This would also fit to them (Alaunt Ventres) being muzzled:

"Cotgrave defines it, (Veantre), as a 'great & ougly curre of that kind, (having a big head, hanging lips, and slowching eares), kept onely to hunt the Beare and wild Boare.' Elsewhere (under Vaultre) he characterizes it as 'a mungrell betweene a hound and a mastife, or of a size between the Allan and great countrie curre; fit for the chase or hunting of wild Beares and Boares.' Godefroy (Diet de I'Ancien Frangais, Veltre defines it as a 'sorte de chien employe surtout pour la chasse de I'ours et du sanglier.'
It is of little doubt that the 'Veantre', as described above, was in fact the descendent of the old German hunting dogs that were first described by Germanic Law in the fifth century AD. There were two known forms of these old German Hunting dogs. One was a large, long legged, agile dog; the ancestor of the German Mastiff or Great Dane: The other was a shorter, stocky, broad headed Bull or Bear Biter, the ancestor of the Boxer and the English baiting Bulldog. "The Bull or Bear Biter is a not too large, but a strong, brave dog breed with a broad, short head. They grip everything that they are set on, but they are heavy. Because of their fierceness and meanness, they can easily become dangerous to people and animals..." Winckell 1800."

P.S. I am still not sure what "Ventre" means exactly here. I learned French at school and "ventre" means "belly", but I think it must have another connotation!