Slugs-- What causes them?

[Alicia]

I'm also trying to find out whether producing slugs could be partially genetic?

Sometimes. Caramel females tend to produce a higher number of slugs -- But! It kinda seems like caramels may be more (perhaps overly?) sensitive to high temperatures. . . . And high temperatures are a big contributor to a female laying slugs.

I'm not entirely sure if true slugs, the yellow, undeveloped eggs, are the fault of the male. Not saying it can't be, either. Infertile eggs, yes. I've seen some people refer to all DOA eggs as slugs, so I kinda just want to be sure we're all talking about the same thing

Slugs are just follicles that were ovulated before they could mature enough to become viable eggs. So, I kinda tend to think that the root cause is hormonal, and so influenced by all the things folks have already listed. High temps, age, too much or too little visceral fat, genetics, stress, diet, all have an impact on an animals hormone levels. Exactly when in the follicles' development a stress and hormonal imbalance occurs may well have something to do with it, also. Sometimes most follicles are good to go and so ovulation is initiated when one or two ova are not ready to finish the process of becoming shelled eggs . . . Or fully shelled eggs, what have you.

Or I'm just rambling