May 4 (Reuters) - Canada’s main stock index opened lower on Tuesday after data showed a C$1.1 billion trade deficit in March, although gains in energy stocks limited losses. * At 09:31 a.m. ET (1331 GMT), the Toronto Stock Exchange’s S&P/TSX composite index was down 15.43 points, or 0.08%, at 19,197.73. Reporting by Shivani Kumaresan in Bengaluru; Editing by Amy Caren Daniel Our Standards: The Thomson Reuters Trust Principles.