study was to identify the levels of BPA in canned pet foods. A total of 26 samples (15 samples of cat food and 11 samples of dog food) were prepared for analysis by high-performance liquid chromatography. BPA in the samples was extracted with acetonitrile and fat in the sample extract was removed with hexane. Solid-phase extraction was used for sample clean-up prior to final analysis. The concentration of BPA ranged from 13 to 136 ng/g in canned cat food and from 11 to 206 ng/g in dog food. Also, to confirm that the BPA had originated from the can coating, distilled water was added to each washed empty can and the cans were autoclaved at 121 degrees C for 30 min. The concentration of BPA leached from empty cans was between 7 and 31 ng/ml.     

Identification and concentration of soy isoflavones in commercial cat foods

OBJECTIVE: To determine the absolute and relative soy isoflavone content in commercial cat foods. SAMPLE POPULATION: 14 dry, 6 semimoist, and 22 moist commercial cat foods. PROCEDURE: Soy isoflavone content of each food was determined by use of acid-methanol hydrolysis and high-pressure liquid chromatography with ultraviolet absorbance detection. Isoflavones were identified and quantified by reference to authentic standards. RESULTS: Genistein and daidzein were the major soy isoflavones identified in 24 of 42 foods, with concentrations ranging from 1 to 163 microg/g of food. Foods labeled as containing soybean solids (16/42) had isoflavone concentrations > 11 microg/g. More dry (13/14) and semimoist (6/6) foods contained isoflavones than moist foods (5/22). Isoflavone content and food cost were negatively correlated for dry and semimoist foods but not for moist foods. Total amount of isoflavone consumed by cats fed these soy-containing foods as a sole maintenance diet was estimated to be between 0.6 and 4.5 mg/kg of body weight/d, which is comparable to concentrations in humans that result in a measurable although modest effect on serum concentrations of steroid and thyroid hormones. CONCLUSIONS AND CLINICAL RELEVANCE: Genistein and daidzein are common constituents of commercial cat foods. Predictors of isoflavone content included ingredient labeling, food type, and food cost. Soy isoflavones in some commercial cat foods were detected in amounts predicted to have a biological effect.     

Diet and periodontal disease in dogs and cats

SUMMARY A review of relevant literature was undertaken because of concerns about a possible relationship between pet foods, development of periodontal disease, and secondary adverse effects on general health. It was concluded that, while changes in feeding methods in recent decades have arguably improved pet health by reducing or preventing diseases associated with nutritional deficiencies and excesses, periodontal disease remains a serious, diet-related problem. There is reasonable evidence that soft diets are associated with increased frequency and severity of periodontal disease, and that harder foods requiring vigorous prehension and mastication are preferable for dogs and cats. While it is plausible that periodontal disease could cause diseases in other organs and tissues, the evidence for this is limited at present. Further research is needed to better define the relationship between diet types and oral health. In the meantime, veterinarians and pet owners should pay attention to the physical qualities (textures, abrasiveness, ‘chewiness’) of foods they provide for dogs and cats, as well as to their nutrient content, and should consider additional methods to control plaque and prevent periodontal disease where necessary.     

Understanding regulations affecting pet foods

In the United States, pet foods are subject to regulation at both the federal and the state levels. The US Food and Drug Administration has jurisdiction over all animal feeds (including pet foods, treats, chews, supplements, and ingredients) in interstate commerce, which includes imported products. Many states adopt and enforce at least in part the Association of American Feed Control Officials Model Bill and Model Regulations for Pet Food and Specialty Pet Food. Thus, all pet foods in multi-state distribution are subject to a host of labeling requirements covering aspects such as product names, ingredient lists, nutrient content guarantees, and nutritional adequacy statements. Ingredients must be GRAS (generally recognized as safe) substances, approved food additives, or defined by Association of American Feed Control Officials for their intended use. Pet food labels may not bear claims that are false or misleading or that state or imply use for the treatment or prevention of disease. Pet foods that are found to be adulterated or misbranded may be subject to seizure or other enforcement actions.     

Variation in food selection among lambs: effects of basal diet and foods offered in a meal.

In studies of behavior and nutrition, we typically determine nutritional needs and formulate diets for the average member of the herd, not for specific individuals within a herd. Nevertheless, variation among individuals could affect productivity of the group if the diet diverges too much from what individuals at the extremes prefer to eat. Thus, it is important to determine the degree to which individuals within a group vary in their food preferences when offered alternatives. Our first objective was to determine the degree to which lambs differed in preference for foods high in energy (barley) or protein (alfalfa) (Exp. 1). When we offered lambs barley and alfalfa for ad libitum consumption for 25 d, individuals varied in the amounts of barley (range: 221 to 991 g/d) and alfalfa (range: 51 to 558 g/d) they consumed (P < .0001). At one extreme, individuals preferred a diet of 6% alfalfa and 94% barley; at the other extreme, individuals preferred a diet of 70% alfalfa and 30% barley. Our second objective was to determine whether lambs from Exp. 1 compensated, when fed a basal diet that was lower in alfalfa than they preferred, by ingesting foods higher in alfalfa when offered a meal (Exp. 2). Lambs were ranked according to the percentage of alfalfa (range from 6 to 70%) and barley (range from 94 to 30%) they ate during Exp. 1 and then assigned alternately to two treatments: 1) basal diet with similar proportions of alfalfa and barley consumed ad libitum (preferred diet) or 2) basal diet with 10% less alfalfa than consumed ad libitum (low-alfalfa diet). We then conducted three trials in which lambs fed the different basal diets were offered a meal for 15 min/d for 2 d of two foods that differed in barley and alfalfa. During Trial 1, when we offered barley and alfalfa, lambs in both groups preferred barley (138 g) to alfalfa (46 g) (P < .05). During Trial 2, when the test foods (barley and alfalfa) were diluted with grape pomace (20%), lambs fed the preferred basal diet ate more barley (116 vs 64 g) and less alfalfa (48 vs 87 g) than lambs fed the low-alfalfa basal diet (P < .05). During Trial 3, when we offered a food high in barley (80% barley and 20% pomace) and a food high in alfalfa (70% alfalfa, 14% cornstarch, and 16% pomace), lambs fed the preferred basal diet ate more of the high-barley food (124 vs 73 g) and less of the high-alfalfa food (45 vs 98 g) than lambs fed the low-alfalfa basal diet (P < .05). Collectively, these results illustrate that lambs varied greatly in their preferences for foods that differ in energy (barley) and protein (alfalfa), and that when their preferred basal diet was altered, lambs compensated by ingesting food that complemented their basal diet during a daily meal. The addition of grape pomace in Trials 2 and 3 reduced the protein content of the high-barley and high-alfalfa foods such that the high-barley food was only marginally adequate to meet needs compared with the high-alfalfa food. Lambs fed the low-alfalfa basal diet compensated by eating more of the high-alfalfa food than lambs fed the preferred basal diet.     

Overt signs of toxicity to dogs and cats of dietary deoxynivalenol

Studies were conducted to determine the dietary amounts of deoxynivalenol (DON; vomitoxin) in dog and cat food that are required to produce overt signs of toxicity (e.g., vomiting or reduced food intake). Wheat naturally contaminated with 37 mg of DON/kg was used to manufacture pet foods containing 0, 1, 2, 4, 6, 8, and 10 mg of DON/kg. Deoxynivalenol concentration in pet food following manufacture was unchanged, indicating that the toxin was stable during conventional extrusion processing. Dogs previously fed DON-contaminated food were able to preferentially select uncontaminated food. Dogs not previously exposed to DON-contaminated food consumed equal quantities of contaminated and uncontaminated food. There was no effect of 6 mg of DON/kg on dog food digestibility. Food intake of dogs was significantly reduced by DON concentrations greater than 4.5 +/- 1.7 mg/kg, and DON greater than 7.7 +/- 1.1 mg/kg reduced cat food intake. Vomiting by dogs and cats was commonly observed at the 8 and 10 mg DON levels.     

Alternative diets

As pet owners become more conscious of their own diets and the impact it has on their health, they naturally become more interested in what their animal companions are eating and how that might be affecting their pet's health. Many are exploring alternatives to standard commercial pet foods, and some are asking their veterinarians for advice. Small-animal nutrition is an ever-changing field. What veterinarians were taught 10 years ago may no longer be sound advice. This article explores some of the reasoning behind the development of both conventional commercial pet foods and the alternative foods and diets. It questions some of the conventional dogma as well as some of the trendy assumptions in the current marketplace. The intent is to provide the veterinarian with some balanced information on which to base nutritional advice to clients, and to begin forming new opinions or at least asking new questions. Guidelines on formulating a homemade diet for dogs are included.     

A comparison of certified and noncertified pet foods.

The market presents the buyer with a wide array of pet food choices. Marketing pet foods has changed in the last decade and today foods may be bought at a variety of outlets. The present study compares nutrient composition, digestibility, and effect on urine pH (cat foods only) of selected certified and noncertified pet foods from different outlets. The selected foods were considered analogous in terms of declared ingredients and macronutrient profiles. The analytical methods used were those of the Association of Official Analytical Chemists as described in the Pet Food Certification Protocol of the Canadian Veterinary Medical Association. The test foods were sampled 4 times from August 1994 to July 1995. Both certified and noncertified products met the nutritional requirements on a consistent basis, although 1 of the noncertified dog foods consistently failed to meet the zinc requirements. This same product also failed to meet the Canadian Veterinary Medical Association's standards for concentrations of protein, calcium, and phosphorus. One of the noncertified cat foods failed to meet the recommended calcium level. With the exception of fat digestion in 1 noncertified food, there were no statistically significant differences in major nutrient digestibility between certified and noncertified pet foods. There were some statistically significant differences in digestibility within both the certified and noncertified groups of foods. The practical significance of any of the statistical differences in digestibility is uncertain. Urine pH observed in cats fed noncertified test diets was variable, with some values greater than 7.0 as a maximum or 6.5 as an average. The general conclusion of this study was that the commonly available certified products were the nutritional equal of those foods that position themselves as "premium."     

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.     

Comparison of the guaranteed analysis with the measured nutrient composition of commercial pet foods

The purpose of this study was to compare the guaranteed analysis of commercial pet foods to their measured nutrient concentrations. Data were collected regarding the guaranteed and measured concentrations of crude protein, crude fat, crude fibre, moisture and ash of pet foods from annual feed inspection reports from South Dakota (2003–2005), Indiana (2004–2005), Rhode Island, New York and New Jersey (2005–2006). The difference for each nutrient was compared among types of food (dry, canned or treat), intended species, target life‐stages, manufacturers and reporting laboratories. Significant differences between the guaranteed and measured nutrient concentrations were found. For all foods, the mean ± one standard deviation of the difference was 1.5 ± 2.0% for crude protein, 1.0 ± 1.7% for crude fat, ‐0.7 ± 1.3% for crude fibre, ‐4.0 ± 3.3% for moisture, and ‐0.5 ± 1.0% for ash. The difference in crude protein was significantly greater for treats than for other food types. The difference in crude fat was significantly less for dry foods than for other food types. The differences in crude fibre and moisture were significantly less for canned foods than for other food types. Only the differences in crude fibre differed significantly among target species, life‐stages, manufacturers or laboratories. More accurate estimations of the nutrient composition and calculated metabolizable energy content of commercial pet foods can be obtained by making adjustments to the guaranteed analysis. This includes adding 1.5% and 1% to the guaranteed minimums for crude protein and crude fat, respectively, and subtracting 0.7%, 4% and 0.5% from the guaranteed maximums for crude fibre, moisture and ash, respectively.     

Development of a polymerase chain reaction-based method to identify species-specific components in dog food

OBJECTIVES: To determine whether there is a relationship between species-specific mitochondrial DNA (mtDNA), especially canine and feline mtDNA, and detectable amounts of pentobarbital in previously analyzed dog food samples. SAMPLE POPULATION: 31 dog food samples previously analyzed for pentobarbital (limit of detection, 1 microg/kg). PROCEDURE: Polymerase chain reaction (PCR) analysis was performed on dog food samples by use of PCR primers specific for either canine, feline, equine, bovine, porcine, ovine, or poultry mtDNA. RESULTS: PCR amplicons specific for feline or canine mtDNA at a 0.007% (70 microg/g [wt/wt basis]) or 0.0007% (7 microg/g) level, respectively, were not found in the 31 dog food samples. Most of the 31 dog food samples had a PCR amplicon on PCR analysis when a PCR primer set capable of simultaneously detecting mtDNA of cows, pigs, sheep, goats, deer, elk, and horses was used. Results of PCR analysis by use of primers specific for bovine, swine, sheep and goat, or horse mtDNA revealed amplicons specific for bovine or swine mtDNA only in 27 of the 31 samples. Analysis of the remaining 4 samples failed to yield amplicons for any mammalian mtDNA. Pentobarbital was detected in 2 of these 4 samples. Results of PCR analysis correlated with the stated ingredient list for most, but not all samples. CONCLUSIONS AND CLINICAL RELEVANCE: Because canine and feline mtDNA were not found in a set of retail dog food samples, these results indicate that the source of pentobarbital in dog food is something other than proteins from rendered pet remains.     

Residues of ochratoxin A in pet foods, canine and feline kidneys

The occurrence of ochratoxin A (OTA) in canned (26 samples) as well as dry pet foods (17 samples) for cats and dogs was investigated. In addition, 26 feline kidney samples with or without kidney alterations were surveyed for OTA-residues. The separation and detection of OTA was carried out by an isocratic high-performance liquid chromatography system based on reversed phase with fluorescence detection. After homogenization and extraction steps, immuno-affinity columns were applied for sample clean up. OTA could be detected in 47% (n=40) of the pet food samples. Those found positive contained generally low amounts of OTA (0.1–0.8  μ g/kg original substance). Higher levels were only detected in two pet food samples (3.2 and 13.1  μ g/kg toxin, respectively). Low concentrations of ochratoxin A could also be found iIn tissue of cat kidneys, with 16 of the analysed kidneys (n=26) being positive. The concentration levels were between 0.35 and 1.5  μ g/kg OTA in tissue. No relation between pathological findings and ochratoxin levels in feline kidneys could be assessed.     

ELISA testing for common food antigens in four dry dog foods used in dietary elimination trials

This study evaluated four over the counter venison dry dog foods available from one on-line retail vendor for potential contamination with common known food allergens: soy, poultry or beef. An amplified, double sandwich type enzyme linked immunosorbent assay (ELISA) test of soy, poultry and beef proteins were performed by an independent accredited food laboratory. The ELISA test for poultry protein was found to be unreliable when testing in dry dog foods because false negatives occurred. ELISA testing of control diets for both soy and beef proteins performed as expected and could be useful in antigen testing in dry dog foods. Three of the four over the counter (OTC) venison canine dry foods with no soy products named in the ingredient list were ELISA positive for soy; additionally one OTC diet tested positive for beef protein with no beef products listed as an ingredient list. One OTC venison diet was not found to be positive for soy, poultry or beef proteins. However, none of the four OTC venison diets could be considered suitable for a diagnostic elimination trial as they all contained common pet food proteins, some of which were readily identifiable on the label and some that were only detected by ELISA. Therefore, if the four OTC venison products selected in this study are representative of OTC products in general, then the use of OTC venison dry dog foods should not be used during elimination trials in suspected food allergy patients.     

Prediction of digestible energy value of extruded dog food: comparison of methods

The proposal of National Research Council (NRC), based on the use of modified Atwater factors, is nowadays the widely used method to estimate digestible energy (DE) content of pet foods. Recently, alternative methods have been suggested for predicting energy content of commercial canine dry food. Factorial equations including food fibre content as estimator, in vitro digestions methods or near-infrared spectroscopy (NIRS) techniques have been considered as good approaches to predict the energy content of dog foods. The aim of this study was to compare the accuracy of some of those estimation methods. Seventeen samples of commercial extruded dog food were used to validate and compare some estimation methods of energy digestibility (Ed, %) and DE value [MJ/kg dry matter (DM)]. The apparent Ed and DE of each food were previously determined by in vivo trials. In vivo Ed and DE of foods ranged from 79.30% to 91.05% and from 16.25 to 21.82 MJ/kg DM, respectively, and their crude fibre (CF) content ranged from 0.72% to 3.28% (in DM base). The % Ed of each sample was estimated by the factorial equation (% Ed = 91.2 - 1.43 x CF %) and by the in vitro digestion method [% Ed(in vitro) = -2.45 + 0.98 organic matter (OM) disappearance(in vitro)%]. The set of samples also was analysed by NIRS, using a calibration equation developed from a set of 69 samples of commercial extruded dog food (0.76 and 0.89 cross-validation r(2) and 2.33 and 0.61 cross-validation SE for Ed and DE respectively). The in vitro method gave better estimations of Ed in vivo than NIRS and factorial methods, although all the methods assessed showed a very good and similar accuracy in the prediction of DE value. These three methods showed a slight better accuracy than that previously proposed by the NRC. To consider constant digestibility values of nutrient content of food can result in bias and error in the estimated energy values. The alternative prediction methods used in this study take into account differences of ingredient composition and availability of nutrients of different extruded dog foods thus could be better systems of valuating energy content in a wider range of different kind of foods than in use method.     

Nutritional myths

Owners are sometimes confused or misinformed about nutritional facts pertaining to pet foods, and three common nutritional myths have been propagated in the popular press. The first myth is that meat by-products are of inferior quality compared to whole meat. The second myth is that feeding trials are unnecessary, and the third myth is that pet food preservatives are bad. This paper examines the known facts related to these three myths and discusses the importance of food trials and the different classes and forms of antioxidants used in pet foods.     

Epidemiologic study of relationships between consumption of commercial canned food and risk of hyperthyroidism in cats

OBJECTIVE: To determine whether the increasing prevalence of feline hyperthyroidism is the result of aging of the cat population and whether consumption of canned foods at various times throughout life is associated with increased risk of hyperthyroidism. DESIGN: Retrospective and case-control studies. STUDY POPULATION: Medical records of 169,576 cats, including 3,570 cats with hyperthyroidism, evaluated at 9 veterinary school hospitals during a 20-year period, and 109 cats with hyperthyroidism (cases) and 173 cats without hyperthyroidism (controls). PROCEDURE: Age-adjusted hospital prevalence of hyperthyroidism was calculated by use of Veterinary Medical Database records. On the basis of owners' questionnaire responses, logistic regression was used to evaluate associations between consumption of canned food and development of hyperthyroidism. RESULTS: Age-specific hospital prevalence of feline hyperthyroidism increased significantly from 1978 to 1997. Overall, consumption of pop-top canned (vs dry) food at various times throughout life and each additional year of age were associated with greater risk of developing hyperthyroidism. In female cats, increased risk was associated with consumption of food packaged in pop-top cans or in combinations of pop-top and non-pop-top cans. In male cats, increased risk was associated with consumption of food packaged in pop-top cans and age. CONCLUSIONS AND CLINICAL RELEVANCE: These findings suggest that the increasing prevalence of feline hyperthyroidism is not solely the result of aging of the cat population and that canned foods may play a role.     

The content of biogenic amines in canned fish from the Turkish market

This paper describes the determination of biogenic amines in a number of canned fish of the Turkish market by means of HPLC. Over all 39 cans of sardine, tuna, sardel, mackerel, pelamide and trout were tested. The determination of agmatine, cadaverine, histamine, putrescine and tyramine was performed by HPLC with post column derivatization with ortho-phthaldialdehyde. Four samples contained higher amounts of biogenic amines (three sardine samples contained more than 1000 mg/kg histamine) while all other samples were acceptable. These results demonstrate the need of instrumental analyses in the quality control system of Turkish producers of canned fish. The quality of the products at least of some producers has to be improved, e.g. by cooperation between the official food control and the quality assurance system of the producers.     

Estimated nutrient content of diets commonly fed to pet birds

The owners of 135 pet birds were surveyed by questionnaire to determine their birds' weekly food consumption. The birds were divided into six food groups on the basis of the amounts of seeds, formulated products and human food they consumed. The formulated products and seeds were analysed for their nutrient content by two independent laboratories, the nutrient content of the human foods was obtained from a standard nutrition reference, and each bird's nutrient intake was estimated. The dietary content of individual nutrients was then compared with the estimated maintenance requirements for pet birds. Birds consuming less than approximately 50 per cent of their diets as formulated products had inadequate intakes of vitamins A and D3, and calcium. Diets high in human food were low in protein, energy, vitamins and minerals. Diets high in seed were excessive in fat and deficient in vitamins A and D3, and calcium.     

Evaluating Pet Foods: How Confident Are You When You Recommend a Commercial Pet Food?

The safety, adequacy, and efficacy of pet foods are important considerations for veterinarians and consumers. Manufacturers of pet foods in the United States are required to comply with multiple regulations from a variety of governmental and state agencies to market foods in the public sector. However, consumers and veterinarians may not be aware of the multiple systems in place that help ensure the safety and adequacy of foods for their pets. Since the veterinarian occupies a key role to make recommendations to consumers regarding pet foods, it is the purpose of this article to review the processes of pet food manufacturing, as well as the processes that have been developed to help ensure safety and adequacy of pet foods in the United States.