There are several criteria which decide how useful animals are as domesticated lifestock. When you pick your lifestock, you first need to consider which animals are actually useful to you. A useful animal is one which provides you with one of these:
- Food: Many animals are solely bred for their meat (like pigs) or their milk (like cows) or their eggs (like chicken). But even with animals which are primarily work animals it can be useful when you can eat them in case of a famine. By the way, when you only want to eat them, consider if it might be more effective to let them feed themselves in the wild and hunt them when you need food.
- Textiles: Animals which produce a lot of hair are useful because you can shear them in regular intervals and turn their hair into clothes, blankets, bags, tents, ropes and many other useful items. Spinning wool to thread and then weaving or knitting it into textiles is very time-consuming, though (especially when you don't have access to the right tools. A spinning wheel and draw loom help a lot). You can also obtain leather and fur when you kill the animal and skin it. But if you want an animal only for this purpose, then domestication has little advantage over hunting.
- Work: Providing you with food and clothing might be nice, but it is even nicer when your animal can do more than that. For example, transport cargo, carry you on its back, help you hunting, defend you and your property, pull your plow, eradicate pests or manage less intelligent lifestock. In order to be trainable, an animal must be intelligent enough to learn new skills and understand your instructions, but also obedient enough to listen to your commands. Domestic animals which fall into this category are horses and dogs.
Preferably you want an animal which ticks many of these boxes. One of the best multi-purpose domestic animals is the camel. You can shear it, you can ride it, you can milk it and you can eat it. But specialized animals can also be worth it. Pigs, for example, have no use for us except their meat, but are still worth it because no other domestic animal gains weight so effectively.
But then you also need to consider if you actually can domesticate them. In order to be domesticable, an animal must fulfill certain criteria:
- Diet: Food is always a scarce resource and you definitely don't want to breed anything which competes with you for it. So you want animals which eat something which exists plenty in your environment but which is worthless as a food source for you. Like grass, for example. Carnivores generally make bad lifestock, unless they eat animals you can't or don't want to eat (like cats do).
- Resilience: A dead animal is a useless animal, so you want animals which are robust. They should not be susceptible to disease and too hot or too cold weather, be stress-resistant and not be too picky about food quality.
- Danger level: You don't want any lifestock which can kill you. So when an animal is stronger than you, venomous and has sharp claws and teeth, that's bad. If it also happens to be aggressive, then you should really look for something else to domesticate.
- Ability to escape: You need to confine your animals somehow. Anything which can easily escape from their pen won't stay your lifestock for long. So you don't want animals which can jump, climb, fly (unless you can clip their wings) or dig very well. Unless, of course, their natural behavior will prevent them from escaping, which leads us to...
- Motivation to escape: There are animals which are loners and do not like living in groups. This makes them very hard to confine. What you want are herd animals which have a high level of loyalty to their herd. A whole herd is easier to control, because you just have to control the alpha animal and all others will follow. Some species might even accept you as their alpha animal and will then not even try to escape.
- Breeding behavior: Some animals have very strange and elaborate mating practices which are hard to accommodate in confinement. Those species which are very picky regarding their mates or require very specific circumstances to get into the mood do not make good lifestock. Preferably you want animals where you just put male and female into a pen and they immediately get it on. A short gestation period and a large number of offsprings makes it easy for you to improve your lifestock in both quantity and quality (through selective breeding).