2.2. Diets and experimental design
All procedures were performed according to the guidelines for
animal experiments of the National Institute of Animal Health. The
animals were allocated to three treatments (each pig was considered
to be a replicate): the control group was fed the basal diet without
palygorskite, and two treatment groups were supplemented with
2000 mg/kg and 3000 mg/kg palygorskite, respectively, to replace the
same amount of powdered rice hulls in the basal diet. The animalswere
fed for 42 days, with ad libitum access to feed and drinking water. All
experimental diets without antibiotics were formulated to meet the
National Research Council (1998) requirements (Table 2).