Evaluation of bull fertility in dairy and beef cattle using cow field data

A successful outcome to a given service is a combination of both male and female fertility. Despite this, most national evaluations for fertility are generally confined to female fertility with evaluations for male fertility commonly undertaken by individual breeding organisations and generally not made public. The objective of this study was to define a pertinent male fertility trait for seasonal calving production systems, and to develop a multiple regression mixed model that may be used to evaluate male fertility at a national level. The data included in the study after editing consisted of 361,412 artificial inseminations from 206,683 cow-lactations (134,911 cows) in 2,843 commercial dairy and beef herds. Fixed effects associated with whether a successful pregnancy ensued (pregnant = 1) or not (pregnant = 0) from a given service were year by month of service, day of the week, days since calving, cow parity, level of calving difficulty experienced, whether or not the previous calving was associated with perinatal mortality, and age of the service bull at the date of insemination. Non-additive genetic effects such as heterosis and recombination loss as well as inbreeding level of the service bull, dam or mating were not associated with a successful pregnancy; there was no difference in pregnancy rate between fresh or frozen semen. Random effects included in the model were the additive genetic effect of the cow, as well as a within lactation and across lactation permanent environmental effect of the cow; pedigree group effects based on cow breed were also included via the relationship matrix. Temporal differences in the AI technician and service bull were also included as random effects. A difference in five percentage units in male fertility was evident between the average effects of different dairy and beef breeds. The correlation between raw pregnancy rates for bulls with more than 100 services (n = 431) and service bull solutions from the mixed model analysis was 0.66. The correlation between the raw pregnancy rates of 288 technicians with more than 100 services and their respective solutions from the mixed model was 0.35. These low to moderate correlations suggest considerable re-ranking among both service bulls and technicians and suggest possibly a benefit of using a statistical model to better estimate the performance of both service bulls and technicians.     

Fundulus heteroclitus: ovarian reproductive physiology and the impact of environmental contaminants

Fundulus heteroclitus, the mummichog or Atlantic killifish, is the dominant small-bodied fish species of the east coast estuaries and salt marshes of Canada and the USA, where it is present as two subspecies, the northern F. h. macrolepidotus and the southern F. h. heteroclitus. Recently identified as the premier teleost model in environmental biology, the species has long been of value in understanding evolved tolerance to toxicants and more lately in adding to our knowledge about reproductive effects of environmental endocrine disruptors. The body of literature on F. heteroclitus ovarian physiology and reproduction, from both field and laboratory studies, provides the foundation for present work focused on understanding the reproductive effects and modes of action of environmental toxicants. In this paper, we review the environmental and endocrine factors controlling ovarian and reproductive cycling in F. heteroclitus, noting specifics related to field and laboratory studies on the two subspecies as well as key research gaps compared to other fish species. We also summarize recent development of methodologies to study the effects of environmental contaminants on endocrine signalling and egg production in F. heteroclitus. Continued efforts to progress both our fundamental understanding of reproductive physiology in mummichog, coupled with studies focused on the modes of action of environmental contaminants, have high potential to further develop this teleost model. While the model may presently lag behind those based on other species of fish, the unique biochemical and physiological adaptations which allow F. heteroclitus to adapt to changing environmental and toxic conditions provide a valuable experimental system for comparative physiologists, ecotoxicologists and evolutionary biologists.     

Effect of growth rate from 6 to 16 months of age on sexual development and reproductive function in beef bulls

Sexual development and reproductive function were studied in 22 Angus × Charolais and 17 Angus bulls from 6 to 16 mo of age. Associations of average daily gain (ADG) and body weight with ages at puberty and at maturity (satisfactory semen quality), scrotal circumference, paired-testes volume and weight, testicular vascular cone diameter and fat thickness, scrotal temperature, sperm production and morphology, and testicular histology, were determined. There were no significant correlations between cumulative average daily gain and any of the end points investigated. Body weight at various ages was negatively correlated with ages at puberty and maturity in Angus × Charolais bulls, positively correlated with paired-testes weight in Angus × Charolais and Angus bulls, and positively correlated with seminiferous tubule volume in Angus bulls (P < 0.05). Semen quality improved gradually with age and the interval between puberty and maturity (mean ± SD; 309.4 ± 29.7 and 357 ± 42 days of age) was approximately 50 days. Age, weight, scrotal circumference, and paired-testes volume were all good predictors of pubertal and mature status, with moderate to high sensitivity and specificity (71.6% to 92.4%). In summary, growth rate between 6 and 16 mo of age did not affect sexual development and reproductive function in beef bulls. However, greater body weight at various ages was associated with reduced age at puberty and maturity, and with larger testes at 16 mo of age, indicating that improved nutrition might be beneficial, but only when offered before 6 mo of age. Average daily gains of approximately 1 to 1.6 kg/day did not result in excessive fat accumulation in the scrotum, increased scrotal temperature, or reduction in sperm production and semen quality, and could be considered “safe” targets for growing beef bulls.     

Impotentia generandi in male dromedary camels: Clinical findings,semen characteristics,and testicular histopathology

The objective of this study was to describe the clinical findings, semen characteristics, and testicular histopathology in male dromedary camels affected with impotentia generandi (IG). According to the history, 82.6% (38/46) of the cases were classified as primary-IG (P-IG; never been able to impregnate a female), whereas 17.4% (8/46) were classified as secondary-IG (S-IG; acquired infertility). Only one scrotal testis was observed in four cases, and no scrotal testis was observed in one case. Overall, testicular length, width, and depth were 6.46 ± 0.2, 3.41 ± 0.1, and 2.8 ± 0.08 cm, respectively. Within the P-IG males, 42.2% of the testes were classified as small, 47.9% as normal, and 9.9% as large. Within the S-IG males, 0.0% of the testes were classified as small, 80% as normal, and 20% as large. Ejaculate volume, total sperm number in the ejaculate, and sperm motility, viability, and abnormal morphology were 4.4 ± 0.3 mL, 25.7 ± 1.0 × 10⁶, 18.7 ± 3.1%, 25.2 ± 3.4%, and 46.6 ± 3.7%, respectively. Azoospermia was observed in 30.4% of the cases, asthenospermia was observed in the 25% of the cases, and necrospermia was observed in 10% of the cases. The proportion of abnormal sperm was between 20% and 50%, and between 60% and 94% in 56.2% and 34.4% of the cases, respectively. Hypospermatogenesis, arrested spermatogenesis, Sertoli cell–only syndrome, and testicular degeneration were the main histopathological findings. In conclusion, IG in male dromedary camels appears to be related mainly to testicular dysfunction, which alters semen quality and reduces fertility.     

Outcomes and treatment patterns as a function of time in stage IS testicular seminoma: A population-based analysis

ObjectivesTo assess outcomes and treatment patterns as a function of time in stage IS pure testicular seminoma patients using a population-based analysis.MethodsOne thousand one hundred and fifty-two stage I testicular seminoma patients with normal alpha-fetoprotein levels were identified in the Surveillance, Epidemiology, and End Results (SEER) database between 1998 and 2005. Three hundred and twenty-three of these patients had persistent elevations of their serum lactate dehydrogenase (LDH) and/or beta subunit of human chorionic gonadotropin (bHCG) level post-orchiectomy, i.e., “stage IS” disease.ResultsMedian follow-up was 86 months. There was persistent elevation of LDH or bHCG levels post-orchiectomy in 19% and 15% stage I patients, respectively. Post-orchiectomy LDH and bHCG did not predict overall survival (OS) or cause-specific survival (CSS) in stage IS patients. There was a decrease in utilization of adjuvant RT in stage IS patients from 1998 (100%) to 2005 (58%, p = .01). The annual percentage decrease in RT utilization for stage IS patients was −5.4% (95% confidence interval: −7.7% to −3.9%). Modern, linear accelerator-based RT was associated with an improvement in OS. However, longer follow up is necessary to determine if the OS benefit persists.ConclusionsPost-orchiectomy LDH and bHCG did not predict OS or CSS in stage IS patients. There was a steady decrease in utilization of adjuvant RT in the United States in stage IS testicular seminoma patients between 1998 and 2005. This may be due to the increasing popularity of chemotherapy or active surveillance.     

A review of some factors affecting the expression of libido in beef cattle, and individual bull and herd fertility

This paper examines some of the factors that affect the expression of libido in beef cattle, focusing on the male and the free-ranging situation. The ways in which bull libido is assessed and the relationship between libido test results and fertility are discussed. Genetics play a role in determining libido, but there are many environmental factors affecting its expression, and a number of these factors influence sexual activity in both tests of libido and paddock mating. Herd fertility is multi-factorial and, consequently, it is difficult to draw definitive conclusions about the relationship between libido and fertility. Multiple males increase the expression of libido, but it is uncertain whether this translates into improvements in herd fertility. However, there are consequences for individual bull fertility, as there is ample evidence of inherent differences between bulls. Male:female ratios appear to have minor effects on libido and fertility. Anecdotal evidence indicates that multiple matings with the same or different bulls may reduce the duration of oestrus. Social relationships between bulls can affect the expression of libido, with subordinate bulls being inhibited by the presence of dominant bulls. There is evidence that dominant bulls may achieve more matings at pasture, but this is not necessarily shown in their fertility. Older bulls show greater expression of libido in tests and appear more efficient in serving, although these changes may reflect greater sexual experience. Provided bulls are sexually mature and physically able to mate, age per se appears not to affect fertility, but age interacts with dominance, which can influence fertility. There is evidence of breed differences in expression of libido, but this appears not to be demonstrated in fertility. There is anecdotal evidence that bulls and females prefer to mate with similar genotypes/phenotypes with implications for fertility. Limited research on thermal and nutritional effects indicate some adverse consequences for libido of climatic extremes for unadapted bulls and of over-feeding, but not under-feeding. Limited research has investigated the effects on libido and fertility of multiple stressors associated with relocation; relocation to dramatically different environments has long-lasting detrimental consequences for fertility. Too few studies have been conducted to draw conclusions about the effects of topography and herd dispersion on libido and fertility. Temperament is likely to affect the expression of libido when animals are put into new situations, but this has not been critically researched. In the light of this review, the implications for managing cattle to optimise fertility are discussed and suggestions made as to areas where further research is needed.     

Effects of environmental factors, age and genotype on sperm production and semen quality in Bos indicus and Bos taurus AI bulls in Brazil

The effects of ambient temperature and humidity, month, age and genotype on sperm production and semen quality in AI bulls in Brazil were evaluated. Data from two consecutive years were analyzed separately. Seven Bos indicus and 11 Bos taurus bulls from one artificial insemination (AI) center were evaluated in Year 1 and 24 B. indicus and 16 B. taurus bulls from three AI centers were evaluated in Year 2. Ambient temperature and humidity did not significantly affect sperm production and semen quality, probably because there was little variation in these variables. Month accounted for less than 2% of the variation in sperm production and semen quality. Increased bull age was associated with decreased sperm motility (P<0.10) and increased minor sperm defects (P<0.001) in Year 1. B. indicus bulls had greater (P<0.005) sperm concentration than B. taurus bulls in both years (1.7×10⁹/ml versus 1.2×10⁹/ml in Year 1 and 1.6×10⁹/ml versus 1.2×10⁹/ml in Year 2, respectively). Ejaculate volume was not significantly affected by genotype in Year 1 (6.6 ml versus 6.9 ml in B. indicus and B. taurus bulls, respectively), but B. indicus bulls had greater (P<0.05) total (11.4×10⁹ versus 8.2×10⁹) and viable (6.7×10⁹ versus 4.9×10⁹) numbers of spermatozoa in the ejaculate than B. taurus bulls. In Year 2, B. taurus bulls had greater (P<0.05) ejaculate volume than B. indicus bulls (8.2 ml versus 6.7 ml, respectively) and total and viable number of spermatozoa in the ejaculate were not significantly different between genotypes (10.3×10⁹ versus 9.1×10⁹ and 6.1×10⁹ versus 5.4×10⁹ in B. indicus and B. taurus bulls, respectively). Sperm motility was not significantly affected by genotype (mean, 59%). In Year 1, B. indicus bulls tended (P<0.10) to have more major sperm defects and had more (P<0.05) total sperm defects than B. taurus bulls (11.8% versus 8.7% and 13.6% versus 10.0%, respectively). In Year 2, B. indicus bulls tended (P<0.10) to have more total sperm defects than B. taurus bulls (16.2% versus 13.3%, respectively). In conclusion, neither ambient temperature and humidity nor month (season) significantly affected sperm production and semen quality. B. indicus bulls had significantly greater sperm concentration and B. taurus bulls had significantly fewer morphologically defective spermatozoa.     

Evaluation of resistance to permethrin,cypermethrin and deltamethrin in different populations of Musca domestica (L.), collected from the Iranian dairy cattle farms

The house fly, Musca domestica (Linnaeus) (Diptera: Muscidae), is a major pest for human and livestock health and is also resistant to different insecticides. Herein, six M. domestica populations were collected, five of them from industrial cattle farms and the Koohrang population from a remote area as a susceptible population. The resistance/susceptibility of populations to three pyrethroids was evaluated. High levels of permethrin resistance were observed in all field populations and the resistance ratios (RRs) were estimated to vary from 52- to 129-fold. Resistant populations also exhibited resistance to other pyrethroids (cypermethrin and deltamethrin), with RRs ranging between 45- and 180-fold. According to synergistic (piperonyl butoxide, diethyl maleate and triphenyl phosphate) and enzymatic assays, resistant populations exhibited multiple resistance phenotypes. Cytochrome P450 monooxygenases (P450s), glutathione S-transferases (GSTs), and carboxylesterases (CarEs) were found to be involved in pyrethroid resistance in Isfahan population, P450s and GSTs in Mobarake population and CarEs detoxified pyrethroids in Natanz and Alavijeh populations. As substitution of Leucine (CTT) with Phenylalanine (TTT) at position 1014 of the voltage sensitive sodium channel (VSSC) gene is the most common mutation conferring resistance to pyrethroids in M. domestica, we sequenced a partial fragment of IIS6 and L1014F mutation was detected in all resistant populations. The present study provides valuable information for early detection of pyrethroid resistance and developing resistance management strategies in the house fly populations.     

Circadian and circannual changes in the testicular function of adult rhesus monkeys

The endocrine and gametogenic status of the testes were studied in 9 healthy adult rhesus monkeys of proven fertility throughout a one-year period. Testosterone levels were estimated by radioimmunoassay in blood samples collected at 4 h intervals over a 24 h period once a month. Semen samples and testicular biopsies were also examined once a month. A well-defined circandian rhythm was evident in serum levels of testosterone. The rhythmicity was less pronounced in February and September. The 24 h mean levels of serum testosterone were high between the months of August to March and low in the months of May to July. All animals did not uniformly respond to electro-ejaculation in April and May. Semen volume and total number of spermatozoa were maximal between September and March and least from April to August. Testicular biopsies indicated that all stages of spermatogenesis were evident between September and March and the spermatogenic activity was less evident between April and August. The contents of Sertoli cells showed a seasonal cyclicity; they were laden with lipid droplets during April to August when spermatogenesis was quiescent and vacuolated during September to March when spermatogenesis was active. These studies indicate that the testing of contraceptive drugs needs to be restricted to months of September to March in male rhesus monkeys otherwise, it is possible that the naturally occurring reproductive quiscence may be attributed to the effect of the drug being tested. The data accrued from the present studies also provide quantitative information on circulating levels of testosterone which could be used as a reference background while evaluating the contraceptive drug-effects in male rhesus monkeys.     

Immunization against GnRH in the male camel (Camelus dromedarius): Effects on sexual behavior, testicular volume, semen characteristics and serum testosterone concentrations

The effect of immunization against gonadotrophin releasing hormone (GnRH) on sexual behavior, total scrotal size, semen characteristics and serum concentrations of testosterone, was evaluated for 24 wks in sexually mature camels (Camelus dromedarius). Eight bull camels were randomly divided into a treatment and control group. Four male camels were immunized using 2 mg GnRH - tandem-dimer conjugated to ovalbumin, (Pepscan Systems, the Netherlands) administered subcutaneously, 4 wks apart. Control male camels received the same amount of saline solution. Significant decline in serum testosterone level was observed in three immunized camels out of four, whereas one camel showed no effect. The testosterone levels reached to <1.0 ng/mL serum by week 4 after booster injection and remained suppressed through the course of the study. The total testicular volume was not affected until the end of the experiment. In treated animals, the sexual behavior negatively affected after the booster injection. Anti-GnRH vaccine had a seriously detrimental effect on the acrosin amidase activity and normal acrosome percentages in treated male camels. It is concluded that the vaccine was effective in reducing serum testosterone levels and libido, and it had a serious harmful effect on the acrosin amidase activity and percentages of spermatozoa with normal acrosome. The immunogen did not affect the total testicular volume.     

Effect of the thyroid on faecal shedding of E. coli O157:H7 and Escherichia coli in naturally infected yearling beef cattle

AIMS: To determine if thyroid function affects faecal shedding of Escherichia coli O157:H7. METHODS AND RESULTS: Eight yearling cattle (n = 4 per treatment group), previously identified as shedding E. coli O157:H7, received either 0 or 10 mg 6-N-propyl-2-thiouracil (PTU) kg(-1) BW day(-1) for 14 days to reduce serum concentrations of the thyroid hormones, T(3) and T(4). Animals were monitored daily for changes in faecal shedding of E. coli O157:H7 and E. coli (EC) for the 14-day treatment period and an additional 7 days post-treatment. Body weight was measured weekly and serum concentrations of T(3) and T(4) were determined every 3 days. No differences in faecal shedding of E. coli O157:H7 were observed during the 14-day treatment period. However, compared with control animals, a greater percentage of PTU-treated cattle ejected E. coli O157:H7 on day 16 (100 vs 25%) and 18 (75 vs 0%) of the post-treatment period. Serum T(3) was lower in PTU-treated cattle during the 14-day treatment period and greater on day 18 of the post-treatment period. CONCLUSION: Cattle with chemically altered thyroid hormones had similar shedding patterns of faecal E. coli O157:H7 and EC during the 14-day treatment period. However, faecal shedding of E. coli O157:H7 tended to be greater, and serum concentrations of T(3), were greater for PTU-treated cattle immediately following the termination of PTU treatment. SIGNIFICANCE AND IMPACT OF THE STUDY: Short-term chemical inhibition of thyroid hormones had minimal effects on faecal shedding of E. coli O157:H7 in naturally infected cattle. However, a hyperthyroid state as observed postdosing might play a role in the seasonal shedding of E. coli O157:H7 in cattle.     

Effects of sub-chronic aluminum chloride on spermatogenesis and testicular enzymatic activity in male rats

Aims

The aim of this study was to determine the effects of sub-chronic aluminum chloride (AlCl₃) on spermatogenesis and testicular enzymatic activity in male rats.

Main methods

Forty Wistar male rats were randomly divided into four groups: control group (CG, 0), low-dose group (LG, 64.18 mg/kg BW AlCl₃), mid-dose group (MG, 128.36 mg/kg BW AlCl₃) and high-dose group (HG, 256.72 mg/kg BW AlCl₃). The rats were orally administered with AlCl₃ for 120 days. At the end of the experiment, the contents of Al, Fe, Cu and Zn, the enzyme activities of testicular acid phosphatase (ACP), succinate dehydrogenase (SDH), lactate dehydrogenase (LDH), lactate dehydrogenase isoenzyme (LDH-x), the sperm count and the sperm malformation rate were examined.

Key findings

The results showed that the Al and Cu contents, sperm count and the enzyme activities of testicular ACP, SDH, LDH and LDH-x decreased, while the Zn and Fe contents and sperm malformation rate increased in AlCl₃-treated rats.

Significance

It suggests that sub-chronic AlCl₃ disorders the balance of trace element and decreases the spermatogenesis and the activities of testicular enzymes, indicating that AlCl₃ has adverse effect on the testicular function in male rats.     

Human sperm proteins from testicular and epididymal origin that participate in fertilization: modulation of sperm binding to zona-free hamster oocytes, using monoclonal antibodies.

In order to identify human sperm surface proteins involved in the gamete recognition process, mouse monoclonal antibodies were directed against human spermatozoa and screened with live spermatozoa by enzyme-linked immunosorbent assay (ELISA). Immunoperoxidase staining of human testis showed the early presence of four corresponding proteins on germinal cells, while six were detected primarily in testis fluid. The presence of 17 proteins was evidenced in the epididymis. Eight were detected with a decreasing gradient from the beginning to the end of the organ, including vasa efferentia for three of them. The other nine were observed in only one defined segment, usually the caput epididymis, which was found to be the most active region. Comparison of spermatozoa patterns from testis, vasa efferentia, and the three regions of epididymis pointed out a progressive coating. By contrast, three antibodies displayed a migration of spermatozoa surface domains in the course of epididymal transit. Six antibodies were found to inhibit human spermatozoa adherence to zona-free hamster oocytes, while nine promoted it. Molecular weights of antigens corresponding to nine of the antibodies ranged from 11 to 215 kDa. No correlation could be established with previously described human proteins. These observations emphasize the role of epididymis in human sperm maturation.     

Aspects of basic reproductive biology and endocrinology in the fathead minnow (Pimephales promelas)

The fathead minnow (Pimephales promelas) has been proposed as a model species for assessing the adverse effects of endocrine-disrupting chemicals (EDCs) on reproduction and development. The purpose of these studies was to develop baseline reproductive biology and endocrinology data for this species to support interpretation of tests with potential EDCs. Pairs of reproductively-active fathead minnows (n=70) were evaluated with respect to reproductive cyclicity in terms of spawning interval and fecundity. The mode and mean (+/-SE) spawning intervals for the fish in this study were 3.0 and 3.7+/-0.1 days, respectively. The mean number of eggs produced per spawn was 85+/-2.8. Animals were sacrificed at periodic intervals during the established spawning cycle and measurements made of gonadal condition (gonadosomatic index [GSI], histopathology) and plasma concentrations of vitellogenin and sex steroids (beta-estradiol, testosterone, 11-ketotestosterone). The GSI in females varied significantly as a function of spawning interval, with the largest values occurring day 2 post-spawn, just prior to the interval of maximum spawning activity. Plasma beta-estradiol concentrations in females also varied significantly relative to peak values in the GSI and spawning activity. Vitellogenin concentrations in the female, and male GSI and steroid concentrations did not vary significantly relative to position in the spawning cycle. Concentrations of beta-estradiol in females and 11-ketotestosterone in males were positively correlated with testosterone concentrations.     

Clinical efficacy of a GnRH-agonist implant containing 4.7 mg deslorelin, Suprelorin, regarding suppression of reproductive function in tomcats. Sandra.Pesch@vetmed.uni-giessen.de

The aim of the present study was to test for the efficacy of a slow release GnRH-agonist implant (4.7 mg deslorelin, Suprelorin®) in the male cat. Ten toms were implanted sc in the neck. Changes in testosterone (T) secretion, testicular size, body weight and behaviour (mounting, mating, urine marking) were monitored. T concentrations were significantly decreased (P < 0.0001) to basal levels (< 0.1 ng/mL) in 5 of 10 cats after 4 weeks and in all but one tom after 11 weeks (T < 0.1 ng/mL). In this respective tom only partial downregulation with T-values from 0.2 to 0.1 ng/mL was achieved until week 27. In weeks 28 and 32, T concentrations were below 0.1 ng/mL. Compared to pretreatment values, testicular volume was significantly decreased by about 60% in week 12 and about 73% after 36 weeks (P < 0.001). Penile spines disappeared 9.4 ± 1.0 weeks after treatment. Food intake was significantly increased during treatment period (P < 0.001). In all tomcats libido, mating behaviour and urine marking were significantly reduced (P < 0.0001) after an initial stimulation. In one tom, mating an oestrous queen on day 20 after implant administration resulted in pregnancy. Mating of another tom that had T-values between 0.1 and < 0.1 ng/mL since day 24 in week 8 revealed the presence of spermatozoa; however, this mating did not result in pregnancy.Subcutaneous implant administration was well tolerated by all tomcats without sedation or anaesthesia and no treatment related negative effects were observed.These results demonstrate the clinical efficacy of the 4.7 mg deslorelin implants (Suprelorin®) in the tom inducing all castration related effects.     

Effects of steroid hormones on reproduction- and detoxification-related gene expression in adult male mosquitofish, Gambusia affinis

The molecular mechanisms that mediate fish reproduction and detoxification in response to steroid hormones were studied by using adult male western mosquitofish (Gambusia affinis) as sentinel species. The expression patterns of three vitellogenins (VtgA, VtgB and VtgC), two estrogen receptors (ERα and ERβ), two androgen receptors (ARα and ARβ), metallothionein (MT) and cytochrome P450 1A (CYP1A) in the liver and testis of adult male mosquitofish were assessed through exposure treatments with progesterone (P), testosterone (T) and 17β-estradiol (E2), alone and in combination for eight days. The results showed that expression patterns of Vtg subtype, ER subtype, AR subtype, MT and CYP1A genes in male mosquitofish varied according to tissue and specific hormone stress. Vtg subtype mRNA expression was induced in the liver in E2-added treatments, and an up-regulation of ERα mRNA expression was also observed. In addition, hormone treatments increased three Vtg subtype mRNA expression levels in the testis, at least to some extent. All hormone treatments significantly inhibited ERα, ERβ and ARβ mRNA expression in the testis. Some of hormone treatments could affect MT and CYP1A gene expression in mosquitofish. In general, multiple hormone treatments showed different effects on target gene expression compared with corresponding hormone alone. The results from the present study provided valuable information on the toxicological effects of steroid hormones in mosquitofish.     

Effects of season and feeding level on reproductive activity and semen quality in Payoya buck goats

The aim of this study was to determine if there is a seasonal pattern of reproductive activity in male Payoya goats and if this seasonality can be modulated by a higher level of nutrition. For a period of 16 months, 10 adult bucks were divided into two experimental groups that differed in their feeding level. The high nutrition group (H, n = 5) received 1.6 times their maintenance food requirements. The control nutrition group (C, n = 5) received a diet that supported 1.1 times their maintenance requirements. Body weight and testosterone concentrations were determined weekly, and testicular weight was determined every 2 weeks. Sexual behaviour and semen characteristics were determined monthly. Feeding level did not affect the onset or the end of the reproductive activity as measured by testosterone concentrations, with high testosterone concentrations between July and November. Ejaculation latency was positively influenced by feeding level: 43.2 ± 2.2 s vs. 61.6 ± 3.2 s for H and C group, respectively (P < 0.001). The percentage of males that ejaculated or that were sexually active was higher in the H group (P < 0.01). No differences between feeding levels were observed in the different semen characteristics studied. However, major differences between months were observed for all studied variables. These results lead us to conclude that Payoya bucks exhibit large seasonal variation in their reproductive activity. Higher feeding level allowed a better sexual behaviour in bucks in late spring, when male effect is used on the local livestock to breed females.     

The fish assemblage of the intertidal salt marsh creeks in North Bull Island, Dublin Bay: seasonal and tidal changes in composition, distribution and abundance

An intertidal salt marsh fish assemblage inhabiting two creeks on North Bull Island, Dublin Bay was sampled monthly from June 2000 until May 2002. Water temperature and salinity were recorded in situ and samples were also taken for Suspended Particulate Matter (SPM) and Chlorophyll a. All fish caught were weighed and measured and classified into functional guilds. A total of 6,549 individuals comprising 10 fish species from 10 families were recorded within the two creeks. The community was dominated by a few species, a feature common to other estuarine fish populations. Of the 10 species found, the common goby, Pomatoschistus microps, the 3-spined stickleback, Gasterosteus aculeatus, the thick-lipped grey mullet, Chelon labrosus and the flounder, Platichthys flesus contributed 98.4% of all fish sampled. The fish population of the channels at Bull Island, Dublin, was dominated by the resident gobies (true estuarine resident species), but also hosted juveniles of species such as the bass, Dicentrarchus labrax (marine juvenile migrant species). In turn, the nekton populations were dominated by the brown shrimp, Crangon crangon and the fairy shrimp, Palaemonetes varians especially in winter when fewer fish (numbers of species and abundance) were found. Multivariate analysis of fish diversity and abundance revealed a strong seasonal pattern but there was little evidence of difference between creeks, nor of tidal (spring/neap) effects. The estuarine fish using the intertidal marsh creeks have been little studied in Europe yet they play a major role with the decapods in these habitats. This role needs to be quantified for a proper understanding of the system’s function.