Breed-specific sterilization should be the first step to curtailing what PETA calls a “human-safety issue” with pit bulls.
http://time.com/2891180/kfc-and-the-pit-bull-attack-of-a-little-girl/

The purpose of mandatory spay and neutering is to control and eventually diminish the stock of pit bulls. In turn, this will decrease the euthanization rate of pit bull type dogs.

It is estimated that raising the pit bull sterilization rate to 70% would keep the annual shelter killing toll of pit bulls close to 900,000 per year.
http://www.animalpeoplenews.org/anp/2011/11/19/editorial-the-shelter-killing-of-pit-bulls/

• Studies estimate that up to 1 million pit bulls are euthanized per year, or 2,800 per day
• Some estimates double that number.
• In the Los Angeles area alone, 200 pit bulls per day are put to sleep.
• A study by the organization Animal People reports a 93% euthanasia rate for pit bull type dogs, with only 1 in 600 pit bulls finding a “forever home”.
• Pit bulls and pit bull mixes average about 33% of shelter intakes nationally, but in large cities the numbers are as high as 40%-65%.
• About 75% of municipal shelters euthanize pit bulls immediately upon intake, without them ever having any chance at adoption.
• Pit bulls offered for adoption are usually the first chosen for euthanasia when overcrowding forces the shelter’s hand and decisions have to be made.

http://www.examiner.com/article/pit-bulls-and-euthanasia-rates

There are so many pit bulls in American shelters, they are often given away free.
http://www.news10.net/story/news/local/stockton/2015/05/14/stockton-animal-shelter-free-pit-bulls/27301167/
http://www.kvia.com/news/Local-animal-shelter-giving-away-pit-bulls-for-free/16832156

Current rates of spay/neuter
Numerous studies in the States show fewer than 25% of pit bull owners spay or neuter their dogs, even when offered at no cost.
http://www.animalpeoplenews.org/anp/2011/11/19/editorial-the-shelter-killing-of-pit-bulls/
http://time.com/2891180/kfc-and-the-pit-bull-attack-of-a-little-girl/” target=”_blank”>http://time.com/2891180/kfc-and-the-pit-bull-attack-of-a-little-girl/
http://www.kshb.com/news/local-news/kansas-city-returns-86365-of-100000-petsmart-pit-bull-grant

Research from veterinarians in over 600 veterinary clinics in the United States and published in the JAVMA in 2011 shows pit bulls have a very low rate of surgical castration.
Golden retrievers – 74% neuter and spay
Labradors – 72% neuter and spay
Beagles – 74% neuter and spay
Dachshunds – 66% neuter and spay
Pit bulls – 27% neuter and spay
http://scorchedearththepoliticsofpitb.blogspot.ca/