| The experiments were conducted to study the requirement of dietary protein and methionine for cage-rearing Jin-ding ducks from 0~18 weeks. The experiments were conducted in four periods, which were 0~4, 5~12. 13-18, 19-28 weeks.In experiment 1, the 1 day 324 Jin-ding ducks of commercial strain were assigned to 9 groups randomly, with 3 replicated per group and 12 ducks per repeats. A grouped feeding trial in 0-4 weeks period, metabolism trials in the 21 day~23 day and slaughter trials in the 28th day for laying ducks were conducted to determine the effect of nine isoenergetic diets (ME:11.91 MJ/kg) with different crude protein (CP) levels (CP: 17%, 19%, 21%) and methionine (Met) levels (Met/CP: 0.020, 0.025, 0.030) on the growth, utilization of nutrients and body deposit. The results indicated that different dietary CP and Met level had significant or great significant (p<0.05 or pO.Ol) effect on body weight gain , feed intake, nitrogen retention ratio, utilization ratio of energy (E), calcium (Ca), phosphorus (P) and deposit ratio of CP, Ca, p . But there were no significant differences (P>0.05) between the dietary Met levels and them with the exception of utilization ratio of P and deposit of Ca. Nitrogen retention ratio, utilization ratio of E. Ca, P decreased with increasing dietary CP level, and there were significant (PO.05) difference among different groups, but they increased with increasing dietary Met level. However no differences (p>0.05) were found in body weight gain among the ducks fed the different diets at 3 weeks of age. The ducks fed lower CP and Met content diets had higher body weight gain than those fed higher CP and Met content diets at 4 weeks of age. The CP retention was not significantly (P>0.05) different between different groups in 3 week, which indicated CP (17%) and Met/CP (0.025-0.030) were enough for the birds growing. The results of interaction: nitrogen retention ratio, utilization ratio of Ex P were not significantly (P>0.05) different, and the third group was the best, the utilization ratio of Ca was better, too. And no differences (P>0.05) were found on body weight gain and feed intake from 0 to 4 weeks. It is suggested that CP=17%, Met/CP=0.030 in diets containing ME=11.91 MJ/kg are suitable for cage-rearing laying ducks in 0-4 weeks period.In experiment 2, the 324 ducks of the experiment 1 were thrown into confusion and were medley, then they were assigned to 9 groups randomly, with 3 replicated per group and 12 ducks per repeats. In 5-12 weeks, the ducks were fed nine isoenergetic diets (ME:11.51 MJ/kg) with different CP levels (CP: 14%, 16%, 18%) and Met levels (Met/CP: 0.017. 0.022, 0.027) on the growth, utilization of nutrients and body deposit. The resultsindicated that there were a weak negative correlation between body weight gain (r=-0.0420) and CP (%) from 5-12 weeks of age and a weak positive correlation between body weight gain (r=0.2748) and Met (%) from 5-12 weeks of age. No differences (p>0.05) were found in body weight gain from 9~12 weeks of age and feed conversion from 5~12 weeks of age among the ducks fed the different diets. With the exception of the utilization ratio of Ca, the utilization ratios of CP, E, P were best when the CP level was 16% and were better when the CP level was 14%. For the results of interaction: the utilization ratios of CP, E, P, Ca were best when the CP level was 16% and the Met/CP level was 0.027. The CP retention (g/kg W0.75) increased with increasing dietary Met level when CP (%) was from 14% to 16% .It is suggested that CP=14%~16%, Met/CP=0.022-0.027 in diets containing ME=11.51MJ/kg are suitable for cage-rearing laying ducks in 5-12 weeks period and CP=14% & Met/CP=0.027 or CP=16% & Met/CP=0.022 are better in practice.In experiment 3, the 324 ducks of the experiment 2 were thrown into confusion and were medley again. The experiment design was the same as experiment 2 except the CP levels were 13%, 1-5%, 17%, metabolism trials in the 15th week and slaughter trials in the 106th day for laying duc... |
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