Seasonal effect on semen availability and quality of racing pigeon in Thailand oleh Suwarak Wannaratana, Em-on Olanratmanee, Kuekaroon Charoenmuang, Thanvarath Boriharnthanawuth, Banpatee Tangtrongwanich, Thanawan Jongpattana, Yanita Sukhor, Arrita Kongthip, Thanida Sananmuang