'Huh... that looks... like a cow? I believe that's an animal native to the planet Earth, usually used as livestock...' Samus thought to herself.
If her information was correct, and this wasn't something she thought of too frequently, cows were kept for meat... and their milk.
What purpose could a cow upgrade have?
'Well... I'm all alone in this station, might as well sate my curiosity,' Samus thought to herself. If she were 'on the job' she probably never would've done something like this, but oh well. She could afford to slack off a bit right now.
Samus took the chip for the cow upgrade, noting the fact that it didn't just depict a cow, but one with a comically-enlarged udder, and installed it. The computer screen informed her that this was a zero-suit only upgrade, so she exited her armor.
The chip was still incompatible, and when she looked at the details on the computer screen again, saw that it wasn't just a zero-suit only upgrade, but one that required her zero suit to be more of a revealing two-piece swimsuit style, rather than a full bodysuit. One quick change later, Samus was standing in front of the computer, chip in hand, wearing her zero-suit with her midriff bare.
Wordlessly, she installed the strange upgrade... not realizing that she'd missed seeing the name entirely- 'massive milkers.'
What does the upgrade do?
1) Metaphorical- It gives her humongous, milk-filled lactating boobs.
2) Partial- Samus grows taller, her hips, butt, and thighs fill out, and a pair of cow horns and ears appear on her head. Oh, and of course her breasts inflate like huge milk-bloated balloons. (appearance based off of the minotaur women from Okayado's Monster Musume manga, except with human legs.)
3) Literal- In addition to her breasts enlarging, Samus sprouts an enormous, ready-to-burst udder crammed full of milk! (Not my thing, but anyone who wants to add go nuts)