GnRH or eCG treatment fails to restore reproductive function in GnRH immunized ewes

Active immunization with GnRH-tandem-dimer peptide in young male rats reduces serum reproductive hormone concentrations, testicular development and spermatogenesis

GnRH sterilization vaccines have been developed for various practical and clinical reasons. However, conjugation of GnRH peptide to carrier protein has many drawbacks, hampering the further commercialization of GnRH vaccines. In this study, a new nonconjugated GnRH vaccine, D-Lys6-GnRH-tandem-dimer peptide (TDK), emulsified in Specol adjuvant was investigated for its immunocastration efficacy in young male rats. Prepubertal male rats were randomly allocated into three groups (n = 12): control (no treatment), surgically castrated or immunized against 100 μg TDK in Specol adjuvant at 6 weeks of age (with a booster 8 weeks later). Blood samples (for antibody titers and hormone concentrations) were collected at 2-week intervals until rats were killed (18 weeks of age). Compared to intact controls, active immunization against TDK reduced (P < 0.05) serum concentrations of testosterone, inhibin B, LH and FSH, prevented the onset of spermatogenesis at puberty. Furthermore, mRNA expressions of GnRH receptor, LH-β and FSH-β in the pituitary, LH receptor, FSH receptor, inhibin α, βA and βB subunit in the testes were decreased in immunocastrated rats compared to intact controls (P < 0.05). These results demonstrate for the first time that GnRH-tandem-dimer peptide emulsified in Specol is a promising veterinary sterilization medicine.

Effect of immunization against GnRH on hypothalamic and testicular function in rams

The objective was to determine effects of active immunization against GnRH on reproductive function in Tibetan rams. Peripubertal Tibetan rams (n = 30) were randomly and equally allocated into three groups: control (no treatment); surgically castrated; or immunized against 100-μg d-Lys6-GnRH-tandem-dimer peptide conjugated to ovalbumin in Specol adjuvant at 24 weeks of age (with a booster 8 weeks later). Blood samples (for antibody titers and hormone concentrations) were collected at 4-week intervals until rams were killed (40 weeks). Immunization triggered a good antibody response in all immunized rams (P < 0.01). Compared with intact controls, anti-GnRH immunization reduced (P < 0.01) serum concentrations of testosterone, inhibin A, LH, and FSH, and it induced testicular atrophy (suppression of spermatogenesis). Androstenone concentrations in fat tissues of GnRH-immunized rams were also rendered nondetectable (P < 0.001). Furthermore, mRNA expressions of GnRH receptor, LH-β, and FSH-β in the pituitary and of LH receptor, FSH receptor, and inhibin α and βA subunits in the testes were decreased in immunized rams compared with intact controls (P < 0.05). This was apparently the first report that active immunization against GnRH-tandem-dimer-ovalbumin conjugate in Specol adjuvant was an effective alternative to surgical castration for Tibetan rams under practical Tibetan plateau conditions.

Immunization against recombinant GnRH-I alters ultrastructure of gonadotropin cell in an experimental boar model

BACKGROUND

Gonadotropin cell is the main responsible for the secretion of follicle stimulating hormone (FSH) and luteinizing hormone (LH), and immunocastration reduces the concentrations of serum FSH and LH. A few studies have reported the histological structure of gonadotropin cells obtained from immunocastration animals at the light microscopy level. However, the ultrastructure of gonadotropin cells remains largely unexplored. The aim of this study was to evaluate and to compare ultrastructure of gonadotropin cell in gonadally intact boars and immunologically castrated male animals.

FINDINGS

In this study, serum and adenohypophysis tissue were collected from nine gonadally intact boars and nine male pigs treated with recombinant gonadotropin releasing hormone I (GnRH-I). Anti-GnRH-I antibodies in serum and the ultrastructure of gonadotropin cell in adenohypophysis were determined by enzymelinked immunosorbent assay and electron microscopy, respectively. The results demonstrated that active immunization against recombinant GnRH-I increased serum GnRH-I antibody levels (P<0.05). Ultramicroscopic analysis of gonadotropin cell revealed a decrease (P<0.05) in the number and size of the large granules and small granules in the recombinant GnRH-I immunized animals.

CONCLUSIONS

We conclude that immunization against recombinant GnRH-I induces severe atrophy of granules in gonadotropin cell of boars, possibly reflecting GnRH-I regulation of gonadotropin cell.

Fattening performance, carcass and meat quality characteristics of Kivircik male lambs

The objective of this study was to determine the fattening performance and carcass and meat quality characteristics of Kivircik twin male lambs. Twelve lambs at approximately 5 months of age were subjected to a finishing diet for 60 days. Average live weight of lambs at the beginning and the end of the fattening were 23.14 ± 0.84 and 39.0 ± 1.01 kg, respectively. Daily live weight gain and feed conversion efficiency were found as 0.265 ± 0.007 and 6.14 kg, respectively. Hot carcass weight, cold carcass weight, and dressing percentage were 19.6 ± 0.6 and 18.9 ± 0.6 kg and 48.1 ± 0.3%, respectively. Kidney-pelvic fat weight, internal fat weight, and m. longissimus dorsi area were 0.117 ± 0.023 and 0.364 ± 0.041 kg and 15.26 ± 0.70 cm(2), respectively. The percentages of leg, back loin, forearm, shoulder, neck, flank-chest, kidney-pelvic fat, and internal fat in carcasses of the lambs were found as 34.1 ± 0.4%, 19.6 ± 0.3%, 21.0 ± 0.2%, 7.0 ± 0.3%, 10.5 ± 0.3%, 7.2 ± 0.2%, 1.3 ± 0.1%, and 1.8 ± 0.1%, respectively. Averages water content, ash, protein content, and fat content of meat samples were 73.4%, 1.0%, 19.5% and 3.6%, respectively. pH and thiobarbituric acid reactive substances values of meat samples were 5.55 and 0.056 ± 0.017. L*(lightness), a*(redness), and b*(yellowness) values were recorded as 43.87, 12.69, and 10.22, respectively. Thus, we conclude that fattening performance, carcass, and meat quality of Kivircik lambs are satisfactory levels than that of other native breeds.