Learning objectives: Identify the six essential nutrient classes; explain the role each plays; recognise the consequences of deficiency or excess.
In nutrition, “essential” means a nutrient the body cannot make in adequate amounts and must get from the diet. For dogs, six nutrient classes are essential.
1. Water
The most critical and most overlooked nutrient. Losing 10% of body water is medically serious; 15% is fatal. A rule of thumb is 50–70 ml per kg per day — a 7 kg dog needs roughly 350–500 ml of total water daily, much of it from food on wet or fresh diets. Always provide fresh water, even to dogs on wet diets. Dehydration in small dogs progresses fast.
2. Protein
Supplies the building blocks of muscle, organs, enzymes, hormones, antibodies and skin/coat. Dogs need ten essential amino acids they cannot synthesise: arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. Quality is measured by biological value (egg = 100, fish 90–95, chicken 85, beef 80, plant proteins 50–75) and digestibility. Adult diets should be at least 18% protein on a dry matter basis; good maintenance diets run 22–28%.
Taurine note: dogs can make taurine from sulphur amino acids, but some breeds (notably Cocker Spaniels) do it poorly. Taurine deficiency is linked to dilated cardiomyopathy.
3. Fat
The most calorie-dense nutrient — 9 kcal/g versus 4 kcal/g for protein and carbs. Fat carries fat-soluble vitamins (A, D, E, K), provides essential fatty acids, and makes food palatable. Essential fatty acids: linoleic acid (omega-6, required), alpha-linolenic acid (omega-3, required), and EPA/DHA (functionally essential from fish oil because dogs convert plant omega-3 poorly). Aim for an omega-6:omega-3 ratio of 5:1 to 10:1. Minimum dietary fat is 5% DM; most diets run 10–20%.
4. Carbohydrates
Dogs have no strict dietary carbohydrate requirement — but carbs are a cheap energy source, carry fibre, make kibble physically possible, and spare protein for tissue maintenance. Useful sources: white rice, brown rice, oats, sweet potato, pumpkin, barley, potato. The DCM concern: grain-free diets heavy in legumes (peas, lentils) have been linked to dilated cardiomyopathy — use exotic legume-heavy diets only with reason and ensure adequate taurine.
5. Vitamins
Fat-soluble (A, D, E, K) are stored in fat and liver — excess accumulates and can be toxic (especially A and D). Water-soluble (B-complex and C) aren’t stored well, so need regular supply; dogs make their own vitamin C.
| Vitamin | Function | Deficiency signs |
|---|---|---|
| A | Vision, immune, skin | Poor vision, dry skin |
| D | Calcium regulation, bone | Rickets, weak bones |
| E | Antioxidant, muscle | Muscle weakness |
| K | Blood clotting | Bleeding disorders |
| B-complex | Energy metabolism | Neurological/skin signs |
6. Minerals
Macrominerals (larger amounts): calcium and phosphorus (bone, teeth, nerves — aim for a 1:1 to 1.5:1 Ca:P ratio), sodium, chloride, potassium, magnesium. Microminerals (trace): iron, zinc, copper, manganese, selenium, iodine. The most common mineral problem in home-prepared diets is calcium deficiency — cooked meat and rice contain almost none, so a home-cooked diet without a calcium source produces deficient bones over months. It’s invisible until the damage is done.
Key takeaways
- Six essential classes: water, protein, fat, carbohydrates (functionally), vitamins, minerals.
- Water is the most critical and most underrated.
- Protein quality matters more than quantity.
- Fat carries fat-soluble vitamins and gives the energy density small dogs need.
- Carbohydrates aren’t strictly essential but are useful.
- The most common home-cooking error is missing calcium.
Practical task: For the dog you chose in Lesson 1.1, list which of the six nutrient classes you think their current diet covers well, and which you’re unsure about. We’ll return to this.