The majority of homes have multiple pets. What happens when it is time for one pet to cross the rainbow bridge? Will the others know? Will they be sad?
At a spiritual level, yes, the other pets will know. But at the physical level they need to say GoodBye.
Most animals have loving relationships with the other pets in the home (or barn). They form bonds and friendships. There are even many circumstances where a “pair’ is together for a decade or longer.
Yes, the transition of one will make the other sad. Maybe even depressed.
Yes, if you don’t explain things to your pet they will wonder why the other pet just disappeared or never came home (barn).

Here are some ways to make this difficult event easier for the other animals in the home.
In either situation, leave something that belonged to your angel pet around the house/barn. Something the others animals can visit, stay close to, to feel comfort from. And explain again.
Explain to the other(s) what will happen and why.
Bring your pets together and tell them all it is time to say GoodBye.
Ideally, allow the remaining pets to see, smell, and process the angel pet’s body after the angel has transitioned.
If that is not possible, allow your angel pet to lay on a blanket while transitioning, wear a collar, or halter or have something on its body. Keep this on during the transition. Bring this item back to the other pets in the home/barn and leave it somewhere the animals frequent. The item (ideally a blanket or collar) will have the angel’s scent, as well as the scent of physical death (harsh term, I know. But it’s what animals smell). The animals will smell these scents and know what happened.
If you do the things above, the pets will understand and process the change. They will be sad. They will grieve. Like humans do.
Don’t forget them in the grieving process. They will need extra love and attention. Especially if they are the last animal left in the home, alone. Or if they lose the friend they were with for decades. Keep checking on them. Keep loving them.
And lastly, YES your angel pet will visit and your in house pets will see and feel the angel. This will help at a spiritual level. But like human, animals have a spiritual level and a physical level. The physical level will continue to grieve, missing their physical friend. Even though, like us, we know the angel is around.
Pets develop friendships, deep love, and connection with each other. They need you to help them get through it.