America’s dog lovers apparently didn’t warm to CBS’s “Greatest American Dog.” The show debuted big last week but lost a lot of viewers in its second outing last night.

“Dog” averaged 7 million total viewers in the 8 p.m. timeslot, according to Nielsen overnights, down 26 percent from last week’s 9.5 million and falling to second place in the hour behind Fox’s “Are You Smarter Than a 5th Grader?” at 7.4 million.

Among adults 18-49, the show slipped 24 percent, from a 2.1 to a 1.6. “Dog” also slid 15 percent among adults 25-54, where it did well last week, going from a 2.7 to a 2.3. It did retain the top spot in the hour for that demo, however.

“Dog” pits pooches and their owners against each other in various competitions, all while forcing them to live together.

The show did jump from its first half hour to its second, always a good sign, though that may also have been in anticipation of 9 p.m. lead-out “CSI,” the night’s No. 1 show among total viewers with 8.7 million.

It was a generally weak night for broadcast, with the exception of Univision, which saw strong numbers among 18-49s for its “Premios Juventud 2008” special.

Univision and Fox tied for first for the night among 18-49s, each with a 2.2 average overnight rating and a 7 share. CBS was third at 1.7/5, NBC fourth at 1.6/5, ABC fifth at 1.3/4 and CW sixth at 0.5/2.
 
At 8 p.m. Univision led with a 2.2 for the first hour of “Premios,” followed by NBC with a 1.8 for the first half of “Last Comic Standing.” Fox was third with a 1.7 for “Are You Smarter than a 5th Grader?,” CBS fourth with a 1.6 for “Dog,” ABC fifth with a 1.0 for a repeat of “Ugly Betty” and CW sixth with a 0.6 for a “Smallville” rerun.
 
Fox took the lead at 9 p.m. with a 2.7 for “So You Think You Can Dance,” while Univision slipped to second with a 2.3 for the middle hour of “Premios.” NBC was third with a 2.1 for more “Comic,” CBS fourth with a 1.9 for a repeat of “CSI,” ABC fifth with a 1.1 for a “Grey’s Anatomy” rerun and CW sixth with a 0.5 for a repeat of “Supernatural.”
 
At 10 p.m. Univision regained the lead with a 2.1 for the final hour of “Premios Juventud,” with ABC second with a 1.8 for “Hopkins.” CBS was third with a 1.6 for “Swingtown” and NBC fourth with a 1.0 for “Fear Itself.”
 
Among households, Fox and CBS led the night, each with a 4.9 average overnight rating and a 9 share. ABC was third at 3.1/6, NBC fourth at 2.6/5, Univision fifth at 2.4/4 and CW sixth at 1.1/2.