Q. What is the nutritional and cholesterol content of pigs' feet? I cook them in boiling water seasoned with a quartered onion and carrot, salt, pepper and thyme. I serve the feet drained, lukewarm or cold, in a simple vinaigrette sauce to which I've added lots of chopped onion and fresh parsley.

A. Pigs' feet are for the most part bone, cartilage, fat and skin. The bone is not eaten. Both cartilage and skin are rich in collagen, a protein of marginal nutritional value. During boiling, collagen is converted to gelatin, which makes the feet more gelatinous but adds nothing to the nutritional value. The vegetables, vinegar and spices used to flavor the feet add little nutritionally. Fresh parsley, however, is an excellent source of vitamins C and A.

The following numbers come from The Composition of Foods, published by the Agricultural Research Service, a branch of the USDA. Vitamin data is not available, probably because very little research has been done on pig's feet. Also, the following numbers are an average of many pickled feet and may not accurately describe yours: 66.9 percent water, 16.7 percent protein and 14.8 percent fat.

Pork fat contains 70 milligrams cholesterol per 100 grams. That's not a lot compared to eating eggs for breakfast. They contain approximately 300 milligrams of cholesterol per yolk.

Q. I saw salsify in a health-food store the other day. They were 12 inch-long, 1-inch-thick, black, two-dollar-per-pound roots. What do they taste like? How many ways can they be prepared? And how much of the roots are wasted after peeling and trimming?

A. There are two types of salsify sold: Tragopogon porrifolius, the salsify or oyster plant, and Scorzonera hispanica, the black salsify. Both belong to the Compositae, one of the largest of all plant families (includes dandelion, artichokes and other thistles, jerusalem artichokes and other sunflowers).

At the beginning of this century, both species of salsify were commonly sold in areas populated by Italian immigrants. Both species have a notable oyster-like flavor when cooked. The flesh of both exudes a white sap when cut and both brown very quickly when peeled.

Prepare either as you would carrots: cut off both ends and peel with a swivel-bladed potato peeler (there is, approximately, a 22-percent waste factor). Then cut into two- or three-inch segments and drop into a bowl of acidulated water (1 tablespoon lemon juice or distilled vinegar per quart of water). Acid inhibits the polyphenolase enzyme responsible for the browning reaction.

Boil in lightly salted water for about 15 minutes. Use the standard knife test to tell doneness: if the tip of a knife can be inserted into the thickest piece with little effort, the vegetable is done. Drain in a colander. From this point, there are numerous, delicious applications. Here are five:

* Salsify Provencale: Saute' in butter until slightly golden, add chopped garlic and parsley, heat 30 seconds and serve.

* Salsify Au Gratin: Place in buttered baking dish and cover with your favorite white sauce (be'chamel), dot with butter and sprinkle with swiss cheese, bake 15 minutes in 450-degree oven.

* Salsify Mornay: Same as au gratin, except mix shredded gruye re into white sauce and add an egg yolk blended with a half cup of whipping cream or cre me fraiche.

* Fried Oysters: Bread each piece by dredging first in seasoned flour (1 cup all-purpose sifted with 1 teaspoon salt and 1/4 teaspoon white pepper), dipping in beaten egg and then rolling in dried bread crumbs, fry until brown in 375-degree oil, drain on paper towel and serve plain or with tomato sauce spiked with horseradish on the side.

* Salsify Salad: Toss with a vinaigrette or vinegar and oil, a little chopped fresh coriander, and then arrange in piles alternating with heart of palm, avocado slices and tomato wedges on a plate lined with a bibb lettuce or radicchio.