When Jessie was on Meloxicam she stopped eating. Once off her appetite came back. Think it has to do with the piggy. Like humans they are all different.I do not recall Metacam resulting in loss of appetite.
Have you thought of investing in a blender and putting veggies into it and blending them in small amount of water and syringe feeding the juice? I use to blend red capsicum and rockmelon in mine and add to Critical Care. Jessie loved it.Unfortunately our Guinea pig doesn’t eat ANY vegetables.
Try warming the Critical Care a little and make watery so she can swallow it easier. For fibre I add Timothy hay and Oxbow pellets to a coffee grinder and add this when I make Critical Care. I put 5 teaspoons of the hay and pellets to 4 teaspoons of the Critical Care. How is your piggy going? Hoping all is well.