A effective way to knock out a giga is to have a tribe mate fly a quetz and let you grapple on to its chest that way you can tranq it from above and when it starts running you'll have a way to keep up with it and continue to tranq it.
I dare you to raise one!! They are savage if you got two high lvl parents (about lvl 140ish) and you get imprinting on it. The thing will become an adult with about 230% melee and basically one chomp any bronto!!! But on the down side you loose your job and your girlfriend
Breeding is best when u raise atleast 6 to 10 at a time. Reward is greater for same time period and time will pass faster for you while occupied feeding so many. Another trick is to run ur gachas for ele while you raise. Two things at once