Small Animal Nutritional Requirements

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Small Animal Nutritional Needs and Diseases

Nutritional problems in dogs and cats are uncommon in industrialized countries, especially when they are fed high-quality, commercial, comprehensive, and balanced diets. When dogs and cats are fed imbalanced homemade diets, cats are fed diets formulated for dogs, or dogs and cats are fed particular human foods, nutritional problems are most common. Dog or cat meals, as well as custom diets based on a single food item, are insufficient. Calcium deficiency and secondary hyperparathyroidism can be caused by feeding dogs and cats primarily meat or even an exclusively hamburger and rice diet.  When fed to cats, raw freshwater fish contains thiamine antagonists, which can cause thiamine insufficiency. Vitamin A poisoning can be caused by feeding the liver to dogs and cats.

With an average body weight of 4–80 kg, dogs are a physiologically varied species. Puppies’ normal birth weight ranges from 120 to 550 grams, depending on the breed. A puppy’s first two weeks are spent eating, seeking warmth, and sleeping. Unless the bitch is unable to produce enough milk or the puppy is orphaned, external food sources other than the bitch’s milk are rarely required. In these situations, the puppy must be raised by hand. Puppy growth is rapid for the first 5 months, with pups gaining an average of 2–4 g/day/kg of their expected adult weight during this time. After 6 months, the rate of growth slows down, and growth can be finished in small and medium breeds by 8–12 months, and in large and giant breeds by 10–16 months.

Domestic cats, on the other hand, have an average mature body weight of 3.2 kg for toms and 2.8 kg for queens. Kittens typically weigh 90–100 g at birth. For the first 3–4 months, kittens grow at a breakneck pace, gaining 50–100 grams each week. At 150–160 days of age, the rate of growth slows down, and growth is normally completed in 200–220 days.

Dogs and cats require different nutrient concentrations in their food depending on their life stage.  AAFCO (Association of American Feed Control Officials) produces nutritional profiles for adult maintenance and reproduction in dogs and cats (Table 1. AAFCO Nutrient Requirements for Dogs a and Table 2. AAFCO Nutrient Requirements for Cats a).

Cats have some dietary requirements that differ from those of dogs, and when fed diets designed to fulfill the nutritional demands of dogs, they can suffer nutritional deficiencies. Unlike dogs, cats, for example, require vitamin A, arachidonic acid, and taurine in their diet. Cats also require more fat and protein, as well as the amino acid arginine and the vitamins niacin and pyridoxine, than dogs (vitamin B6). Cats lack the enzyme glucokinase, which has led to the misconception that cats can’t digest carbs. Hexokinase is an enzyme produced by cats that allows them to digest and utilize correctly processed food carbohydrates.

When well-intentioned owners give their dogs and cats certain human foods, they can cause difficulties. Raisins and grapes, for example, contain an unknown chemical that is toxic to dogs and can harm their kidneys. Chocolate includes theobromine, a methylxanthine, as well as a much lesser quantity of caffeine. Theobromine is metabolized much more slowly by dogs and cats than it is by humans. GI symptoms such as vomiting and diarrhea are the first signs of poisoning. Polyuria, muscle spasms, heart arrhythmias, convulsions, and death are all possible outcomes. Weakness, depression, vomiting, ataxia, muscle tremors, fever, and tachycardia are among symptoms of macadamia nut poisoning in dogs and cats. Thiosulfate is found in onions and garlic, and it can induce oxidative damage to RBCs, resulting in anemia. Garlic is less poisonous than onions. Persin is a chemical found in Guatemalan avocados that causes dyspnea, pulmonary edema, and pleural and pericardial effusion in goats and potentially dogs. Foods heavy in fat, such as chicken skin, might cause pancreatitis in some dogs. Broccoli poisoning has been noted in dairy cattle, but it is a little-known issue in dogs and cats. Sugar-free foods containing xylitol can harm a dog’s liver.

Nutrient deficits have also been observed in dogs and cats fed “natural,” “organic,” or “vegetarian” diets made with good intentions by their owners. Many published recipes have only been rudimentarily balanced using nutrient averages, if at all. Furthermore, most DIY diets are not subjected to the same level of inspection and testing as commercial complete and balanced meals. If pet owners want to feed their pets homemade diets, they should prepare and cook them according to veterinary nutritionist-created recipes.

Some nutritional illnesses are discovered as a result of other pathologic problems, anorexia, or a combination of the two. Malnutrition is frequently caused by carelessness on the part of the owner.


The most effective metric of energy for nutritional reasons is metabolizable energy (ME), which is defined as the percentage of a diet’s total energy retained by the body. Calories or joules are the most used units of measurement. Pet food caloric content is commonly stated in kilocalories (kcal), which equals 1,000 calories. Through growth, maintenance, activity, pregnancy, and breastfeeding, dogs and cats require sufficient energy to allow for effective protein usage and to maintain optimal body weight and condition.

The energy requirements of dogs and cats are not proportional to their body weight. Recent research suggests that dogs housed in households require fewer calories per day than dogs kept in kennels, but there is a lot of variation. Independent of body size, breed differences affect caloric needs; for example, Newfoundlands tend to require fewer calories per day than Great Danes. Activity level, life stage, % lean body mass, age, and environment are all factors that influence daily energy consumption. Even when precise calculations are employed, each animal may require up to 30% more or less than the specified amount. As a result, overall recommendations may need to be tweaked within the 30% range, and body condition assessment should be done frequently.

Many dog food ingredients have not had their ME values determined experimentally, hence they are frequently estimated using those for other monogastric species (such as pigs) or calculated using Atwater physiologic fuel values adapted for use with normal dog food ingredients. Similarly, the exact ME values for many cat meals are unknown, while it is thought that the same reasons that apply to dogs may apply. For dogs, the modified Atwater ME values are 3.5 kcal/g carbohydrates, protein, and fat, and 8.5 kcal/g fat. The impact of varying environmental temperatures on the nutritional requirements of dogs and cats is addressed in a recent NRC report and has been documented under certain conditions.

As ambient temperatures dropped from 14°C in summer to –20°C in winter, Huskies’ energy requirements increased from 120 to 205 kcal/kg0.75. Because most of the research was done under thermoneutral (68°–72°F [20°–22°C]) circumstances, the effects of ambient temperature on cats are not well understood. When exposed to temperatures of 23°C and 0°C, however, unacclimatized adult cats increased their daily calorie intake about 2-fold.

Caloric Requirements

Dogs and cats have a wide range of energy requirements. Age, neutering status, physiologic status (growth, gestation, breastfeeding, etc.), physical activity, environmental temperature, and any underlying disorders can all change daily kcal requirements in animals of the same body weight. Any kcal requirements recommendations are simply guidelines and may need to be adjusted based on the individual dog’s or cat’s response.

Calorie requirements for dogs and cats can be calculated using a variety of formulas. Calculating the resting energy needs is the first step in a simple procedure for healthy dogs and cats (RER). The RER is the amount of energy required by a healthy, well-fed animal at rest in a thermoneutral environment. It includes energy spent on physical activity recuperation and nutrition. RER can be calculated using both an exponential and a linear formula. The exponential formula (RER = 70 [body wt in kg0.75]) is applicable to any weight, but the linear formula (RER = 30 [body wt in kg] + 70) is only applicable to animals weighing between 2 and 45 kg.

The energy demand of a moderately active animal in a thermoneutral environment is known as the maintenance energy requirement (MER). It encompasses both the energy required to obtain, digest, and absorb food in sufficient quantities to maintain body weight and the energy required for spontaneous activity. The formulas used to determine MER take age and neuter status into account.

Daily Maintenance Energy Requirements for Dogs and Cats contains formulas for daily maintenance energy requirements (kcal/day).

Table 1. AAFCO Nutritional Requirements for Dogsa

Nutrient (% or per kg of diet) Growth and Reproduction Minimum Adult Maintenance Minimum Adult Maintenance Maximum
Protein (%) 22.0 18.0
Arginine (%) 0.62 0.51
Histidine (%) 0.22 0.18
Isoleucine (%) 0.45 0.37
Leucine (%) 0.72 0.59
Lysine (%) 0.77 0.63
Methionine + cystine (%) 0.53 0.43
Phenylalanine + tyrosine (%) 0.89 0.73
Threonine (%) 0.58 0.48
Tryptophan (%) 0.20 0.16
Valine (%) 0.48 0.39
Fat (%) 8.0 5.0
Linoleic acid (%) 1.0 1.0
Calcium (%) 1.0 0.6 2.5
Phosphorus (%) 0.8 0.5 1.6
Ca:P ratio 1:1 1:1 2:1
Potassium (%) 0.6 0.6
Sodium (%) 0.3 0.06
Chloride (%) 0.45 0.09
Magnesium (%) 0.04 0.04 0.3
Iron (mg/kg) 80 80 3,000
Copper (mg/kg) 7.3 7.3 250
Manganese (mg/kg) 5.0 5.0
Zinc (mg/kg) 120 120 1,000
Iodine (mg/kg) 1.5 1.5 50
Selenium (mg/kg) 0.11 0.11 2
Vitamin A (IU/kg) 5,000 5,000 250,000
Vitamin D (IU/kg) 500 500 5,000
Vitamin E (IU/kg) 50 50 1,000
Thiamine (mg/kg) 1.0 1.0
Riboflavin (mg/kg) 2.2 2.2
Pantothenic acid (mg/kg) 10 10
Niacin (mg/kg) 11.4 11.4
Pyridoxine (mg/kg) 1.0 1.0
Folic acid (mg/kg) 0.18 0.18
Vitamin B12 (mg/kg) 0.022 0.022
Choline (mg/kg) 1,200 1,200

a Nutrient requirements are indicated on a dry-matter basis and are per kg of diet, not per kg of body weight of animal. These AAFCO nutrient profiles for dog foods presume an energy density of 3.5 kcal ME/g dry matter. Rations >4 kcal/g should be corrected for energy density.

Table 2. AAFCO Nutritional Requirements for Cats a

Nutrient (% or per kg of diet) Growth and Reproduction Minimum Adult Maintenance Minimum Adult Maintenance Maximum
Protein (%) 30.0 26.0
Arginine (%) 1.25 1.04
Histidine (%) 0.31 0.31
Isoleucine (%) 0.52 0.52
Leucine (%) 1.25 1.25
Lysine (%) 1.20 0.83
Methionine + cystine (%) 1.10 1.10
Methionine (%) 0.62 0.62 1.5
Phenylalanine + tyrosine (%) 0.88 0.88
Phenylalanine (%) 0.42 0.42
Taurine (extruded, %) 0.10 0.10
Taurine (canned, %) 0.20 0.20
Threonine (%) 0.73 0.73
Tryptophan (%) 0.25 0.16
Valine (%) 0.62 0.62
Fat (%) 9.0 9.0
Linoleic acid (%) 0.5 0.5
Arachidonic acid (%) 0.02 0.02
Calcium (%) 1.0 0.6
Phosphorus (%) 0.8 0.5
Potassium (%) 0.6 0.6
Sodium (%) 0.2 0.2
Chloride (%) 0.3 0.3
Magnesium (%) 0.08 0.04
Iron (mg/kg) 80 80
Copper (mg/kg) 5 5
Iodine (mg/kg) 0.35 0.35
Zinc (mg/kg) 75 75 2,000
Manganese (mg/kg) 7.5 7.5
Selenium (mg/kg) 0.1 0.1
Vitamin A (IU/kg) 9,000 5,000 750,000
Vitamin D (IU/kg) 750 500 10,000
Vitamin E (IU/kg) 30 30
Vitamin K (mg/kg) 0.1 0.1
Thiamine (mg/kg) 5.0 5.0
Riboflavin (mg/kg) 4.0 4.0
Pyridoxine (mg/kg) 4.0 4.0
Niacin (mg/kg) 60 60
Pantothenic acid (mg/kg) 5.0 5.0
Folic acid (mg/kg) 0.8 0.8
Biotin (mg/kg) 0.07 0.07
Vitamin B12 (mg/kg) 0.02 0.02
Choline (mg/kg) 2,400 2,400

a Nutrient requirements are indicated on a dry-matter basis and are per kg of diet, not per kg of body weight of animal. These AAFCO nutrient profiles for cat foods presume an energy density of 4 kcal ME/g dry matter. Rations >4.5 kcal/g should be corrected for energy density.


AAFCO (Association of American Feed Control Officials)

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