Then they go further into the wagon. That smell that so few sheep smell grows stronger. They may see a pool or two as they walk. They may take a sip and think, "this tastes familiar". It is familiar. They may have tasted it from themself when growing up, they may have tasted it in the milk they drank, or something like that. It is a common thing to drink one's own blood, however, it is not common to drink from the blood of others. It's what makes vampires and stories like that so, eerie. The feeling that you could easily just, be influenced in a way that leads to your death and your blood to be drank. But, back to the sheep, they taste the blood and are filled with a sense of dread. Something's not right, and they know it, but they still push on.