Increased germ cell loss rates and poor semen quality in stallions with idiopathic testicular degeneration

Five mature stallions with poor semen quality were tentatively diagnosed as having testicular degeration of unknown cause. Testis samples from these five stallions, and from three mature stallions with normal semen quality, were obtained by castration and prepared for histomorphometry. Increased germ cell loss rates during late meiosis and spermiogenesis occurred in the stallions with idiopathic testicular degeneration. Poor semen quality, represented by a low percentage of morphologically normal, progressively motile sperm in ejaculates, appeared to be a good predictor of testicular degeneration in these stallions.     

Effect of GnRH and hCG administration on plasma LH and testosterone concentrations in normal stallions, aged stallions and stallions with lack of libido

Gonadotrophin-releasing hormone (GnRH) (a single intravenous injection with 0.042 mg busereline acetate) was administered to control stallions (n=5), aged stallions (n=5) and stallions with lack of libido (n=5). Jugular blood samples were taken at -10, 0, 10, 20, 40 and 80 minutes after treatment and measured for luteinizing hormone (LH) and testosterone concentrations. A single intravenous injection of hCG (3000 IE) was given 1 day later. Venous blood samples were taken at -60, 0, 15, 30, 60, 120, and 240 minutes after treatment and measured for the testosterone concentration. The experiment was performed in the breeding season. There was a wide variation between stallions in basal concentrations of LH and testosterone. The treatment groups all showed a significant increase in LH and testosterone concentrations after treatment with GnRH. There was a significant difference (P<0.05) between the control, the lack of libido stallions and the aged stallions in the production of LH before and after stimulation with GnRH. The aged stallions had higher basal LH concentrations. GnRH induced a rise in plasma LH in all groups, but the greatest response was observed in aged stallions. No response to GnRH was seen with respect to plasma testosterone. There was an increase in plasma testosterone following hCG; however, this increase was very small in aged stallions. After stimulation with hCG the control and lack of libido stallions had a significant increase (P<0.05) in testosterone production. In conclusion, stimulation with either GnRH or hCG can be a valuable method to test whether the function of the stallion's reproductive endocrine system is optimal.     

Anti-oxidative status and semen quality during cooled storage in stallions

Activity of the anti-oxidative enzymes glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and catalase (CAT), content of thiobarbituric acid reactive substances (TBARS) and SH-groups were determined in native stallion semen (n = 8 stallions). Semen was then diluted in Kenney extender, EquiPro((R)) extender either with or without addition of N-acetyl cysteine or phosphate-buffered saline (PBS) and stored for 72 h at 5 degrees C. Correlations between initial activity of enzymes and development of semen motility and membrane integrity were calculated. Activities of GSH-Px, SOD and CAT immediately after semen collections were 10.0 +/- 0.6 picokatals, 0.40 +/- 0.03 SOD units and 0.70 +/- 0.05 nanokatals/10(6) spermatozoa respectively. TBARS content was 0.06 +/- 0.01 nmol and SH-group content 1.7 +/- 0.5 mmol/10(6) spermatozoa. The loss of motile spermatozoa during storage did not differ between extenders. N-acetyl cysteine had no effect on semen motility and membrane integrity. The loss in membrane-intact spermatozoa was highest (P < 0.05) in semen diluted in PBS. Motility and membrane integrity after addition of extender were positively correlated with GSH-Px and CAT, indicating that anti-oxidative mechanisms contribute to the initial high percentage of motile and membrane-intact spermatozoa. However, in these samples the decrease in semen quality was most pronounced. No correlations existed between initial activity of anti-oxidative enzymes, peroxidation products and semen quality during storage. This indicates that once extender has been added, peroxidative damage to sperm membranes is not the predominant cause of losses in semen quality.     

Immunization against gnRH in mature mares: antibody titres,ovarian function,hormonal levels and oestrous behaviour

The aim of the present study was to investigate the effect of active immunization against GnRH in mature Standardbred mares (three experimental and one control mare) on antibody titres, ovarian function, hormonal levels and oestrous behaviour. The mares were individually teased with a stallion once each day. During the first part of the experiment (period I: late April until November), blood was sampled every third day during the first 3 months, thereafter once per week. In the second part of the experiment (period II: December until August), sampling was carried out every second week. Progesterone, oestradiol-17beta and LH were analysed. Rectal gynaecological examination was made with the same intervals as the blood samplings and included palpation of the genital organs and ultrasonography. The experimental mares were immunized against GnRH with a GnRH-BSA conjugate. Equimune (Vetrepharm, Bracetown, Business Park, Clonee, Co. Meath, Republic of Ireland) was used as adjuvant. The mares were immunized on four occasions (20-30 day intervals) and GnRH antibody titre was determined. All immunized mares produced antibodies against GnRH but the maximum titres as well as the duration of a greater than 10% binding capacity varied between the mares (1 : 1600 to 1 : 50 000; 5 to 12 months, respectively). After the first injection, all mares showed one oestrus and ovulated at the regular time. In two of the mares, the immunization resulted in ovarian atrophy. Their hormone levels of progesterone, oestradiol- 17beta and progesterone decreased to basal levels and the cyclical hormone pattern was interrupted from approximately 30 days onwards. They continued to show oestrous signs but with irregular durations and intervals. The third mare showed ovarian suppression only for short periods and not in both ovaries at the same time; the hormone levels were basal for only about 20 days (days 50-70) and the mare ovulated on day 75 after start of immunization. The other mares ovulated after 13.5 and 15 months, respectively. It is concluded that the effect of immunization against GnRH in mature mares was individual concerning antibody titre response and the suppression of ovarian activity and hormone levels. Mares with totally inactive ovaries continued to show oestrous signs but with irregular intervals and durations.     

Testosterone serum profile,semen characteristics and testicular biometry of Mangalarga Marchador stallions in a tropical environment

This study was conducted to characterize the daily profile of testosterone secretion and its mean concentrations in the four seasons as well as to evaluate the semen characteristics and testicular biometry of Mangalarga Marchador stallions throughout the year in a tropical region. Three stallions were submitted to semen collections and evaluation of testicular biometry every 14 days along a year. Blood samples were collected once at the middle of each season, in a 20‐min interval during 24 hr in order to evaluate the testosterone secretion profiles among seasons. Testosterone concentrations along the day were higher at the beginning of the afternoon (from 12:00 to 15:00 hr), but a circadian secretion was not clearly observed. Mean testosterone concentrations did not differ among seasons (p > .05), but a pattern of secretion along the day showed variations with higher concentrations in the afternoon during the winter. Ejaculate volume was higher during summer; however, sperm motility decreased in summer and spring. Total sperm in ejaculate, sperm morphology and testicular biometry kept constant along the year showing no differences among the seasons. The results demonstrated that in a tropical region, reproductive aspects of stallions did not show a clearly defined seasonal variation, and months of autumn and winter were not unsuitable for reproduction of the males.     

Influences of season and artificial photoperiod on stallions: pituitary and testicular responses to exogenous GnRH

Effects of season and photoperiod on the anterior pituitary gland and testes were studied by responses to exogenous GnRH. Stallions were assigned to one of three treatments: 1) control, exposed to natural day length; 2) S-L, 8 h of light and 16 h dark (8:16) for 20 wk beginning July 16, 1982 then 16:8 from December 2, 1982 until March 5, 1984; or 3) S-S, 8:16 from July 16, 1982 until March 5, 1984. Approximately every 8 wk, stallions were administered GnRH (2 micrograms/kg BW) and blood was sampled at 20-min intervals for 2 h before and 8 h after GnRH administration. Concentrations of LH, FSH and testosterone were determined. Baseline concentrations (mean of pre-GnRH samples) of all hormones fluctuated seasonally (P less than .05), but only LH and testosterone displayed seasonal changes (P less than .05) in maximum response to GnRH (highest concentration above baseline after GnRH). The FSH response to GnRH was not affected (P greater than .05) by season, photoperiod or the season X treatment interaction. Exposure of S-L stallions to 16:8 in December resulted in early recrudescence of baseline concentrations of LH, FSH and testosterone. Maximum concentration of testosterone in response to GnRH was stimulated by 16:8, but the increase in baseline LH concentrations in S-L stallions was not associated with an increase in maximum LH response to GnRH. Seasonal patterns of baseline concentrations of FSH and testosterone and maximum LH response to GnRH in S-S stallions were similar to those for control stallions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influences of season and artificial photoperiod on stallions: testicular size, seminal characteristics and sexual behavior

To investigate the influence of daylength on the seasonal reproductive cycle of stallions, 21 stallions were assigned to one of three treatments: control, ambient (natural) photoperiod; S-L, 8 h light and 16 h dark (8:16) for 20 wk beginning July 16, 1982 then 16:8 from December 2, 1982 until March 5, 1984; S-S, 8:16 from July 16, 1982 until March 1984. Temperature was not controlled and was similar for all groups. Total scrotal width (TSW) was measured every 4 wk throughout the experiment. During 10 periods, semen was collected and evaluated every other day for 3 wk and sexual behavior was assessed. The S-L stallions exposed to 16 h light in December had twice as much sperm output in February than in November. Within the February collection period, the sperm output for S-L stallions was greater (P less than .05) than that for either control of S-S stallions. The stimulatory effect of the S-L photoperiod also resulted in larger (P less than .05) testes and decreased (P less than .05) time to ejaculation for S-L stallions in February as compared with either controls or S-S stallions. Despite continued exposure to a 16:8 photoperiod, TSW and sperm output for S-L stallions eventually declined; presumably a consequence of photorefractoriness. The S-S stallions had seasonal cycles coincident with those for control stallions. Based on a sine wave model for TSW and sperm output, stallions in all three groups displayed significant seasonal cycles.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of active immunization against GnRH on testosterone concentration,libido and sperm quality in mature AI boars

Background

The aim of the present study was to investigate the efficacy of the Improvac on testosterone concentration in blood serum, sexual behavior and sperm quality in matured AI boars. A total of nine Danish Landrace AI boars were included in the analysis.

Methods

The trial period lasted for 15 weeks and was divided into four periods: Control period: three weeks before vaccination; Period I – four weeks after first vaccination; Period II – four weeks after second vaccination, Period III – four weeks after third vaccination. Blood and sperm samples were collected at weekly intervals. Freshly collected sperm samples were analyzed.

Results

Testosterone concentration correlated with libido (r = 0.531; p < 0.001), volume of ejaculate (r = 0.324; p < 0.001) and the percentage of morphologically normal spermatozoa (r = 0.207; p < 0.05). Testosterone concentration rised significantly (p < 0.05) in 5–6 week of trial, e. i. after the first dose of Improvac and after this peak the level of testosterone further progressively decreased (p < 0.05).

Conclusions

Results from this study indicate that active immunization of sexually matured boars against GnRH has negative impact on testosterone concentration, sexual behavior, volume of ejaculate and total number of normal spermatozoa in ejaculate.     

Development of semen quality following reversible downregulation of testicular function in male dogs with a GnRH agonist implant

Slow-release GnRH agonist implants have shown to be an effective and reversible alternative to surgical castration. Testicular function is downregulated with an arrest of spermatogenesis on the level of spermatogonia/primary spermatocytes but is fully restored after abolition of downregulation. Aim of this study was to assess the quality of ejaculates after active abolishment of downregulation by implant removal and to follow recrudescence of spermatogenesis. Five dogs - which served as their own controls - were treated with a slow-release implant containing the GnRH agonist azagly-nafarelin. Implants were removed during full downregulation (testosterone <0.1 ng/ml), and attempts to collect ejaculates started from week 4 onwards to week 29. First ejaculates could be obtained between weeks 8 and 12 with the first fully elongated spermatozoa observed in week 10. Volume, %motility and total sperm count increased and %pathomorphology decreased during the course of the study with all ejaculates being in the normal range by week 29. Our data indicate that onset of recrudescence of spermatogenesis coincides with the first testosterone increase after active abolishment of downregulation. Semen quality was fully regained with a significant improvement of %pathomorphology (p < 0.05) and a tendency of improved %motility. However, these observations on an improved semen quality need further validation and no final conclusions can be drawn yet.     

种公牛微量元素营养状况对精液品质的影响

为了查找种公牛精液品质下降的原因并探讨精液品质与微量元素的关系,试验测定了种公牛基础日粮及血液、被毛、精液中锌(Zn)、铜(Cu)、铁(Fe)、锰(Mn)、铬(Cr)5种微量元素含量。结果表明:饲料中Zn、Cu含量明显低于美国NRC推荐标准,Fe、Mn、Cr三种元素能满足种公牛的营养需要;精液品质正常牛及异常牛血液、被毛、精液中Fe、Mn、Cr差异不显著(P>0.05),被毛、血液中Zn、Cu两种元素含量差异显著(P<0.05),精液中Zn元素含量差异极显著(P<0.01)、Cu元素含量差异显著(P<0.05)。     

地衣芽孢杆菌对热应激公兔精液品质及激素水平的影响

选择体质量基本一致、性欲旺盛的健康公兔25只,设常温对照组、热应激对照组(饲喂配合日粮)和热应激试验1~3组(分别在配合日粮中添加地衣芽孢杆菌500,1 000,1 500mg/kg),热应激温度控制在33~35℃。测定采食量和体质量;采用动物精子测定仪检测精液品质;放射免疫法测定血浆FSH、LH、TSH、T、T_3、T_4含量。结果显示:日粮中添加1 000mg地衣芽孢杆菌采食量除第10,15天显著高于热应激对照组外,其他日期差异不显著;体质量略高于热应激对照组,较常温对照组低;对采精量无明显影响,10d后精子密度和精子活力极显著低于常温对照组,极显著高于热应激对照组,精子畸形率明显降低;对血浆FSH影响不明显,能提高热应激公兔前20d血浆LH和TSH浓度,提高血浆睾酮(T)和T_3、T_4含量。结果表明:在公兔日粮中添加1 000mg/kg地衣芽孢杆菌能够短期缓解热应激,提高精液品质,有升高血浆LH、TSH、T、T_3、T_4浓度的作用,并对地衣芽孢杆菌的添加量有剂量依赖性。     

不同营养水平日粮对马头山羊种公羊体重和精液品质影响的研究

通过对马头山羊种公羊39只在配种期、30只在非配种期应用不同营养水平的日粮饲养,然后检测公羊的性欲、射精量、精子密度和精子活力等项指标,分析日粮营养水平对配种期和非配种期种公羊体重和精液品质的影响.结果表明,无论在配种期还是在非配种期,种公羊的体质和繁殖性能与营养水平呈正相关,高水平和中等水平营养日粮对其影响差异不显著,建议采用中等水平的日粮,在配种高峰期可以适当提高营养水平,添加精料和矿物质元素的比例,以保持其健康的体质和良好的繁殖性能.     

Experimentally induced testicular alterations in boars: hormonal changes in mature and peripubertal boars

Eleven sexually mature boars and 10 peripubertal boars were used to study the effects of elevated testicular temperature on plasma hormonal levels. The scrotum of the boars was covered with a textile-aluminium foil insulation device for 100 h. Insulation of the scrotum in the peripubertal boars took place at an age of 100 days. Blood samples were drawn 3 times daily for 12 days in the mature boars, starting 3 days before scrotal insulation. In the peripubertal boars, blood sampling was performed once a day for 11 days, starting the first day of scrotal insulation. During scrotal insulation, the plasma levels of testosterone, oestradiol-17 beta and oestrone sulphate decreased continuously in the mature boars. After removal of the scrotal insulation device there was a continuously increase, back to normal levels of oestradiol-17 beta and oestrone sulphate. The plasma levels of testosterone showed an immediate rise of brief duration after removal of the device in 5 of the boars, while in the other 6 boars the rise in testosterone levels came 4 days after removal and lasted for 3 days. In the peripubertal boars, there were no significant differences in the hormone levels between the experimental and control animals during and after scrotal insulation. However, the decrease in testosterone concentration over time, during scrotal insulation, was significant within the experimental group.     

Poor semen quality in Irish wolfhounds: A clinical, hormonal and spermatological study

On the basis of clinical observations, Irish wolfhounds were suspected as being subject to a relatively high incidence of soft testicular consistency and low semen quality. Thirty-seven Irish wolfhounds and 67 dogs of other breeds (control group) were therefore examined. Conventional andrological studies were performed in both groups, these included libido testing, palpation and measurement of testes and semen evaluation. Semen evaluation was performed both manually and by videomicrographic analysis. Testosterone concentrations were measured both before and after human chorionic gonadotropin challenge in the Irish wolfhounds. The Irish wolfhounds had lower libidos than the control group. More Irish wolfhounds (21-2 per cent) exhibited low semen quality than the control group (6-1 per cent). Soft testicular consistency occurred more frequently in Irish wolfhounds (25-7 per cent) than in the control group (10-5 per cent). In the control group, bodyweight correlated significantly with total sperm count. Serum testosterone concentration did not correlate with semen quality parameters.     

Effect of semen collection frequency on seasonal variation in sexual behaviour,testosterone, testicular size and semen characteristics of tropical hair rams (<Emphasis Type="Italic">Ovis aries</Emphasis>)

The purpose of this study was to examine the effect of day length on seminal characteristics, testicular size, sexual behaviour and testosterone (T4) concentration in Pelibuey rams subjected to different semen collection frequencies. Eighteen intact males were assigned randomly to one of two semen collection frequencies: in the high rate (HR) treatment, two ejaculations per week were obtained from each ram; one ejaculation every two weeks was collected under the low rate (LR) treatment. All animals were housed individually in contiguous 5 m × 5 m wire mesh pens and evaluated over a 12-month period. At the beginning of the experiment rams were 20 months old and 40–50 kg in weight. All rams ejaculated and produced semen throughout the year. Semen volume, sperm per ejaculation, testicular circumference and testicular volume were significantly (p < 0.05) greater during short days in all rams, regardless of the semen collection frequency, with the exception of sperm concentration, for which no variation was found in HR individuals, and reaction time and T₄ levels, for which no variation was found in LR males. Rams subjected to HR collection were more affected by the short-day photoperiod than rams collected twice per week, exhibiting greater reduction (p < 0.05) in time to achieve their first ejaculation and in sperm per ejaculation, as well as greater increases (p < 0.05) in T₄ concentration than LR rams (14.65 ± 1.22 vs 23.53 ± 5.34 s, (3.37 ± 0.17) × 10⁹ vs (3.52 ± 0.20) × 10⁹ sperm and 8.68 ± 0.44 vs 6.85 ± 0.74 ng/ml, respectively). It was concluded that: (a) the magnitude of the seasonal effects was not sufficient to prevent the rams being used for breeding throughout the year, and (b) seasonal variation within variables was affected differently between semen collection frequencies.     

Changes in plasma testosterone levels and semen quality after 3 injections of a GnRH analogue in 3 dogs with spermatogenic dysfunction

Three male Beagles with low plasma luteinizing hormone and testosterone levels and spermatogenic dysfunction (SD-dogs) were given 3 weekly subcutaneous injections of a gonadotropin-releasing hormone analogue (Buserelin; GnRH-AB). The plasma T level of all of the SD-dogs increased and peaked at 4-6 weeks after the first injection. The total number of sperm and the sperm motility of the three SD-dogs increased 5-7 weeks after the first injection. Therefore, the authors concluded that 3 weekly injections of GnRH-AB transiently improves semen quality in some cases of canine spermatogenic dysfunction.     

Effect of blocking vision and olfaction on sexual responses of haltered or loose stallions

Ten stallions were used in a modified split-plot design involving four treatments and two handling methods. Treatments were: a) vision and olfaction not blocked; b) vision blocked, olfaction not blocked; c) vision not blocked, olfaction blocked; and d) vision and olfaction blocked. The methods of handling were: a) stallions turned loose in teasing area, and b) stallions handled on a lead shank. Stallions teased four estrous mares, four diestrous mares and four geldings. Criteria for evaluation of stallion behavior was duration of investigation (sec), of area as well as various portions of the stimulus animal's anatomy, and other pre-copulatory sexual behaviors (Table 1) in duration and frequency. Except for area investigation and no investigation, there were more frequent or longer responses when vision was not blocked compared to blocked (P<0.05). Events associated with display of flehmen and mounting activity were lower (P<0.05) when vision was blocked. Handling a stallion on a lead shank, while teasing, resulted in 23 longer or more frequent pre-copulatory sexual behaviors than when the stallions were loose. There were more frequent or longer (P<0.05) behavioral responses when stallions were handled on a lead shank and olfaction was not blocked. Events such as duration and number of flehmen responses were lower (P<0.05), and time of no investigation was longer (P<0.001) when olfaction was blocked. There was no difference (P>0.05) in the time spent inyestigating estrous mares, diestrous mares or geldings, except for number of flehmen responses. Number of flehmen responses to estrous mares was higher (P<0.05) than to diestrous mares, while number of flehmen responses to diestrous mares was higher (P<0.001) than to geldings. Blocking olfaction did not decrease frequency or duration of sexual behaviors as much as blocking vision (P<0.05), resulted in decreased (P<0.05) flehmen responses. Blocking vision significantly decreased (P<0.05) teasing behaviors, duration of erection, flehmen, and number of mounts regardless of stimulus animal. Stallions utilized visual stimuli to a greater extent than olfactory stimuli. Handling stallions on a lead shank appeared to enhance expression of precopulatory behavior compared to when the stallions were loose.