Dietswere prepared by first grinding the dry ingredients (b0.3mm),
weighed accurately (~0.1 g) and mixed using a Groove-type mixer
(CH-50, Changzhou Golden Ball Drying Equipment Co., Ltd., China).
The oil was then blended into the mixture. After mixing, ZnSO4·7H2O
previously dissolved in water was added and mixed. The mash was
then pressed through a meat grinder (TY-432, Shang Hai Tai Yi
Machinery, China) and dried to approximately 10% moisture using electrical
fans at room temperature, then broken into small pieces, and
sieved to obtain pellets that were approximately 2.0 mm in diameter.
The dry pelletswere placed in plastic bags and stored at−20 °C until fed.