HOUSTON—Lou Piniella finally decided to see what the youngsters could do for the Cubs, and, they delivered.Tyler Colvin hit a two-run home run and Koyie Hill had a two-run double as the Cubs snapped a four-game losing streak with an 8-5 victory over Roy Oswalt and the Houston Astros on Saturday night.Aramis Ramirez also homered and drove in two runs for the Cubs, but it was Colvin and Hill who made a big difference while each making their 15th starts of the season. The loss ended Houston’s four-game winning streak, tied for its longest this season.Ryan Dempster (4-5), who had lost five of his last six decisions, allowed six hits and three earned runs over 6 1/3 innings. He struck out seven. Oswalt (3-8) fell behind early on Ramirez’s second-inning homer. Ramirez added a run-scoring single in the fourth, and a sacrifice fly by Alfonso Soriano gave the Cubs a 3-2 lead after four innings.Consecutive doubles by Derrek Lee and Marlon Byrd provided the Cubs with another run in the sixth.Colvin hit his sixth homer in the seventh. Hill extended the lead with a two-run double in the eighth off Jeff Fulchino.Jeff Keppinger extended his hitting streak to seven games with his first homer of the season in the third for the Astros. Humberto Quintero homered in the seventh and added an two-run double in the ninth.Oswalt pitched seven innings and allowed nine hits, six earned runs and had one walk and one strikeout.Lance Berkman had an RBI single in the first, but the lead held only until the bottom half, when Ramirez slugged his 269th career homer over the left-field fence.Dempster had control problems in the first. He walked leadoff man Michael Bourn, who stole second and went to third on Keppinger’s grounder. Dempster then went to a 3-0 count against Berkman, who singled up the middle to score Bourn. Dempster had a full count on Hunter Pence, who grounded out to end the inning.Astros manager Brad Mills was impressed with the Cubs’ offense.Piniella also liked what he saw.

NOTES—Lee and Soriano each need one home run to reach 300. … Houston has the highest comeback percentage in the majors. They’ve rallied to win in 13 of their 21 victories, a .619 percentage. … Hunter Pence ranks second in the NL with 12 infield hits. … Oswalt started his 283rd game as an Astros pitcher, moving him into third place on the all-time list, one more than Nolan Ryan.