Effect of Natural Photoperiod on Epididymal Sperm Quality and Testosterone Serum Concentration in Domestic Cat (Felis silvestris catus)

Collection of epididymal semen in the tomcat (Felix catus) by stereomicroscope-aided retrograde flushing (SARF) improves sample quality

In small and laboratory animals epididymal spermatozoa can be collected only by the mincing technique however, blood and cell debris contamination may adversely affect the quality of the samples. This study aimed at performing the retrograde flushing technique, for the first time, in the tomcat. In the first experiment attempts to insert a blunted needle into tomcats' ductus deferentes were made and the cannulation time and the success rate were recorded. In the second experiment, insertion of the needle into the ductus was carried out under a stereomicroscope for one testis, while the other was submitted to mincing for sperm recovery and the samples obtained from paired testes were compared. In the first study, only twenty-eight percent of the cannulation attempts were successful whereas in the second experiment, 91% of the deferentes were successfully cannulated: 80% of the ducts were cannulated in less than three minutes. The stereomicroscope-aided retrograde flushing samples showed significantly higher sperm viability, motility and velocities, as compared to those resulted from mincing. The domestic cat serves as a model for more than 36 species of wild felids; the developed stereomicroscope-aided retrograde flushing technique has the potential to become the gold standard method for harvesting spermatozoa of endangered species that have a small ductus deferens.

Effect of season on the dynamics of cat sperm DNA fragmentation

BACKGROUND

Feline species undergo reproductive seasonality; thus, sperm characteristics, such as DNA integrity, can be affected by the photoperiod. This study was conducted to determine the effect of seasonal changes on sperm quality and on the dynamics of sperm DNA fragmentation. Epididymal spermatozoa were collected from 36 tomcats subjected to bilateral orchiectomy during breeding (BS) and non-breeding (NBS) seasons. Sperm samples were obtained by cutting the cauda epididymis and assessed for sperm motility, concentration, acrosome integrity, plasma membrane integrity and sperm morphology. Sperm DNA fragmentation was evaluated by the sperm chromatin dispersion test after 0, 6, and 24 h of incubation at 37 °C.

RESULTS

The total sperm motility and plasma membrane integrity values were greater during the BS, while the percentages of abnormal sperm and head defects were lesser (p < 0.05). No significant differences in DNA fragmentation were found between seasons after sperm collection. DNA damage was greater after 24 h of incubation at 37 °C in both seasons, although the percentage of spermatozoa with fragmented DNA was significantly lesser in the BS than in the NBS at 24 h (p < 0.05).

CONCLUSIONS

The study suggests seasonal changes in some of the quality parameters of cat sperm. DNA fragmentation dynamics were affected by the time of incubation and reproductive season; therefore, this technique might be used as an additional tool to test the potential fertility of semen samples used in feline-assisted reproduction.

Proliferation and Apoptosis of Cat (Felis catus) Male Germ Cells during Breeding and Non-Breeding Seasons

Simple Summary

Spermatogenesis is a complex process through which male gametes, spermatozoa, are produced starting from stem germ cells called spermatogonia. The existing information on cat spermatogenesis is limited and somewhat contradictory. In fact, although this species is considered a long-day breeder with a reproduction period starting when the day length increases and ending in late autumn, spermatogenesis and sperm production occur throughout the year. In order to assess whether cat spermatogenesis is modulated according to a season pattern, we analyzed testes taken from feral cats orchiectomized during reproductive (February–July) and non-reproductive (November and December) periods. The results of the analyses carried out in the present study showed that spermatogonial proliferation was more intense during the reproductive period and germ cell death via apoptosis (a programmed form of cell death) increased during the non-reproductive period. Our results confirm the hypothesis that cat spermatogenesis is seasonally modulated through changes of germ cell proliferation and apoptosis, according to a common paradigm of seasonally breeding species.

Abstract

The domestic cat (Felis catus) is a seasonal-breeding species whose reproductive period starts when the day length increases. Since the existing information on cat spermatogenesis is limited and somewhat contradictory, in the present study, germ cell proliferation and apoptosis in feral adult tomcats orchiectomized during reproductive (reproductive group, RG; February–July) and non-reproductive (non-reproductive group, NRG; November and December) seasons were compared. Cross-sections taken from the middle third of the left testis were chemically fixed and embedded in paraffin wax. Histological sections were processed for the immunohistochemical detection of proliferating germ cells (PCNA) and for the identification of apoptotic cells (TUNEL method). The percentage of PCNA-positive spermatogonia was higher in the RG than in the NRG. On the contrary, germ cell apoptosis was higher in the NRG than in the RG. Our results confirm that cat spermatogenesis is modulated on a seasonal basis and suggests that spermatogenesis control involves changes in germ cell proliferation and apoptosis according to a common paradigm of seasonally breeding species.

Relationship between semen quality and seminal plasma cholesterol, triacylglycerols and proteins in the domestic cat

OBJECTIVES

The current study aimed to evaluate the relationship between specific seminal plasma components - cholesterol (CHOL), triacylglycerols (TAG) and total protein (PROT) concentrations - and semen quality in cats. A further aim was to determine the relationship between specific seminal protein bands and semen quality.

METHODS

Thirteen toms, 2-5 years of age, were included. Semen collection was performed by electroejaculation every 4 weeks. Fifty-eight ejaculates were assessed for motility, velocity, volume, sperm concentration, total sperm count, viability, acrosome integrity, plasma membrane integrity and sperm morphology. Samples were divided into two groups: good semen quality (GSQ) and poor semen quality (PSQ). After evaluation, seminal plasma was separated from the sperm by centrifugation and stored at -20°C. CHOL, TAG and PROT concentrations were then assessed and seminal plasma protein profile was determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE).

RESULTS

Seminal plasma CHOL and TAG concentrations, motility, velocity, sperm concentration, total sperm count and sperm morphology were significantly higher in GSQ cats compared with PSQ cats (P <0.01). Moreover, seminal plasma SDS-PAGE analysis showed an identifiable extra band exclusively in the GSQ group.

CONCLUSIONS AND RELEVANCE

Data obtained in this study showed that seminal plasma CHOL and TAG concentrations and specific protein bands could be used to improve semen evaluation in toms. In this sense, the 14 kDa protein band could be a valuable marker for semen quality in the cat and should be further investigated. However, more studies are necessary to determine its relationship with fertility.

Interval between Removal of a 4.7 mg Deslorelin Implant after a 3-, 6-, and 9-Month Treatment and Restoration of Testicular Function in Tomcats

Deslorelin implants have been used to produce a reversible sterilization in several species. In cats, the prolonged duration (12-15 months in tomcats and 18-22 months in queen) is often too much for cat breeders who request early implant removal. The interval between implant removal and resumption of reproductive function in cats has never been investigated. Eighteen tomcats received a 4.7 mg deslorelin implant placed in the periumbilical area and surgically removed during all seasons of the year after 3, 6, or 9 months (n = 6, 6, and 6 cats, respectively). Following implant removal, all cats received a clinical exam every two weeks, including testicular ultrasonographic measurement, observation of penile spikes, and blood collection for serum testosterone assay. Restoration of serum testosterone secretion occurred after 23 ± 6, 23 ± 6, and 22 ± 7 days in the 3-, 6-, and 9-month groups, respectively. Restoration of testicular function was confirmed by histology in 13/15 cats undergoing orchiectomy at the end of the study while the owners of the remaining two cats opted to maintain their animals intact. Removal of a 4.7 mg deslorelin implant after 3, 6, or 9 months is followed by resumption of serum testosterone secretion after about 3 weeks independent of age or season.

Effect of exogenous melatonin treatment on the reproductive characteristics and progeny of male rats exposed to different periods from light and darkness

Light is an important environmental factor that controls the regulation of physiological functions of organisms. Melatonin is considered as one of the major hormones that play an important role in protecting body from many harmful effects and acts as a powerful anti-oxidant source to controlling the levels of antioxidant enzymes within the body. The main objectives of this work were to study the effect of 1) photoperiod changes and 2) exogenous melatonin hormone treatment on the sperm properties, body and testis weight, embryo characteristics, and concentration level of melatonin and testosterone in treated rat serum. This study has been conducted using thirty-six male rats and one hundred and twenty female rats. Animals were divided into six groups, each group containing six males and twenty female rats. Our results showed a significant influence of photoperiod changes on the melatonin and testosterone hormones concentration in rats serum, body weight only, while the other characteristics not affected. As for the effect of melatonin it has been found that the movement of sperm in GIII and IV, as well as embryos absorbed and newborns weight traits has been significantly affected, while the rest of the properties were not significantly affected by melatonin treatment.

Use of the gonadotropin-releasing hormone (GnRH) stimulation test to monitor gonadal function in intact adult male cats

The gonadotropin-releasing hormone (GnRH) stimulation test is a common procedure used to investigate normality of the pituitary-gonadal axis in mammals. There is very little information on the technique, its efficacy and side effects in small animals and in particular no information for male cats. In dogs, such test is performed by intravenous (IV) administration. With cats, the number of times the animal needs to be restrained for blood sampling should be the least possible. The purpose of this study was to assess efficacy and side effects of the GnRH stimulation test in tomcats comparing the IV with the intramuscular (IM) route of administration. A GnRH stimulation test was performed in eight adult tomcats through IM or IV administration of 50 μg gonadorelin. The response of the pituitary-gonadal axis was assessed by measuring serum testosterone on blood samples collected prior to and 1 hr following treatment. When considering each single group of cats, the post-stimulation serum testosterone values were significantly higher than the pre-treatment ones (p < .05). When comparing the two groups of cats, basal testosterone concentrations did not differ, and also post-GnRH testosterone concentrations did not differ. In conclusion, in the cats of our study, the GnRH stimulation test produced the same results following the IM or the IV route of administration. Therefore, in tomcats, the IM route can be considered as effective as the IV one and should be preferred when doing a GnRH test.

Alternative methods for feline fertility control: Use of melatonin to suppress reproduction

PRACTICAL RELEVANCE

Reversible contraceptives are highly desired by purebred cat breeders for managing estrous cycles and by scientists managing assisted reproduction programs. A variety of alternative medicine approaches have been explored as methods to control feline fertility.

SCOPE

In the field of veterinary homeopathy, wild carrot seed and papaya have been used for centuries. Both appear to be safe, but their efficacy as feline contraceptives remains anecdotal. In contrast, the use of melatonin in cats has been investigated in a number of studies, findings from which are reviewed in this article.

RATIONALE

Cats are seasonally polyestrous (they cycle several times during their breeding season) and are described as long-day breeders because endogenous melatonin negatively regulates estrous cyclicity. Exogenous melatonin administered parenterally also suppresses ovarian activity in cats, and long-term oral or subcutaneous melatonin administration is safe.

CHALLENGES

The therapeutic use of melatonin is limited by its short biological half-life (15-20 mins), its poor oral bioavailability and its central effects in reducing wakefulness. Research is required to determine whether higher doses, longer-release formulations, repeated administration or combination implants might overcome these limitations.