A dog is considered senior from the age of 7 in medium-sized breeds, and earlier in giant breeds (from 5-6 years). In Spain, thanks to advances in veterinary medicine and nutrition, many dogs reach 14-16 years with good quality of life. But to achieve this, feeding must adapt to the physiological changes that accompany aging. What worked at 3 years may be insufficient, or even harmful, at 10.
Physiological Changes in Older Dogs
With age, the dog's body undergoes transformations that directly affect its nutritional needs:
- Reduced basal metabolism: older dogs burn 10-20% fewer calories at rest. If intake is not adjusted, overweight is almost inevitable.
- Loss of muscle mass (sarcopenia): progressive physiological process beginning at 7-8 years. Paradoxically, the dog may gain fat weight while losing lean mass.
- Lower digestive efficiency: the ability to absorb proteins, fat-soluble vitamins and minerals decreases.
- Reduced kidney function: kidneys lose filtering neurons (nephrons) with age, limiting their ability to concentrate urine and eliminate waste products.
- Sensory changes: decreased sense of smell and taste can reduce appetite.
- Reduced intestinal motility: increases the risk of constipation.
Proteins: The Great Misunderstanding About Older Dogs
For years, protein restriction in senior dogs was recommended to protect the kidneys. This concept is now outdated. Protein restriction is only justified in dogs with confirmed chronic kidney disease (CKD) at advanced stages (IRIS 3-4). In healthy senior dogs, the current recommendation is to maintain or increase protein intake compared to the adult diet to combat sarcopenia.
Studies from the University of California (Davis) and the Waltham Centre for Pet Nutrition show that a protein intake of 28-32% dry matter (or more) with highly digestible proteins helps preserve muscle mass in older dogs. Quality is key: chicken, turkey, egg or fish proteins are better absorbed than soy or corn.
Energy and Weight: The Challenge of Balance
Many senior dogs tend to gain weight due to reduced metabolism. However, in very old dogs (over 12 years) or those with chronic diseases, the risk reverses: weight loss and poor appetite are warning signs. The key is to individualize:
- Overweight senior dog: reduce calories, increase fiber, maintain protein.
- Thin or weight-losing senior dog: increase caloric density, prioritize quality protein and fat, investigate underlying causes (dental disease, neoplasia, hypothyroidism).
Key Nutrients in the Senior Diet
Omega-3 fatty acids (EPA and DHA): EPA and DHA from marine sources have documented anti-inflammatory effects that benefit joint (osteoarthritis), cognitive (cognitive dysfunction syndrome) and kidney health. The therapeutic dose is usually 40-100 mg/kg/day of EPA+DHA.
Antioxidants: vitamin E, vitamin C, beta-carotene and lutein help neutralize oxidative stress associated with cellular aging. Some studies suggest that antioxidants may slow the progression of canine cognitive dysfunction syndrome.
Phosphorus: in dogs with compromised kidney function, moderate phosphorus restriction (0.3-0.6% DM) slows the progression of kidney damage. In senior dogs with healthy kidneys, this restriction is not necessary.
Fiber: moderate amounts of soluble and insoluble fiber improve intestinal motility and contribute to weight control. Prebiotics (FOS, inulin) also benefit the gut microbiota of older dogs.
Practical Feeding for Day-to-Day Life
Foods labeled "Senior" vary enormously in their formulation. Not all are better than a good quality adult food. When choosing food for an older dog, look at the protein (source and percentage), phosphorus content (if kidney disease is suspected), and caloric density. For dogs with specific conditions (kidney, cardiac, joint disease), veterinary prescription diets will always be superior to supermarket products.
Dividing the ration into two or three meals improves digestion and appetite. Slightly warming wet food can increase its palatability in dogs with reduced sense of smell.
