As I said in How big would a dog like the one described need to be to survive an attack by the big cat I’ve described?, A dog bred to defend livestock against liguars would need to be big, strong and agile, which are rather contradictory goals.

The mechanics of bones and joints means that for a given mass of muscle, an animal can be stronger, by having its muscles attach further from the joint, or faster, by having its muscles attach closer to the joint, but it's a trade-off between the two.

By adding more muscle, an animal can be both stronger and still fast, but muscle has mass, which slows a creature down.

So, the best compromise is going to be a tall dog with a muscular body and long, fairly slender limbs for its size, since like a pendulum, the closer the mass is to the fulcrum, the faster the limb will be able to move.

The dog will ideally have a long, narrow, relatively light head with a wide gape and long sharp teeth, but with large jaw muscles, to be both a physical and visible threat.

I would imagine that such dogs would weigh between 150 and 200 kg, so that they are big enough to be a threat to a liguar, but still small enough to be more agile than the 750kg cats.

I would fully expect that a small pack of such dogs could easily defend a herd against solitary liguars.

However, here comes the frame challenge:

By making liguars non-solitary hunters, even if during a small window of time, you drastically change their psychology. A pack hunter, especially one that is trying to impress a mate, is no longer cowardly. I can easily envision a pair or liguars deliberately stalking a separated dog, and killing it quickly and together, just to get it out of the way. It is common for predators to attempt to kill other predatory species if it can be achieved reasonably safely, and as a pair, the cats' odds go way up.

So, pairs of liguars could easily slaughter their way through a small pack of dogs over a night or two, and then it would be open season on the herd they were protecting.

In this scenario, it would make sense for the dogs to be armoured with spiked metal armour so that they could survive a surprise attack from a pair of liguars and potentially have the liguar injured in the attack on the dog. However, predators are seldom dumb, and they may well find a weakness to exploit even in this situation.

As I said in How big would a dog like the one described need to be to survive an attack by the big cat I’ve described?, A dog bred to defend livestock against liguars would need to be big, strong and agile, which are rather contradictory goals.

The mechanics of bones and joints means that for a given mass of muscle, an animal can be stronger, by having its muscles attach further from the joint, or faster, by having its muscles attach closer to the joint, but it's a trade-off between the two.

By adding more muscle, an animal can be both stronger and still fast, but muscle has mass, which slows a creature down.

So, the best compromise is going to be a tall dog with a muscular body and long, fairly slender limbs for its size, since like a pendulum, the closer the mass is to the fulcrum, the faster the limb will be able to move.

The dog will ideally have a long, narrow, relatively light head with a wide gape and long sharp teeth, but with large jaw muscles, to be both a physical and visible threat.

I would imagine that such dogs would weigh between 150 and 200 kg, so that they are big enough to be a threat to a liguar, but still small enough to be more agile than the 750kg cats.

I would fully expect that a small pack of such dogs could easily defend a herd against solitary liguars.

However, here comes the frame challenge:

By making liguars non-solitary hunters, even if during a small window of time, you drastically change their psychology. A pack hunter, especially one that is trying to impress a mate, is no longer cowardly. They have friends who can help injured group members to hunt and survive long enough to heal. I can easily envision a pair or liguars deliberately stalking a separated dog, and killing it quickly and together, just to get it out of the way. It is common for predators to attempt to kill other predatory species if it can be achieved reasonably safely, and as a pair or a pride, the cats' odds go way up.

So, pairs or prides of liguars could easily slaughter their way through a small pack of dogs over a night or two, and then it would be open season on the herd they were protecting.

In this scenario, it would make sense for the dogs to be armoured with spiked metal armour so that they could survive a surprise attack from a group of liguars and potentially have a liguar injured in the attack on the dog. However, predators are seldom dumb, and they may well find a weakness to exploit even in this situation.