| It is very meaningful for husbandry industry to construct simulation model of amino acid requirements.According to the principles of factorial method,the study conducted simulation model of amino acid requirements for AA broilers.By the use of introducing time by Compertz equation, dynamic model,which described amino acid requirements for broilers as function of time was constructed. Accur-acy of model was validated.Experiment 1 Prediction of Potential Growth Performance and Fitting Growth Curve of AA BroilersFour hundred and eighty of 1-day-old Arbor Acres (AA) broilers were randomly arranged into ten treatments with 6 replicates of 8 broilers by sex and diet.The growth curves of AA broilers of 0-8-week-old fed diets with different digestive energy levels were analyzed and fitted with Gompertz model.The results indicated that male and female broilers grew slowly before the age of 1-week-old,and then,more quickly than before,and got to the peak of growth rate about the age of 5-week-old.As for the male broilers,after the age of 7-week-old the growth rate of broilers fed diets with digestive energy levels of 14.23,13.39,11.72MJ/kg had less decline than that before the age of 7-week-old.As for the female, the growth trend was similar to the male's, however, for the age of 1-2-week-old, the female had greater growth rate than the male's (P>0.05).After the age of 3-week-old,the growth rate of the female under the same digestive energy level was evidently slower than the male's(P<0.05).Gompertz equation was considered to be better to fit the growth curves of broiler, in which the ultimate weight of the treatment(13.39MJ/kg) was highest, and the value of the fitness of male and female broilers of the age of 0-8-week-old were 99.9%,99.6%,respectively.The model of the male,female and mixture for fitting body weight to day were:BWt=4823.04exp(-exp(-0.045*(t-34.96))), BWt= 5040.23exp (-exp(-0.045*(t-35.53))),respectively.The constructed model could be used to predict the potential growth performance of broiler.Experiment 2 The Amino Acid Pattern of Carcass and Feather Protein and Parameters of Carcass Performance in BroilersAmino acid pattern of carcass and feather protein and parameters of carcass performance in broilers were investigated by feeding and comparative slaughter experiments.Two hundred and sixteen one 1-day-old broilers were arranged into 2 treatments with 6 replicates of 18 broilers randomly by sex.Broilers were fed with standard diet which was formulated according to nutritional level of the treatment (ME:13.39MJ/kg).At the age of 0,14,28,42 and 56 day-old,after weighted, two broilers with body weights near to the average weight of replicate were chosen and slaughtered,and the amino aicd content of the carcass and feather were determined and expressed as the percentage of crude protein,separately.The results showed that sex didn't affect the amino aicd pattern of the carcass and feather protein significantly (P>0.05),however, age significantly affected the amino aicd pattern of the carcass and feather protein(P<0.05).Except for the data of 0-day-old influenced by yolk sac,contents of most amino aicds of the carcass and feather protein of broilers of 14-day-old were significantly different from that of 28,42 and 56-day-old(P<0.05).So,the average value of 14,28,42 and 56-day-old should not be considered as the amino acid model of carcass and feather protein, the experiment established the parameters of carcass and feather protein and carcass performance by the use of Gompertz equation in broilers during 0 to 8 weeks.In view of results above, it was fit for the model established by the factorial method that the amino aicd model of the carcass and feather crude protein during 0 to 3 weeks should be determined by the value of 14-day-old, and determined by the mean value of 28,42,and 56-day-old as for the amino aicd model of the carcass and feather crude protein during 4 to 8 weeks.Experiment 3 The Amino Acid Pattern for Maintenance Requirements of AA BroilersA total of seventy-two of 2-week-old,6-week-old AA broilers were randomly arranged into two treatments with 6 replicates of 6 broilers(3:male,3:female), fed diets with nitrogen free diet and low nitrogen diet,separately.Endogenous amino acid excretion was determined by nitrogen free diet.Amino acid excretion from feather loss, scurf loss et al was determined by low nitrogen diet.The results indicated that the requirements of fifteen amino acids except Gly,Cys for maintenance were significantly different between 14 and 42-day-old(P<0.05).Amino acid pattern was different between broilers of 0-3-week-old and adult broilers.In conclusion,the amino acid patterns of 2-week-old and 6-week-old broilers for maintenance could be regarded as that of 0-3-week-old and 4-8-week-old broilers, respectively.Experiment 4 Study on the True Protein Availability and True Amino Acid Digestibility for BroilersTwo hundred and sixteen of 2-week-old,5-week-old,7-week-old AA broilers were randomly arranged into 6 treatments with 6 replicates of 6 broilers by sex per phase,of those,2 male treatments,2 female treatments,2 mixture treatments including half male and half female,and fed nitrogen free diet and experiment diet per phase separately for three and another three treatmens to study the true protein availability and true amino acid digestibility for broilers.The apparent and true protein availability of 2-week-old broilers in male group,female group and mixture group were 61.59%,55.50%,63.89%, 64.10%,57.47% and 66.57%, separately.The apparent and true protein availability of 5-week-old broilers in male group,female group and mixture group were 73.47%,67.98%,69.16%,75.83%,70.29% and 72.69%,separately.The apparent and true protein availability of 7-week-old broilers in male group,female group and mixture group were 74.97%,67.64%,74.50%,78.00%,72.00% and 78.32%, separately.The apparent and true amino acid digestibility of 2-week-old broilers in male group,female group and mixture group were 84.31%,80.61%,85.36%,84.76%,80.64% and 85.89%,separately.The apparent and true amino acid digestibility of 5-week-old broilers in male group,female group and mixture group were 88.95%,80.84%,89.22%,90.43%,84.37% and 90.33%,separately.The apparent and true amino acid digestibility of 7-week-old broilers in male group,female group and mixture group were 89.16%,86.25%,89.70%,91.72%,89.61% and 92.42%,separately.Results above laid a foundation for constructing the model to predict the amino acid requirements for broilers for different phases. Experiment 5 Modeling of Energy Requirement for Broiler in Different PhasesThe growth curve of protein and fat of broilers from 0 to 8 weeks and effects of varying energy and protein intakes on the performance, body protein and body fat of broilers at three stages phases were investigated to identify the growth rule of protein and fat of carcase and feather,and the efficiencies of energy utilization for protein and fat deposition.Three hundred and twenty-four of 1-day-old,21-day-old, 42-day-old AA broilers were randomly arranged into 18 treatments with 3 replicates of 6 broilers by sex and diet in first experiment.Broilers were fed with 90%,70% and 50% restriction of ad libitum intake,separately.Each day,broilers were supplied with three allowances of high-protein basal feed and appropriate amount of starch which were determined by 3 feeding levels.Thus,9 diets with different energy:protein ratios were formulated.One hundred and forty-four 1-day-old AA broilers were randomly arranged into 2 treatments with 4 replicates of 18 broilers by sex in second experiment. At the beginning and end of the trials,broilers were killed to determine the body compositions.The results showed that Gompertz function could describe the growth curves of the protein and fat of AA broilers.There was significant difference in the ultimate weight of proein,feather protein(P<0.05),and the growth rate of feather proein and fat(P<0.05),but no significant difference in the growth rate of carcase proein and fat(P>0.05),by sex.Average energy requirements of male, female and mixture groups for maintenance at three phases were 387.53,373.21,379.09,458.73,416.60,437.14,470.44,420.04 and 441.42 kJ/kgBW2/3/d.The energy utilization of male, female and mixture groups for protein deposition at three phases were 0.62,0.60,0.60,0.66,0.62,0.67,0.66,0.62 and 0.64, the energy utilization of male, female and mixture groups for fat deposition were 0.59,0.64,0.61,0.75,0.80,0.79,0.77,0.81 and 0.80. The results above could construct the model to predict energy requirement for broilers.Experiment 6 Evaluation of Simulation Model of Amino Acid RequirementsEight hundred and sixty-four 1-day-old broilers were arranged into 8 treatments with 6 replicates of 18 broilers randomly by sex.The diets were formulated by the model under 10%,0% and over 10% and NRC(1994).At the age of 21,42 and 56-day-old, after weighted, three broilers with body weights near to the average weight of replicate were chosen and slaughtered to determine the performance and carcass perforamance.The results indicated that the Average Body Weight(ABW) and Feed Conversion Ratio (FCR) of model of 90% were lower than that in other groups(P<0.05).The Average Daily Feed Intake (ADFI) of male broilers in groups of model of 90% and 100% were higher than that in model of 110%(P<0.05).The Average Daily Gain (ADG) of male broilers in group of model of 90% were lower than other groups (P<0.05),and ADG of model of 100%,110% groups were higher than that in other groups(P<0.05) for female broilers.For male broilers,the Weight of Pectoraly Major Muscle(PMAW), Weight of Pectoraly Minor Muscle(PMIW)of male broiler model of 100% were higher than that in other groups(P<0.05), which in group of NRC were higher than that of model of 90%,110%(P<0.05). Weight of Abdomen Fat (AFW) of model of 90% were higher than other groups(P<0.05); For female broilers,the PMAW, PMIW, Weight of Leg Muscle (LW) of four groups were not significantly different (P>0.05),AFW of model of 90%,100% and NRC,110% were significantly different (P<0.05).For male broilers,there was no significant difference in the Percentage of Pectoraly Major Muscle (PMAP), Percentage of Pectoraly Minor Muscle (PMIP) between four groups, but, Percentage of Leg Muscle(LP) of model of 90% group was lower than that of in other groups(P<0.05), and the Percentage of Abdomen Fat (AFP) of model of 90% group was higher than other model groups(P<0.05). For female broilers, Percentage of Leg Muscle (LP) of model of 100% and NRC groups were higher than that in other groups(P<0.05).In view of results above,there was no significant difference between diets formulated by the model(except 90%) and NRC on the performance.Compared with female broilers,male broilers had better performance,the group of model of 100% could improve the performance of broiler,and decrease AFP of the group of model of broiler,which indicated the model having higher accuracy.
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