Temporal changes in serum luteinizing hormone following ovariohysterectomy and gonadotropin-releasing hormone vaccination in domestic cats.

Measurement of circulating luteinizing hormone (LH) concentrations in cats and temporal changes following ovariohysterectomy (OHE) or possibly GnRH vaccination may be informative for assessing their fertility, contraception or sterilization status. In this study, serum LH concentrations were measured in domestic cats (n = 6) immediately prior to and up to 120 days post-OHE. Basal LH concentrations of females previously subjected to OHE (n = 4; ~1.5 years post-OHE) were compared pre- and post-vaccination with a GnRH immunocontraceptive, and to LH concentrations in intact females. Basal serum LH concentrations (2.67 ± 0.43 ng/ml; mean ± SEM) in intact females increased (p < .01) by 30 days post-OHE (5.65 ± 0.87 ng/ml) but then declined (p < .05) to pre-OHE levels (mean range, 3.26-3.62 ng/ml) at days 60-120 post-OHE. Serum LH (3.84 ± 0.51 ng/ml) in four females ~1.5 years after OHE tended to be higher (p = .10) than those of intact females prior to OHE. Three months following first or second GnRH immunocontraceptive vaccine treatment, serum LH values in females previously subjected to OHE decreased (p < .05) to concentrations similar to those observed in intact females. Our preliminary results suggest that OHE of domestic cats causes a marked increase in basal LH levels within the first few weeks after ovariohysterectomy followed by a return to pre-OHE basal values over the next several months. Reduced LH concentrations after GnRH vaccine may indicate the effectiveness of the immunocontraceptive in reducing the circulating levels of GnRH, thereby reducing secretion of LH.

Safety and effectiveness of a single and repeat intramuscular injection of a GnRH vaccine (GonaCon™) in adult female domestic cats.

Sterilization is a key strategy to reduce the number of domestic cats entering and killed in shelters each year. However, surgical sterilization is expensive and labour-intensive and cannot fully address the 70 million free-roaming cats estimated to exist in the United States. GonaCon™ is a gonadotropin-releasing hormone vaccine originally developed for use as a wildlife immunocontraceptive. An earlier formulation was tested in domestic cats and found to be safe and effective for long-term contraception. However, the current Environmental Protection Agency (EPA)-registered formulation consists of a different antigen-carrier protein and increased antigen concentration and has never been tested in cats. A pilot study was undertaken to evaluate the short-term safety of a single GonaCon immunization, assess the consequences of vaccinated cats receiving an accidental second GonaCon injection and determine the humoral immune response to immunization. During Phase 1, cats in Group A (n = 3) received a single intramuscular injection of GonaCon and Group B (n = 3) received a single intramuscular injection of saline. During Phase 2, Group A received a second GonaCon injection and Group B received their initial GonaCon injection. All cats developed GnRH antibodies within 30 days of vaccine administration. The endpoint titre (1:1,024,000) was similar among all cats, and levels remained high throughout the duration of the study. Four cats developed a sterile, painless, self-limiting mass at the site of injection. The mean number of days to mass development was 110.3 (range, 18-249 days). In conclusion, this preliminary study suggests that the EPA-registered GonaCon formulation is safe for continued testing in domestic cats, an accidental revaccination should not increase the risk of a vaccine reaction and the EPA-registered formulation effectively elicits a strong humoral immune response.

Urethral catheterization and sperm vitrification for simplified semen banking in felids.

Semen banking of domestic cats and wild felids represents a vital resource for their long-term conservation, but current methods require access to advanced training and specialized equipment. A newer method of semen collection, urethral catheterization of medetomidine-treated cats, allows recovery of high sperm numbers, but it is unclear if this approach permits maximal sperm recovery or is feasible using less expensive alpha-2 agonists. Similarly, a newer sperm preservation approach, vitrification, offers advantages of simplicity and minimal equipment needs, but its efficacy in combination with urethral catheterization has not been investigated. Our specific objectives were to (i) evaluate sequential semen recovery with urethral catheterization and electroejaculation in domestic cats, (ii) assess the effectiveness of a weak (xylazine) versus strong (dexmedetomidine) alpha-2 agonist for inducing sperm release, and (iii) compare post-thaw sperm motility, acrosome status and fertilizing capacity of catheter-recovered samples after vitrification or straw freezing. Results indicated that electroejaculation following repeated catheterization allowed recovery of additional spermatozoa (range, 11-32 × 106  sperm/male) and that xylazine was ineffective for inducing meaningful sperm release (range, 0-0.4 × 106 sperm/male). Post-thaw motility and acrosome status of vitrified catheter samples did not differ (p > .05) from that of straw frozen samples. Preliminary results indicated that in vitro fertilization success (9/30, 30%) of vitrified catheter sperm did not differ (p > .05) from that observed with straw frozen samples (17/30, 57%). In conclusion, urethral catheterization of dexmedetomidine-treated cats allows recovery of substantial sperm numbers but electroejaculation still may be warranted for maximal sperm recovery. Xylazine is not suitable as an inexpensive alternative to dexmedetomidine for catheterization. Vitrification of catheter samples results in comparable post-thaw parameters to straw freezing and may be adequate for use with oviductal insemination procedures.

Molecular markers of spermatogonial stem cells in the domestic cat.

Spermatogonial stem cells (SSCs) represent an exciting new avenue for assisted reproduction in endangered and genetically valuable species. Before this technology can be applied to wildlife, species-specific markers are required to evaluate SSC enrichment strategies and monitor subsequent in vitro culture. This study was designed to evaluate six conserved SSC markers (THY1, GPR125, GFRalpha1, PLZF, UCHL1 and OCT4) in the cat. Testes from three juveniles and three adults were obtained following routine castrations and processed for mRNA extraction. RT-PCR of whole testis and cell suspensions enriched for SSCs by differential plating confirmed that all six SSC markers are expressed in both the whole testis and SSC-enriched cell fractions. The expression of all six putative SSC marker genes in the cat testis suggests conservation of SSC markers, and perhaps self-renewal mechanisms, in felids.