Basic Nutrients

Protein
Protein is a great source of energy, which is needed for growth and repair. It is also very important for promoting the production of antibodies for the immune system. This is why Puppy and Kitten formulas are much higher in protein. It also helps to maintain good muscle mass, stimulate hair growth and protect the skin. Protein is an essential nutrient and comes from many different sources (meat, cereal, dairy etc). Some protein sources are not as digestible as others and this is determined in its "Biological Value". In basic terms, this tells us how digestible the protein source actually is. For example, we know that chicken has a higher biological value than that of a cereal protein such as maize and therefore, it will be more digestible and you would need to feed less of it to get the correct amount of nutrients into your pet. Chicken is also much more palatable!
Carbohydrate
This is another good source of energy! Although dogs can live with low amounts of carbohydrates in their diets, they are not obligate carnivores like cats and therefore, do enjoy some carbohydrates like rice or pasta. There are many forms of carbohydrate and sometimes, diets can contain carbohydrate fillers, which are simply used to bulk the food out. These ingredients are cheaper and although you are likely to be paying less for the product, you will buy it more frequently and the dog may be going to the toilet more than necessary.
Fats
Believe it or not, fat is a very important nutrient……in moderation!!! Fat provides us with twice as much energy as protein and carbohydrates do. Fats provide the essential oils like Omega 3 and 6, which are great for the skin, coat and joints. They are also a natural anti-inflammatory! Fat also helps with the uptake of fat soluble vitamins (A,D,E & K) and makes the food more palatable.
Vitamins
There are two types of vitamin….Fat Soluble and Water Soluble.
Fat soluble vitamins are A,D,E &K. These are stored within the fat reserves of the body and released slowly into the system. Water soluble vitamins are B & C. These are released and used much quicker and can be lost through urination. If your pet is on a good quality food, all the vitamins they require will be in there and it is not advisable to supplement the food with multivitamins etc. Sometimes it can do more harm than good! So unless advised to supplement the food by your vet, just stick to a good quality diet.
Minerals
Once again, these should not be supplemented unless advised to by your vet for a particular condition. Minerals include Calcium and phosphorus (for good bones and teeth), sodium (for maintaining fluid balance), Iron (for transporting Oxygen around the blood) and Zinc (great for healthy skin).
Water
This is the MOST important nutrient for life. It helps to hydrate the body, regulate the body temperature, transport nutrients and eliminate waste products. Fresh clean water MUST be available to your pet at all times!
Dogs DO have a different nutritional requirement to humans and to cats and therefore they should not be fed human food or a diet specifically designed for cats. Long term, feeding these diets to your dog can lead to nutritional disorders. It is never too late to introduce your dog to a good quality dog food.