| A series of experiments were conducted to study the effects of dietary crude protein levels on production performance, nutrients utilization, serum biochemical indexes, body composition, and protein deposition of Laiwu Pigs. Factorial models had been established by means of rearing, metabolism, comparative slaughter experiments, and concluded protein requirement of Laiwu Pigs. Growth model had been established by analyzing data of rearing and metabolism experiments.A single factor design was used to the experiment to study the effects of dietary crude protein levels on production performance of Laiwu Pigs. A total of twenty-four Laiwu Pigs were randomly divided into four experimental treatments with six replicates of one pig each. The feeding period was divided into three periods: 17 to 30 kg, 30 to 60 kg, 60 to 90 kg. Each period own four dietary crude protein levels and the same digestible amino acid pattern respectively.Results showed that average daily feed intake was no t significantly affected by dietary crude protein levels(P > 0.05); average daily gain, feed to gain, final body weight were significantly affected by dietary crude protein levels(P < 0.05). Body weight and average daily gain increased, and feed to gain decreased as dietary crude protein increased(P < 0.05), however, the production performance appeared to provide lower when the crude protein beyond a certain level.A single factor design was used to study the effects of dietary crude protein levels on nutrients utilization of Laiwu Pigs. The total fecal collection method was used to study the effects of dietary crude protein levels on nutrients utilization in 4 period metabolic experiments with ten day each started at 62 d, 108 d, and 173 d of age, respectively.The results showed as follows: From 62 to 72 d, the metabolic rate of dry matter, organic matter, ether extract, crude protein, biological value, and net protein utilization increased as dietary crude protein increased, and group 15.51% appeared to provide the highest(P < 0.05). From 108 to 118 d, the metabolic rate of biological value, dry matter, and crude protein increased as dietary crude protein increased, and group 14.61% appeared to provide the highest(P < 0.05). From 173 to 183 d, the metabolic rate of dry matter, organic matter, ether extract, crude protein, biological value, and net protein utilization increased as dietary crude protein increased, and group 13.74% appeared to provide the highest(P < 0.05). However, the metabolic rate decreased when the crude protein beyond a certain level.A single factor design was used to study the effects of dietary crude protein levels on serum biochemical indexes of Laiwu Pigs. Blood samples were obtained from venous at 1 d, 36 d, 92 d, and 165 d of age.Results showed that glucose was not significantly affected by dietary crude protein levels(P > 0.05). Between nursery and finishing, the contents of total protein, and total cholesterol increased as dietary crude protein increased, and group 15.51%, 13.74% appeared to provide the highest(P < 0.05), the contents of urea nitrogen reduced as dietary crude protein increased, and group 15.51%, 13.74% appeared to provide the lowest(P < 0.05); The total cholesterol in the growing was not significantly affected by dietary crude protein levels(P > 0.05), the contents of total protein was the highest(P < 0.05), and the contents of urea nitrogen was the lowest(P < 0.05) in the group 14.61%.Study on requirement of crude protein of Laiwu Pigs. Crude protein intake(Y), and average daily gain(X) were regarded as dependent variable(Y), and independent variable(X) respectively, then linear regression were made, the result as follows:From 17 to 30 kg: Y = 73.69 + 0.28X(R2 = 0.872,P < 0.05)From 30 to 60 kg: Y = 88.46 + 0.51X(R2 = 0.907,P < 0.05)From 60 to 90 kg: Y = 58.76 + 0.88X(R2 = 0.910,P < 0.05)According to each phase of Laiwu b lack pigs' weight measured value converted to the corresponding metabolic weight, then linear regression were made, the result as follows:From 17 to 30 kg: RCP = 6.72W0.75 + 0.28BGWFrom 30 to 60 kg: RCP = 5.11W0.75 + 0.51BGWFrom 60 to 90 kg: RCP = 2.25W0.75 + 0.88BGWIn the regression equation above, RCP means crude protein requirement(g/d); W0.75 means metabolic weight(kg); BGW means average daily gain(g).Daily crude protein requirement of each stage were 164.76 g, 290.21 g, and 278.73 g, respectively, according to the regression equation above. Dietary crude protein levels of each stage were 15.63%, 14.73%, and 13.82% combined to the average daily feed intake of each stage, and nutrients utilization, respectively.Research the growth pattern of production performance. Average daily feed intake(ADFI), body weight(BW), average daily gain(ADG) were regarded as dependent variable and weeks of age(t) was regarded as independent variable; then regression equation were made, the result as follows:ADFI =- 6.45 t2 + 280.49 t – 874.38(R2 = 0.908,P < 0.001);BW = 105.373/(1 + 8.826e-0.143t)(R2 = 0.997,P = 0.009);ADG =- 1.872t2 + 65.233 t + 4.466(R2 = 0.961,P < 0.001)?... |
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