Residue Of GnRH-liked Vaccine In Rats And Safety Of Meat From Immunocastrated Animals

In late 1960s, Hormone immuno-nutralization techniques emerged on the foundation of immunology, biochemistry and endocrinology. Hormoneimmuno-nutralization techniques offered a new alternative to traditional surgical castration in animal production. Gonadotrophin releasing hormone(GnRH) is released from the basal hypothalamus median eminence and stimulates the anterior pituitary gland to secrete luteinising hormone (LH) and follicle stimulating hormone (FSH),which together regulate testicular and ovarian functions. Immunization against the hormone prevents circulating GnRH from binding to pituitary receptors through immuno-neutralization(i.e.binding by antibodies), hence blocking further interaction and physiological events. Studies on the avtive immunization against GnRH were carried out in animals such as pigs, catlles, goats and chikens. And much progress were obtained. However, customers asked: whether there is residue of the vaccine in the animals?How about the meat safety of the immunized animals?As far as we know, no reported on the residue of the vaccine in the animals and the meat safety of the immunized animals was found. In order to answer those questions, the residue of the vaccine in the animals and the meat safety of the immunized animals were investigated in current study, the results obtained are as follows:1. Radioiodine-labeling of GnRH-Tandem-Dimer (GnRH-TDK)The two-phase chloramine-T method was uesd in the radioiodine-labeling of GnRH-TDK. The iodine incorporation was determined by trichloroacetic acid (TCA) and aγ-ray survey meter. The labeled compound was purified by ultrafiltration. The purity of the labeled GnRH-TDK was determined by TCA and the immunologic activity in vivo was determined. The results demonstrated that the iodine incorporation, radiochemical purity and specific radioactivity of¹²⁵I-GnRH-TDK was 78.69%, 91.26% and 1.94×105 Bq.μg-1 respectively, and the immunological activity of¹²⁵I-GnRH-TDK was not affected by the radio-labeling.2. Residue of¹²⁵I- GnRH -TDK-OVA in ratsTissue distribution and excretion of GnRH-TDK-OVA in rats were investigated. The results demonstrated that 24days after immunization, trace quantity on the level of 0.45±0.23μg/g was found in the injection site and no residual was found in the other tissues. 49.30±9.07% of vaccine was excreted in urine and feces, and other vaccine was degradated and eliminated by the way of immunological reaction and metabolic transformation.2. Safety of meat from immunocastrated animalsEffects of active immunized with new GnRH-likcd vaccine on reproduction performance of rabbits were studied. The meat from immunocastratcd rabbits was mixed in the feedstuff of some rats and someothcr rats was fed with the immunogen or antiserum for 8weeks. The reproduction performance of the rats was evaluated. The results demonstrated the testosterone level, sexual behaviour, testes size and histological analysis of the rats which having meat of immunocastrated animals were similar to that of normal rats. Meat from animals immunized against GnRH did no harm to the health of rats.