Our Gretna Fair Grounds OTB Casino has in Gretna, Louisiana and is open Mon-Tue. The. Gretna Fair Grounds OTB Casino has in Gretna, Louisiana and is open Mon-Tue 8am-1am, Wed-Thu 8am-2am, Fri-Sat 8am-4am, Sun 8am-1am. . Join online poker freerolls to win real money while practicing poker.