Chicken has nearly as much tryptophan in it as turkey does. This is likely the issue, especially if you've noticed this feeling before when eating turkey.

Turkey isn't especially high in tryptophan, either - if I recall correctly, all animal meat has a lot. The post-thanksgiving 'turkey crash' is more an aspect of stuffing yourself silly than any tryptophan effect.

One belief is that heavy consumption of turkey meat (as for example in a Thanksgiving or Christmas feast) results in drowsiness, which has been attributed to high levels of tryptophan contained in turkey.[54][55][56] However, while turkey does contain high levels of tryptophan, the amount is comparable to that contained in most other meats.[18] Furthermore, post-meal drowsiness on Thanksgiving may have more to do with what else is consumed along with the turkey and, in particular, carbohydrates.[57] It has been demonstrated in both animal models[58] and in humans[59][60][61] that ingestion of a meal rich in carbohydrates triggers release of insulin. Insulin in turn stimulates the uptake of large neutral branched-chain amino acids (BCAA), but not tryptophan (an aromatic amino acid) into muscle, increasing the ratio of tryptophan to BCAA in the blood stream.

-- http://en.wikipedia.org/wiki/Tryptophan#Turkey_meat_and_drowsiness

There are actually lots of foods with tryptophan! It is particularly plentiful in chocolate, oats, bananas, durians, mangoes, dried dates, milk, yogurt, cottage cheese, red meat, eggs, fish, poultry, sesame, chickpeas, sunflower seeds, pumpkin seeds, spirulina, and peanuts. It is also found in turkey at a level typical of poultry in general. Tryptophan occurs naturally in nearly all foods that contain protein, but in small amounts compared to the other essential amino acids. The following foods contain tryptophan in significant quantities: red meat, dairy products, nuts, seeds, bananas, soybeans and soy products, tuna, shellfish, and turkey.

I do get a weird temporary lethargic feeling after eating a chicken. I don't get that with other meats. I can't offer an explanation.

Are you eating grain fed chicken? In my experience it's very hard to find chicken that are NOT grain fed (I live in Chicago). It's possible if you're very sensitive to grain that you are reacting to that and not the chicken. I've noticed this effect on me with wheat and soy in particular.

This is starting to happen to me. I made "beer butt chicken" the other night (drink half of a beer, put garlic, lemon, pepper, and herbs in the can, then set a chicken upright on the can, cover it in butter, salt, pepper and lemon juice, and grill/roast it for an hour), one of our favorite chicken preps.

I ate a bunch of it because I hadn't eaten all day (4-5 pieces), and the next day had a pretty wicked hangover. While I was eating it I had a bit of that oogie feeling like I'm eating McDonald's or something, but I was hungry... the chickens were "Nature's Promise" organic chickens, but these days I suspect the difference between "organic" chickens and "Frank Purdue chickens raised in a feed lot fed chicken manure" is unfortunately pretty small.

I was recently re-reading some Archevore stuff about omega-6 and omega-3 fats, and am wondering if being Paleo and losing weight is making me more sensitive to omega-6 fats or possibly some of the compounds that are found in factory-raised meat.