Strict hygiene needs to be observed around your dog’s food, as you would with your own. An essential is a good air-tight container – there are some available quite cheaply in pound shops and the like. Make sure it is big enough to take a full bag of your chosen food. Empty the bag of food into the container. I always fill a smaller airtight box too, and put it in my freezer for 24 hours or so before feeding my dogs as this kills off any storage mites which may be lurking unseen. When the box is empty, wash it out and dry thoroughly before adding the new bag of food. Never mix bags of food. If one is contaminated, the whole lot will need to be thrown away. Far better to be safe now than sorry later.