Blood trailing is not the same as a track. or at least that is what I was told. Blood scent does not break down like a tract will, So a 16 hour hog track is not the same as a 16 hour blood trail.
On the contrary it is most of the time a deer is lost, it is done so because they lost the blood trail. Meaning the bleeding has stopped or plugged itself up. The dog has trailed it long enough to start to trail the animal now by scent. I truly believe some dogs might have a better nose than others but you seperate them on their drive some have the ability to trail or push a track but won't. The handler sometimes must make the dog push the track and teach them what you want out of them.
In 1991 we were rounding up cattle south of Marfa and the hunter's found a fresh kill, this was at 9am. We called a buddy Rick to let him know if he wanted to run the Lion. We walked up the mountain to scout and verify the kill we found the kill and jumped the lion and pushed him off the kill. We went back to Ft. Davis to load up everything mules and dogs we got back out their the next morning at 6am. I was was telling myself there was no way these dogs were ever going to run this almost 20+ old track. I be go to hell if the dogs circled the kill and picked up the exact path the Lion bolted out. Those dogs ran for almost 9hrs before they lost him down a very steep bluff. I was truly amazed by that pack of dogs.