Is it likely that my future chicks get an underbite too if I keep him? Is it purely aesthetical, or could it be a sign of a more serious condition?
Count on it!
After hatching close to a thousand chicks.. more things are blamed on incubation parameters than the truth about genetics. Genetics
always matter.
There is nothing aesthetic about the beak misalignment.. it's about function.. misalignment *can* cause issues with eating and drinking AND preening.
I agree with the first poster, things get worse with age.
Thing about breeding.. if it's with intent.. often it means not keeping your "favorite". It's to me THE hardest choice. But it makes room for the next favorite.. And if you're lucky before long you will come up with one that has ALL the attributes you're looking for..
My first very "favorite lap cockerel" turned out to be the biggest bastard ever.. I was so nice to him, I was shocked, I thought he trusted me. I no longer make lap boys and I haven't been attacked like that since. Now they're handled by MY will instead of at their own convenience (not with any dominance intent, just clear communication).. Confidence in chickens is seen as friendliness when what it actually is is fearlessness.. not all fear is created equal..
healthy fear equals respect. I STILL expect ALL good boys and know that every single one is an individual. So please don't take my sharing as any sort of fear mongering.
I see opportunity.. for chicken dinner.
Understand please that I mean NO rudeness but speak point blankly with tons of compassion (+chicken incubating/rearing/breeding experience) but also understanding of life as a whole... and noting that you are specifically asking about culling.. that's what I would do.. IF my other choices were better.