Abstract:
In the present study, a methionine-eficient (0.48% methionine) diet was formulated as control. Crystal methionine, encapsulated methionine, methionine hydroxy analogue (MHA), and methionine hydroxyl analog calcium salt (MHA-Ca) were added separately into the control diet to form four experimental diets with the methionine level at 0.58%. Jian carp with an initial body weight of 8.6 g were fed with these five diets and their growth rates were compared after eight weeks. The weight gain (WG) of the control group, crystal methionine group, encapsulated methionine group, MHA group and MHA-Ca group were 343.51%, 350.77%, 382.80%, 384.02%, 385.59% respectively; the feed conversion ratios (FCRs) of the five groups were 1.58, 1.55, 1.42, 1.42, 1.41 respectively. Compared to the control group, the WG increased by 11.4%, 11.8%, 12.2% in the encapsulated methionine group, the MHA group and the MHA-Ca group respectively (P0.05); the FCR decreased by 10.1%, 10.1%, 10.8% respectively (P0.05). However the growth was not affected by the addition of crystal methionine. There were no significant differences in the muscle moisture and crude fat contents between the five groups. The crude protein content in the muscles from the MHA group was significantly lower than that from the crystal methionine group. The free essential amino acids (FEAA) in the serum peaked at the first hour after feeding for both the crystal methionine group and the MHA group, which was one hour earlier than the control group. The serum FEAA of the encapsulated methionine group reached the maximum around the same time as the control group. The serum FEAA of the MHA-Ca group was observed to peak three hours after feeding. These results indicated that the growth of Jian carp could be improved by the addition of dietary encapsulated methionine, MHA, and MHA-Ca, but not crystal methionine.