| Models and parameters to estimate energy and amino acid requirements for broiler chickens were determined by factorial methods with Arbor Acres broilers. By the method of introducing time b\ Gompertz equation, dynamic models, which describe metabolizable energy and amino acid requirements for broiler chickens as functions of time, were constructed. Accuracy and currency of models were verified with Arbor Acres and Avian broiler chickens.Expcriment 1 Modeling of broiler Growth, Carcass Protein and Feather Protein DepositionTwo hundred and forty newborn Arbor Acres healthy broiler chickens were used to conduct feeding and comparative slaughter experiments for 42 days. Body weights and corresponding body compositions of chicks were measured at weekly intervals. Gompertz equation was adopted for modeling the growth cure of sexes. Correlations between the amount of carcass protein, feather protein and live body weight of birds at various times were described with different mathematic equations, respectively. The corresponding optimal models screened out were introduced growth curve equations, respectively. The differential equations from growth curve equations and those models suggested the dynamic function relations between body gain, carcass protein deposition, feather protein deposition and corresponding age, which reflect accurately the laws of growth and protein deposition of Arbor Acres broiler chickens.Experiment 2 Amino Acid Pattern of Carcass and Feather Protein for Broiler ChickensSix male and six female Arbor Acres birds were selected to kill by cervical dislocation at 0, 14, 28. and 42 day, respectively. Crude protein and amino acid contents in carcass and feather were determined and various Amino acid contents were expressed as the percentage of crude protein after carcass and feather were separated and treated severally,. The results of statistics showed that sex had no effect on amino acid composition of carcass and feather protein. Except of Asp, Gly, Ala, Lys, Trp of carcass and Asp, Ser, Glu, Cys, Val, Ile, Leu of feather, other amino acids of carcass and feather were influenced by age (P<0.05). However, differences were not observed in Thr, Ser, Glu, Cys, Met, Leu, His, Arg, Tyr, Phe, Pro of carcass and Thr, Gly, Ala, Tyr, Phe, Arg, Pro of feather among 14, 28, and 42 day-old (P> 0.05). There was a significant difference in Val, lle of carcass and Met, Lys, His, Trp of feather at various days(P<0.05). In view of results above, amino acid patterns of carcass and feather of broiler chickens should be determined according to the mean value of 14,28, 42 day-old.Kxpcriment 3 Amino acid Pattern and Its Requirements for Maintenance of Broiler ChickensNitrogen requirements for maintenance of broiler chickens were considered to be the sum of the needs for the endogenous losses and the skin integuments losses. The endogenous losses covered three parts: amino nitrogen, non amino nitrogen and creatinine excretion. Parameters used to calculate protein requirement for maintenance were obtained from two balance trials with 6 week-age broilers. Nitrogenretention and creatinine excretion were determined at 509.27mg/day and 12.22mg/day in protein-fed birds to estimate skin protein loss and creatitine loss. When fed an N-free diet, bids excreted 510.71 ing/day nitrogen as a result of endogenous losses to estimate endogenous protein and amino acid excretion. The protein requirement for maintenance was calculated at 19.20mg/day/g07:iof body weight by summing up the different losses. Protein and amino acid analyses of nude carcass and feather were used to obtain their own amino acid patterns which were regarded as amino acid composition of non amino nitrogen in endogenous nitrogen and skin integuments nitrogen, respectively. Creatinine excretion was replaced by equivalent mohof glycine, arginine and methionine. Summed the endogenous amino acid excretion and losses of the skin integuments, amino acid pattern and requirement for maintenance were calculated.Experiment 4 Parameter Determination of True Digestibility of Dietary Amino Acid and Net Availability of dietary Protein for Broiler Chickens in Different Growth StagesSeventy two 2 week-age and 5 week-age Arbor Acres chickens were used respectively in two bioassays conducted to determine average true digestibility of dietary amino acid and net availability of dietary protein by the method of collecting complete excreta. Body weights of same age birds were similar. In each assay, chickens were divided into two treatments which were fed experimental diet and nitrogen-free diet, respectively. Each treatment comprised 6 repetitions with 3 male and 3 female each. The results showed that true digestibility of amino acid and net availability of crude protein of diet I during 2 to 3 week were 84.77% and 57.49% and that of diet 2 during 5 to 6 week were 87.90% and 73.78%, respectively.Experiment 5 Modeling of Metabolizable Energy Requiremnet for Broiler ChickensTwo trials were undertaken to evaluate metabolizable energy (ME) requirement for broiler chickens. In the first trial, 36 newborn Arbor. Acces chickens were reared in cages for 6 weeks. Two points in the chick feeding period were designed for the apparent ME (AME) and nitrogen-corrected AME (AMEn) assay of two diets: 3 and 6 weeks of age. Compared with AME, AMEn decreased by 5%, and there was a good correlation between AMEn and AME. In the second trial, 240 newborn Arbor Acres broiler chickens with half male and half female were fed in cages for 6 weeks, and empty Body weights and feed intake of chickens were measured weekly. The growth curves of both sexes were modeled and the gain was given by the time derivative of Gompertz equation, then resolved in energy requirement models constituted by the one-way linear regress method and formed dynamic prediction model.Experiment 6 Accuracy Evaluation of Models to Estimate Energy and Amino Acid Requirements for Broiler Chickensl-our hundred eighty newborn Arbor Acres healthy chickens were used in the feeding and slaughter trials conducted to evaluate model accuracy of estimate amino acid requirements for broiler chickens under a commercial feeding program. Diets formulated based on 90%, 100%, and 110% of model...
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