| As a variety with good milk production performance,Holstein dairy cows often have the problem of heat stress in large-scale breeding.In high temperature weather in summer,heat stress can reduce conception rate and milk yield of dairy cows.In order to reduce the effect of heat stress on the reproduction of dairy cows,this experiment uses genetic engineering to obtain inhibin fusion protein from the perspective of endocrine.The method of immunoinhibin combined with estrus synchronization can solve the reproductive problems of dairy cows under heat stress,such as follicular dysplasia and estrus difficulty.Based on the recombinant vector constructed in the early stage of the laboratory,it contains porcine inhibin α.The fusion protein with 175 amino acid residues was obtained by expression,purification and identification.The fusion protein was prepared into a 1 mg/mL immunogen vaccine for subsequent animal experiments.Fifty one Holstein cows were randomly divided into two groups(immunization group n=28,control group n=23).The cows were immunized by single immunization.On the first day,the cows in the immunization group were injected with inhibin immunogen vaccine,the cows in the control group were injected with placebo,and the cows in both groups were injected with CIDR and GnRH.On the 7th day of the experiment,the cows were given PGF2α.The second injection of GnRH was given on the 9th day,and then the artificial insemination was completed within 16-20h.On the 1st,6th,7th,8th,9th,10th,12th,13th,15th,17th,19th,21st,23rd,25th,27th,29th,31st,33rd,35th and 39th day of the experiment,the blood samples of dairy cows were collected,and the FSH,activin,E2,P4 and IFN-τ were detected.The conception rate of cows was recorded.The main results are as follows:1.The recombinant inhibin immunogen vaccine was successfully prepared.SDSPAGE electrophoresis gel verified that the molecular weight of the recombinant protein was correct;the plasma antibody titer test results showed that a single injection of inhibin vaccine can achieve a good active immune effect.By fitting a mathematical model to the antibody titer data,it is inferred that the immunogenic vaccine can be completely degraded on the 50th day after injection,so that the cow can return to normal reproductive performance.2.During the experiment,the test results of various hormones in the blood of cows showed that:on the first day of the test,there were no significant differences in FSH,Activin,E2 and P4(P>0.05),and there were significant differences between FSH and Activin on the second to 25th days of the test.While P4 showed significant differences on the 25th to 35th days of the test,and interferon-τau showed significant differences on the 19th,21st,23rd,and 25th days.The specific results are as follows:(1)Follicle stimulating hormone(FSH):From the first day to the 25th day of the experiment,the change trend of dairy cows in the immune group and the control group was almost the same,showing a trend of first rising,then declining,and then rising;On the 6th to 25th day of the experiment,the difference of FSH between the two groups was very significant(P<0.01),and reached the peak on the 10th day of the experiment.The concentration of FSH in INH group was 26.14±0.34 mIU/mL and control group was 22.09±0.85 mlU/mL.(2)Activin:The change in concentration is similar to that of follicle stimulating hormone,and both show a trend of first rising,then falling and then rising.From the 6th to 25th day of the experiment,the difference of activin concentration between the two groups was very significant(P<0.01),and reached the peak on the 10th day of the experiment.The activin concentration of the INH group was 838.13±11.15 pg/mL and the control group was 638.79± 11.60 pg/mL.(3)Estradiol(E2):Both the test group and the control group showed a single peak change trend.On the 9th day of the experiment,the estradiol concentration of the two groups increased to the peak and showed a significant difference(P<0.05).The estradiol concentration of the INH group was 9.30±0.78 pg/mL and the control group was 6.32±0.75 pg/mL;there was no significant difference between the two groups on the 10th to 25th day(P>0.05).(4)Progesterone(P4):On the first to the 13th day of the test,it rose first and then fell;on the 13th to the 35th day of the test,it gradually rose to a significant difference(P<0.01);the concentration of progesterone in INH group were 2.06±0.12 ng/mL and control group was 2.68±0.24 ng/mL,respectively and the level of progesterone in INH group was lower than that in control group.(5)Interferon-τ au(IFN-τ):On the 19th day of the experiment,the IFN-τ of the two groups have a significant difference(P<0.01).With the extension of pregnancy time,there was a very significant difference(P<0.01),reaching the peak on the 25th day of the experiment.The concentration of IFN-τ:au in INH group was 539.35 ± 13.17 pg/mL,in control group was 194.06±41.22pg/mL.3.Inhibin combined with CIDR-Ovsynch program for the first pregnancy examination on the 47th day,the conception rate of the immunized group at this time was 64.7%,which was significantly higher than that of the control group 26.7%(P<0.05).Experiments have proved that immunosuppressin combined with CIDROvsynch program is of great significance to increase the conception rate of dairy cows under heat stress conditions. |
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