This study investigated the effects of Improvac and Bopriva, two anti-GnRF immunization products, on testicular function in boars. We predicted that both products would diminish testicular function; however, we specifically tested the hypothesis that the duration of efficacy for Bopriva would be longer than that of Improvac. Animals were immunized with either Improvac or Bopriva and then observed ten weeks after the second injection. Serum GnRF antibody titers rose after the second injection and peaked approximately two weeks later. At the same time testosterone concentrations decreased to undetectable levels and remained below assay detection for at least six weeks. At approximately eight weeks, testosterone began to increase in animals treated with Improvac though levels remained decreased in Bopriva treated animals throughout the ten weeks. Daily sperm production at 10 weeks was significantly reduced in both treatment groups; however, the reduction was greater in Bopriva treated boars. Examination of testes of both treatments revealed incomplete spermatogenesis with impaired spermatid production and reduced seminiferous tubule diameter. These findings were universal in Bopriva treated animals, but Improvac treated animals exhibited morphologies intermediate between Bopriva treated animals and control boars. Overall testicular function in Bopriva boars remained suppressed ten weeks post-immunization while Improvac boars appeared to be recovering.
Keywords: Anti-GnRF; Boar; Spermatogenesis; Testis; Testosterone.
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