Donkeys are good guard animals.
This is a popular myth that has been perpetuated throughout history due to the donkey's fight response and natural aversion to canines. Donkeys are not inherently, guard animals, but will fight a predator if they feel threatened. They will only guard another animal if they have bonded with him/her, however it is unlikely that a donkey will bond with a different species. If a donkey is simply placed with a flock of sheep that it does not know, it is possible that it will not protect the sheep against predators.
Many of the donkeys at the Sanctuary were purchased with the intent to have a guard animal. When they did not perform their guarding duties as expected, they were neglected and/or abandoned.
Donkeys are good for calming a herd of horses or calves.
This practice is not in the donkey's best interest. Most livestock are fed an extremely rich diet full of grains and lush pasture. If a donkey is fed a rich diet, it can become extremely obese, which can cause hoof problems and lameness for the donkey.
Also, donkeys are herd animals and most content with their own kind. There is little, if any, reason for them to bond directly with cattle, and in our experience, horses tend to push donkeys around because they have a herd mentality that donkeys do not. There is a significant risk that a horse will not get along with a donkey amicably.
Donkeys are stubborn and stupid.
Donkeys are not flight animals like horses, so you cannot as easily scare them into certain action or behaviour. This is usually the reason that people believe that donkeys are stubborn. Horses evolved on plains where they have lots of space to run and many resources to choose from, whereas donkeys evolved in mountainous desert areas. The desert doesn't provide an abundance of resources such as food, shelter, etc and the mountains did not give them much space to run away. A donkey had to take the time to assess the situation to decide if it was dangerous enough to run, or if they should stay and fight. This cautiousness has led to a very developed sense of self preservation. If a donkey is unsure of where they're being led, it will stop and consider the situation before proceeding. Some call this characteristic stubbornness or stupidity. We call this naturally analytical behaviour "common sense".
Donkeys are horses with long ears.
Donkeys and horses evolved in very different environments, giving them very different anatomical characteristics.
For example, the donkey's long ears are an evolutionary example of their desert-walking ancestors. Their ears give them the ability to hear the call of another donkey up to 60 miles away. Their large ears also help to keep them cool by using them as a fan.
The digestive tract of the donkey is also different than a horse. Because food is scarce in the desert, donkeys utilize 95% of the nutrients in what they eat. Their digestive system can break down inedible vegetation and extract moisture from food much more efficiently than a horse. Donkeys do not need (and should not eat) alfalfa, high carbohydrate, protein, or sugar feeds. In fact, donkeys do not need any grain at all unless they are experiencing weight loss issues. Donkeys can become overweight very easily and will develop fat pads along their crest, back, and croup.
These are only a few of the differences between horses and donkeys.
Donkeys have a reputation for being strong pack animals and while this is true, they are not stronger than another animal of the same size. Donkeys can only hold up to 20% of their weight. Unlike horses, donkeys did not evolve as herd animals. Instead, donkeys traveled in small groups of around five donkeys and do not have a true leader like a herd of horses. While a herd of horses will run from a predator and the slowest of the herd will be killed, donkeys are more likely to stay and fight. Fight animals cannot show vulnerability to their opponents and so donkeys do not show their pain until they are very sick or critically injured. If you notice that a donkey is in pain or sick, it has likely been this way for some time and might not recover.