largest litter of rats

hi i have a female that just had a large little of 19 baby rats. could this be gentic her first litter was 12

I feel that it is genetic, at least to a certain degree. I try hold back at least a few from each extra large litter for future breeders. Although I haven't really kept tabs on the average litter size in my entire colony, I rarely get litters under 12, and 20 isn't unheard of :D . When I get big litters like that, I try to pull a few when they are pinks so the ones left can grow quicker.

yeah i have pulled two two feed to my spotted python.