Alliant Energy Corp. announced first-quarter earnings of $50.5 million, or 45 cents per share, compared with $32.2 million, or 30 cents per share, for the first quarter of 2009. Earnings for the Madison, Wis.-based utility business were positively affected by retail rate increases, weather and lower capacity costs, the company said. Operating results were "in line with our expectations," said Bill Harvey, the company's chairman, president and CEO, in a press release.