WASHINGTON, April 27 (Reuters) - The U.S. economy slowed in the first quarter as consumer spending grew at its weakest pace in nearly five years, but the setback is likely temporary against the backdrop of a tightening labor market and large fiscal stimulus. Gross domestic product increased at a 2.3 percent annual rate, the Commerce Department said in its snapshot of first-quarter GDP on Friday, also held back by a moderation in business spending on equipment and investment in homebuilding.