Grevyi zebras jizz about 1.3 liters, most of which is an incredibly viscous gel, like hot glue. They have the largest balls of any equine, each the size and weight of a Nutella jar.
This evolved because ancient predation left 11 males for every 1 female, forcing them to reproduce by gang-rape, and selecting for sperm count over speed, grace, or intelligence, contrasting North African and Central Asian horse breeds.
t. horse semen expert
The breed had reached its limit in the early 70s. Grevyis zebras metabolically cannot support producing any more sperm than they already do, as a whole 85% of their 21 hour waking day is spent browsing. They physically cannot take in any more nutrients for their testicles naturally.
In a way they're OVER their limit, because testes tissue has become competitive with brain tissue for dietary zinc and reduced cranial volume significantly. They are literally too dumb to be trained and can't sustain complex herding behaviors.
