Something like “Mom, Dad, could we take like fifteen minutes to talk about the current situation with our animals? It’s become apparent that they aren’t healthy and taken care of the way they need to be. I’d like your permission to spend more time feeding, cleaning, and doing any other necessary chores for the animals to give them the best possible quality of life that we can.”
You could also talk about vet check ups and medical emergency bills…. Maybe you could make an agreement with your parents that if you do certain chores or something weekly/daily, they can cover vet bills. That, or you could ask if you can try to make some money or your own, whether that’s by washing cars, mowing lawns, etc, or get a job if you’re old enough.