Cat food

Cat with a bowl of dry cat food

Cat food is formulated to address the specific nutritional requirements of cats. Although cats are obligate carnivores, most commercial cat food contains both animal and plant material, supplemented with vitamins, minerals and other nutrients. An important nutrient is the amino acid derivative taurine, as cats cannot synthesize the compound. Cats fed a taurine-deficient dog food may develop retinal degeneration and go blind, for example.^[1]

Commercial cat food

Cat food for sale at an Istanbul animal market

Most store-bought cat food comes in either dry form, also known in the US as kibble, or wet canned form. Some manufacturers sell frozen raw diets and premix products to cater to owners who feed raw.

Dry food

Dry (Extruded) cat food example

Dry food (8-10% moisture) is generally made by extrusion cooking under high heat and pressure. Fat may then be sprayed on the food to increase palatability, and other minor ingredients, such as heat-sensitive vitamins, which would be destroyed in the extrusion process, may be added.

Major brand-name dry cat food manufacturers often use primarily grain-based ingredients with animal protein by-products or animal digest to cut cost. Higher end foods offered as 'premium', 'natural' or 'holistic' formulas contain less or no grain, and a higher percentage of animal protein. However, grain-free dry diets still contain carbohydrates, from sources such as potato or tapioca. The starch in those ingredients allows the kibble to hold its shape. Cats have no metabolic need for carbohydrates as the feline system prefers to create glucose from protein.^[2]

Dry cat food has an advantage over wet in convenience and price – besides usually being significantly cheaper, dry cat food can also be left out for the cat to eat at will over the course of several days, whereas canned or raw cat food spoils or becomes unappetizing after several hours. It should be noted, however, that even dry food, since it is sprayed with fats as noted above, becomes rancid and stale as it oxidizes. Using a free feeding practice can also contribute to overeating, and ultimately obesity.^[3]

Dry food is recommended by some based on the idea that cats break apart dry foods with their teeth, which causes the food to scrape off dental calculus. The degree of benefit this provides has been disputed in recent years.^[4]

Since the occurrence of BSE infection through contaminated meat and bone meal, the use of meat meal in pet foods has been prohibited in parts of the world (e.g. Japan and France) but is still common practice in other parts (e.g. USA).^{[citation needed]} Comparative studies conducted by Japanese researchers have shown that meat meal is superior to the other protein meal sources in terms of dry-matter digestibility and nutritional value for cats, while corn gluten meal is the least nutritional.^[5][6][7]

The same studies showed that cats fed with these dry food diets excreted alkaline urine. Urine pH has been implicated in the formation of struvite crystals in feline urolithiasis, and many dry food manufacturers address this by adding urine-acidifying ingredients to their food. However, this practice may lead to the formation of calcium oxalate stones, therefore water intake rather than urine pH appears to be the most crucial diet related factor for the prevention and treatment of feline stones.^[8]

Wet food

Wet (Canned) cat food example (Fish flakes in jelly)

Canned or wet food (75-78% moisture) generally comes in common can sizes of 3 oz (85 g), 5.5 oz (156 g), and 13 oz (369 g). It is also sold in foil pouch form by some manufacturers.

Owners and veterinarians who recommend a diet consisting largely or entirely of canned, homemade or raw cat food point to higher water content of such food and the increased total water consumption in comparison to a dry food diet as an important health benefit. Wet food also generally contains significantly less grain and other carbohydrate material. Many foods are made with fish, however an excessive consumption of fish (which contains high levels of unsaturated fatty acids) can cause yellow fat disease.^[9] In comparison to dry food, canned food is thought to either help treat or noticeably reduce the likelihood of numerous health issues including urinary tract disorders^[10][11], diabetes, chronic renal failure^[12], constipation (sometimes leading to megacolon), and obesity.^{[citation needed]}

Canned cat foods in pop-top containers may play a role in the development of hyperthyroidism in cats^[13]. This may be due to bisphenol A used in the pop-top can coating leaching into the food, so it is suggested to place unused food in reusable containers to prevent contamination.^[14]

Prescription food

Prescription foods for specific disease such as feline lower urinary tract disease and chronic renal failure are available through a vet or pet pharmacy.

Homemade Food

Many pet owners feed cats homemade diets. These diets generally consist of some form of cooked or raw meat, bone, vegetables, taurine supplements, and other multivitamin supplements.

Vegetarian or vegan food

Vegetarian or vegan cat food has been available for many years, and is targeted primarily at vegan and vegetarian pet owners. While a small percentage of owners choose such a diet based on its perceived health benefits, the majority do so due to ethical concerns. Despite this, most believe that a vegetarian diet is healthier than a conventional diet.^[15]

As obligate carnivores, cats require nutrients (including arginine, taurine, arachidonic acid, vitamin A, vitamin B12 and niacin) found in meat sources that cannot be obtained in sufficient amount in plant sources. Vegetarian pet food companies attempt to correct these deficiencies by supplementing their products with synthetically produced nutrients.^[16] According to the National Research Council, "Cats require specific nutrients, not specific feedstuffs."^[17] While there is "no scientific reason why diets comprised entirely of plant, mineral and synthetically based ingredients" cannot satisfy the nutrient requirements of cats, Former HSUS Vice-President Dr Michael W. Fox argues that "To use the science of nutrition that is still in its infancy to support the feeding of vegetarian food to cats is to ignore the precautionary principle with regard to 'synthetically based ingredients', as well as the basic biology of the cat as a carnivore."^[18]

While there are anecdotal evidence that cats do well on vegetarian food,^[16] studies on commercial and homemade vegetarian cat foods have found nutritional inadequacies. One study evaluated cats whose owners were knowledgeable about vegetarian cat diets and had self-selected to feed commercial and/or homemade vegetarian diets.^[15] Cobalamin (vitamin B12) and taurine, two nutrients lacking in vegetarian food, was tested for. The study found that all the cats had serum cobalamin levels within the reference range but 3 of 17 cats had serum taurine values below the reference range. While low blood taurine level is indicative of long-term deficiency, the values were described as "marginal, but... not clinically deficient".

Even when adequately supplemented, vegetarian diets may present other risks, such as urine acidity problems. While there are anecdotal reports linking a vegetarian diet with urinary tract problems, no documented case report or study exist.^[15] One vegan cat food manufacturer has stated that "because of the relative acidity of meat to vegetable protein, many vegan cats suffer from [Urinary tract problems]."^[19] A survey done during the above study showed that a quarter of respondents perceive feline lower urinary tract disease as a health risk of feeding a vegetarian diet.^[15]

A few vegetarian cat food brands are labeled by their manufacturers as meeting AAFCO's Cat Food Nutrient Profile while other manufacturers recommend their products to be supplemented and not used as a standalone. A 2004 study evaluated two commercial pet foods for nutritional adequacy;Vegecat KibbleMix supplement and Evolution canned diet for adult cats. The study concluded that these two foods, counter to labeling claims, had multiple nutritional inadequacies when compared against the AAFCO minimal nutrient profile for cat diets. The authors recommended that these vegan diets should not be used as a sole source of nutrition for cats.^[20]

In response, Evolution Diet denied that their product is nutritionally inadequate, citing the "ten to twenty thousand healthy and long living dogs, cats and ferrets living on the Evolution Diet" as an example. They attribute the discrepancy as a likely formulation error. In an apologetic reply, the manufacturer of Vegecat attributed the test results to a manufacturing error during the mixing process and an inaccurate nutrient profile of a food yeast, and asserted they were taking steps to correct the problems.^[21]

Organizations that advocate vegan or vegetarian diets for people have split opinions regarding vegetarian or vegan cat food. The International Vegetarian Union^[22], the Vegan Society^[23] and Peta^[24] are some of the organizations that support a vegan or vegetarian diet for cats. On the other hand, the Vegetarian Society suggests people "consider carefully" and that many cats will not adjust to a vegetarian diet. They provide a list of necessary nutrients that will need to be supplemented with a recommendation to consult a veterinarian or animal nutritionist for those who want to try.^[25] The Animal Protection Institute also does not recommend a vegetarian diet for cats and cautions that dietary deficiencies may take months or years to develop and may be untreatable. They do not recommend relying on supplements because they may not contain necessary co-factors and enzymes and have not been studied for long term implications.^[26] The animal welfare organization American Society for the Prevention of Cruelty to Animals, although suggesting a supplemented vegetarian diet for dogs,^[27] recommends against a vegetarian and vegan diets for cats.^[28]

The Association of Veterinarians for Animal Rights (now Humane Society Veterinary Medical Association) accepts that it is possible for a plant based diet to be nutritionally adequate but stated that they "cannot at this time be reliably assured", referring to the inadequacy of the diets tested in the 2004 study. The organization states that

While those humans who make an ethical and healthful choice to sustain themselves on a plant-based diet should be applauded, there remains an ethical quandary over imposing human philosophy regarding the harming and killing of animals onto other species. Further, until such time that a vegan diet for cats can be formulated so that there is no risk of harm to that animal’s life or health when fed that diet over time, cats should continue to be fed a diet containing animal flesh.^[29]

Vegan activist Joanne Stepaniak says that "vegans and vegetarians often like to underscore the anatomical differences between carnivores and herbivores to support their belief that humans are not designed to eat meat. They are also repulsed and furious that some 'food animals'... are commonly fed ground-up animal products... If we belief that it is wrong for natural vegetarians to be force-fed meat, the inverse should be equally morally objectionable" and argues that it's not right to impose one's ethical beliefs on another species.^[30]

In Obligate Carnivore - a book arguing in favor of vegan cat food - Jed Gillen rejects the nutritional deficiency argument, reasoning that the suffering and death of food animals outweighs any potential negative health effects of a vegan diet.^[31]

Labeling

In the United States, cat foods labeled as "complete and balanced" must meet standards established by the Association of American Feed Control Officials (AAFCO) either by meeting a nutrient profile or by passing a feeding trial. Cat Food Nutrient Profiles were established in 1992 and updated in 1995 by the AAFCO's Feline Nutrition Expert Subcommittee. The updated profiles replaced the previous recommendations set by the National Research Council(NRC).

Critics^[who?] argue that due to the limitations of the trial and the gaps in knowledge within animal nutrition science, the term "complete and balanced" are inaccurate and even deceptive. An AAFCO panel expert has stated that "although the AAFCO profiles are better than nothing, they provide false securities. "^[32]

Certain manufacturers label their products with terms such as premium, ultra premium, natural and holistic. Such terms currently have no legal definitions.

Energy requirement

The energy requirement for adult cats range from 60-70 kcal metabolizable energy/kg body weight per day for inactive cats to 80-90 kcal/kg BW for active cats. Kittens at 5 weeks of age requires 250 kcal/kg BW. The requirement drops with age, to 100 kcal/kg BW at 30 weeks and to the adult requirement at about 50 weeks. Gestating cats require about 90-100 kcal/kg BW and lactating cats 90-270 kcal/kg BW depending on litter size.^[33]

Nutrients and functions

Vitamins are organic compounds that take part in a wide range of metabolic activities. Vitamin deficiencies can lead to widely ranging clinical abnormalities that reflect the diversity of their metabolic roles. Twelve minerals are known to be essential nutrients for cats. Calcium and phosphorus are crucial to strong bones and teeth. Cats need other minerals, such as magnesium, potassium, and sodium, for nerve impulse transmission, muscle contraction, and cell signaling. Many minerals only present in minute amounts in the body, including selenium, copper, and molybdenum, act as helpers in a wide variety of enzymatic reactions.^[34]

The table below lists the AAFCO nutritional profiles for cat foods along with the roles of vitamins and minerals in cat nutrition according to the National Research Council.

Diet and disease

Food allergy

Food allergy is a non-seasonal disease with skin and/or gastrointestinal disorders. The main complaint is Pruritus, which is usually resistant to treatment by steroidal anti-inflammatory drugs. The exact prevalence of food allergy in cats remains unknown. There is no breed, sex or age predilection, although some breeds are commonly affected. Before the onset of clinical signs, the animals have been fed the offending food components for at least two years, although some animals are less than a year old. In 20 to 30% of the cases, cats have concurrent allergic diseases (atopy / flea-allergic dermatitis). A reliable diagnosis can only be made with dietary elimination-challenge trials. Allergy testing is necessary for the identification of the causative food component(s). Therapy consists of avoiding the offending food component(s).^[36]

Malnutrition

Cats fed exclusively on raw, freshwater fish can develop a thiamine deficiency. Those fed exclusively on liver may develop vitamin A toxicity. Malnutrition has been seen in cats fed "natural", "organic", or "vegetarian" diets produced by owners with good intentions, and most published recipes have been only crudely balanced (by computer) using nutrient averages. Because the palatability, digestibility, and safety of these recipes have not been adequately or scientifically tested, it is difficult to characterize all of these homemade diets. Generally, most formulations contain excessive protein and phosphorus and are deficient in calcium, vitamin E, and microminerals such as copper, zinc, and potassium. Also, the energy density of these diets may be unbalanced relative to the other nutrients. Commonly used meat and carbohydrate ingredients contain more phosphorus than calcium. Homemade feline diets that are not actually deficient in fat or energy usually contain a vegetable oil that cats do not find palatable; therefore, less food is eaten causing a calorie deficiency. Rarely are homemade diets balanced for microminerals or vitamins. Owner neglect is also a frequent contributing factor in malnutrition.^[37]

Recalls

The 2007 pet food recalls involved the massive recall of many brands of cat and dog foods beginning in March 2007. The recalls came in response to reports of renal failure in pets consuming mostly wet pet foods made with wheat gluten from a single Chinese company, beginning in February 2007. After more than three weeks of complaints from consumers, the recall began voluntarily with the Canadian company Menu Foods on March 16, 2007, when a company test showed sickness and death in some of the test animals.

Overall, several major companies have recalled more than 100 brands of pet foods, with most of the recalled product coming from Menu Foods. Although there are several theories of the source of the agent causing sickness in affected animals, with extensive government and private testing and forensic research, to date, no definitive cause has been isolated. As of April 10, the most likely cause, according to the FDA, though not yet proven, is indicated by the presence of melamine in wheat gluten in the affected foods.

In the United States, there has been extensive media coverage of the recall. There has been widespread public outrage and calls for government regulation of pet foods, which had previously been self-regulated by pet food manufacturers. The economic impact on the pet food market has been extensive, with Menu Foods losing roughly $30 Million alone from the recall. The events have caused distrust of most processed pet foods in some consumers.

Environmental impact

In a study on the impacts of the pet food industry on world fish and seafood supplies, researchers estimate that 2.48 million metric tonnes of fish are used by the cat food industry each year.^[38][39] It was suggested that there needs to be "a more objective and pragmatic approach to the use of a limited and decreasing biological resource, for human benefit." Marine conservation activist Paul Watson argues that the reduction in forage fish such as those commonly used in cat food (sardines, herring, anchovy etc.) negatively affects fish higher up the food chain like cod, tuna and swordfish, not to mention marine mammals and birds.^[40]

Based on 2004 numbers, cats in the US consumes the caloric equivalent of what 192,000 American consumes. While pet food used to be made predominantly using byproducts from human food productions, the increase in popularity of human-grade and byproduct-free pet food means that pets play an increasing burden on agriculture.^[41]

See also

• Cat food brands

References

Further Information

Wikimedia Commons has media related to: Cat food

• From the U.S. Food and Drug Administration - Center For Veterinary Medicine
  • Pet Foods
  • Information For Consumers - FDA's Regulation Of Pet Food
  • Information For Consumers - Information On Marketing A Pet Food Product
  • Information For Consumers - Interpreting Pet Food Labels
  • Information For Consumers - Interpreting Pet Food Labels - Special Use Foods
  • Vegetarian Diets For Pets?
  • Report on the risk from pentobarbital in dog food
• The Vegetarian Society UK on concerns relating to a vegetarian diet for cats
• The Cat That Ate Tofu Alternet article on vegan cat food
• Vegan Pet Food: A Discussion Animal Voices audio interview with Evolution pet food CEO
• From Max's House Feline Medical And Behavior Database
  • Feline Nutrition
  • Cat Food Nutrient Profiles
  • Dry food v/s canned (wet) food
• Buffington CA (June 2008). "Dry foods and risk of disease in cats". Can. Vet. J. 49 (6): 561–3. PMID 18624064.  – disputes the claim that dry food is harmful
• Get The Facts - What's Really In Pet Food from Animal Protection Institute
• From AAFCO
  • Regulating Pet Foods (pdf)
  • Questions and Answers Regarding Pet Food Regulations (pdf)