The NYT Magazine has an interesting piece on Postville, Iowa, a small town whose major employer is a meatpacking plant. Postville gained notoriety in 2008 because of a raid on the plant by immigration authorities that resulted in dozens of undocumented workers being arrested and deported.
At one point the article notes the low pay and bad working conditions in the industry and explains that only immigrants would be willing to take these jobs. Actually the pay in the meatpacking industry was not always bad. In the 70s the meatpacking industry was heavily unionized. The jobs were fairly well paying for workers with relatively education and generally had pensions and health care insurance.
During the 80s, many union plants were closed, driven out by lower paying non-union facilities that often operated with immigrant workers. While meatpacking may inevitably be an unpleasant job, there is nothing about the work that necessitates that it pay poorly.