If you're feeding your pet food that can sit on the shelf for months, it cannot have life in it. Live things begin to die. Cut an apple and sit it out - even if you put some lemon juice on it which has antioxidant properties to keep it from browning, it still won't keep for long. The small amount of Vitamin E in a package of pet food will not keep it fresh for very long either. Adding herbs and supplements to a pet's diet helps to build and maintain health, especially if you know there is a genetic weakness with a particular breed.
Herbs are rich in trace minerals which are the foundation of life.
Essential fatty acids are important for many functions of the body. Think about what you feed your pet and research the topic. It will not only educate you, but will save you and your pet much heartache down the road. We have had cats since 1977 and they have lived to 18 and 20 years old without the need for vet bills and the agonies of all the now common health problems. The kind of food you feed your pets is going to determine your pet's health problems more than anything else other than abuse.