A day after banning polystyrene foam food and beverage containers, Brookline Town Meeting voted Wednesday to prohibit supermarkets and some other retailers from using disposable plastic checkout bags. The ban was approved by a vote of 142 to 53 after proponents showed Town Meeting members pictures of a cow chewing on a plastic bag and other animals entangled in the bags. Only disposable polyethylene bags will be banned. The new law will go into force in December 2013. Supermarkets, as well as some pharmacies and other retail stores, will be prohibited from using plastic bags that are not compostable or marine degradable.