| It is very meanful for husbandry industry to construct mechanistic growth models to predict the growth of the animals. According to the principals of factorial method and the deposition of body compositions, five feeding and slaughtering trials were conducted to identify the functions and parameters which were necessary for constructing the mechanistic growth model of Arbor Acer broilers. Then, according to these functions and parameters, the software of predicting the growth of Arbor Acer broilers was developed with computer programming language. And the results of prediction were evaluated.EXP.1 Study on the Prediction of Average Daily Intake of Broiler Based on Multiple Linear RegressionTwo feeding trials were conducted to investigate the effects of energy and body weight on the average daily intake of broiler and establish the regression equation between average daily intake and body weight and energy. Trial 1 and 2 were performed during 0 to 3 weeks of age and 4 to 6 weeks of age, especially. In each trial, Four hundred Arbor Acer (AA) broilers with similar body weight were assigned to 10 groups with 5 replicates of 8 chicks. In both trials, broilers were fed 5 diets with different energy-protein ratios (during 0-3 weeks of age, the energy-protein ratios were 0.58 MJ/kg, especially; during 4-6 weeks of age, the energy-protein were 0.67 MJ/kg, especially). Each week, the body weight and the following 24-hour intake of broilers were recorded. According to the data, the regression models to predictive the average daily intakes were set up by multiple linear regression. The equations of male, female and gender- mixed broilers were DFI = 0.084 + 0.093 BW - 0.005ME, DFI = 0.085 + 0.088 BW - 0.005 ME and DFI = 0.084 + 0.091 BW - 0.005 ME, especially. Significant test were made on these models by F-test, t-test and goodness-of-fit test. The results showed that the regression relations and the coefficients of equations were significant (P<0.05), and the goodness-of-fit test showed that the adjusted R square of equations were 0.947, 0.928 and 0.936, especially. These results indicated that the established models could be used to predict the average daily intake of broilers.EXP.2 Establishment of the Models on the Potential Rates of Protein Retention of Body, Carcass, Feather of BroilersThe regulations of growth and development of broilers were investigated and the models on the potential rates of protein retention of body, carcass, feather of broilers were established in order to develop further the model to predict the growth of broilers. One hundred and eighty one-day-old Arbor Acres (AA) broilers were randomly arranged into 2 treatments with 5 replicates of 18 chicks by sex. Broilers were fed with standard diet which was formulated according to requirements of National Requirement Council. At 0, 7, 14, 21, 28, 35, 42 days old, after weighted, two broilers with body weights near to the average weight of replicate were chosen and slaughtered, and the body compositions and components were determined. The equations between live weight, carcass weight, feather weight, body components and time were fitted with Gompertz growth fuction; the equations of body protein, carcass protein and feather protein with body weight, carcass weight and feather weight were fitted with curve regressions. Based on the fitted equations, the models on the potential rates of protein retention of body, carcass, feather in broilers were established. The results showed that Gompertz growth function could well fitted the equations between live weight, carcass, feather body components and time. The correlation indexes (R2) of equations were all above 0.969, and the results of F-test showed that the equations were all significant(P<0.01); power fuction could well fitted the equations of body protein, carcass protein and feather protein with body weight, carcass weight and feather weight, the R2 of fitted equations were all above 0.998, F-test showed that the equations were all significant(P<0.01); Based on the equations above, the models of on the potential rates of protein retention of body, carcass, feather of broilers were established. These results indicated that the models established could be used to predict the potential retention of body protein, carcass protein and feather protein according to the body weight, carcass weight and feather weight.EXP.3 Study on the Allometric Relationships of Body Compositions and Components in Broilers Based on Curve RegressionsThe allometric relationships of body compositions and components in broilers were investigated in order to establish the growth model to predict the growth of broilers. One hundred and eighty one-day-old Arbor Acres (AA) broilers were randomly arranged into 2 treatments with 5 replicates of 18 chicks by sex. Broilers were fed with standard diet which was formulated according to requirements of National Requirement Council. At 0, 7, 14, 21, 28, 35, 42 days old, after weighted, two broilers with body weights near to the average weight of replicate were chosen and slaughtered, and the body compositions and components were determined. The trial data collected were fitted with curve regulation by statistical software. The results showed that the power function could well describe the relationships between carcass, feather and body weight, the relationships between body water, fat, ash and body protein, the relationships between carcass water, fat, ash and carcass protein, and the relationships between feather water, fat, ash and feather protein. The fitted equations were tested through F-test, the results showed that the fitted equations were all significant (P<0.01), and the correlation indexes (R2) of fitted equations were all above 0.95. These results indicated that the fitted allometric equations with power function could be well used to predict the body compositions and components of broilers.Exp.4 Effects of Varying Energy and Protein Intakes on the Performance, Body Protein and Body Fat Depositions of Broilers during 0-3 WeeksThe effects of varying energy and protein intakes on the performance, body protein and body fat of broilers during 0-3 weeks were investigated to identify the relationships between efficiency of protein utilization for body protein deposition (ep) and energy: protein ratio and the efficiencies of energy utilization for protein and fat deposition. Four hundred and thirty-two one-day-old Arbor Acres (AA) broilers were randomly arranged into 24 treatments with 3 replicates of 6 chicks by sex and diets. Broilers were fed with 95%, 80%, 65% 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 4 feeding levels. Thus, 12 diets with different energy: protein ratios were formed. At the beginning and the end of the trials, broilers were killed, and the body compositions were determined. The results showed: (1) the varying energy, protein intakes significantly affected the finial body weight, body protein and body fat of broilers (P<0.05); (2) the varying energy, protein intakes significantly affected the average daily gain of body weight, body protein and body fat (P<0.05); (3) with the increase of energy: protein ratio, ep increased linearly at first, then kept constant at last. When the energy: protein reached 69.28 MJ/kg, the eps of male and female broilers attained their maximum values, were 0.64 and 0.63 separately; (4) the efficiencies of energy utilization for protein deposition in male and female broilers were 0.72 and 0.68, the efficiencies of energy utilization for fat deposition in male and female broilers were 0.59 and 0.65, male and female broilers needed 32.88,34.82kJ of ME/g for fat deposition and 66.43,60.12kJ of ME/g for protein deposition. The results above laid a foundation for further improving the body composition of the broilers by nutritional methods and constructing the model to predict the growth of broilers.EXP.5 Effects of Varying Energy and Protein Intake on the Performance, Body Protein and Body Fat of BroilersThe effects of varying energy and protein intakes on the performance, body protein and body fat of broilers were investigated to identify the relationships between efficiency of protein utilization for body protein deposition (ep) and energy: protein ratio and the efficiencies of energy utilization for protein and fat deposition. Four hundred and thirty-two 21-day-old Arbor Acres (AA) broilers were randomly arranged into 24 treatments with 3 replicates of 6 chicks by sex and diets. Broilers were fed with 95%, 80%, 65% 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 4 feeding levels. Thus, 12 diets with different energy: protein ratios were formed. At the beginning and the end of the trials, broilers were killed, and the body compositions were determined. The results showed: (1) the varying energy, protein intakes and the gender significantly affected the finial body weight, body protein and body fat of broilers (P<0.05); (2) the varying energy, protein intakes and the gender significantly affected the average daily gain of body weight, body protein and body fat (P<0.05); (3) with the increase of energy: protein ratio, ep increased linearly at first, then declined slightly and kept constant at last. When the energy: protein reached 69.28 MJ/kg, the eps of male and female broilers attained their maximum values, were 0.58 and 0.56 separately. The linear equations of male and female broilers were ep=0.010Re/p and ep=0.009Re/p before energy: protein ratio reached 69.28MJ/kg, and the determined coefficients were 0.989 and 0.988, separately. F-test showed that the equations were both significant (P<0.05); (4) the efficiencies of energy utilization for protein deposition in male and female broilers were 0.70 and 0.65, the efficiencies of energy utilization for fat deposition in male and female broilers were 0.75 and 0.81, male and female broilers needed 34.04,36.38kJ of ME/g for fat deposition and 52.12,48.32kJ of ME/g for protein deposition. The results above laid a foundation for further improving the body composition of the broilers by nutritional methods and constructing the model to predict the growth of broilers.EXP.6 Validation of the mechanistic growth prediction model of AA broilersThe predictive values were compared with the actual values of feeding-slaughtering trial to validate the accuracy and practicability of the mechanistic growth predictive model of broilers. Two hundreds and sixteen 7-days-old broilers were attributed into 6 treatments with 6 replicates of 6 broilers randomly by sex and diets. At the age of 14, 21 and 28 days, the broilers were weighted and the feed intakes were recorded. At the end of the trial, two broilers with body weights near to the average body weight of the replicate were slaughted and the body composition were determined. At the same time, the informations of initial weight, sex, feeding days, metabolitic energy and protein level of diets were input into the mechanistic growth predictive model to predict the accumulative feed intakes, body weights and body composition of broilers. The results showed that the changing regularity of predictive value were similar to the one of actual value, and the relative differences of the accumulative feed intake between the predictive and actual values during the trial period was among 0.4-4.8, the relative differences of the final body weight between the predictive and actual values were among 0.9-6.6, and the relative differences of the final body water, body protein, body fat and body ash between the predictive and actual values were among 0.3-8.9, 0.8-8.9, 3.0-8.4 and 4.8-10.8, respectively. The results indicated that the model were accurate and practical in some extent. |
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