Purebreds vs Mixed Breeds
When it comes to any domestic animal species in which distinct breeds exist it's easy to see a stark difference between those animals selectively bred to meet a breed standard, and those that are not.
To say one is better than the other is really silly and inaccurate. Both purebred and mix bred animals have their own pros and cons, and when choosing a new pet or breeding it's very important to keep this in mind.
In general the big pros of purebreds are predictability, and desired trait selection. You know what this animal should look like, and that gives you directional focus on selecting potential mates. They are predictable, which is very useful in domesticated animals, especially when it comes to breeding them for a specific purpose, be it work, production, or companionship. It's also a great source of pride for many breeders!
There are cons as well, though. Selectively breeding removes natural variety from the gene pool, which can have consequences such as weakened immune systems, lowered fertility, and susceptibility to different illnesses. There is also of course animals that are selectively bred for unhealthy traits, such as brachyphelmic snouts, lack of cartilage, and overproduction.
Mix bred animals have some wonderful pros that often directly counter the cons of purebreds. They are genetically varied, are extremely useful in understanding genetics, and generally have excellent fertility rates and strong immune systems.
Then the major downside to hybrids is that a lack of predictability and uniformity can result in unwanted and unexpected traits appearing. Without knowing what's in either parents' background you can accidentally produce terribly unhealthy animals.
Predictability is good, but so is genetic diversity. That's why many dedicated breeders of purebred animals will occasionally outcross their stock carefully. This requires work to be done to return to the breed standard and remove unwanted traits, but dramatically boosts diversity, and may also be used to add a trait missing in your lines.
For example, with my Langshans they are a solid, well-developed breed that really needs no improvement other than continuing to make wise decisions to keep them healthy and well mannered. They're also genetically diverse enough that crossing in a new breed would almost definitely do more harm than help. With them I boost diversity just by adding Langshans from other lines.
Orloffs, however, nearly died out which left them with a seriously inhibited gene pool and we lost the best examples, so we're building the population back from a small handful of subpar birds. The result is that, despite being a 400 year old breed, they're a project breed. In this case it may be worth it to outcross to other breeds in order to return them to what they're supposed to be. In the USA our birds are tragically undersized. We can line breed extensively, as we have, but this decreases fertility and eventually plateaus. So carefully introducing a different but similar breed to a line could seriously improve the breed, and after just a few generations (3 to 7 on average iirc) you end up with birds breeding true and looking like some really fine purebred Orloffs again. For me, specifically, I'm looking into getting a pair of Malay hens to put Miles over. Malays are part of the Orloff's original lineage and they have the type, size, build, and skull shape that were once typical of Orloffs. They do not, however, have the correct feather type, comb, temperament, or intense cold hardiness of Orloffs. So it's a trade off, and requires serious dedication to do right.
When crossing breeds it is extremely important to have a solid understanding of the genetics for your animals so that even when producing hybrids you have an idea of what to expect.
Sometimes, though, it can be fun and educational to cross breeds to see what comes of it! Chickens are great because if you already have a mixed flock like we do then it does no harm to add some barnyard mutts to the mix. Things like dogs, which are harder to keep in large groups, really should never be bred just to see what happens. Irresponsible breeding comes in both purebred and mix bred forms, as does responsible breeding.
Well, that's all of my babbling for tonight. Here's Miles in all his glory. He would like some giant wives.