Effects Of Extract Of Star Anise On Production Performance,Immune Performance And Nutrient Utilization Of Broilers Under Different Nutrient Levels

This study aimed to investigate the effects of extract of star anise on production performance,immune performance and feed nutrient utilization of broilers under different nutrient levels,in order to provide a theoretical basis for the development of green plant additives and the application of low protein low energy diet.The 2 × 2 factorial design was adopted in this study.A total of 1440 1-day-old commercial AA broilers with almost equal initial weight were randomly divided into four treatments with nine replicates per treatment and 40 broilers per replicate.Treatment 1 was positive control group,which was fed normal-nutrient-level diet.Treatment 2 was negative control group,which was fed low-protein-low-energy diet(0.12 MJ/kg energy and 0.5% crude protein less than normal-nutrient-level diet.For treatments 3 to 4,500 mg/kg extract of star anise was added on the basis of treatments 1 and 2,respectively.Production and immune performance were analyzed at 21 and 42 days of age,and the apparent utilization of the conventional nutritive ingredients was determined by acid-insoluble-ash indicator method during the 28 to 35 days of age.The results of this study are as follows:(1)Comparative analysis of production performance:(1)Growth performance: compared with the control group,extract of star anise significantly increased the average daily feed intake(ADFI)of broilers at 21 days of age and the body weight(BW)of broilers at 42 days of age,as well as the average daily gain(ADG)during the whole rearing period(P < 0.05).Extract of star anise also significantly reduced the Feed/Gain ratio(F/G)of broilers during the whole rearing period(P < 0.05).Low dietary nutrient level significantly decreased ADG and BW of broilers at 42 days of age(P < 0.01),and significantly increased F/G of broilers during the whole rearing period(P < 0.01).There was an interaction between extract of star anise and dietary nutrient level on F/G of broilers during the whole rearing period(P < 0.05).(2)Slaughter performance: compared with the control group,extract of star anise significantly increased the leg muscle percentage of broilers at 21 days of age(P < 0.05);low dietary nutrient level had no significant effect on all indicators of broiler slaughter performance of broilers at either 21 or 42 days of age(P > 0.05).There was no interaction between extract of star anise and dietary nutrient level on all indicators of slaughter performance(P > 0.05).(3)Production antioxidant performance: compared with the control group,the content of malondialdehyde(MDA)in breast muscle and liver of broilers during the whole rearing period and in leg muscle of broilers at 42 days of age was significantly reduced by adding extract of star anise(P < 0.05).Extract of star anise significantly increased the activity of total superoxide dismutase(T-SOD)in breast and leg muscle of broilers at 21 days of age and in liver of broilers at 42 days of age(P < 0.05).The activity of glutathione peroxidase(GSH-Px)in leg muscle and liver of broilers during the whole rearing period was also significantly increased by adding extract of star anise(P < 0.05).Low dietary nutrient level had no significant effect on all antioxidant properties of products(P > 0.05).No interaction between extract of star anise and dietary nutrient level was detected on all antioxidant properties of products(P > 0.05).(4)Meat quality: compared with the control group,extract of star anise had no significant effect on all indicators of meat quality(P > 0.05).The drip loss rate of leg muscle was significantly reduced by reducing the dietary nutrient level(P < 0.05).There was no interaction between extract of star anise and dietary nutrient level on all indicators of meat quality(P > 0.05).(2)Comparative analysis of immune performance:(1)The immune organ index: addition of star anise extract and low dietary nutrient level had no significant effect on the immune organ indices(P > 0.05).No interaction between extract of star anise and dietary nutrient level was detected on the immune organ indices(P > 0.05).(2)Serum content of cytokines: compared with the control group,extract of star anise significantly reduced the serum cotent of tumor necrosis factor-α(TNF-α)and interleukin-10(IL-10)of broilers during the whole rearing period,as well as the serum content of interleukin-6(IL-6)of broilers at 21 days of age and interleukin-1β(IL-1β)of broilers at 42 days of age,respectively(P < 0.05).Low dietary nutrient level significantly reduced the serum cotent of TNF-α and serum IL-6 in broilers during the whole feeding period(P < 0.05),as well as the serum content of IL-10 in broilers at 42 days of age(P < 0.05).There was no interaction between extract of star anise and dietary nutrient level on all indicators of serum content of cytokines(P > 0.05).(3)Comparative analysis of nutrient apparent utilization rate: compared with the control group,the extract of star anise significantly increased the apparent utilization rate of dry matter(DM),organic matter(OM),crude protein(CP),ether extract(EE)and gross energy(GE)of broilers(P < 0.05).Low dietary nutrient level significantly increased the apparent utilization rate of DM,OM,CP,EE and GE(P < 0.05).There was an interaction between extract of star anise and dietary nutrient level on nutrient apparent utilization rate of broilers(P < 0.05).(4)Comparative analysis of economic benefit: the optimal economic benefit was obtained by addition of star extract under normal nutritional level,and addition of star anise extract under low nutritional level took second place.Low nutritional level alone could not improve the economic benefits.Overall conclusion: dietary addition of star anise extract could significantly improve the production performance,antioxidant properties and nutrient apparent utilization efficiency of broilers,and significantly reduce the serum content of cytokines.Although the nutrient apparent utilization efficiency of broilers was significantly improved by decreasing the dietary nutrient level,the production performance was also significantly decreased.There was an interaction between extract of star anise and dietary nutrient level on F/G and nutrient apparent utilization rate of broilers.The economic benefit assessment showed that addition of star anise extract under normal nutrient level could obtain optimal economic benefit.