In news that is rocking the country music industry, Garth Brooks, the biggest-selling act in country history, announced Wednesday he “probably” will retire by next fall to spend more time with his three young daughters. “I never, ever thought in my life I’d say this,” Garth, 37, admitted on the Nashville Network’s “Crook & Chase” show, “but music is not the first thing in my life any more.” Of his daughters (with his wife, Sandy), who are aged 7, 5 and 3: “They just take your energy, and all of a sudden all you want to do is you want to do things that make them smile.” Garth plans to “lay low” for nine or 10 months, set up a big party and “probably announce our retirement at the end of next year.” Without elaborating on what “retirement” means, Garth did indicate he would no longer tour but would still write songs and, perhaps, movie scripts. “Writing seems to be what my bag is,” he said.