Effects Of Different Dietary Selenium Supplement On Growth, Silenium Retention In Tissues, Rumen Fermen Tation And Reproductive Performance In Growing Ewes

The selenium could adjust the activity of thyroxin and insulin-like growth factor,enhance the decomposition of animal organism to glycogen,protein and adipose,and contribute to body energy supply as well as promote animal growth.In addition,selenium has an effect of anti-oxidation in vivo,so it is able to inhibit lipid peroxidation and scavenge needless free radicals,thus protecting the membrane structure and function of organism and affecting the growth and reproductive capability of animals and human beings.In the present study,48 ewes in six-month-age were fed with distinct TMR diet which contained different sources and levels of selenium,then we studied their influence on growth performance,rumen fermentation,slaughter performance,meat quality and so on.This study provides a scientific basis for adding appropriate concentration of selenium in sheep breeding.Experiment one:Effects of different sources and levels of dietary selenium supplementation on growth and rumen fermentation in growing sheepA total of 48 ewes in six-month-age with 27.95±0.27 kg weight that were randomly divided into four groups with 12 ewes every group which were fed(by selenium)with 0.5 mg/kg selenium yeast(Group 0.5 SY),0.3 mg/kg selenium yeast(Group 0.3 SY),0.3 mg/kg sodium selenite(Group 0.3 SS)and 0 mg/kg(Group C)as well as the same daily ration with the same quantity respectively.The experimental period was 70 days which contained 10-days preliminary trial period and 60-days formal experiment period.The results indicated that:compared with the group C,the addition of selenium in feedstuffs could increase the daily gain of Hu sheep and decrease feed-weight ratio(P<0.05).Among which the weight gain of group 0.3 SY was the best,the feed-weight ratio of group 0.5 SY and group 0.3 SY was significantly decreased(P<0.05);Dietary nutrient digestibility was improved,apparent digestibility of NDF and ADF for group 0.3 SS was significantly higher than other groups(P<0.05);Apparent digestibility of CP for group 0.3 SY and group 0.3 SS were significantly higher than that of group C(P<0.05);Tumor gastric juice pH value of Group 0.5 SY was significantly higher than that of group C(P<0.05);Ammonia nitrogen level of Group 0.5 SY and 0.3 SY group were significantly lower than that of group C(P<0.05);Acetic acid concentration and the concentration of total volatile fatty acids of group 0.3 SY were significantly higher than other groups(P<0.05).In summary,0.3 SY contributed to promote the growth and rumen fermentation of Hu sheep.Experiment two:Effects of different sources and levels of dietary selenium supplementation on meat quality,serum biochemical parameters and selenium content in muscle,liver and blood of growing sheepAfter feeding with different concentrations and sources of selenium,Slaughter performance,meat quality,serum biochemical parameters and selenium content in muscle,liver and blood in of growing sheep were detected.The results reveled that:The TP of group 0.3 SY and group 0.3 SS were significantly higher than that of group C(P<0.05);The ALB of group 0.5 SY and group 0.3 SY were significantly higher than that of group C(P<0.05);The GLO and GPT of group 0.3 SY were significantly higher than those of other groups(P<0.05);Compared with the group C,the addition of selenium in feedstuffs significantly increased the GOT and the GOT of group 0.3 SY was remarkably higher than other groups(P<0.05).The ALP of group 0.3 SY and group 0.3 SS were significantly higher than that of group C(P<0.05);The TG of group 0.3 SY was significantly higher than that of group C(P<0.05);In addition,the PH of longissimus dorsi(P<0.05)of group 0.3 SY was significantly higher than the control group.Moreover,the selenium deposition in the liver and longissimus dorsi of group 0.3 SY were remarkably higher than those of other groups.In summary,0.3 mg/kg dietary selenium supplementation contributed to promote the growth of growing Hu sheep and increase the selenium deposition in the liver and longissimus dorsi.Experiment three:Effects of different dietary selenium yeast supplementation level on reproductive hormones in the initial cycle blood of growing sheepA total of 36 ewes in six-month-age with 27.95±0.27 kg weight that randomly divided into three groups with 12 ewes every group which were fed with 0.5 mg/kg selenium yeast(Group 0.5 SY),0.3 mg/kg selenium yeast(Group 0.3 SY)and 0 mg/kg(Group C)as well as the same daily ration with the same quantity.The experimental period was 70 days,the first 10 days was the preliminary trial period and the last 60 days was the formal experiment period.The results indicated that:The average FSH value of the experimental group was significantly higher than that of the control group,and group 0.3 SY was remarkably higher than that of other groups(P<0.05);Serum FSH concentration peaks appeared at the 3th,10th and 15th day of estrous cycle of all groups,and the peak value of the experimental group was significantly higher than that of the control group,and group 0.3 SY was remarkably higher than that of other groups(P<0.05);The average LH value of the experimental group was significantly higher than that of the control group,and group 0.3 SY was remarkably higher than that of other groups(P<0.05);Serum LH concentration peaks appear at the 5th,9th and 15th day of estrous cycle of all groups,and the peak value of the experimental group was significantly higher than that of the control group,and group 0.3 SY was remarkably higher than that of other groups(P<0.05);The average P4 value of the experimental group was significantly higher than that of the control group,and group 0.3 SY was remarkably higher than that of other groups(P<0.05);Serum P4 concentration peaks appeared at the 5th day of estrous cycle of all groups,and the peak value of the experimental group was significantly higher than that of the control group,and group 0.3 SY was remarkably higher than that of other groups(P<0.05);The average E2 value of the experimental group was significantly higher than that of the control group,and group 0.3 SY was remarkably higher than that of other groups(P<0.05);Serum E2 concentration peaks appeared at the 1th,5th,11th and 15th day of estrous cycle of all groups,and the peak value of the experimental group was significantly higher than that of the control group,and group 0.3 SY was remarkably higher than that of other groups(P<0.05);In summary,0.3 SY contributed to increase the blood hormone content of the growing Hu sheep and improve their reproductive performance.Experiment four:Effects of different dietary selenium yeast supplementation level on the estrus rate,follicular development and expression of follicular development associated genes of growing sheepThe results revealed that:The estrous rate of sheep fed with 0.3 mg/kg and 0.5 mg/kg selenium yeast was increased by 37.52%and 25.01%;The age of puberty of 0.3 SY(204.4 d)was significantly shorter than the group C(210.83 ±8.18 d)(P<0.05).The ewes were slaughter at estrus and the follicle number were counted,the total numbers of follicle in 0.3 SY and 0.5 SY were increased by 60.71%and 25%respectively and compared with the control,the follicle number in 0.3 SY was significantly increased(P<0.05);The numbers of follicles with diameter>3 mm and<3 mm were significantly more than the group C(P<0.05);The corpus luteum number of 0.3SY was also significantly more than the group C.qPCR analysis of follicular development associated genes revealed that the expression of FSHR and LHR in 0.3 SY group were significantly higher than in group C(P<0.05);The expression of Selw and GPx4 in 0.3 SY group was significantly higher than that in the group C(P<0.05);The expression of ACE in 0.3 SY group was significantly lower than that in the group C.All together,0.3 mg/kg dietary selenium yeast supplementation contributed to promote estrus,follicular development and significantly increased the expression of FSHR,LHR,Selw and GPx4 and decreased the expression of ACE in ovary.