Discussion
The presence of chitin interferes with the determi-
nation of crude protein in crustacean meal because
chitin contains nitrogen that is calculated as protein-
nitrogen. Cruz-Suárez et al. (1993) reported that a by-
product meal of Pacific white shrimp contained 11%
chitin and Calvo-Carrillo et al. (1995) determined that
RCM contains about 9% chitin. If these different
contents of chitin are considered to calculate real
protein content, then the crude protein content for the
red crab and shrimp-head meals are overestimated by
about 0.62% and 0.75%, respectively. Hence, crude
protein content of the experimental diets might be
slightly overestimated by about 1%. Nutrient compo-
sition of red crab varies seasonally and according to
method of preparation (Castro-González et al., 1995),
so the results presented in this study may not be
applicable to all red crab meals.