I have found that the crop size doesn't shrink significantly if they've lost weight. For example, right not I have a sick peacock that has lost about half of his weight. Normal weight for him is about 4kg (8.8 pounds). At his normal weight, his 5% crop volume is 200 ml. I started with 60 ml, and...
The amount one gives is based on crop volume.
Most crops can hold 5% of their body weight, but you want to start off with 2-3% depending on how sick they are, and build up to 5%.
A one pound is 454 grams
2% of 454 grams = 9.08 ml (round up to 10)
3% of 454 grams = 13.62 ml (round up to 14)
5%...