I own a working farm, I care about my animals, I have had sex with some of them, at times some of those animals have met their end by decisions I have directly made, but these are not easy decision for me to make. And I am far from driven only by money, given the choice I will always sell an animal in live sales to go and live more of their life on another farm rather than going to be directly be turned into meat. This has meant at times I have got less money in my pocket from the sale, but I feel far better about the transaction. If an animal is to die for my own consumption it is done quickly and humanely so they never get stressed or suffer.
Would the animal under my care have lived a better life while on my farm if I never had sex with them? No because I don't force animals into sex so whether or not I had been intimate with them does not effect how well I care for them. A happy life for the animal while here is always important to me.
I don't have pigs, but let me try and look at things from the farmers view point: So lets say that the breeding boars you were talking about were kept alive till they died natural deaths does the farm have adequate facillities to keep them separate once they've been retired, after being able to have sex for years are they going to be happy suddenly being told, no you can't do that any more. This might lead to fighting or aggression if the retired boar still thinks they are dominanent over their replacement. They could always be castrated to fix a lot of these issues, but where does the money come from to get a vet out to do this, does the farmer do the operation themselves they may not know how to do it properly to avoid pain to the animal. These boars still need to be fed which is going to use up pasture or cost money to keep them fed if food has to be brought in for them. yet they are no longer working on the other side of the equation to make any money for their upkeep. So at this point they are pets. This might be perfectly fine, but pigs live a good number of years so at what point do you end up with a yard full of pets that need more and more medical treatment to keep them happy and healthy as they age. What if the boars get out one night and breed every sow they can get a trotter over. Were they retired in the first place because their genes were becoming to dominant in the herd, could birth defects occur in the piglets if the sows they bred when they got out that night are line bred (in breeding with daughters and grand daughters) So you could sell the boars to another farmer, will anyone want to buy an older boar past his breeding prime? Have you spend generation refining for qualities that give you an advantage in the market place over the farmer next door, and if they got hold of the boar could they not steal all the effort you put into getting an animal that gave you an edge over the competition. If you sell them as a pet, is their temperament suitable for a hobby farm or to be around kids. Would they decide one day that little janie with that bucket of slops might be good to jump on and try and have sex with, they are not light animals a human as a partner isn't a new idea if they have done it before back in their breeding days.
If you are emotionally attached to an animal it can certainly sway the equation to going down the pet path without a question, but as I've tried to point out there is a lot more to it than first might appear. Sometimes a bullet is just the best out come in the situation.
I had a bull, I had had sex with him numerous times, I had a bond with him, but wasn't in love with him as such, he was hand raised and had no fear of humans he knew a human (me) could give him sexual pleasure, he weighed 800kg 10x my weight, which proved to be an issue when his foreplay got out of hand one night and he broke my leg. I needed to keep him seperate from some new calves and their mothers, but he wanted to breed the cows so he started smashing gates in attempts to get to the cows. Basically something had to give, he was well built enough for my needs, but he wasn't a prized breeding specimen so had no real value to other farmers as a bull for breeding purposes, so that meant the only place he would be going was to be turned into hand burgers. But how could I send him off for others to eat, who never knew his other side that friendly calf had been who followed you around or that strong lover who could milk ever last drop of cum out of me as I was draped over his back hugging his back while balls deep in his tail hole. So I made the phone call to a butcher who would come out to the farm and shot him out in the small paddock so he never saw it coming one minute he was eating fresh juicy grass he loved and the next it was all over. He kept me fed for well over 18 months and I thanked him every day for his gift of nourishment he had given me and vowed to remember him. Taking his life being a healthy young animal was very hard, but at the end of the day he had become a danger and it had to be done. So I did it the best way I could think to resolve the situation.
It's all far more black and white when your not the one making the call, life and death is not always easy when you hold it in your hands. How emotionally involved you are with an animal can hold a lot of weight and I would have moved heaven and earth to get one more day of life for my beloved GSD. But sadly farm animals bring a whole host of complicating factors with them it's far to often not a simple thing even for a zoo who cares about them.