The Nutrient Requirements of Dogs and the Digestibility of Nutrients in Light of the BARF Diet

Proper nutrition for dogs is essential for their health and well-being. In recent years, the popularity of the BARF (Biologically Appropriate Raw Food) diet has been increasing as many owners seek a more natural and healthier way to feed their pets. To properly formulate our dog's diet, it is important to know the nutrient requirements of dogs and the digestibility of various nutrients. 

Ensuring the appropriate nutrients not only improves their overall health but also prevents many diseases.

The Nutrient Requirements of Dogs

The nutrient requirements of dogs depend on several factors, including age, size, activity level, and health status. The main nutrients include proteins, fats, carbohydrates, vitamins, and minerals. Proteins are particularly important as they provide essential amino acids (arginine, phenylalanine, histidine, isoleucine, lysine, leucine, methionine, tryptophan, threonine, valine) necessary for muscle building and overall growth. Fats serve as a concentrated energy source and aid in the absorption of vitamins. Although carbohydrates are not essential for dogs, they can provide an important energy source, and plant fibers help with digestion and nourish the gut flora.

The Digestibility of Raw and Processed Proteins

The biological value and digestibility of proteins found in raw meats are often higher than those in processed foods. During cooking, the structure of proteins changes, reducing their digestibility. Some studies have shown that the digestibility of proteins in raw meats is over 90%, while in processed foods, this value can be significantly lower.

1. Enzyme Presence: Natural enzymes present in raw foods aid digestion. These enzymes can be destroyed during cooking, requiring the body to produce more of its own enzymes for digestion.
2. Nutrient Preservation: Heat from cooking can break down or reduce the amount of some vitamins and minerals (e.g., vitamin C, folic acid). Consuming raw foods allows for maximum utilization of these nutrients.
3. Fiber and Water Content: Raw foods have higher fiber and water content, contributing to better digestion and regulation of bowel movements.
4. Biological Value: The biological value of proteins is higher in a raw diet because proteins denature during cooking, reducing their utilization in the body.
5. Probiotics and Prebiotics: Raw foods, especially fermented raw foods, can contain natural probiotics and prebiotics that promote gut health and, thereby, digestive efficiency.

These factors all contribute to the higher digestibility and biological value of a raw diet compared to cooked or processed foods.

Resting Energy Requirement (RER)

Resting energy requirement is the energy a dog needs to maintain basic life functions at rest. This value is often calculated using the following formula: RER (kcal/day) = 70 * (weight in kg) ^ 0.75.

Gross, Absorbable, and Metabolizable Energy

1. Gross Energy (GE): The total energy found in food, regardless of how much is utilized. For example, the gross energy content of raw meats can be 5-6 kcal/g.
2. Digestible Energy (DE)The amount that is actually absorbed from the digestive system. It is derived by subtracting the energy of undigested parts from GE
3. Metabolizable Energy (ME)The amount the body actually uses. It is derived by subtracting the energy lost in urine and other metabolic products from DE.

RER and MER Calculation

Energy Needs Based on Activity Level

Example Calculations

1. RER Calculation for a 10 kg dog:
   • RER = 70 * (10^0.75)
   • RER = 70 * 5,62
   • RER ≈ 393 kcal/day
2. MER Calculation for a 10 kg moderately active dog:
   • MER = RER * 1,8
   • MER = 393 * 1,8
   • MER ≈ 707 kcal/day
3. RER Calculation for a 30 kg dog:
   • RER = 70 * (30^0.75)
   • RER = 70 * 14,73
   • RER ≈ 1031 kcal/day
4. MER Calculation for a 30 kg moderately active dog:
   • MER = RER * 1,3
   • MER = 1031 * 1,3
   • MER ≈ 1340 kcal/day

Gross (GE) and Metabolizable Energy (ME) Values of Nutrients

Explanation:

• Gross Energy Value (GE): The total energy value of nutrients, given in kilocalories (kcal) per gram.
• Metabolizable Energy Value (ME): The portion of the gross energy value that the animal can actually utilize. Some energy is lost during digestion, hence ME values are lower than GE values.

These values help determine how much energy different nutrients provide to the dog's body and aid in formulating the appropriate diet, whether traditional or BARF diet.

Digestibility Coefficient and Biological Value

1. Digestibility Coefficient: The ratio that expresses what percentage of a given nutrient is digestible. For example, the digestibility coefficient of raw meats is 90-95%, while that of processed foods is often 80-85%.
2. Biological Value (BV): The ratio that expresses how well a given protein is utilized by the body. The biological value of raw meats is generally higher as proteins can denature during cooking, reducing their utilization. The BV of raw meats is often above 90%, while that of processed foods is 70-80%.

Digestibility Coefficients for Raw and Processed Pet Foods

Explanation:

• Raw Pet Food: Higher digestibility coefficients as natural form nutrients are better utilized.
• Processed Pet Food: Lower digestibility coefficients as some nutrients degrade or become harder to digest during processing.

These values naturally vary depending on the individual animal's needs and the specific composition of the food. Digestibility can affect the animal's overall health and energy supply, so it is crucial that the diet is properly formulated.

Biological Value (BV) of Some Common Ingredients

Explanation:

• Egg: Highest biological value as it contains all essential amino acids in the right ratio.
• Lamb, Chicken, and Beef Meat: High biological value proteins but slightly lower than eggs.
• Rice: Plant-based protein source with lower biological value compared to animal-based proteins.
• Carott: Low biological value as it contains little protein and lacks all essential amino acids in the right ratio.
• Fish: High biological value, especially cold-water fish.
• Milk and Cheese: High biological value as they have a good amino acid profile.

Protein Requirements by Age and Life Stage

1. Puppies:
   • Puppies have higher protein requirements during growth and development. In the BARF diet, their diet should contain 22-28% protein on a dry matter basis for optimal growth and muscle development. This can be achieved by feeding raw meats, eggs, and dairy products.
2. Adult Dogs:
   • Adult dogs have more moderate protein requirements but still need high-quality protein intake. For the BARF diet, the diet of average adult dogs should contain 18-25% protein on a dry matter basis, provided by raw meats, organs, and other raw protein sources.
3. Senior Dogs:
   • Senior dogs also need adequate protein to maintain muscle mass and support a healthy immune system. Their BARF diet should contain 20-25% protein on a dry matter basis, and the protein should be easily digestible, such as in the form of raw meats and organs.

Protein Requirements by Activity Level

1. Low Activity Dogs:
   • Dogs with low activity, living indoors or older dogs have lower protein requirements but still need high-quality protein intake. Such dogs need a BARF diet containing 18-20% protein, provided by raw meats, fish, and eggs.
2. Moderate Activity Dogs:
   • Dogs with regular walks and moderate activity levels require a BARF diet containing 20-25% protein, consisting of raw meats, organs, and bones.
3. High Activity Dogs:
   • Active, athletic, or working dogs have higher protein requirements to maintain muscle mass and meet energy needs. These dogs require a BARF diet containing 25-30% protein, which includes a large amount of raw meats and organs.

Protein Requirements in Special Cases

1. Pregnant and Nursing Dogs:
   • Pregnant and nursing bitches have significantly increased protein requirements as the puppies need protein for growth and development. Such dogs need a BARF diet containing 25-30% protein, provided by raw meats, eggs, and dairy products.
2. Sick or Recovering Dogs:
   • During illness or recovery from surgery, dogs may have increased protein needs to aid tissue regeneration. In such cases, it is necessary to follow a veterinarian-recommended special BARF diet, often higher in protein content.

High-Quality Protein Sources in the BARF Diet

The best quality protein sources for dogs include:

• Raw meats: chicken, beef, lamb, rabbit, duck
• Raw fish: salmon, mackerel, herring
• Egg: raw or lightly cooked
• Dairy products: yogurt, kefir, cheese (in small amounts)
• Organsliver, kidney, heart
• Bones: raw, edible bones that provide calcium and phosphorus

The Role and Importance of Fats in a Dog's Diet

1. Energy Source:
   • Fat is a concentrated energy source, providing about 9 kcal per gram, compared to 4 kcal/gram for proteins and carbohydrates. The high fat content of the BARF diet is especially important for active and athletic dogs.
2. Essential Fatty Acids:
   • Fats contain essential fatty acids such as omega-3 and omega-6, which are vital for skin and coat health, brain function, and have anti-inflammatory effects.
3. Vitamin Absorption:
   • Fat is needed for the absorption of fat-soluble vitamins (A, D, E, K). The BARF diet contains these vitamins in natural form, and adequate fat intake aids their utilization.

Fat Requirements by Age and Life Stage

1. Puppies:
   • Puppies have higher fat requirements during growth. In the BARF diet, their fat intake should be around 15-20% of their total caloric needs.
2. Adult Dogs:
   • For adult dogs, fat intake should be about 10-15% of their total caloric needs, depending on their activity level.
3. Senior Dogs:
   • For senior dogs, fat intake should be slightly lower, typically around 10-12%, to avoid weight gain and potential cardiovascular issues.

Fat Requirements by Activity Level

1. Low Activity Dogs:
   • For low activity dogs, fat intake should be moderate, around 10-12%, to prevent overweight.
2. Moderate Activity Dogs:
   • For moderate activity dogs, fat intake should be 12-15% to provide enough energy for activity.
3. High Activity Dogs:
   • For high activity or working dogs, fat intake can be as high as 15-20% to provide sufficient energy for high physical demand.

High-Quality Fats in the BARF Diet

The best quality fats for dogs include:

• Animal Fats: chicken fat, beef fat, lamb fat, duck fat, goose fat
• Fish Oil: salmon oil, mackerel oil (rich in omega-3 fatty acids)
• Egg: egg yolk is an excellent fat source
• Coconut Oil: provides medium-chain triglycerides (MCT) when given in moderate amounts

Carbohydrates

1. Energy Source:
   • While fats and proteins are the primary energy sources for dogs, carbohydrates can also contribute to energy supply, especially for high-activity dogs. Fiber Source: Carbohydrate-rich vegetables and fruits provide fiber, which helps regulate digestion and maintain bowel movements.
2. Fiber Source:
   • Carbohydrate-rich vegetables and fruits provide fiber, which helps regulate digestion and maintain bowel movements.
3. Vitamins and Minerals:
   • Vegetables and fruits used as carbohydrate sources are rich in essential vitamins and minerals that contribute to the dog's overall health.

Carbohydrate Sources in the BARF Diet

1. Vegetables:
   • Low in calories but rich in fiber, vitamins, and minerals. Examples include:
     • Carrots: good fiber source and rich in vitamin A.
     • Spinach: high in iron and calcium.
     • Broccoli: rich in vitamin C and fiber.
     • Zucchini: low in calories but a good fiber source.
2. Fruits:
   • Can be excellent sources of vitamins and antioxidants when fed in moderation. Examples include:
     • Apples: rich in fiber and vitamin C but seeds should be removed.
     • Blueberries: high in antioxidants.
     • Bananas: good potassium source but should be given in moderation due to high sugar content.
3. Grains (optional):
   • Strict followers of the BARF diet avoid grains, but in some cases, they can be given in small amounts:
     • Rice: easily digestible and can serve as an energy source.
     • Oats: good fiber source and helps with digestion.

Carbohydrate Digestion and Tolerance

• Digestion: Dogs' digestive systems are better adapted to digesting proteins and fats, but they can also utilize certain carbohydrates, especially when given in cooked or pureed forms.
• Tolerance: Some dogs may be sensitive to certain carbohydrates, such as grains or high-sugar fruits. New carbohydrate sources should always be introduced gradually, and the dog's reactions should be monitored.

Vitamin and Mineral Requirements

Vitamins

1. Vitamin A:
   • Function: Essential for eye health, immune system support, skin, and coat health.
   • Sources: liver, egg yolk, and fish oil.
2. Vitamin B Complex:
   • Function: Important for energy metabolism, nervous system function, skin, and coat health.
   • Sources: liver, meat, eggs, and leafy green vegetables.
3. Vitamin C:
   • Function: antioxidant, supports the immune system, and aids in collagen synthesis.
   • Sources: While dogs can synthesize vitamin C, vegetables, and fruits (e.g., broccoli, blueberries) can serve as supplementary sources.
4. Vitamin D:
   • Function: Important for calcium and phosphorus absorption and bone health.
   • Sources: fish oil and egg yolk.
5. Vitamin E:
   • Function: antioxidant, protecting cells.
   • Sources: eggs, vegetable oils (e.g., olive oil), and leafy green vegetables.
6. Vitamin K:
   • Function: Important for blood clotting and bone health.
   • Sources: liver, eggs, and leafy green vegetables.

Mineral substances

1. Calcium:
   • Function: Essential for bone and teeth health, muscle, and nerve function.
   • Sourcesbones, eggshell powder, and leafy green vegetables.
2. Phosphorus:
   • Function: Essential for bone and teeth health and energy metabolism.
   • Sources: meat, fish, and bones.
3. Magnesium:
   • Function: Important for muscle and nerve function and bone health.
   • Sources: fish, meat, and leafy green vegetables.
4. Potassium:
   • Function: Essential for muscle and nerve function and water balance regulation.
   • Sources: meat, fish, and vegetables (e.g., spinach, broccoli).
5. Iron:
   • Function: Essential for red blood cell formation and oxygen transport.
   • Sources: liver, meat, and fish.
6. Zinc:
   • Function: Important for immune system support, wound healing, and skin and coat health.
   • Sources: meat, eggs, and fish.
7. Copper:
   • Function: Important for red blood cell formation and nerve function.
   • Sources: liver, meat, and fish.
8. Selenium:
   • Function: antioxidant and supports the immune system.
   • Sources: liver, meat, and fish.

Natural Supplements in the BARF Diet

1. Fish Oil:
   • Nutrients: omega-3 fatty acids (EPA, DHA), and vitamin D.
   • Benefits: anti-inflammatory effects, cardiovascular health, and skin and coat condition.
2. Eggshell Powder:
   • Nutrients: Rich in calcium.
   • Benefits: bone and teeth health and maintaining calcium-phosphorus balance.
3. Liver:
   • Nutrients: Rich in vitamin A, B vitamins, iron, and copper.
   • Benefits: nutrient density and supporting blood formation and immune system function.
4. Spirulina:
   • Nutrients: Rich in proteins, B vitamins, iron, and magnesium.
   • Benefits: immune system strengthening and antioxidant effects.
5. Apple Cider Vinegar:
   • Nutrients: potassium and enzymes.
   • Benefits: upporting digestion and maintaining pH balance.
6. Green-lipped Mussel Extract:
   • Nutrients: glucosamine, chondroitin, and omega-3 fatty acids.
   • Benefits: joint support and anti-inflammatory effects.
7. Coconut Oil:
   • Nutrients: medium-chain triglycerides (MCT) and lauric acid.
   • Benefits: energy source, skin, and coat condition, and antibacterial effects.

Following the BARF diet requires that a dog's vitamin and mineral needs be met through natural sources. A varied diet of raw meats, fish, vegetables, fruits, and natural supplements ensures that the dog receives all necessary nutrients. Consultation with a veterinarian or nutrition expert is recommended to tailor the dog's diet to its individual needs and potential health issues.

Consequences of Excessive and Deficient Nutrient Intake

1. Proteins
   • Excessive Intake: Excessive protein intake can strain the kidneys as the elimination of nitrogen from amino acid breakdown requires increased kidney function. This can be especially dangerous for older or kidney-diseased dogs. Excessive protein intake can also contribute to obesity and increased uric acid formation, leading to gout.
   • Deficient Intake: Protein deficiency can result in slow growth, muscle weakness, reduced immune function, and overall health deterioration. The dog's skin and coat may also become weaker, leading to skin problems.
2. Fats
   • Excessive Intake: Excessive fat consumption can lead to obesity, increasing the risk of various health issues such as heart disease, diabetes, and joint problems. Additionally, excessive fat intake can cause digestive problems, such as diarrhea and pancreatitis.
   • Deficient Intake: Fat deficiency can cause energy deficiency, dry skin, dull coat, and reduced vitamin absorption. The lack of essential fatty acids can be particularly harmful as they play important roles in cell membrane formation and immune system function.
3. Carbohydrates
   • Excessive Intake: While not essential for dogs, excessive carbohydrate intake can lead to obesity and blood sugar fluctuations. This can cause insulin resistance and diabetes.
   • Deficient Intake: Carbohydrate deficiency can cause energy problems, especially for high-activity dogs. However, with adequate protein and fat, carbohydrate deficiency is less significant.
4. Vitamins and Minerals
   • Excessive Intake: Overdosing on certain vitamins and minerals can cause toxic effects. For example, excessive vitamin A intake can lead to bone and joint problems, while excessive calcium intake can cause kidney stones and bone issues.
   • Deficient Intake: Deficiencies in vitamins and minerals can cause various health problems. Vitamin D deficiency, for instance, can cause bone deformities, while vitamin C deficiency (though dogs can synthesize it) can lead to poor immune response and overall health deterioration.

Specific Deficiencies and Excesses in the BARF Diet

1. Calcium and Phosphorus Balance
   • Excessive Calcium Intake: A common issue in the BARF diet, especially if too many bones are fed to the dog. Excessive calcium intake can cause hypercalcemia, leading to kidney damage, muscle weakness, and heart rhythm disturbances. Vékony Blanka, Dr. Mák Erzsébet, and Balogh Lívia, in their book "Dog-friendly Diet," also mention that excessive bone intake can cause constipation and calcium overdose.
   • Calcium Deficiency: If the diet does not contain enough calcium, osteomalacia (bone softening) and bone fragility can develop, especially in growing puppies. Nadine Wolf's articles emphasize the importance of proper calcium and phosphorus ratios for healthy puppy growth.
2. Vitamin A
   • Excessive Intake: Overfeeding liver can lead to vitamin A overdose, causing bone and joint problems and liver damage. Vékony Blanka and colleagues in their book warn about the dangers of excessive liver consumption, especially for adult dogs.
   • Vitamin A Deficiency: While rarer in the BARF diet, insufficient liver and carrot consumption can cause skin problems, vision loss, and poor immune response.
3. Vitamin D
   • Excessive Intake: Overfeeding fish liver oil or other vitamin D sources can cause hypercalcemia, leading to kidney damage and bone deformities. Nadine Wolf's articles also warn about the risks of vitamin D overdose, especially in homemade diets.
   • Vitamin D Deficiency: Can cause bone deformities and weak bones, particularly in young growing dogs.
4. Iodine
   • Deficient Intake: Iodine deficiency can cause hypothyroidism (underactive thyroid), leading to weight gain, lethargy, and coat deterioration.
   • Excessive Intake: Excessive iodine intake, for example, through overfeeding seaweed, can cause hyperthyroidism (overactive thyroid).

The nutrient requirements and digestibility of nutrients in dogs are closely related to the mode of feeding. The BARF diet offers numerous benefits, including higher nutrient digestibility and better overall health. However, it is important for owners to be well-informed and consult with a veterinarian before switching to a raw diet to ensure adequate nutrient intake and minimize risks.

References

1. Freeman, L. M., Chandler, M. L., Hamper, B. A., & Weeth, L. P. (2013). Current knowledge about the risks and benefits of raw meat-based diets for dogs and cats. Journal of the American Veterinary Medical Association, 243(11), 1549-1558.
2. Varga, M., Dudás-Györki, Z., & Fébel, H. (2019). The effect of raw meat-based diet on the gastrointestinal microbiome and health of dogs. Magyar Állatorvosok Lapja, 141(6), 339-348.
3. Case, L. P., Daristotle, L., Hayek, M. G., & Raasch, M. F. (2011). Nutrition for Dogs and Cats: A Resource for Pet Professionals. Elsevier Health Sciences.
4. Vékony, Blanka, Mák, Erzsébet, Dr., & Balogh, Lívia. (2020). Dog-friendly Diet. Budapest: ABC Publisher.
5. Wolf, N. (2021). "Basics of Raw Diets for Dogs." Dog Magazine, 45(3), 56-63.