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When Can I Spay?
http://www.vetslovepets.com/articles/390/1/When-Can-I-Spay/Page1.html
Dr. Shawn Smith
Dr. Smith has raised and trained German Shorthaired Pointers for over 20 years. He raised and trained 3 of the first 12 Versatile Champion German Shorthairs in North America including the first two bitches. He is also a field judge. 
 
Practicing veterinary medicine for over 25 years, Dr. Smith uses conventional medicine and surgery, acupuncture, homeopathy, nutrition, and education to promote and restore optimal health in pets and animals. To educate and inform pet owners, he invites your questions, comments, stories, and humor to promote better pet ownership and health. He can be reached at veterinaryhospital@rogers.com
 
By Dr. Shawn Smith
Published on June 6, 2007
 
When can I have my dog or cat spayed after having puppies/kittens?

When Can I Spay?
When can I have my dog or cat spayed after having puppies/kittens?
 
Female cats may be spayed 6 (six) to 8 (eight) weeks after having puppies or kittens. This allows time for weaning and mammary glands to shrink in size. Caution should be taken with cats however, because they have been known to get pregnant while they are still nursing.
 
Female dogs are usually spayed 30-60 days after the pups are weaned, at about 6-7 weeks of age. Bitches won’t usually come back into heat until four months after the pups are born.