Reproduction In Domestic Animals, vol.44, no.4, pp.593-599, 2009 (SCI-Expanded)
This study was designed to evaluate the effectiveness
of a luteinizing hormone releasing hormone (LHRH) fusion protein immunization
on reproductive traits in ram lambs including the changes in histology and
ultrasonographic appearance of testis. Thirty native ram lambs at 19 weeks of
age were divided into control (C, n = 10), immunization (I, n = 10) and
castration (E, n = 10) groups. Animals in immunization group were immunized
against LHRH using ovalbumin-LHRH-7 (OL) protein generated by recombinant DNA
technology as a primary and a booster injection at 19 and 23 weeks of age
respectively. Animals were bled via jugular venepuncture at 2-week intervals to
determine LHRH antibody and testosterone concentrations. Bi-weekly
ultrasonographic examination of the testes was performed to determine the
changes in ultrasonographic appearance as the age increased. Biopsied
testicular tissues taken at 19, 29 and 41 weeks age were also evaluated. At 41
weeks of age, animals were slaughtered. Semen and epididymis were evaluated for
the presence of sperm cells. Testicular development and sperm production were
suppressed in the immunized animals. Semineferous tubule diameters decreased,
basal membrane of the tubule was thickened and hyalinized in immunized ram
lambs. While testes of control animals gained their normal ultrasonographic
appearance as the age increased, immunized animals had uniform hypoechogenic
testicular structure as observed at 19 weeks of age until slaughter.
Simultaneous histological and ultrasonographic evaluations indicated that the
changes in testicular histology could partly be monitored via ultrasonographic
imaging. Nevertheless, it is difficult to claim that ultrasonographic image
reflects the exact changes in such instances. In conclusion, these results
indicate that recombinant OL fusion protein is effective in immunocastration in
ram lambs and has a potential to be used as an alternative to physical
castration. Further research studies should be conducted to help assess
reproductive status of testes from ultrasound images.