Effect Of Active Immunity Of LHR Extracellular Protein On Reproductive Performance And Muscle Quality Of Boar

Boars are often castrated in order to enhance growth performance and to facilitate easier management.Different methods of castration are in practice including surgical or mechanical castration,drug castration,and immune vaccine castration.The first two methods tend to cause severe pain and other complications and do not meet the requirements and concepts of modern animal welfare.Immuno-castration is the use of antibodies produced against castration vaccines to neutralize the corresponding endogenous hormones or receptors in the gonadal axis feedback system,which inhibits the production of sex steroid hormones,the occurrence of gametes and the development of gonads.This method is not only effective but also causes less pain and injury to boars.Previous studies have shown that luteinizing hormone(LH)released from the pituitary gland binds to the luteinizing hormone receptor(LHR)on testicular stromal cells and activates LHR-mediated cyclic adenosine monophosphate/protein kinase A.The(cAMP/PKA)pathway regulates the production of androgen testosterone and regulates its physiological functions.Therefore,the development of a castration vaccine using LHR as an immune pathogen may inhibit the production of steroid hormones and gonadal development.Based on the combination of the structure and function of LHR by immunogenicity analysis,the conserved parts of LHR that combined with LH were cloned,and the prokaryotic expression system was used to express and purify them.The obtained LHR extracellular protein fragment was,separately formulated with two different adjuvants(ISA 61 and ISA 201)to immunize weaned piglets.The Improvac vaccine produced in the United States was used as a positive control.After immunization,the antibody and sex hormone levels of each group were detected,and the muscle quality after slaughtering was examined to explore the feasibility of preparing male piglet castration vaccine with LHR.The main findings are as follows:1.The quantification of serum antibodies and serum testosterone showed that both the ISA 61 and the ISA 201 adjuvant group stimulated the body to produce corresponding antibodies and reached the highest-level 40 days after the initial immunization and then the antibody titer began to decline.The antibody titer of the ISA 201 adjuvant group began to rise again after the second booster,but there was no change in the ISA 61 adjuvant group.The serum testosterone level of the ISA 201 adjuvant groups increased gradually after initial immunization and secondary booster immunization,peaked at 40 days of initial immunization,but was lower and remained lower than that of the blank control group.Whereas the serum testosterone level of ISA 61 adjuvant groups reached the highest level at 40 days of initial immunization and was much higher than in the blank control group,and remained high.The above results indicate that the use of ISA 201 as an adjuvant for the LHR of the outer membrane fragment can stimulate the production of the corresponding antibodies to neutralize the endogenous LHR and inhibit the production of testosterone.However,the adjuvant does not produce a strong long-term immune response,and the antigen presentation time is short.The use of ISA 61 as an adjuvant can also stimulate the production of the corresponding antibodies,but it is far from enough to play the role of neutralizing endogenous LHR.2.The detection of testicular and epididymis size and sperm count in epididymis showed that the Improvac vaccine group had the most apparent atrophy of testicles and epididymis compared with other three groups,and the spermatogenic cells were absent at all levels in testicular tissue and the sperm count in the epididymis was the lowest.Compared with control and ISA 61 adjuvant group,the ISA 201 adjuvant group had relatively smaller testicles and epididymis.Spermatogenic cells at all levels of the testicular tissue and the sperm count in the epididymis were also lower in ISA 201 adjuvant group.There was little change in the ISA 61 adjuvant group compared with the blank control group.These suggest that the LHR targeted castration vaccine prepared by ISA 201 adjuvant can inhibit the development of male testicles and epididymis and spermatogenesis in boars,whereas ISA 61 is no the suitable adjuvant for this type of castration vaccine.3.The detection of muscle quality and body weight during slaughtering showed that the intramuscular fat and marble score was lower in the ISA 201 adjuvant group than the other three groups.However,the muscle color value,meat score,pH value,system hydraulic,moisture,tenderness,and other indicators were consistent among the four groups and showed no significant difference.Intramuscular fat is an important indicator of meat quality assessment.These results suggest that ISA 201,as a castration vaccine adjuvant,can reduce intramuscular fat and improve meat quality.There was no significant difference in the body mass and daily weight gain among these groups,suggesting that the castration vaccine did not affect the growth of boars.In summary,this trial validated the effectiveness of LHR as a target for castration vaccines,which can affect the reproductive performance of boars.Our experiments provide a reference and basis for the immune castration of livestock,the breeding control of wild animals and the development of human contraceptive vaccines.