Cottonseed meal
Cottonseed meal is a by-product of oil extraction from cotton seeds. Cottonseed meal contains around 40% crude protein and 20-25% neutral detergent fiber, which is similar to that in canola meal (NRC, 2012). Compared to soybean meal, canola meal contains lower crude protein, lower concentration of lysine and most essential amino acids, and greater fiber content. The limitation to the use of canola meal in swine diets is the anti-nutritional factor gossypol found in the pigment glands of cotton seeds. The free form of gossypol is toxic and not allowed over 100 ppm in complete diets for pigs (Gadelha et al., 2014). Heat processing of cotton seed is used to inactivate gossypol, but heating allows free gossypol to bind to lysine and reduce lysine digestibility (González-Vega and Stein, 2012). New varieties of cotton seed so-called glandless cottonseed do not contain gossypol, but unfortunately are not common (Stein et al., 2016).