At places like the ASPCA mobile spay/neuter clinics where they spay and neuter thousands of kittens every year, I assure you the staff is always much less worried about kittens than adult cats on Spay Day. Kittens can eat the morning of the surgery since their metabolism is so fast. In fact they SHOULD eat a small meal 4 hours before to prevent hypo-glycemia. If you were ever to get to watch surgery on a kitten, you'll see that the blood flow to the reproductive organs in minimal so there is much less risk of bleeding than in mature animals.
Kittens wake up very quickly after the surgery and don't have the long sluggish recovery of older cats. Kittens can and should be fed right away after the surgery. Older cats must be fasted several hours and sometimes won't eat for a couple days due to recovery pain and discomfort. All in all, S/N surgery is quite simply easier on kittens than on older cats.
There are a couple of unfounded fears and false arguments going around about early S/N that are baseless.
1. I heard one uninformed person say that as adults the kittens will have underdeveloped urinary tracts and genital organs. The vets who have seen hundreds of these kittens later as adults say this is untrue.
2. Another myth is that the kittens will not grow to full adult size. This is actually not only un-true but the exact opposite is the case. The body's signal to tell the bones to stop growing is cued from a hormone excretion at puberty. Kittens who have been neutered before puberty actually grow very slightly larger than they would have normally. In cats, this isn't as noticeable as it is with dogs. Dog Breeders will often use this knowledge and timing to their advantage if they want a dog to meet specific Breed Standards. Neutering the dog early will cause the dog to grow larger, so the timing of S/N is important to meet specific category size standards to compete at the Dog Shows.
In the next blog, I'll talk about the importance of timing neutering when socializing kittens. Best, Mike