Dog food

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Dog food is food specifically formulated and intended for consumption by dogs and other related canines. Like all carnivores, dogs have sharp, pointed teeth, and have short gastrointestinal tracts better suited for the consumption of meat. In spite of this natural carnivorous design, dogs have still managed to adapt over thousands of years to survive on the meat and non-meat scraps and leftovers of human existence and thrive on a variety of foods, with studies suggesting dogs' ability to digest carbohydrates easily may be a key difference between dogs and wolves.

In the United States alone, the dog food market is expected to reach $23.3bn by 2022.[1]

History[edit]

Prior to being domesticated, dogs, being canines, fended for themselves and survived on a carnivorous diet. Once Man adapted them for protection, work, and companionship, he began to care at least in part for their nutritional needs. The historic record of his changing approach dates back at least 2,000 years.

In 37 BCE Virgil talks about the feeding of dogs in his Bucolics:

Nec tibi cura canum fuerit postrema; sed una Veloces Spartae catulos, acremque Molossum, Pasce sero pingui:[2]

"Do not let the care of dogs be last; but the swift Spartan hounds, and fierce Mastiff, Feed the whey"

Around 70 CE, Columella wrote his book On Agriculture in which he addresses the feeding of dogs:

Cibaria fere eadem sunt utrique generi praebenda. Nam si tam laxa rura sunt, ut sustineant pecorum greges, omnis sine discrimine hordeacea farina cum sero commode pascit. Sin autem surculo consitus ager sine pascuo est, farreo vel triticeo pane satiandi sunt, admixto tamen liquore coctae fabae, sed tepido, nam fervens rabiem creat.[3]

"Provisions of victuals are almost the same for both [types of dog]. If the fields are so large as to sustain herds of animals, barley meal mixed with whey is a convenient food. But if it is an orchard without grain, spelt or wheat bread is fed mixed with the liquid from cooked beans, but warm, for boiling creates rabies."

In the Avesta, written from 224 to 651 CE, Azura Mazda advises:

Bring ye unto him milk and fat with meat; this is the right food for the dog.[4]

In France, the word pâtée began to appear in the 18th century and referred to a paste originally given to poultry. In 1756, a dictionary indicates it was made of a mixture of bread crumbs and little pieces of meat given to pets.[5]

In 1781, an encyclopedia mentioned an earlier practice of removing the liver, heart, and blood of a downed stag and mixing it with milk, cheese, and bread; and then giving it to dogs.[6]

In 1844, the French writer, Nicolas Boyard, warned against even giving tallow graves (the dregs of the tallow pot) to dogs, though the English favored them (see below), and suggested a meat-flavored soup:

By a misguided economy dogs are given meat scraps and tallow graves; one must avoid this, because these foods make them heavy and sick; give them twice a day a soup of coarse bread made with water, fat and the bottom of the stew pot; put a half-kilogram of bread at least in each soup.[7]

In England, care to give dogs particular food dates at least from the late eighteenth century, when The Sportsman's dictionary (1785) described the best diet for a dog's health in its article "Dog":

A dog is of a very hot nature: he should therefore never be without clean water by him, that he may drink when he is thirsty. In regard to their food, carrion is by no means proper for them. It must hurt their sense of smelling, on which the excellence of these dogs greatly depends.

Barley meal, the dross of wheatflour, or both mixed together, with broth or skim'd milk, is very proper food. For change, a small quantity of greaves from which the tallow is pressed by the chandlers, mixed with their flour ; or sheep's feet well baked or boiled, are a very good diet, and when you indulge them with flesh it should always be boiled. In the season of hunting your dogs, it is proper to feed them in the evening before, and give them nothing in the morning you take them out, except a little milk. If you stop for your own refreshment in the day, you should also refresh your dogs with a little milk and bread.[8]

In 1833, The Complete Farrier gave similar but far more extensive advice on feeding dogs:[9]

The dog is neither wholly carnivorous nor wholly herbivorous, but of a mixed kind, and can receive nourishment from either flesh or vegetables. A mixture of both is therefore his proper food,[10] but of the former he requires a greater portion, and this portion should be always determined by his bodily exertions.

It was not until the mid-1800s that the world saw its first food made specifically for dogs. An American electrician, James Spratt, concocted the first dog treat. Living in London at the time, he witnessed dogs around a shipyard eating scraps of discarded biscuits. Shortly thereafter he introduced his dog food, made up of wheat meals, vegetables and meat. By 1890 production had begun in the United States and became known as "Spratt’s Patent Limited".

In later years, dog biscuit was sometimes treated as synonymous with dog food:

The first three prize winners at the late coursing meeting at Great Bend were trained on Spratt's Patent Dog Biscuit. This same dog food won no less than three awards, including a gold medal, at the Exposition in Paris which has just closed. It would seem that the decision of the judges is more than backed up by the result in the kennel. Another good dog food is that manufactured by Austin & Graves, of Boston. They, too, seem to be meeting with great success in their line.[11]

Canned horse meat was introduced in the United States under the Ken-L Ration brand after World War I as a means to dispose of deceased horses. The 1930s saw the introduction of canned cat food and dry meat-meal dog food by the Gaines Food Co. By the time World War II ended, pet food sales had reached $200 million. In the 1950s Spratt's became part of General Mills. For companies such as Nabisco, Quaker Oats, and General Foods, pet food represented an opportunity to market by-products as a profitable source of income.[12]

Foods dangerous to dogs[edit]

A number of common human foods and household ingestibles are toxic to dogs, including chocolate solids (theobromine poisoning), onion and garlic (thiosulfate, sulfoxide or disulfide poisoning[13]), grapes and raisins (cause kidney failure in dogs), milk (some dogs are lactose intolerant and suffer diarrhea; goats' milk can be beneficial), nutmeg (neurotoxic to dogs),[14] macadamia nuts, as well as various plants and other potentially ingested materials.[15][16] A full list of poison/toxic substances can be found on the ASPCA's website.[17]

Food allergies in dogs and hypoallergenic diets[edit]

Dogs are prone to have adverse allergic reactions to food similar to human beings. The most common symptoms of food allergies in dogs include rashes, swelling, itchy or tender skin, and gastrointestinal upsets such as uncontrollable bowel movements and soft stools.[18] Certain ingredients in dog food can elicit these allergic reactions. Specifically, the reactions are understood to be initiated by the protein ingredients in dog food, with sources such as beef, chicken, soy, and turkey being common causes of these allergic reactions.[19][20] A number of "novel protein" dog foods are available that claim to alleviate such allergies in dogs.[21]

Hypoallergenic diets for dogs with food allergies consist of either limited ingredients,[22] novel proteins,[19] or hydrolyzed proteins.[23] Limited ingredients make it possible to identify the suspected allergens causing these allergic reactions, as well as making it easy to avoid multiple ingredients if a canine is allergic to more than one.[22] In novel protein recipes, manufacturers use ingredients which are less likely to cause allergic reactions in dogs such as lamb, fish, and rice.[19] Hydrolyzed proteins do not come from a novel source; they could originate from chicken or soy for example. Hydrolyzed proteins become novel when they are broken apart into unrecognizable versions of themselves, making them novel to allergic gastrointestinal tracts.[23]

Grain-free and low-carbohydrate[edit]

Some dog food products differentiate themselves as grain- or carbohydrate-free to offer the consumer an alternative, claiming carbohydrates in pet foods to be fillers with little or no nutritional value. However, a study published in Nature suggests that domestic dogs' ability to easily metabolize carbohydrates may be a key difference between wolves and dogs.[24]

Studies published in 2018 suggest a possible link between grain-free diets and severe heart disease in dogs. While the FDA is continuing to investigate, recommendations against grain-free and exotic diets, based on findings of taurine deficiencies found in dogs on such diets suffering from heart diseases that are uncommon for their breed.[25]

Carbohydrates in dog food contribute to approximately 3.5 cals of energy per gram, the same as protein per the modified Atwater method of calculating metabolizable energy.[26]

Contamination issues[edit]

Melamine[edit]

In 2007, following a series of reports of renal failure in pets, there was a widespread recall of pet foods due to contamination found in ingredients produced in China. The contaminant was identified as melamine[27][28][29][30][31] which had been added as an adulterant to simulate a higher protein content.

Salmonella and other concerns[edit]

Recently, the FDA has released a video focusing on another major threat in commercial pet food: Salmonella bacterial contamination. They also cite other major toxins of concern.[32] The video references the case of a specific commercial pet food plant that was also the subject of a March 2014 study published in the Journal of the American Veterinary Medical Association. It details how at least 53 known human illnesses were linked to commercial pet foods made at that plant in 2012.[33] A class action lawsuit linked to this outbreak was recently settled.[34]

The video also cites the dangers of over supplementation of nutrients in pet food. A study published in the Journal of the American Veterinary Medical Association in February 2013 suggested a correlation between liver disease and the amount of copper supplementation in AAFCO diets.[35]

In addition "taurine deficiency" has been found in dogs[36][37] and cats[38] fed commercial diets intended to be "complete and balanced". Not usually considered an essential nutrient in dogs, taurine is plentiful in most whole meats whether raw or cooked,[39] but is reduced in extruded diets. Cats require more taurine in their diets due to their increased rate of protein metabolism; taurine is usually synthesized in the body from methionine and cysteine, but cats' increased use of these amino acids in normal bodily functions mean that taurine itself must also be provided in the diet.

The above observations could also be explained by the rendered, highly processed source of meat being less rich in taurine and by the fact that some of the taurine is denatured during extrusion. Cats are obligate carnivores[40] and their natural diet would consist of high amounts of whole meat - thus what has been termed "taurine deficiency" causing dilated cardiomyopathy in cats, is more likely to be a deficiency in the production of commercial feed diets. Taurine is now artificially supplemented back into the diet after processing in the production of most commercial pet food. A similar dynamic occurred in the first half of the twentieth century with an epidemic of Pellagra[41] in humans living in the Southern United States. The cause was determined to be a deficiency of the essential vitamin niacin (B3), which was being destroyed in the mass processing of corn. Niacin was supplemented back into Southern diets and the disease was eradicated.

Mycotoxins[edit]

In April 2014, aflatoxin B1, a known carcinogenic toxin, melamine, and cyanuric acid were all found in various brands of USA pet food imported into Hong Kong. Since 1993, the FDA has confirmed concerns of toxins in feed grade (animal grade) ingredients, yet to date no comprehensive federal regulation exists on mycotoxin testing in feed grade (animal grade) ingredients used to make pet food.[42]

In 1997, the journal of Food Additives and Contaminants established that low levels of various mycotoxins could cause health concerns in pets, and was found in feed grade ingredients.[43]

A study published in the Journal of Food Protection in 2001 cited concerns regarding fungi (the source of mycotoxins) in commercial pet foods and warned about the "risk for animal health".[44]

In 2006, a study published in the Journal of Agricultural and Food Chemistry confirmed mycotoxins in pet foods around the world and concluded that contamination of mycotoxins in pet foods can lead to chronic effects on the health of pets.[45]

In 2007, the International Journal of Food Microbiology published a study that claimed "mycotoxin contamination in pet food poses a serious health threat to pets", and listed them: aflatoxins, ochratoxins, trichothecenes, zearalenone, fumonisins and fusaric acid.[46]

A 2008 study published in the Journal of Animal Physiology and Animal Nutrition found high levels of mycotoxins in the raw ingredients used for pet food in Brazil.[47]

A 2010 study in the journal of Mycotoxin Research tested 26 commercial dog foods and found mycotoxins at concerning sub-lethal levels. It was determined that long-term exposure to low levels of confirmed mycotoxins could pose chronic health risks.[48]

For all the above reasons, a current trend away from feed ingredients, and toward USDA certified ingredients fit for human consumption has developed.[49]

Commercial varieties[edit]

A cup of kibbles.

Most commercially produced dog food is made with animal feed grade ingredients and comes dry in bags (also known in the US as kibble) or wet in cans. Dry food contains 6–10% moisture by volume, as compared to 60–90% in canned food. Semi-moist products typically run 25–35%.

Dry food[edit]

Dry food is both convenient and typically inexpensive, with over $8 billion worth being sold in 2010 – a 50% increase over just seven years earlier.[50] Dry food processing is popular in the pet food industry as it is an efficient way to supply continuous production of feed in various variety as it is energy efficient, allows for large amounts of feed to be used, and is cost effective.[51] To make dog kibble, a process known as extrusion is done.[51]

A simple extruder consists of a barrel, helical screws, and a die (tool to cut and shape food).[51] Some extruders in the United States also contain a fat distributor, where the food mixture enters the barrel of the extruder through a funnel-like structure.[52] Fat is stored in a container where it is pumped through a heat exchanger and fed through a line connected to the barrel of the extruder with a valve to prevent backflow of fat.[52] A metering device connected to this line allows for control of fat amounts deposited in the mixture.[52] Pressure is applied by helical screws that is driven by a motor.[52] Food mixture is shaped through a die when extrusion process concludes; allowing fly knife to cut extruded feed.[52]

Mixture of feed ingredients are solid at room temperature, therefore, the extrusion process of these ingredients requires a temperature higher than this in order to soften or melt the mixture and allow for fluidity through the barrel.[51] In the United States, before entering the extruder, water is added to the starch mixture to elevate the moisture content to 20 to 35%.[52] During the extrusion process, the high amounts of pressure applied to the mixture forces it to enter through the die before exiting the extruder completely.[51] The material is put through high amounts of shear stress that generates heat which allows for mixture to come together.[51] Temperature in the extruder is raised to above 100 degrees Celsius by the use of steam, hot water, or other heat sources.[52] The pressure is increased to allow starch granules to gelatinize.[52] Fat used in US extruders is then added into the mixture at the metering zone of the extruder which allows for the incorporation of fat, but without affecting the product's ability to expand.[52] Feed mixture stays in the extruder for only 15 to 120 seconds before exiting through die openings.[52] As the feed exits the extruder, it is subjected to relatively lower amounts of heat and pressure, that results in the expansion of the product, creating its “puffed” kibble appearance.[52] The feed is expelled in one long sequence where it is cut to its desired size by a rotating fly knife.[52] As moisture of this extrudate is at roughly 20 to 35% of its weight, it is dried further in an oven to reduce its moisture content to 8 to 10%.[52]

Wet food[edit]

Wet or canned dog food is significantly higher in moisture than dry or semi-moist food.[53] Canned food is commercially sterile (cooked during canning); other wet foods may not be sterile. Sterilizing is done through the process of retorting.[54] A given wet food will often be higher in protein or fat compared to a similar kibble on a dry matter basis (a measure which ignores moisture); given the canned food's high moisture content, however, a larger amount of canned food must be fed. Grain gluten and other protein gels may be used in wet dog food to create artificial meaty chunks, which look like real meat.

After ingredients are combined, they are placed in a tank at the end of a canning machine.[54] From there, the mixture is forced through an opening and onto a metal sheet, forming a thickness of 8 to 12mm.[54] Next, the mixture is heated to thoroughly cook the ingredients.[54] Heating can be done through the means of ovens, microwaves or steam heating.[54] The sheet containing a layer of feed is passed through the heat source that displays heat to the top and bottom of the tray, allowing the internal temperature to reach 77 degrees Celsius at a minimum.[54] Once cooked, this mixture can be directly placed into cans to form a loaf or it can be cut into “meaty” pieces for chunks and gravy formulas.[54]

For canned pet foods in the United States, a process known as retort is employed to sterilize the product using steam.[55] It is important to ensure that the formulation made is resistant to bacterial contamination and spoilage.[55] The now canned mixture is placed in a retort where steam brings the temperature up to 121 degrees Celsius.[55] To ensure that heat reaches the center of the mixture, the can stays inside the retort for roughly 75 minutes.[55] However, some steam retorts are able to reach the center of the can in only 10 minutes.[55] 

Alternatives[edit]

In recent years, alternatives to traditional commercial pet foods have appeared. Many companies have been successful in targeting niche markets, each with unique characteristics. Some popular alternative dog food types are:

  • Frozen, also called fresh-prepared, comes in raw or cooked (not processed) form, some of which is made with ingredients that are inspected, approved, and certified by the USDA for human consumption, but formulated for pets.[56] Part of this growing trend is the commercialization of home-made dog food for pet owners who want the same quality, but do not have the time or expertise to make it themselves.[57] The idea is to skip the processing stage traditional dog food goes through. This causes less destruction of its nutritional integrity.
  • Dehydrated or freeze-dried comes in raw and cooked form. Products are usually air dried or frozen, then dehydrated (freeze-dried) to reduce moisture to the level where bacterial growths are inhibited. The appearance is very similar to dry kibbles. The typical feeding methods include adding warm water before serving. There is some concern of nutrients, such as vitamins, being lost during the dehydration process.
  • Pastuerized, requiring refrigeration. ‘’Freshpet’’ type products are lightly cooked and then quickly sealed in a vacuum package. Then they are refrigerated until served. This type of dog food is extremely vulnerable to spoiling if not kept at a cool temperature and has a shelf life of 2–4 months, unopened.
  • Specialty ‘‘small batch’’ type feeds sold through specialty stores or over the Internet. These generally consist of some form of cooked meat, ground bone, pureed vegetables, taurine supplements, and other multivitamin supplements. Some pet owners use human vitamin supplements, and others use vitamin supplements specifically engineered for dogs.[58][59]
  • Vegetarian dog foods are produced to assuage pet owner ethical concerns or for animals with extreme allergies. They are usually balanced and contain ingredients such as oatmeal, pea protein, and other protein substitutes for meat. A dog owner may choose to feed a vegetarian food for ethical and/or health reasons, or in cases of extreme food allergies.

Contents[edit]

Many commercial dog foods are made from materials considered by some authorities and dog owners to be unusable or undesirable.[60] These may include:

Less expensive dog foods generally include less meat, and more animal by-products and grain fillers. Proponents of a natural diet criticize the use of such ingredients, and point out that regulations allow for packaging that might lead a consumer to believe that they are buying natural food, when, in reality, the food might be composed mostly of ingredients such as those listed above.[61][62] More expensive dog foods may be made of ingredients suitable for organic products or free range meats. Lamb meal is a popular ingredient. Ingredients must be listed by amount in descending order.

According to the Association of American Feed Control Officials (AAFCO), animal by-products in pet food may include parts obtained from any animals which have died from sickness or disease provided they are rendered in accordance to law. As well, cow brains and spinal cords, not allowed for human consumption under federal regulation 21CFR589.2000 due to the possibility of transmission of BSE, are allowed to be included in pet food intended for non-ruminant animals.[63] In 2003, the AVMA speculated changes might be made to animal feed regulations to ban materials from "4-D" animals – those who enter the food chain as dead, dying, diseased or disabled.[64]

Dog treats are special types of dog food given as a reward, not as a staple food source.

One emerging differentiation between pet food qualities in the United States is the use of standard feed grade (animal grade) ingredients versus the use of USDA-inspected, approved, and certified ingredients fit for human consumption.[65][unreliable source?][66][unreliable source?] The USDA certification and approval process is among the best quality control programs in food production in the world.[67] The US Food and Drug Administration (FDA) has recently commented that the ingredients defined as feed in pet food (feed grade or animal grade) are not classified as generally recognized as safe (GRAS).[68] Examples of potential toxins include melamine, Salmonella, and mycotoxins. Only the language "USDA certified" or "USDA approved" is legally meaningful.[citation needed] Some companies will say "Made with ingredients from a USDA facility", or "USA Meat", which is misleading as it can include dead or dying animals or carcasses rejected from the human food chain and is not the same as USDA inspected, approved, or certified, which are FDA approved for human consumption.[69]

Packaging[edit]

Dry dog food (kibbles) is most often packed in multi-wall paper bags, sometimes with a plastic film layer; similar bag styles with film laminates or coextrusions are also used. Wet dog food is often packed in aluminum cans or steel cans. Packaging regulations for dog food are often very similar to corresponding regulations for human foods.[citation needed]

Raw dog food[edit]

Raw feeding is the practice of feeding domestic dogscats and other animals a diet consisting primarily of uncooked meat, edible bones, and organs. The ingredients used to formulate raw diets can vary. Some pet owners choose to make homemade raw diets to feed their animals but commercial raw food diets are also available.[70]

The practice of feeding raw diets has raised some concerns due to the risk of foodborne illnesses, zoonosis and nutritional imbalances.[71] People who feed their dogs raw food do so for a multitude of reasons, including but not limited to: culture, beliefs surrounding health, nutrition and what is perceived to be more natural for their pets.[72] Feeding raw food can be perceived as allowing the pet to stay in touch with their wild, carnivorous ancestry.[72] The raw food movement has occurred in parallel to the change in human food trends for more natural and organic products.[70]

Senior dog food[edit]

Senior dogs require specialized diets that are catered towards the aging animal. There are various physiological changes which a dog goes through as it ages. Commercially available senior dog diets address these changes through various ingredients and nutrients.

When looking for a senior dog food, one of the first things that should be noted is the energy content of the diet. The maintenance energy requirements decrease as a dog ages due to the loss in lean body mass that occurs.[73] Therefore, senior dogs will require a diet with a lowered energy content compared to non senior diets. Although senior dogs require lower energy content diets, they will also require diets that are higher in protein and protein digestibility. This is due to the fact that does have a reduced ability to synthesize proteins as they age.[74]

Joint and bone health is an important factor to be considered when purchasing a senior dog food. The addition of glucosamine and chondroitin sulfate have been shown to improve cartilage formation, the composition of synovial fluid as well as improve signs of osteoarthritis.[75] The calcium to phosphorus ratio of senior dog foods is also important. Calcium and phosphorus are considered essential nutrients according to AAFCO.

Gastrointestinal health is another important factor to consider in the aging dog. Sources of fibre such as beet pulp and flaxseed should be included within senior dog foods to help improve stool quality and prevent constipation.[76][77] A current technology that is being used to improve gastrointestinal health of aging dogs is the addition of fructooligosacchardies and mannanoligosaccharides. These oligosaccharides are used in combination to improve the good gut bacteria while eliminating the bad gut bacteria.[78]

The aging dog goes through changes in brain and cognitive health.[79] There are two highly important ingredients that can be included in senior dog foods to help prevent cognitive decline and improve brain health. These ingredients are vitamin E and L-carnitne. Vitamin E acts as an antioxidant which can prevent oxidative damage that occurs during aging.[79] L-carnitine is used to improve mitochondrial function which can also help to prevent and lower rates of oxidative damage.[79]

Skin and coat health is important in all dogs, but especially becomes important as dogs age. An important nutrient to look for in senior dog foods to support coat health is linoleic acid which can be found in corn and soybean oil.[80] Another important nutrient is vitamin A which helps with keratinization of hair.[81] Good sources of vitamin A for skin and coat health include egg yolk and liver.[82]

Immune system health has been shown to decline in aging dogs. The ratio of omega-6 to omega-3 fatty acids play an important role in providing optimal health.[83] Vitamin E can be used as an antioxidant in senior dog foods.[83] Pre- and probiotics can also be added to senior dog foods to help improve the good bacteria in the gut which furthers provides support for the immune system.[84]

Low-protein dog diets[edit]

According to The Association of American Feed Control Officials (AAFCO) nutrient guideline for cats and dogs, the minimum protein requirement for dogs during adult maintenance is 18% on a dry matter (DM) basis.[85] Other parts of the world would have a guideline similar to AAFCO. The European Pet Food Federation (FEDIAF) also stated a minimum of 18%.[86] AAFCO only provided a minimum, but majority of the diets found on the market contain a protein level exceeding the minimum. Some diets have a protein level lower than others (such as 18-20%). These low-protein diets would not be seen with growth and reproductive life stages because of their higher demand for protein, as such, these diets are for dogs meeting maintenance levels.[85] They can be purchased, such as vegetarian, vegan, weight control, and senior diets. Furthermore, this protein requirement varies from species to species. Cats have a higher protein requirement, stated 26% for adult maintenance by AAFCO, where a dog low-protein diet would not be suitable as a cat diet.[85]

Quality, digestibility and energy density[edit]

There are a few key components in regards to providing protein in a diet that need to be taken into consideration when evaluating the needs and if they are being met. These factors include the quality and digestibility of the protein provided in the diet, as well as the composition of the amino acids included, and finally the energy density provided in the diet.[87] As the quality, composition, and digestibility of the protein increase in a diet, there is less need to increase the amount of protein present in the diet, and the same can be said in regards to the energy density.[87] In contrast, high-protein diets will provide excess protein content after meeting maintenance demands; this can therefore lead to the protein being utilized in fat and energy storage.[87] Ultimately increasing risks for developing obesity and other health related issues.[88] However, higher protein in the diet helps reduce lean body mass loss,[89] but will not lead to an increase in size of muscle[90] unless paired with resistance exercises[91] or anabolic steroids under maintenance conditions.

Disadvantages[edit]

There is an increasing risk of the practice of coprophagy when providing low-protein diets to dogs, a negative correlation exists between the amount of protein fed and the occurrence of coprophagy.[92] Maintenance needs should still be met by low-protein diets, and the muscle turnover (i.e. synthesis and breakdown) will also remain at an optimal rate, as long as the amino acid intake remains balanced and there is no limiting amino acids.[92] However, there is a greater opportunity for amino acids to be balanced in diets containing higher protein content.[87]

Advantages[edit]

The dog's simple gastrointestinal tract contains a vast array of microbial populations; some members of this very diversified community include fusobacteria, proteobacteria, and actinobacteria.[93] The gut microbiota of the dog will be comparable to that of the owners due to similar environmental impacts. Not only are the microbes influenced by the dog's environment, but they are also impacted by the macronutrient content of the dog's diet.[93] The populations present and health status of the microbiota found within the gut can alter the physiological and metabolic functions of the dog, which then subsequently affects susceptibility to disease development.[93]

Fermentation and digestion in the hindgut of a dog can potentially be improved depending on the source and the concentration of protein provide in a diet. Greater digestibility due to higher quality ingredients, in addition to lower protein concentrations within a diet, will help promote beneficial outcomes in assisting the health of a dog's gastrointestinal tract.[94] Higher protein entering the gut will lead to more putrefaction that give rise to various toxins including carcinogens and increase the chances of many bowel diseases, such as colorectal cancer.[95]

The age of dogs and cats is inversely proportional to protein consumption.[96] As they age, the protein requirement decreases due to lower level of pepsin in their stomachs.[96] There has also been discussion about higher protein content in diets being inversely related with lifespan (i.e. negative relationship), where lower protein content diets were related to longer lifespans.[92]

Differences from low-protein cat food[edit]

Low-protein dog diets are fundamentally different from low-protein cat diets, due to significant differences between the protein requirement of the two species. A minimum of 26% crude protein on a DM basis is required for adult maintenance in cats according to AAFCO, compared to only 18% in dogs.[85] In addition, there is slightly more protein found in cat milk compared to dog milk, meaning that kittens are consuming more protein at birth compared to puppies.[97][98]

Cats are considered as obligate carnivores and dogs are known as omnivores.[87] Cats are thus unable to down-regulate the amount of enzymes they are using based on the amount of protein in the body.[87] Regardless if they were on a high- or low-protein diet, they would be using the same amount of the enzymes to break down protein.[87] In contrast, dogs are able to regulate the amount of nitrogen catabolic enzymes based on if they are consuming a high- or low-protein diet.[87] Cats also use much more protein for body maintenance than for growth, which is the opposite to dogs, meaning that cats have a higher protein turnover that consequentially increased their protein requirements.[87]

Vegetarian and vegan dog food[edit]

Like the human practice of veganism, vegan dog foods are those formulated with the exclusion of ingredients that contain or were processed with any part of an animal, or any animal byproduct.[99] Vegan dog food may incorporate the use of fruits, vegetables, cereals, legumes, nuts, vegetable oils, soya, as well as any other non-animal based foods.[100] The omnivorous domestic canine has evolved to metabolize carbohydrates and thrive on a diet lower in protein, and therefore, a vegan diet may be substantial if properly formulated and balanced.[101]

Popularity of this diet has grown with a corresponding increase in people practicing vegetarianism, and there are now various commercial vegetarian and vegan diets available on the market.[101]

Due to the exclusion of animal products and by-products which are primary ingredients of conventional dog food, many nutrients that would otherwise be provided by animal products need to be provided by replacement, plant-based ingredients.[101] While both animal and plant products offer a wide range of macro and micronutrients, strategic formulation of plant ingredients should be considered to meet nutritional requirements as different nutrients are more abundant in different plant sources.[102] Despite the large differences in ingredient sourcing, studies have demonstrated that a plant-based diet can be just as edible and palatable as animal-based diets for dogs.[102]

Some nutrients that require special consideration include protein, calcium, Vitamin D, Vitamin B12, taurine, L-carnitine, and omega-3 fatty acids, particularly DHA and EPA. Although their sources are more limited without animal products, it is possible to formulate a diet adequate in these nutrients through plant and synthetic sources.[102]

Potential risks in feeding a plant-based diet include alkaline urine and nutrient inadequacy, especially in homemade diets.[103][102] Adherence to recommendations by reliable sources is strongly advised.

Labeling[edit]

In the United States, dog foods labelled 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. The Dog Food Nutrient Profiles were last updated in 1995 by the AAFCO's Canine Nutrition Expert Subcommittee.

Critics argue that due to the limitations of the trial and the gaps in knowledge within animal nutrition science, the term "complete and balanced" is inaccurate and even deceptive. An AAFCO panel expert has stated that "although the AAFCO profiles are better than nothing, they provide false securities."[104]

Certain manufacturers label their products with terms such as premium, ultra premium, natural and holistic. Such terms currently have no legal definitions. There are also varieties of dog food labeled as "human-grade food". Although no official definition of this term exists, the assumption is that other brands use foods that would not pass US Food and Drug Administration inspection according to the Pure Food and Drug Act or the Meat Inspection Act.[citation needed]

The ingredients on the label must be listed in descending order by weight before cooking. This means before all of the moisture is removed from the meat, fruits, vegetables and other ingredients used.[citation needed]

Recalls[edit]

Dog food at a supermarket in Brooklyn, New York.

The 2007 pet food recalls involved the massive recall of many brands of cat and dog foods beginning in March 2007.[105] 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, 2007, the most likely cause, according to the FDA, though not yet proven, was 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 have been calls for government regulation of pet foods[by whom?], 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.

In 1999, another fungal toxin triggered the recall of dry dog food made by Doane Pet Care at one of its plants, including Ol' Roy, Wal-Mart's brand, as well as 53 other brands. This time the toxin killed 25 dogs.[106]

A 2005 consumer alert was released for contaminated Diamond Pet Foods for dogs and cats. Over 100 canine deaths and at least one feline fatality have been linked to Diamond Pet Foods contaminated by potentially deadly aflatoxin, according to Cornell University veterinarians.[107]

In recent years, recalls of traditional and raw commercial pet foods have become frequent due to increased awareness and testing by the FDA. A dynamic list of recall alerts is continually updated by the FDA.[108]

See also[edit]

References[edit]

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External links[edit]