My bad, i assumed after you drank the tuna brine, you then ate it at some point during that difficult period and yes 2 oz of jerky isn't much all in all. In any case, to simplify it, i agree with what John Shannon wrote, as i suspect there were multiple factors. Keep the protein thing in mind though for the future, though that may not have been a big factor in this particular case. I have largely stopped eating any foods higher in protein while being very active on warmer or hot days, and i've noticed a bit of a difference in how much water i will need, how much i sweat, how hot i feel, etc. Btw, Cody Lundin is one of the people who talks about this in one of his books, and as he is a desert survivalist par excellence, he should know what he is talking about.
Conversely, i do the opposite when it's very cold and/or i'm less active on cooler days. I will eat more protein and fat, and definitely notice a difference in being warmer and more comfortable then. I saw some idiot on a reality, comedic t.v. show once, decide to eat only meats for a period, and he ended up being tired all the time, got the "meat sweats" bigtime and generally ran hotter than usual.