Since the dogs were little we have occasionally bought them dried liver as a treat. When Bertie became diabetic we had to stop buying commercial treats and went on the hunt for dried liver.
Our local pet shop lady told us we could make it ourselves and it would be much cheaper. We set about experimenting and have been producing our own treats for some time. It is really easy and just requires a bit of planning.
We use any liver but prefer ox as it is the least expensive and our favorite butcher now keeps one permanently ready for us. We wash the liver to remove all traces of blood then dry it very carefully to stop it sticking as much as possible. then we slice it as thin as possible. We cover baking racks or trays in non-stick baking parchment and put the oven on to somewhere between 70 and 100 degrees Celsius. This would be a low gas or warming oven in a range. In the winter we have the warming oven on all the time so we can do it at any time but in the summer we cook over night.
Lay the strips of liver on the trays so they are not quite touching and put them in the oven. We find the top tray cooks first for us so in the morning we then take that out and swap the other two trays over until they have dried. The liver is ready when it is dry and brittle at which point we remove it from the trays and break it into dog munchable pieces. This keeps really well in a sealed container for some weeks as long as it is thoroughly dry, although Bertie and Vickie would eat it all in a day if given the chance.
Our dogs love the treats and our neigbours dogs try and stop by for a treat as well.