DES MOINES — State legislators don’t seem eager to wade back into the hot-button issue of regulating giant livestock production centers despite pleas from environmental officials for help. The issue has dogged the Legislature for nearly a decade, since livestock production techniques began to shift toward giant confinement operations. Many operations, especially hog production sites, now raise thousands of animals under the same roof. The matter has come up again following a decision Tuesday by the state Environmental Protection Commission to deny permits needed to build two operations in Dallas County that together would house nearly 15,000 hogs. The panel made the decision although the proposed operations met all the standards set out by a state matrix that assigns point values to different qualities, such as manure management plans, distance from neighbors and construction standards.