If you're considering having a nursing mother cat spayed in order to prevent physical hardships and future litters, you may want to wait until her little ones are ready to wean. However, that scenario isn't realistic in all cases, especially when it comes to feral kitties.
Trapping feral cats isn't easy, even if you own a humane trap. If you are lucky to catch the mother cat in a trap one time, you are unlikely be so fortunate again. Cats are smart, and she will remember the trauma of being confined to a trap. Very likely she won't ever step in one a second time.
If you trap a lactating feral cat, the situation calls for a major decision on your part. If you're confident you will be able to trap her again later, you may opt to release her so she can continue nursing her wee kittens. If you're worried that you won't be able to repeat the success, you can speak to your veterinarian about doing a flank spay procedure instead of the more usual midline spay.
Kittens are totally dependent on their mothers until they're about a month old. The little guys need her milk to survive and thrive. Around 4 weeks after birth, mother cats typically start the weaning process, the gradual introduction of solid foods to the little fluff balls. The Animal Protective League advocates that if at all possible you not trap the mother cat until her babies have started eating solid foods. At this point, the litter should be able to handle as long as 24 hours without their mamma during the surgery and recovery. Even after kittens start weaning, mother cats usually continue nursing them intermittently.
Spaying does not disrupt the ability of a cat to nurse, no matter which spay procedure is used. When a veterinarian performs a flank spay on a lactating cat, it enables her to more comfortably nurse her kittens as she heals from the surgery. It also helps a caretaker to more easily monitor healing and see problems if they occur. According to the Austin Humane Society, the special ovariohysterectomy is done through an incision on the left side of the cat's body, rather than at the center line of the lower abdomen. The procedure gives a nursing cat the best of both worlds: Her reproductive organs are eliminated, but she's still fully able to comfortably nourish her existing litter.
Recovery time is crucial for all spayed cats, and the same instructions generally apply to flank spaying, notes the Austin Humane Society. The surgery is an invasive procedure, and rather intricate. Just to be safe, ask the veterinarian about any special instructions you may need to follow while helping the nursing cat recover.