You ain't seen nothin' till you see sausage being made.
As has been said, "Those who love law or sausage should not view too closely the process by which it is made."
everything except the squeal The phrase is used in Upton Sinclair's description of Chicago's meat packing industry (The Jungle, ch. 3: the tour guide says "They use everything about the hog except the squeal"), but I believe Sinclair was using what was already a commonplace description of the industry's efficiency.
Edit: Ch. 14 of The Jungle makes clear that the phrase predates with that book. In The Yankee of the Yards (1927), a biography of Gustavus Swift, it is at called a "hackneyed remark", with conjecture that it originated with a remark by Swift had been heard to make.
Edit #2: The remark does not mean that Chicago meatpackers systematically adulterated food products with unpalatable parts to the animal. Rather, "The enormous volume of animals meant that even body parts that had formerly been wasted now became commercial products: lard, glue, brushes, candles, soaps." A later federal report listed six hundred separate products produced by the pork and beef packers. The industry required such efficient use of the whole animal, for meat-sales alone did not cover costs of production, without the sales of hides and other by-products.
