“World Spay Day” was proclaimed Tuesday in Seattle, a city known for its advocacy of family planning for both two-footed and four-footed residents.  The observance comes with the offer of free spay/neuter packages for pets, complete with vaccinations, through Friday at the Seattle Animal Shelter.The purpose of World Spay Day, as explained by Mayor Ed Murray, is to control pet populations, and keep dogs and cats off the streets and out of shelters.  Murray took a firm stand on animal population control, on which he is not likely to take heat.