Effects Of Dietary Protein And Energy Levels On Performance, Digestibility Metabolism, And Serum Biochemical Indices In CRP Complete Set Line's Commercial Growing Pigs

This experiment was designed to study the influence of energy and protein levels on performance, nutrient digestibility, nitrogen & energy metabolism, Calcium and phosphorus metabolism. Comprehend its functional mechanism to serum biochemical indices, and endocrine hormone. Finally, offer some theory on the CRP determining nutrient indexes and generalizing.Feeding experiment and digestibility metabolism experiment were involved in the study. The metabolism experiment used two factors (DE and CP) two levels cross classification design. Two levels of the DE were 12.78MJ/kg and 15.6MJ/kg, and two levels of CP were 15.3% and 18.7%. The control group (12.78MJ/kg, 17%) was designed. Twenty CRP complete set line's commercial growing pigs(average initial BW=30±2kg) were in metabolism cages, they were randomly divided into five groups, fed five different diets containing different energy and protein levels, with four replicates per group, and each replicate had one pig. After totally collecting the fecal and urine for four days and handling, contents of nutrients were determined. About eighty CRP complete set line's commercial growing pigs(average initial BW was 43±2kg)were used in the feeding experiment, they were randomly divided into five groups, four replicates per group, and each replicate had four pigs(two boars and two gilts). The feeding experiment lasted thirty days, then testing the performance, biochemical indexes of serum, endocrine hormone, et al. The results were as follows:(1) Increasing the dietary energy levels can significantly raise nutrient digestibility. The effects of energy on DM, CP, CF, EE and ash digestibility all achieved the extremely significant level (P<0.01). Protein remarkably effected the EE digestibility (P<0.01), and the interaction of energy and protein affected the ash digestion significantly (P<0.01). The fecal nitrogen evacuated was remarkably affected by dietary energy levels. The higher the energy levels in the diet, the lower the fecal nitrogen evacuated. Protein affected nitrogen intake and deposited nitrogen significantly (P<0.05), but didn't affected other indexes at the statistic level. The higher protein levels in the diet, the higher nitrogen intake and evacuated. There were no significant differences among nitrogen metabolic rate, BV, urine nitrogen evacuated, and total nitrogen evacuated.(2) Dietary energy levels affected the FE, GE digestibility and GE metabolic ratio extremely (P<0.01), could elevate the DE and ME significantly (P<0.05). Protein only affected FE remarkably (P<0.05). There were no differences on DE metabolic rate. Increasing dietary energy levels could enhance the digestibility of Calcium and Phosphorus extremely (P<0.01), that was decreasing the fecal Calcium and Phosphorus evacuated. The interaction of protein and energy affected Calcium digestibility extremely (P<0.01).(3)The effects of increasing or decreasing the dietary energy and protein levels on F/G were not significant, but the F/G of 15.6MJ/kg groups was lower than that of 12.78MJ/kg groups. The ADG of 15.6MJ/kg groups were significantly lower than that of control group (P<0.05), and slightly lower than that of 12.78MJ/kg groups. The ADFI of 15.6MJ/kg-18.7% group was extremely higher than that of control and 12.78MJ/kg-18.7% group (P<0.01). The energy only significantly affected ADFI; protein had little contribution to the performance.(4)Compared with control group, the contents of TP and GLO in treatments were increased, and the 12.78MJ/kg-18.7% group achieved the significant level, and the contents of ALB were not different among the groups. Energy, protein and their interaction didn't affect the contents of TP, GLO and ALB remarkably. The contents of BUN were significantly affected by dietary protein levels (P<0.01), the contents of BUN in CP18.7% groups were remarkably higher than that in CP15.3% groups. The contents of TG₃ and CHO were not different significantly among all groups. Energy, protein and their interaction didn't affect them remarkably. Dietary protein levels affected the contents of GLO significantly (P<0.01). 15.6MJ/kg groups were remarkably higher than 12.78MJ/kg groups (P<0.05), but not significant compared with control group.(5) There were no significant differences on AKP and ALT activity among all groups. Energy and protein levels didn't affect the AST activity significantly, but compared with control group, the AST activity in other groups was all enhancing. Energy affected CHO activity significantly (P<0.05), All the CHE activity in treatment groups were higher than that in control group. The effects of energy and protein on T₃,T₄,TSH,Cor and ACTH concentration was not remarkable.(6) According to all the data above, this experiment suggested that we could increase the energy levels and decrease the protein levels, compared with the control group's nutrition levels (DE was14.2MJ/kg, CP was 17%) on the CRP complete set line's commercial growing pigs.