from https://en.wikipedia.org/wiki/Orc_(Middle-earth)
> Tolkien indicates that Orcs are "always hungry".[24] Orcs eat all manner of flesh, including men and horses, and there are frequent hints of cannibalism among Orcs. Grishnákh, leader of the Mordor Orcs, accuses Saruman's Uruks of eating Orc-flesh, which they angrily deny.[22] In Cirith Ungol, Gorbag suggests that Frodo (recently poisoned by Shelob) should "go in the pot"; Shagrat indicates that Gorbag could be "for the pot" for making such a suggestion.[25] Shagrat threatens to eat a disobedient orc, and after killing Gorbag he licks his blood from the blade.[26]
The interesting part is Uruks "angrily denying" eating ork flesh which might mean it was an insult to suggest they do. Furthermore, https://middle-earth.xenite.org/what-do-orcs-eat says the books give some descriptions of orcish cooking.
However, based on the overall attitude of orcs, I believe they would kill and eat each other to survive. But I think I was wrong to suggest that would be an acceptable solution to problem of long-term military supply logistics.