Leading stock exchange NSE today began trading in T-91 Bills, the shortest tenure debt securities issued by the government to meet its short-term borrowing requirements.In a statement, NSE said the interest rate futures of T-91 bills or 91-day Treasury Bills were received well by the market and 39,755 trades worth Rs 731.24 crore were conducted on the first day today.In order to meet its short-term borrowing requirements, the government issues three types of treasury bills through auction -- 91-day, 182-day and 364-day, which derive their names from their tenure or duration.NSE said trading members, including 14 prominent PSU and private banks and corporate clients, participated in trading the interest rate futures on T-91 day bills.The interest rate future for T-91 bills was announced by RBI in April last year, subsequent to which Sebi and RBI issued relevant circulars for the product and it was launched today by the NSE.