Preheat an oven to 350. Bake the windpipes until just cooked through, about 15 minutes. Cool the windpipes until you can handle them. Meanwhile, cut the liver and trim into pieces the size of a nickel, then pass through the large die of a meat grinder.
Fit the meat grinder with a small gauge sausage stuffing attachment as shown in the picture. Put one end of a windpipe onto the stuffer, then stuff each windpipe full of the lamb liver-meat mixture.
When all the windpipes are stuffed, bake or smoked them for 20 minutes at 350, or until cooked through. Smoking the windpipes will give them a nice color, and extend the shelf life, but is optional.
Cool the windpipes, then cut into 1 inch pieces to make dog treats. From here, the windpipe pieces should be dehydrated at 145-150 F until crisp and dried, about 24 hours, or frozen for storage, as there is no salt to extend the shelf life. Under refrigeration they will last a few days.