ArticleLiterature Review

Documented and anecdotal effects of certain pharmaceutical agents used to enhance semen quality in the dog

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Documented and anecdotal effects of certain pharmaceutical agents used to enhance semen quality in the dog

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Abstract

Prostaglandin F(2alpha), gonadotropin releasing hormone, cabergoline and various nutriceuticals have all been recommended by reproductive practitioners to improve sperm motility and morphology and to increase sperm numbers in the ejaculate of the dog. Increasing sperm quantity and quality in the canine ejaculate would benefit all assisted reproductive techniques used in this species. The purpose of this manuscript is to review the documented and anecdotal effects of certain pharmaceuticals used to enhance semen quality in the dog.

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... Moreover, the biological functions of a dopamine agonist depend on species, age, hormonal status, dosage, and treatment period. Cabergoline may affect the suprabasal secretion of PRL and suppresses the pulse frequency of testosterone in male dogs (Hess, 2006;Koch et al., 2006). In male patients with hyperprolactinemia, cabergoline treatment can normalize serum PRL levels and restore libido as well as the number and quality of sperms (De Rose et al., 1998. ...
... significantly decreased by 48.6% compared with that in the control group, which suggested that PRL may play an important role in the secretion of testosterone, like in the human testes in vivo (Oseko et al., 1991). In male dogs, cabergoline may suppress the pulse frequency of testosterone (Hess, 2006;Koch et al., 2006). However, bromocriptine can increase the plasma levels of testosterone in male mice at higher doses (Rao et al., 1984). ...
... Cabergoline may improve sperm motility and morphology of dogs with poor sperm quality and increases sperm count in hyperprolactinemic patients (Ormandy et al., 1997;De Rose et al., 1998Hess, 2006). This drug also allows multiple orgasms in rapid succession in normal male humans (Krüger et al., 2003;Egli et al., 2010). ...
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Studies have rarely focused on the effect of cabergoline dosage and duration on normal male animal and human. We examined the serum concentrations of four hormones, reproductive organ weight, and sperm quality of adult male lesser rice-field rats (Rattus losea) after cabergoline treatment. Forty male rats were randomly divided into five groups and treated with cabergoline given by gavage daily for 3 d at three doses (0, 50, and 100 μg/kg). Animals were euthanized at 7 and 24 days after the end of treatment. Results showed that cabergoline did not affect follicle-stimulating hormone levels. Compared with control, testosterone concentrations decreased significantly by 48.6% at 7 d after treatment with 100 μg/kg cabergoline. Luteinizing hormone concentrations were significantly reduced by cabergoline dosage and time course. Time course affected sperm density and sperm deformity rate. Cabergoline dosage and time course significantly affected male sperm vitality at 50 μg/kg. Moreover, cabergoline significantly decreased the percentage of 'rapid', 'slow or sluggish' progressive motility sperms, and increased the percentage of "immotility" sperms. The present study suggests that cabergoline may reduce luteinizing hormone level, and impair sperm quality, which hint weakening reproductive effects on male R. losea.
... The use of trained dogs for search and rescue, police surveillance, to diagnose diseases, and helping disabled people is growing, and certain breeds of dogs are being selected, trained, and bred for these purposes as well [1]. One of the issues facing the breeding programs of dogs is the male dog semen quality [2]. Hormones such as GnRH, PGF2α, cabergoline and some food ratios are used to improve dog`s semen quality [2,3]. ...
... One of the issues facing the breeding programs of dogs is the male dog semen quality [2]. Hormones such as GnRH, PGF2α, cabergoline and some food ratios are used to improve dog`s semen quality [2,3]. ...
... In this study administration of cabergoline generally improved two semen quality factors (concentration and volume), but no significant difference was observed in the other four factors of semen quality. Hess et al., (2006) summarized studies about the effects of prostaglandin F-2 alpha, GnRH, and cabergoline on the quality and quantity of dogs' semen. By inhibition of GnRH and thus LH, FSH and testosterone, increased prolactin leads to hypogonadism. ...
Article
In the present study, the concentration of prolactin, FT4 and semen quality were investigated in 5 clinically healthy fertile mixed breed dogs (1 to 3 years old) treated with cabergoline (5 μg/Kg) during 9 weeks. Semen analysis was performed for volume, live/dead, concentration and motility factors every week. The results indicated that cabergoline administration caused a minor but significant reduction of the mean prolactin concentration (p<0.05) and did not affect the secretion of FT4 (p>0.05). Also, there was not a significant effect of cabergoline on semen quality, statistically. We could not find any relationship between prolactin and FT4 concentration and changes in semen characteristics.
... Genital tactile stimulation is only part of the stimuli (Corona et al., 2012) that triggers neuronal (Traas and Kustritz, 2004) and hormonal (Hess, 2006) pathways for erection and ejaculation. However, although the dog had reduced the area for tactile stimulation after penectomy, libido, erection of the remaining penis, and ejaculation were preserved after surgery, which is similar to previous reported cases of horses with penectomy (Silva et al., 1995;Schumacher and Varner, 2011). ...
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This study describes a case of a dog with a lacerated penile tear treated with partial penectomy followed by successful semen collections for artificial insemination. A 1.5-year-old Jack Russel Terrier with normal libido, genital organs and semen, had a penile laceration after copulation. The dog underwent a partial penectomy without orchiectomy, thus preserving the possibility of semen collection. Semen was successfully collected at 45 and 53 days after surgery, and it was used for artificial insemination of two bitches, one of which became pregnant. Therefore, this report demonstrated that semen may be collected from dogs with partial penectomy for artificial insemination, this technique has the potential to preserve fertility of dogs with penile lesions that require penectomy.
... Prostaglandin F2-alpha (PGF2a) increases ejaculate volume by intensifying contraction of the smooth muscles responsible for semen discharge (Hess 2006;Kustritz and Hess 2007). Sensory stimuli by sex pheromones of synthetic origin, or secreted by an oestrous bitch, such as methyl 4-hydroxybenzoate (Goodwin et al. 1979), may also increase the amount of semen collected through manual stimulation of the penis (Kutzler 2005;Kustritz and Hess 2007). ...
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Electroejaculation is a technique that can be used to collect semen from canines, but its use with this group of animals is restricted by low success rate and low semen quality. Here, we evaluated whether pharmacological and sexual sensory stimuli, which may affect ejaculation, can increase electroejaculation efficiency and improve ejaculate quality. We worked with 20 dogs of mixed breed weighing between 5.3 and 22.2 kg, divided into two groups. Both groups were exposed to a spayed female for 10 min, but in the second group, the same spayed female had her vagina impregnated with methyl 4-hydroxybenzoate synthetic pheromone for 10 min and after receiving dinoprost tromethamine IM, 0.1 mg /kg. After stimulation, all dogs were chemically restrained with ketamine, 8 mg/kg, IM; and xylazine, 1 mg /kg, IM, and subjected to electroejaculation protocol. We obtained 100% of antegrade ejaculate in treatments when the spayed female had her vagina impregnated with pheromone and 80% when she did not. Sperm motility was significantly different (p < 0.05) between controls and the test group (10.1 ± 4.5 and 43.0 ± 8.3, respectively). We concluded that the adopted electroejaculation protocol was efficient and that the PGF2α associated with sexual sensory stimulation can improve semen quality in dogs undergoing the procedure.
Article
The aim of this literature review is to present and discuss the available data on the effects of drugs on male dog fertility. Apart from hormones and antihormonal agents, there is still only little information available regarding the effect of other drugs on sexual function and fertility in male dogs. A negative impact on fertility in male dogs has been reported for vincristine, cyclophosphamide, tetracycline and ketoconazole. However, preclinical safety studies of drugs for human use indicated that spermatogenesis in dogs may be sensitive to a wide variety of drugs. Thus, in cases of reduced fertility or infertility in male dogs, medical treatment should always be considered. In most cases, the effects of drugs on sexual function and spermatogenesis are reversible after the discontinuation of the drug. Further studies on the effects of drugs on male dog fertility are needed.
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To investigate the effects of cabergoline dosage and duration on the reproductive system of normal male animals, forty male rats were randomly divided into five groups and treated with cabergoline for 3 consecutive days at varying doses (0, 50 μg/kg, and 100 μg/kg).Rats from T750 and T7100 were sacrificed by decapitation on 7 d after cabergoline administration, and those from T2450 and T24100 were sacrificed by decapitation on 24 d after cabergoline administration.We then observed changes in testicular tissue cells and examined the activities of enzymes in testis such as acid phosphatase (ACP), alkaline phosphatase (AKP), lactate dehydrogenase (LDH) and glutathione peroxidase (GSH-Px) by colorimetry. Results showed that endogenous germ, stromal and supporting cells in seminiferous tubules were damaged, or even fell off and disintegrated.Cabergoline treatment at 100 μg/kg decreased the ACP enzyme activity, but it was restored on 24 d after cabergoline administration. Cabergoline did not affect AKP levels. The dose increased will decreased the amount of increasing of LDH enzyme activity, and recovery on 24 d after cabergoline treatment. The activity of GSH-Px was significantly increased at 24 d at 100 μg/kg cabergoline compared with the control group, and more than those in 50 μg/kg group. Hence, cabergoline has some influence on the reproductive system of males, and can significantly affect the activities of enzymes in the testis.
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An intact testicular capsule was not necessary for flow of rete testis fluid in anesthetized rats fitted with efferent duct cannulae. Flow was unaffected by i.v. injections of FSH, LH or prolactin, or by intratesticular injections of prostaglandin E1, E2 or A1. However, small increases in intratesticular pressure resulting from injection of 2–20 μl saline resulted in transient (3–7 min) increases in flow rate, while PGF2α increased rete testis fluid flow 2–3-fold over a 20–40 min period. PGF2α effect was reduced or eliminated when the testicular capsule was cut open. Sperm concentration in the rete fluid was unaffected by any of the treatments mentioned above, suggesting that spermiation was unaffected. Since short term sperm output could not be disassociated from fluid output in these experiments, it seemed likely that PGF2α exerted an emptying effect on the existing fluid in the tubules and rete rather than stimulating fluid production. However, in hypophysectomized rats given replacement androgens for 8 weeks (2.5–25 mg testosterone propionate/day), sperm concentration in rete fluid was similar to normal, although rate of fluid flow, and therefore sperm output rates, were significantly reduced. These data suggest a link between testicular fluid production and sperm release in the rat.
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This study evaluated the effects of chronic treatment with cabergoline (CAB), a new, potent and long-lasting ergoline-derived dopamine agonist, on seminal fluid parameters and sexual and gonadal function in hyperprolactinemic males in comparison with the effect of bromocriptine (BRC) treatment. Seventeen males with macroprolactinoma were treated with CAB at a dose of 0.5-1.5 mg/week (n = 7), or BRC at a dose of 5-15 mg/day (n = 10) for 6 months. Baseline prolactin (PRL) was 925.7 +/- 522.6 microg/l in the CAB-treated group and 1059.4 +/- 297.6 microg/l in the BRC-treated group. All the patients suffered from libido impairment, ten from reduced sexual potency, and six had infertility. In five patients provocative bilateral galactorrhea was found. Seminal fluid analysis, functional seminal tests and penis rigidity and tumescence, measured by nocturnal penile tumescence (NPT) using Rigiscan equipment, were assessed before and after 1, 3 and 6 months of CAB or BRC treatment. Hormone profiles were assessed before and after 15, 30, 60, 90 and 180 days of both treatments. Before treatment, all patients had a low sperm count with oligoasthenospermia, reduced motility and rapid progression with an abnormal morphology and decreased viability, and a low number of erections. After 1 month, serum PRL levels were significantly reduced in both groups of patients (20.6 +/- 6.6 microg/l during CAB and 256.3 +/- 115.1 microg/l during BRC treatment) and were normalized after 6 months in all patients (CAB: 7.9 +/- 2.2 microg/l; BRC: 16.7 +/- 1.8 microg/l). After 6 months, a significant increase of number, total motility, rapid progression and normal morphology was recorded in patients treated with both CAB and BRC. An increase in the number of erections during the first 3 months of both treatments was noted by NPT. However, the improvements in seminal fluid parameters and sexual function were more evident and rapid in patients treated with CAB. The number of erections was normalized after 6 months of treatment in all patients submitted to CAB treatment, and in all patients but one treated by BRC. In addition, a significant increase of serum testosterone (from 3.7 +/- 0.3 to 5.3 +/- 0.2 microg/l) and dihydrotestosterone (from 0.4 +/- 0.1 to 1.1 +/- 0.1 nmol/l) was recorded. At the beginning of treatment, mild side-effects were recorded in two patients after CAB and mild-to-moderate side-effects in five patients after BRC administration. The treatment with CAB normalized PRL levels, improving gonadal and sexual function and fertility in males with prolactinoma, earlier than did BRC treatment, providing good tolerability and excellent patient compliance to medical treatment.
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The ultrastructure and the spontaneous and drug-induced contractility of the testicular capsule of 18 boars were investigated. Isometric recordings were obtained in vitro using strips of the tunica albuginea isolated from various regions of the testis. Maximal contractile activity was found in the strips of the posterior border of the testis, in which the histological studies (light and electron microscopy) showed abundant typical smooth muscle cells distributed in layers parallel to the testicular long axis. These cells were largely aggregated in the inner layer of the testicular capsule, which displayed contractile activity similar to that of the entire tunica albuginea. The outer layer of the tunica albuginea was almost totally devoid of smooth muscle fibres and showed little or no contractility. The spontaneous contractions were rhythmic and exhibited an amplitude of 20--70 mg and a frequency of 5--30 contractions/10 min. Norepinephrine, acetylcholine and oxytocin all produced an increase of the contractility of the tunica albuginea, consisting mainly in a rise of the tone.
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Hyperprolactinemia induces hypogonadism by inhibiting gonadotropin-releasing hormone pulsatile secretion and, consequently, follicle-stimulating hormone, luteinizing hormone, and testosterone pulsatility. This leads to spermatogenic arrest, impaired motility, and sperm quality and results in morphologic alterations of the testes similar to those observed in prepubertal testes. Men with hyperprolactinemia present more frequently with a macroadenoma than a microadenoma. Symptoms directly related to hypogonadism are prevalent. In men hypogonadism leads to impaired libido, erectile dysfunction, diminished ejaculate volume, and oligospermia. It is present in 16% of patients with erectile dysfunction and in approx 11% of men with oligospermia. Treatment with bromocriptine or cabergoline (CAB) is effective in men with prolactinomas, with a response that is in general comparable to treatment in women. Seminal fluid abnormalities rapidly improve with CAB treatment, while other dopaminergic compounds require longer periods of treatment. Moreover, to improve gonadal function in men, the integrity of the hypothalamic-pituitary-gonadal axis is necessary. New promising data indicate that a substantial proportion of patients with either micro- or macroprolactinoma do not present hyperprolactinemia after long-term withdrawal from CAB. Whether this corresponds to a definitive cure is still unknown, but treatment withdrawal should be attempted in patients achieving normalization of prolactin levels and disappearance of tumor mass to investigate this issue.
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The sperm output value of false mounting relative to other sexual preparation stimuli was assessed by ejaculating 151 mature dairy bulls weekly for ten consecutive weeks after imposition of zero, one, two, or three false mounts during a planned duration of 0, 5, or 10 min of active sexual preparation. The average values for motile sperm per ejaculate obtained from the bulls with a planned duration of 0 min were 4.95, 8.35, 10.12, and 9.84 billion for zero, one, two, and three false mounts, respectively. The comparable averages for the bulls with a planned duration of 5 min were 10.22, 10.14, 10.99, and 12.66, respectively; and for the bulls with a planned duration of 10 min were 11.61, 12.35, 10.94, and 14.31, respectively. The averages of 8.32, 11.00, and 12.30 billion motile sperm for 0, 5, and 10 min of preparation, respectively, differed significantly (P < .01). Similarly, the averages of 8.93, 10.28, 10.68, and 12.27 billion motile sperm for zero, one, two, and three false mounts, respectively, differed significantly (P < .01). This result is primarily a factor of volume of semen per ejaculate, which was significantly (P ≅ .02) affected by the number of false mounts; whereas, the concentration of sperm was not (P ≅ .29). The evidence supports the contention that the various sexual preparation stimuli are additive and that they conform to Fechner's Law.
Two experiments were conducted, the first to compare sperm output and the second to determine serum testosterone in rabbits given PGF2α or PGE2. In the first, six rabbits were ejaculated twice each Monday, Wednesday and Friday for 5 weeks. Each rabbit was given subcutaneously (sc) each of the following treatments five times: 1) saline, 2) 5 mg PGF2α and 3) 5 mg PGE2. Treatments were given, half at 4 hr and half at 2 hr before first ejaculations. Both PGF2α and PGE2 caused increased (50% and 84%) sperm content of first ejacula, without significantly altering characteristics of second ejacula. The extra sperm in first ejacula was a function of increased sperm density, because seminal volume was unaltered.In the second experiment, 15 rabbits were bled at 0.5-hr intervals for 9 hr and given (sc): 1) saline at 1 and 3 hr (n=4), 2) 2.5 mg PGF2α at 1 and 3 hr (n=4), 3) 2.5 mg PGE2 at 1 and 3 hr (n=4) or 4) 5 mg PGF2α at 1 hr after the onset of blood sampling. In saline-treated controls, episodic surges of testosterone occurred on the average every 5 hours. After the injection of 2.5 or 5.0 mg PGF2α, serum testosterone began to rise at 0.5 hr, peaked (8 to 13 ng/ml) at 1 hr and approached a nadir (0.5 ng/ml) within 4 hours. The second injection of 2.5 mg PGF2α failed to significantly affect serum testosterone. PGE2 treatment was followed by significantly depressed serum testosterone; only 1 of these 4 rabbits had any surge of testosterone for the 8 hr after treatment. In conclusion, PGF2α and PGE2 both increased sperm output, but PGF2α increased serum testosterone while PGE2 depressed serum testosterone. Thus, the sperm output effect of these prostaglandins probably is independent of the acute changes in testosterone secretion.
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Testicular spermatozoa are functionally immature in that they cannot fertilize ova. It was first demonstrated by Young that spermatozoa undergo certain changes as they migrate through the epididymis. He proposed that spermatozoa ripen during epididymal transit. It is now known that specific maturational changes occur in spermatozoa during epididymal transit which result in their developing the ability to fertilize ova. Concomitant with this functional maturity are changes in spermatozoal morphology, motility, chemistry, permeability, density and metabolism. It is apparent that in some way not understood these changes are necessary for sperm to achieve the ability to complete the fertilization process. When these mechanisms are understood, we may be able to effectively treat conditions such as necrospermia or abnormally low sperm motility. Furthermore, with the development of the hamster-egg penetration test a "new" type of male infertility has become evident in recent years; the inability of otherwise normal sperm to penetrate an ovum. It is during epididymal transit that this ability is normally acquired. Thus, any insight into how sperm attain the capacity to penetrate an ovum could lead to an effective treatment of patients whose sperm do not have this ability. In addition, the epididymis holds significant promise as the site of action for a male contraceptive. Thus, it is the purpose of this review to describe the structure and function of the mammalian epididymis with particular emphasis on the factors regulating sperm maturation.
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Prostaglandin F(PGF) was measured in the testes, epididymides, vasa deferentia, seminal vesicles, coagulating glands, ventral prostate and dorsolateral prostate of adult male rats. Most of the PGF present in the vas deferens was located in its luminal contents but apparently was not associated with spermatozoa. The secretions of seminal vesicles and coagulating glands contained very little PGF. Castration reduced PGF concentration in the vas deferens and seemed to have caused a similar change in the epididymis and the seminal vesicles. Administration of testosterone propionate to castrated rats increased concentrations of PGF in the vas deferens, seminal vesicles and apparently in the epididymis. These observations suggest that the synthesis of PGF in the reproductive system of the male rats is under androgen control. In mice, concentrations of PGF in the epididymis and in the seminal vesicle were increased after castration. However, in rats and mice, the content of PGF in these tissues was reduced in long term castrates.
Seven rabbits were ejaculated four times once weekly, and saline or 2.5 mg PGF2α tromethamine salt was injected sc at 4 and 2 hours or at 8 and 4 hours before ejaculation. First ejacula taken at 2 hours after the second injection of PGF2α contained 150% more () sperm than those after injections of saline. The comparable difference (60%) at 4 hours after PGF2α was not significant. PGF2α did not influence sperm output in second, third or fourth ejacula. After 28 daily sc injections of 5 mg PGF2α in another experiment, the fertility of four treated rabbits was as high as that for four controls. Without sexual preparation in seven bulls, im injections of 40 or 80 mg PGF2α 30 minutes before ejaculation resulted in 33% greater (P<.05) sperm output than that after injection of 0, 7 or 20 mg PGF2α, but the highest sperm output after PGF2α was 30% less (P<.05) than that after sexual preparation in the same bulls. We conclude that injections of PGF2α result in increased sperm output in ejacula taken without sexual preparation within 2 hours in rabbits and in bulls.
Caput and cauda sperm incubated with prostaglandin F2α were inseminated into the oviduct of recipient does which were given 75 I.U. of HCG (APL, Ayerst) at the same time. None of the 18 eggs exposed to caput sperm and all of 13 eggs exposed to cauda sperm were fertilized. Capacitated ejaculate sperm incubated with prostaglandin F2α were inseminated into the oviduct of recipient does given 75 I.U. HCG 12–13 hours earlier. Of 74 eggs recovered, 53 were fertilized. The results are consistent with those found utilizing sperm without prostaglandin treatment.
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It seems that short term treatment of hamsters with PGE1 or PGF(2α) does not affect fertilizing ability and is consistent with a recent report that such treatment does not influence the fertilizing ability of rat spermatozoa.
Article
Four experiments were conducted to test the influence of PGF2α on the distribution of sperm in male rabbits. In the first, nine rabbits were anesthetized, one side of the reproductive tract was removed, and 5 mg PGF2α was injected around the remaining testis and epididymis. Relative to the controls, the deferent duct contained more than twice as many sperm at 10, 30, or 60 min after PGF2α. Results from the second trial showed that the deferent duct of rabbits did not accumulate sperm during 30 min under anesthesia without PGF2α treatment, but deferent duct sperm were more than doubled at 30 min after 5 mg PGF2α injected subcutaneously. In the third experiment, four unanesthetized rabbits injected subcutaneously three times (at 20-min intervals) with 10 mg PGF2α had about threefold more deferent duct sperm and significantly fewer sperm in the head-body epididymis than four saline-injected control rabbits. Relative to ten controls in the final experiment, after five sc injections of 1 mg PGF2α at 12-min intervals, ten rabbits had more sperm in the paired deferent ducts (70 vs 224 × 106, P <0.01), a greater percentage of the total excurrent duct sperm in the deferent duct (3.6 vs 10.3%, P <0.01), and more deferent duct sperm per 100 × 106 testicular sperm (18 vs 58, P <0.01). We conclude that PGF2α causes increased numbers of sperm in the deferent duct, possibly by increasing the rate of movement of sperm out of the epididymis.
Article
Three intensities of sexual preparation were compared with none using 9 rabbits which each furnished 2 ejaculations every second day for 38 days. The average sperm content of first ejaculations after one false mount (102.9 × 106) was 178% greater than that following no sexual preparation (37.0 × 106) and 3 false mounts resulted in an additional 40% increment in sperm output over one false mount. Sexual preparation also increased average sperm content of second ejaculations, although the increments were not as large as those obtained in first ejaculations. Analyses of seminal volume and total fructose content revealed that sexual preparation stimuli also affected accessory glands, but the magnitude of effect was proportionately smaller than the magnitude of the effect on epididymides. Sexual preparation also reduced the relative magnitude of the within-buck variance of total sperm output.
Article
In Expt 1, gonadotropin-releasing hormone (GnRH) (Cystorelin, CEVA) was administered intramuscularly to two intact male dogs; one dog received one injection of 50 micrograms GnRH and one dog received four daily injections of 50 micrograms GnRH. Both dogs exhibited a significant and immediate rise in luteinizing hormone (LH) following GnRH administration, with a peak observed at 15 min following injection. Testosterone was increased over baseline concentrations for 5 and 7 days, respectively, after the injection. In Expt 2, eight intact male dogs were injected intramuscularly with 0.7 microgram GnRH (Factrel, Fort Dodge) kg-1. Baseline testosterone concentrations were established by daily sampling for 14 days before treatment. All dogs exhibited an LH peak 15 min and a testosterone peak 60 min after the GnRH injection. Testosterone concentrations had returned to baseline concentrations by 4 h after the injection. Testosterone tended to fall below baseline concentrations for several days following the injection of GnRH. No peak was noted for follicle-stimulating hormone. In Expt 3, five additional dogs were injected with 0.7 microgram GnRH (Factrel, Fort Dodge) kg-1. Testosterone concentrations rose in all dogs 1 h after the injection and returned to baseline concentrations by 24 h after injection. In the male dog, GnRH stimulated an LH peak 15 min and a testosterone peak 1 h after injection. Further investigations are needed to elucidate the different effects on testosterone concentration observed with two different GnRH preparations.
Article
Dose-response relationships between GnRH and LH, and between GnRH and testosterone, were investigated in six male dogs by intravenous administration of a GnRH analogue at different doses. Each dose of GnRH analogue induced an immediate rise in the plasma concentration of LH and then a rise in plasma testosterone concentration. Irrespective of the dose used, the rise in testosterone began 10 min after the GnRH injection. Administration of GnRH at doses of 0.01, 0.1, 1, 10 and 100 micrograms kg-1 resulted in maximum LH concentrations in plasma (mean +/- SEM; n = 6) of 22 +/- 7, 27 +/- 6, 40 +/- 7, 57 +/- 13 and 56 +/- 10 micrograms l-1, respectively. These doses induced maximum concentrations of testosterone in plasma (mean +/- SEM; n = 6) of 16 +/- 4, 20 +/- 4, 22 +/- 3, 22 +/- 4 and 24 +/- 7 nmol l-1, respectively. The lag time between peak concentrations of LH and testosterone varied from 35 to 55 min. The calculated maximum response of testosterone to LH, secreted by the anterior pituitary after GnRH injection, was 1.8 times higher than to GnRH. It was concluded that intravenous administration of GnRH induced marked and dose-dependent increases in plasma concentrations of LH and testosterone, and that there does not appear to be a direct effect of GnRH on Leydig cells in male dogs.
Article
Plasma luteinizing hormone (LH) and testosterone (T) levels in three normal male Beagles increased markedly, the LH levels peaking at 30 or 45 min and the T levels at 45 or 60 min respectively, after a subcutaneous injection of 1 microgram kg-1 gonadotropin releasing hormone agonist (GnRH-A). Two Collies and a Great dane diagnosed as oligozoospermic and two Shetland sheep dogs diagnosed as azoospermic by evaluation of semen quality were treated with 1 microgram kg-1 GnRH-A after blood collection. Their plasma levels of LH, T and estradiol-17 beta (E2) were measured by radioimmunoassay for the purpose of investigating the effect of hormone therapy on spermatogenic dysfunction and the mechanism on improvement of semen quality. The semen quality of one of the Collies had improved 4 weeks after the GnRH-A treatment. The dog was treated with GnRH-A again and mated with a bitch 4 days later. The bitch gave birth to five puppies. The other dogs, whose semen quality had not improved, were treated with an intramuscular injection of 500 or 1000 IU human chorionic gonadotrphin (hCG) per animal. Since the semen quality of the other Collie and the Great Dane improved temporarily 2 and 4 weeks, respectively, after hCG treatment, the former was mated with a bitch 5 days later. The bitch gave birth to a litter of seven puppies. These hormone treatments, however, had no effect on the azoospermia in the two Shetland sheep dogs. Although the mean plasma LH and T levels in the dogs with oligozoospermia had been low, their LH levels gradually increased after hormone treatment. There were no marked changes in plasma T or E2 levels. These findings indicate that the semen quality of dogs with oligozoospermia can be temporarily improved between 2 and 4 weeks after a single injection of GnRH-A or hCG and the fertility of the dogs restored by the injection.
Article
Plasma LH and testosterone (T) levels and semen quality after a single intramuscular injection of 1,000 IU hCG were investigated in a Beagle dog with azoospermia and a Beagle dog with poor semen quality. The plasma LH levels of both dogs did not change after the treatment. Although the plasma T levels of the dog with azoospermia increased temporarily, no sperm were detected in its semen. In the dog with poor semen quality high levels of plasma T were maintained for 2 weeks after hCG treatment and its semen quality was temporarily improved between 3 and 4 weeks after treatment. These findings indicate that the semen quality of dogs with oligozoospermia can be temporarily improved after a single injection of hCG.
Article
Eight stallions were used in 2 x 2 crossover study to determine if feeding a nutriceutical rich in docosahexaenoic acid (DHA) would improve semen quality. Stallions were randomly assigned to one of two treatment groups (n = 4 per group). Stallions were fed their normal diet (control) or their normal diet top-dressed with 250 g of a DHA-enriched nutriceutical. Feeding trials lasted for 14 week, after which a 14-week washout period was allowed and the treatment groups were reversed for another 14 week feeding trial. Feeding the nutriceutical resulted in a three-fold increase in semen DHA levels and 50% increase in the ratio of DHA to DPA in semen. Sperm motion characteristics in fresh semen were unaffected by treatment. After 24 h of cooled semen storage in an Equitainer, total and progressive motility did not differ between treatment groups, but sperm from stallions fed the nutriceutical exhibited higher velocity and straighter projectory (P < 0.05). After 48 h of cooled storage, increases in the percentages of sperm exhibiting total motility (P = 0.07), progressive motility (P = 0.06) and rapid motility (P = 0.04), were observed when stallions were being fed the nutriceutical. For a subset of four stallions, whose progressive sperm motility was <40% after 24 h of cooled storage when fed the control diet, feeding the nutriceutical resulted in improvements in mean progressive motility of sperm after 24 h (P = 0.10) and 48 h (P = 0.03) of storage. Feeding the nutriceutical resulted in similar improvements in motion characteristics being observed in frozen-thawed semen. While it appears that feeding the nutriceutical may improve the motion characteristics of cool-stored stallion semen, it may be most beneficial for stallions of marginal fertility whose sperm do not tolerate the rigors of cooling and storage. The nutriceutical also appeared to improve the freezability of semen. More dramatic improvements in semen quality may be observed if modifications in the main fat content of the diet are incorporated with the DHA supplement.
Article
Four mature Murrah buffalo bulls on a regular semen collection schedule of twice a day, two days per week, were injected with 30 mg prostaglandin F2 alpha THAM salt(PGF) intramuscularly 30 minutes prior to each alternate first ejaculation for six weeks. Effects of PGF on time to initial false mount on the decoy, time to ejaculation after two false mounts (reaction time), seminal volume, sperm concentration, total sperm output, motility of fresh and thawed semen and the semen doses obtained per collection were evaluated. Treatment caused significant (P < 0.01) reduction in the time to first false mount and the reaction time for the first ejaculations but had no effect (P > 0.05) on these for the second ejaculations. Values for other quantitative and qualitative parameters did not differ (P > 0.05) due to PGF treatment. It is concluded that PGF at the dosage and frequency of administration used may be of some value in improving libido in low-libido bulls but does not alter the reproductive capacity of buffalo bulls.
Sperm output and quality after PGF2a in bulls
  • Marshall
Marshall CE, Hafs HD. Sperm output and quality after PGF2a in bulls. J Animal Sci 1976;43:296 [Abstract].
Regulation of rabbit testicular capsular motility: the interaction of prostaglandins, acetylcholine and sympathomimetic agents
  • J L Hargrove
Hargrove JL. Regulation of rabbit testicular capsular motility: the interaction of prostaglandins, acetylcholine and sympatho-mimetic agents. Utah State University, 1975.
Structure and function of the epidi-dymis
  • Cosentino Mj
  • Cockett
  • At
Cosentino MJ, Cockett AT. Structure and function of the epidi-dymis. Urol Res 1986;14:229–40.
Effect of prostaglandin F 2 alpha on seminal characteristics of the stallion
  • Cornwell
Cornwell JC, Koonce KL, Kreider JL. Effect of prostaglandin F 2 alpha on seminal characteristics of the stallion. J Anim Sci 1974;38:226 [Abstract].
Structure and function of the epididymis
  • Cosentino