Evaluation On The Effectiveness And Tolerance Of Zinc Selenomethionine In Weaned Piglets

Selenium is a trace element necessary for animal life and has important functions such as growth promotion,anti-oxidation and immune enhancement.At present,the organic selenium additives commonly used in animal feed are selenomethionine and yeast selenium,but they have some problems in practical application,such as unstable yield and further improvement of bioavailability.Zinc selenomethionine?Zn-L-SeMet?is a new type of organic selenium,which is characterized by good water solubility,high bioavailability,strong stability,and not easy to be degraded by digestive tract microorganisms.In this paper,the effectiveness and tolerance of Zn-L-SeMet in weaned piglets were investigated to provide basis for its use as a new feed additive.?Effectiveness of Different Levels of Zn-L-SeMet in Weaned Piglets288 weaned piglets with a body weight of 8.09±0.07 kg were selected in the experiment,male and female were equally divided.They were randomly divided into 6 treatment groups,each treatment group 8 repeats,each repeat 6 piglets.Six diets were treated as follows:the negative control group was fed with the basal diet without selenium,the positive control group was added with 0.3 mg/kg Na₂Se O₃?calculated as Se?,and the treatment groups I,II,III and IV were added with 0.1,0.2,0.3 and 0.4 mg/kg Zn-L-SeMet?calculated as Se?respectively.The test period is 42 d,0-14 d in the early stage and 15-42 d in the late stage.The test results are as follows:?1?Growth performance.Theaverage daily feed intake?ADFI?,average daily gain?ADG?and feed-to-weight ratio?F/G?of piglets in each stage of the experiment were not significantly different among the treatment groups?P>0.05?.The addition level of Zn-L-SeMet showed a highly significant quadratic curve relationship with the weight of piglets at 42 d?P<0.01?,the ADG and ADFI at 0-42d?P<0.05?.The 0.2 mg Se/kg Zn-L-SeMet group had the highest value among all treatment groups.The addition level of Zn-L-SeMet showed a significant quadratic curve relationship with F/G at 0-42 d?P<0.05?.The 0.2 mg Se/kg Zn-L-SeMet group had the lowest value among all treatment groups.?2?Serum antioxidant index.At the 42 d of the experiment,the serum GSH-Px activity was significantly different?P<0.05?,and the SOD and CAT activities were extremely significant among the treatment groups?P<0.01?.Compared with negative control group,GSH-Px activity in treatment group I,III was significantly increased?P<0.05?,GSH-Px activity in treatment group II was significantly increased?P<0.01?,Zn-L-SeMet addition level and GSH-Px activity showed a quadratic curve relationship?P<0.01?.The serum SOD activity in treatment group I,II,III was significantly higher than that in negative control group?P<0.01?.The serum CAT activity in treatment group II was significantly higher than that in negative control group and positive control group?P<0.05?.?3?Immune and metabolic indexes.At the 42 d of the experiment,the content of serum Ig G,Ig M,T₃ and T₄ was significantly different among the treatments groups?P<0.01?.Ig G content in treatment group II,III was significantly higher than that in negative control group?P<0.01?.Ig M content in treatment group I,II,III was significantly higher than that in negative control group?P<0.01?,and the addition level of Zn-L-SeMet showed a quadratic curve relationship with Ig M content?P<0.01?.T₃and T₄content in treatment group II was significantly higher than that in negative control group?P<0.01?,and T₄content in treatment group III was significantly higher than that in negative control group?P<0.05?.?4?Selenium content in serum and tissues.At 14 and 42 d of the experiment,the difference of serum selenium content among the treatment groups was extremely significant?P<0.01?.The level of Zn-L-SeMet addition was linear and quadratic with serum selenium content?P<0.01?.The difference of selenium content in liver and kidney among the treatment groups was extremely significant?P<0.01?.The selenium content in liver and kidney of treatment group II,III was significantly higher than that of negative control group?P<0.01?,while the selenium content in liver and kidney of treatment group III was significantly higher than that of positive control group?P<0.05?.?5?Se protein gene expression.Atthe 42 d of the experiment,the expression levels of Trx R1and SPS2 gene m RNA in liver of were significantly different among the treatment groups?P<0.05?.The expression levels of Trx R1 gene m RNA in treatment group II were significantly higher than those in negative control group?P<0.01?,and the expression levels of SPS2 gene m RNA were significantly higher than those in negative control group?P<0.05?.The expression levels of GSH-Px1,DIO1,Sel P gene m RNA were not significantly different among the treatment groups?P>0.05?,but the expression levels of GSH-Px1,DIO1 gene m RNA in liver of treatment group II were significantly higher than that of negative control group?P<0.05?.?Tolerance of Multiple Doses of Zn-L-SeMet to Weaned Piglets144 weaned piglets weighing 8.17±0.09 kg were selected in the experiment,male and female were equally divided.They were randomly divided into 3 treatment groups,each treatment group 8 repeats,each repeat 6 piglets.The three dietary treatment groupswere:The control group was fed with basic diet without selenium,the effective dose group was added with 0.3 mg/kg Zn-L-SeMet?calculated as Se?in the basic diet,and the multiple dose group was added with 3 mg/kg Zn-L-SeMet?calculated as Se?in the basic diet.The test period is 42d,initial period 0-14 d,and later period 15-42 d.The test results are as follows:?1?Growth performance.There was no significant difference in the growth performance index of piglets among the treatment groups during the experiment?P>0.05?.?2?Blood routine index.There was no significant difference in WBC count,hemoglobin and other blood routine indexes among the three treatment groups?P>0.05?.?3?Blood biochemical indexes.There was no significant difference in total protein,albumin and other serum biochemical indexes among the three treatment groups?P>0.05?.?4?Organ index.There was no significant difference in heart index,liver index and other organ indexes among the three treatment groups?P>0.05?.?5?Histopathology.No pathological changes were found in heart,liver and other tissues and organs among the three treatment groups.?ConclusionThe effectiveness test results showed that the addition of 0.1-0.3 mg Se/kg Zn-L-SeMet to the basic diet could improve the growth performance,increase the serum and tissue selenium content and the expression of tissue selenoprotein genesof weaned piglets,and enhance the body's antioxidant and immune functions.It indicated that Zn-L-SeMet was an effective selenium source for weaned piglets.Important indicators such as production performance and blood biochemistry perform well in the range of 0.1-0.3 mg Se/kg.It is recommended that Zn-L-SeMet should be added in the diet of weaned piglets in an amount of0.1-0.3 mg Se/kg,and the optimal addition amount is 0.2 mg Se/kg.The tolerance test results showed that the addition of 3 mg Se/kg Zn-L-SeMet to the basic feed had no adverse effect on the growth performance of piglets.No abnormality was found in blood routine,blood physiological and biochemical indexes and organ coefficient of piglets,and no pathological changes were found in all tissues and organs.It is suggested that3 mg Se/kg Zn-L-SeMet is within the safe dose range tolerated by weaned piglets.