The word "knackers" is a term that is commonly used to refer to individuals who work in the animal slaughter industry. However, because it can be considered as a derogatory term, there are other words that can be used to denote the same meaning without being offensive. Some of these synonyms include slaughterers, butchers, meat processors, abattoir workers, and meat packers. These words are more professional and do not carry the negative connotations that "knackers" may have. It's important to use respectful language and avoid derogatory terms when referring to any profession or group of people.