What is the ruling on eating horse meat when other meats are available, and is it permissible to eat part of it and throw the rest away? Is this considered extravagance?

Eating horse meat is permissible. Scholars have adduced as proof for this the hadith of Jabir ibn Abdullah (may Allah be pleased with them both): "On the day of Khaybar, the Messenger of Allah (peace and blessings be upon him) forbade the meat of domestic donkeys but permitted the meat of horses." And the hadith of Asma bint Abi Bakr (may Allah be pleased with her): "We slaughtered a horse during the time of the Messenger of Allah (peace and blessings be upon him) and ate it while we were in Medina."