During puppyhood, it is not necessary to worry too much about the exact growth pattern of a Schnauzer, as long as the dog does not become excessively fat. Once the dog enters adulthood, usually around one to one and a half years old, it is better to give one or two meals a day and to avoid excessive fat intake.
Pet dogs generally begin entering early old age at around seven to eight years. So if your Schnauzer has already reached that age, even though it is still technically an adult, you should start thinking about prevention of age-related disease. Meals should stay light and should not include sweet foods. To prevent obesity, daily exercise becomes even more important. Ideally, the dog should first go for a walk, relieve itself, and be groomed, and only then eat. In general, fixed meal times and fixed meal quantities are among the biggest secrets to maintaining the health of an adult dog.
Dogs are naturally carnivores. Their sharp teeth are designed for tearing meat, and much of their digestion happens in a very large stomach. However, after long life with humans, dogs have become much more omnivorous and can eat a wider variety of foods.
Even so, after generations of domestication, the dog's stomach is no longer as powerful as that of a wild animal. For that reason, a nutritionally balanced dog food is generally preferable to an unsystematic mixed diet. Unless the owner lives somewhere that commercial dog food is truly unavailable, long-term homemade feeding is usually not recommended for Schnauzers.
Water, meanwhile, is vital. Lack of water is even more dangerous to life than lack of food. So unlike meals, water should not be restricted to certain times. Fresh clean water should always be available so the Schnauzer can drink whenever it wants.
Just like humans, dogs need the three main nutrient groups to grow and stay healthy: protein, fat, and carbohydrates. A small dog may need around 90 kilocalories per kilogram of body weight, while a large 50-kilogram dog may only need around 49 kilocalories per kilogram. The heavier the body, the lower the requirement per kilogram becomes. Puppies also need roughly double the energy of adult dogs to support rapid growth.
Protein is broken down into amino acids and supports the development of organs, muscles, blood, bones, coat, skin, and claws. Fat stays in the digestive system longer and provides a sense of fullness, but too much fat with too little exercise leads easily to obesity.
Besides these major nutrients, minerals and vitamins are also indispensable. If they are lacking, bone development and disease resistance will both be affected. If a Schnauzer is mainly fed quality dog food, malnutrition is uncommon. But if the owner often makes food at home, then the ingredients must be properly matched, with meat, grains, and coarse staples included so that both protein and carbohydrate needs can be met.