Improvac Induces Immunocastration By Affecting Serum Testosterone Levels And Disrupting Spermatogenesis In Male Broiler Chickens

Improvac is a vaccine for animal immunocastration through the immune neutralization of gonadotropin releasing hormone?GnRH?.To date,Improvac has been used for boar immunocastration,and there is no relevant literature on the application of Improvac in broiler chickens immunocastration.In the present study,we evaluated the effects of Improvac-based immunocastration on testosterone levels and spermatogenesis in broiler chickens and the effects of Improvac on the expression of genes related to testosterone biosynthesis and metabolism as well as spermatogenesis,to reveal whether Improvac can be used in immunocastration in male broiler chickens,and to lay a foundation for exploring immunocastration product based on the immune neutralization of GnRH.120 two-week-old roosters were randomly divided into four groups?n=30?:control group,early group,late group,and early+late group.Each of bird in control group was injected with 0.6 ml saline at week 3 and 6.Each of bird in early group was injected with 0.6 ml Improvac at 3 week,and 0.6 ml saline at week 6,and bird in late group was injected with 0.6ml saline at week 3 and 0.6ml Improvac at week 6.In early+late group:each of bird was injected with 0.6ml Improvac at weeks 3 and 6.And then,live weights of all birds were weighed weekly,and comb and wattle size were measured at 5^th,11^th and 14^th week post-hatching.Blood was collected at 3^rd,6^th,9^th and 14^th week to determine testosterone concentrations.These testes were collected at 5^th,9^th and 14^th week post-hatching to detect testicular development and testosterone synthesis and metabolism,and spermatogenesis related gene expression.The results showed that:?1?No significant differences were observed in the comb length and height or wattle width and length in all four groups on weeks 5,11and 14 and the testicular coefficient showed no significant differences in all four groups at 14^th week?P>0.05?.At age of 7-week-old,the ADG was significantly higher in the Improvac-immunized groups than that in the Control group?P<0.05?.At14-week-old,ADG of Early and Early+Late groups was significantly higher than that of Control group?P<0.05?.?2?At 6 weeks of age,the testosterone levels in the immunized groups were significantly higher than those in the control groups?P<0.05?.At 9 weeks of age,the testosterone levels in the Control group were significantly higher than those in all the immunized groups?P<0.05?.At 14 weeks of age,the testosterone levels in the Control group and Early+Late group were significantly higher than those in the Early and Late groups?P<0.05?.?3?At 5 weeks of age,HSD₃B₁ expression was significantly higher?P<0.05?in the Early group than that in the Control group.The expression levels of Cyp₁₇A₁,Cyp₁₉,HSD₃B₁ and HSD₁₇B₃ were significantly lower in Control group than those in the immunized groups at 9 weeks of age?P<0.05?,the expression level of the HSD₁₇B₂ gene was significantly higherin the Early group than that in the Control,Late and Early+Late groups?P<0.05?.At 5 weeks of age,the expression of the Cyp₁₇a₁and Cyp₁₉ genes was significantly lower in the Early group than that in the Control and Early+Late groups?P<0.05?.The expression level of the HSD₃B₁ gene was significantly lower in the Late group than that in the Early+Late group?P<0.05?;the expression levels of HSD₁₇B₂ and HSD₁₇B₃ were significantly lower in the immunized groups than those in the control group?P<0.05?.?4?At 9 and 14 weeks of age,the area and diameter of the STs in the Control group were significantly larger than those in the Improvac immunized groups?P<0.05?;at 14 weeks of age,the height of the germinal epithelium was significantly higher in the Control group than that in the immunized groups?P<0.05?.?5?At 14 weeks of age,the percentage of STs containing intact sperm was significantly higher in the Control group than that in the Improvac-immunized groups?P<0.05?.The expression levels of CyclinA₁ and CyclinA₂ were significantly lower in the Improvac-immunized groups than those in the Control group?P<0.05?.The expression level of M₁ap was significantly lower in the early group than that in the Control,Late and Early+Late groups?P<0.05?.No significant difference was observed in the expression level of the Scp3 gene among four groups?P>0.05?.Conclusion:Improvac immunocastration increases the average daily gain;inhibits the development of STs,spermatogenesis and down-regulates the expression levels of testosterone anabolism(CYP₁₇A₁,CYP₁₉,HSD₃B₁,and HSD₁₇B₃)and spermatogenesis?Cyclin A₁,Cyclin A₂?genes.