I mentioned previously that orcs in my world have some extensive breeding traditions. While I do think that I could probably fill a book on the subject, let me try to summarize it here. After all the title of the post did mention elves vs orcs, so I should probably comment on orcs.
When an orc kills enemies, loots treasure, or generally succeeds in military ventures, he brings honor on his tribe/family. The way that he brings honor on himself is to father strong sons. His legacy is unquestionably dependent on his offspring.
I base this on the idea that orcs fight in more of a “mob”. There is no armored knight on a horse surrounded by his retinue. There is no general giving all the orders. The tribe attacks as a tribe and wins or loses as a tribe. Maybe it would help you to think more along the lines of “a zerg rush” or a “horde”. In order to win this type of warfare, you need overwhelming numbers which can only be produced by efficient breeding.
To establish efficient breeding, the various tribes have various ways of determining mating partners. One of the more common styles is that male orcs are assigned a wife for the “season” based on their successes the prior year. Some tribes measure success with war games or sports, while others base it on booty taken or trophies. But in some way, they figure out who their “best” are, and these best are allowed to breed with the best women. Sure, there is politics and scheming involved, but the ideal is to get the strongest men and the best breeding women together to produce the best orc warriors for the next generation of army. Yeah, the losers get to breed too, but they wind up with the least successful breeders if any are left for them.
Tangent course - this leads to a bunch of cultural issues. Men are not “married” to women for more than a season, though sometimes they may get the same “wife” for maybe three years running. After that, the tribe wants to increase their best chances by mixing things up. So the boys are raised by the women (in the women’s quarters) for a few years and then turned over to the military trainers. They don’t really know their fathers, though they most likely know which one of them it was. This lack of family makes them put more faith in their trainers and their tribe. Their father figure becomes the war chief or drill sergeant, so their loyalties are different than people raised in families. In fact most drill sergeants (forgive me for using that term, but you all know what I mean) are sterile orcs - successful in battle, but unable to father, meaning they won’t play favorites, at least in theory. Oh, and if they don’t have enough males, it is the duty of the chief to take on more wives. Yeah! duty!
But in many situations, the tribe’s women decide which male gets which female every season. So in some tribes, the women are absolutely in charge. Yes, matriarchal orcs! It actually makes sense if you consider that if this is a raiding tribe, then the men are normally gone for long periods of time anyway. The females are the craftsmen, because the men are gone. The men are the hunters and gatherers, because the women are to be kept at home where it is safe. You don’t want to lose a stronger breeder because she was attacked by a boar while picking mushrooms; but the males are worth that risk.
This is a topic for another post, but I tried to research matriarchal societies. I wanted to see if there might be something I could steal from history and make my own. Guess what - There really aren’t any successful matriarchal societies. Don’t tell me that culturally men rule the world. We know enough history that there had to be matriarchal societies at one point or another. Why did they fail? I’ll link to the post when I write it.
So what other cultural points about orcs and their breeding programs? Well, the tribes are so entrenched in their breeding programs, that they cannot even have multiple tribes within the same military unit. Sure, multiple tribes can join together as a massive war band, but each tribe will fight mainly on its own. Rivalries between the tribes also justify them raiding each other, something that puts a constant strain on the Wembic Empire that is attempting to hold them all together. If random chance causes a tribe to have more girls than they believe they can afford to feed, they will sell the daughters of poor breeders, expecting them to be poor breeders themselves. So, yes, orcs will sell their own children as slaves, but it is not common. With the glory of the tribe being more important, there is a tendency by some poorer performing orcs to rely on avoiding the most dangerous aspects of combat and then rejoining their tribe at the end of the battle. Whatever you think of communal or socialist societies should come into play here, especially if you believe they lead to mediocre performance and a lack of risk taking.