Zexious - I strongly disagree. I live with my horses. I am with them 24/7, there's not much they can hide from me as for what they're feeling.
About a week ago our rescue lost a member of our herd. She was a mare born with us 26 years ago. She was raised with us and knew every rescue that came and went. She developed cancer (the same thing that killed the rest of her family). The horses at our rescue have seen lots of death, their response is always the same. In this case the mare got progressively more sick for weeks on end. She lost weight and couldn't sleep. At first the herd carried on as normal, some overtaking her in leadership, she slipped to the bottom of the herd. But as her weight dwindled I watched as her friends would find food for her, they would dig up some grass under the snow and call to her, when she came they stood over her as she tried her best to eat it. Of course we offered her a buffet of food, anything she would eat she could have, but she couldn't eat and couldn't sleep. On the last day of her life we knew it was over, we brought her to her paddock and let her friends be with her. They stood around her all day, she trembled and fell to the ground (the vet was at an emergency but on her way). Her owner and I stayed with her, holding her head out of the mud. The entire herd, even the ones in other fields were at their fences watching. All of them quiet, no one asking for food or fighting with each other, just watching. Her friends in her field let us be with her. The vet arrived and euthanized her, as the life fell from her eyes there was a collective sigh among the horses. Even our 8 month old colt who had only known her for two was watching with his head low. They licked their lips submissively, they shifted their weight around uncomfortable, and but they were all quiet. When we left to get the tarp to cover her until the backhoe arrived, her friends surrounded her. They took turns touching her body and nosing at her gently. They knew she was gone and they were sad.
Our barn is usually loud with horses demanding their next feeding and their blankets changed or to come in or go out or their friend not being where they could see them - there's always a fuss. But not this week. The week went by eerily quiet. Even our obnoxious OTTB stallion, who was her over-the fence buddy for 8 year, was quiet in his stall, not pawing or sticking his head out to moose anyone who walked by.
No one called to her - they knew she was dead.
NO one can tell me horses don't love, have empathy, or have sorrow. It's just not true. If you live with them every day and you really pay attention - not asking things of them, not being with them just to perform a job, not living with them on your terms - just share your existence with them, you will see what they're capable of.
I believe people choose not to believe horses are capable of sorrow, pain and loss because it would only make us feel guilty for what we put our animals through for our own benefit. But I believe there is a balance to be mutually beneficial. I will never tell anyone not to ride or work their animal - I would only say do it kindly and Ride with Empathy.