Effects Of Effective Temperature And Dietary Energy And Protein Level On The Digestive Function Of Broilers

Two experiments were conducted to study the effects of dietary protein (CP) and metabolizable energy (ME) levels, and their interaction with effective temperature (ET) on performance and function of digestive system in broiler chicks, in which the development of digestive organs, digestive enzymes activities, nutrient digestibility, some blood physiological and biochemical indices and abdominal fat were determined during the age of 21-42 days.Exp. 1 Effects of ET xDietary ME on Broiler Chicks' Digestive FunctionsIn a 4 × 3 factorial design trial 216 21 -day-old Arbor Acre (AA) broiler chicks were randomly allocated into 12 groups, each with 3 replicates of 6 birds, reared in 4 temperature-controlled chambers. ET was 15℃, 21.2℃, 35.3℃ and 37.6℃ respectively, dietary ME was 2800 kcal/kg, 3000 kcal/kg and 3200 kcal/kg, respectively, dietary CP was kept 20.00%. The results showed that:1. Under high temperature (35.3℃ or 37.6℃), daily feed intake (DFI) and daily weight gain (DWG) decreased and feed conversion rate (FCR) increased significantly (P<0.01). The growth rate and feed utilization efficiency of broiler chicks were also lowered by low temperature (15℃) and low dietary ME. Under appropriate temperature of 21.2℃, the performance increased as the dietary ME elevated.2. The intestinal digestive enzymes and the nutrient digestibility and hepatic lipase activities were decreased with the increase of ET (P<0.01). No significant changes were observed in digestive enzymes and digestibility of some nutrients under low temperature, however intestinal lipase activity significantly increased in the chicks fed with high dietary ME (P<0.05).3. The weight of digestive organs and length of intestine of birds reduced under high temperature (P<0.05), while no significant changes were observed under low temperature (15℃) and appropriate temperature (21.2℃).4. The concentration of serum cholesterol (P<0.05) and liver triglyceride (P<0.01) of broiler chicks were greatly influenced with ET and dietary ME interaction. The abdominal fat increased with the increase of dietary ME (P<0.05), while no changes observed with ET.Exp. 2 Effects of ET xDietary CP on Broiler Chicks' Digestive FunctionsThe same 4X3 factorial experiment and ET levels as the Exp.1 were designed and dietary CP was set at18.67, 20.00 and 21.33%, respectively. Dietary ME was 3000 kcal/kg. The results showed:1.DFI, DWG and FCR significantly decreased with the increase of the ET (P<0.01). The performanceincreased under appropriate temperature, but didn't improve under high and low temperature withdietary CP increased.2. The interaction between ET and dietary CP influenced the intestinal lipase (P<0.01) and pancreaticlipase significantly (P<0.05). The nutrient digestibility significantly increased with the increase ofdietary CP(P<0.01).3. Higher dietary CP can improve the development of digestive organs which was inhibited by hightemperature. The abdominal fat wasn't significantly influenced by ET.In summary, temperature is one of important factors that affected the growth performance of broiler chicks. The retarded development of digestive organs and the lower digestive enzyme activities resulted in the poor performance under high temperature. Under low temperature, maintenance requirement increased and feed conversion rate was elevated.