Effects Of Stevia Extract On Growth Performance,Serum Physiological And Biochemical Indices And Intestinal Development Of Yellow-feathered Broilers

The purpose of this study was to investigate the effects of different levels of Stevia extract(total chlorogenic acid content ≥ 50%)on growth performance,serum physiological and biochemical indexes and intestinal development of yellow-feathered broilers.To provide scientific basis for the rational application of Stevia extract in broiler production.425one-day-old yellow-feathered broilers were randomly divided into 5 treatments with 5replications per treatment and 17 chickens per replicate.The five treatments were as follows:the control group in the basic diet and the experimental group supplemented with 100 mg/kg,200 mg/kg,300 mg/kg and 400mg/kg Stevia extract respectively in the basic diet for 63 days.The results showed that:(1)Compared with the control group,the final weight of the chickens treated with 100 mg/kg Stevia extract in the basic diet increased by 6.79%(P <0.05),the average daily gain increased by 6.93%(P < 0.05),and the feed-weight ratio decreased by 8.58%(P > 0.05).(2)There were no significant differences in slaughtering percentage,semi-eviscerated rate,eviscerated rate,chest muscle percentage,leg muscle percentage and other slaughtering performance indexes among different treatments(P >0.05).(3)Compared with the control group,the serum superoxide dismutase in the treatment group supplemented with 100 mg/kg and 200 mg/kg Stevia extract increased by 31.94%(P <0.05)and 10.88%(P > 0.05),respectively.The serum glutathione peroxidase of chickens treated with 200 mg/kg Stevia extract was 11.12%(P > 0.05),higher than that of the control group.(4)The content of serum total cholesterol in all groups supplemented with Stevia extract was significantly lower than that in the control group(P < 0.05).The level of serum albumin in the treatment group supplemented with Stevia extract 300 and 400 mg/kg was significantly lower than that in the control group,but there was no significant difference in the level of serum albumin between the treatment group and the control group.(5)There was no significant difference in liver index,bursa index,spleen index and thymus index among different treatments(P > 0.05).(6)Compared with the control group,the serum Ig G level of the treatment group supplemented with 200 mg/kg and 400mg/kg Stevia extract increased by51.54%(P < 0.05)and 65.48%(P < 0.05)respectively,and the Ig A level increased by26.75%(P < 0.05)and 45.92%(P < 0.05),respectively.At the same time,the serum Ig M level of the experimental group supplemented with 300 mg/kg and 400 mg/kg Stevia extract was 65.11%(P < 0.05)and 79.97%(P < 0.05)higher than that of the control group,respectively.(7)There was no significant difference in villous height,crypt depth and cashmere ratio of duodenum,jejunum and ileum among different treatments(P > 0.05).(8)Compared with the control group,the cecal n-butyric acid content of the diet supplemented with 200 mg/kg Stevia extract was significantly increased(P < 0.05).To sum up,adding Stevia extract to the basic diet of yellow-feathered broilers can significantly improve the growth performance,antioxidation and immunity of yellow-feathered broilers.It is considered that it is appropriate to add Stevia extract with100～200mg/kg total chlorogenic acid content more than 50% in the diet of yellow-feathered broilers.