I have a sheltie that was over weight. All he wanted to do was sleep. I was only feeding him 1.5 cup of food a day and he went from 25 lbs to 34 it seemed like overnight. The vet did blood work and put him on thyroid meds for hypo -thyroidism and he is about 30 lbs now. He also is more playful and is very active on walks. I Dont think you are a bad parent. Good luck!
How tall is your sheltie? That's a lot of food IMO. My biggest 16 1/2" only gets a cup a day and my smallest 14.25" gets 1/2 cup a day.
I luv my furry little babies!
Does anyone else have Big Shelties? Also how do you measure yours? Maybe I didnt do it right...but I dont think I an far off