Relative efficacy of conventional sperm parameters and sperm penetration bioassay to assess bull fertility in vitro

Acquisition of fertilization competence in guinea pig spermatozoa under different capacitation protocols

Guinea pig in vitro fertilization (IVF) are poorly developed due to the limited accessibility to oocytes and the lack of an efficient method of sperm capacitation. Thus, we aimed to evaluate different capacitation protocols that we validated through sperm analysis and using heterologous (He) IVF with zona-intact bovine oocytes. Spermatozoa of guinea pigs were collected and processed separately by 4 different protocols: A) Spermatozoa were obtained by flushing the lumen of one cauda epididymis and incubated in a minimal culture medium (MCM); B) One epididymis was placed in a prewarmed of M2 medium and gently minced with fine scissors. Spermatozoa were incubated in a modified human tubal fluid medium (HTF). In both protocols, the spermatozoa were capacitated at 37 °C under an atmosphere of 5% CO2 for 2 h. In the protocols C and D, the spermatozoa were collected by flushing the lumen of the cauda epididymis and selected by commercial density gradient Bovipure® (Nidacon Laboratories AB, Göthenborg, Sweden), according to the manufacturer's instructions. Then for Protocol C) spermatozoa were incubated in MCM medium supplemented with 10 mg/mL heparin (MCM-Hep); while for Protocol D) spermatozoa were incubated in FERT medium supplemented 10 mg/mL heparin (FERT-Hep). Incubation of C and D protocols were performed at 38.5 °C under an atmosphere of 5% CO₂ for 2 h. Capacitation protocols C and D showed a higher percentage of viability, total and hyperactive-like motility, and acrosome reaction compared to protocols A and B. For this reason, protocols C and D were used for further He-IVF analysis. Guinea pig sperm and matured zona-intact bovine oocytes were co-incubated at 5% CO₂ and 38.5 °C. Sperm-oocyte interaction was assessed at 2.5 h post-insemination (hpi) and pronuclear formation (PrF) were evaluated at 18, 20, 22, 24 and 26 hpi, while the cleavage rate was evaluated at 48 hpi. In protocol D, PrF was significantly higher than in protocol C (P ≤ 0.05) at every time point evaluated. Also, the cleavage rate at 48 hpi was higher (P ≤ 0.05) in He-IVF protocol D (69.8 ± 1.7%) compared to He-IVF protocol C (49.1 ± 1.1%). In conclusion, we determined the most adequate sperm capacitation conditions for guinea pig that allow zona-intact bovine oocyte penetration and lead to hybrid embryo formation, suggesting that these conditions could be optimal to develop IVF in guinea pigs.

Seasonal variation in bull semen quality demonstrates there are heat-sensitive and heat-tolerant bulls

Using semen data from 1271 ejaculates (79 different bulls, 11 different breeds) we have investigated the variability of semen quality in cattle living in sub-tropical conditions. Modelling shows definitive evidence of seasonal variation. Semen quality from the same bulls had a 90% "pass rate" for cryopreservation purposes in winter, dropping to less than 50% in summer. Notably, individual bulls could be classified as either "heat-tolerant" (produce good quality spermatozoa all year regardless of temperature) or "heat-sensitive" (only produce good quality sperm in summer). Nominal logistic regression demonstrated when temperatures reach 30.5 °C, 40% of heat-sensitive bulls fail a semen analysis 17 days later. At 34 °C, the proportion of bulls failing reached 63%. Ratifying this, the purposeful heating of bulls to 40 °C for 12 h showed that individual animals had different degrees of heat-sensitivity. Using historical temperature data, we then modelled how many days/decade bulls would be subject to heat-events. Beginning from 1939 to 1949, on average, the area in which bulls were kept recorded 19, 7 and 1 day over 38 °C, 39 °C and 40 °C respectively. This number steadily increases and of last decade (2010-2010), the numbers of days per decade over 38 °C, 39 °C and 40 °C jumped to a staggering 75, 39 and 15 respectively. These data show the urgent need to identify heat-tolerant bulls as future sires. Such variation likely explains why the veterinary bull breeding test often fails to accurately predict bull breeding potential.

Effects of dietary supplementation of different sources and levels of selenium on the semen quality and reproductive performance in aged broiler breeder roosters

Fertility has a great impact on economic outcome in poultry sector. However, several physiological stressors such as aging adversely affected fertilization capacity and hatching quantity and quality. This study investigated the effect of dietary supplementation of different sources and levels of inorganic and organic selenium on the semen quality and reproductive performance of aged broiler breeder roosters. A total of thirty-six 50-wk-old Ross 308 roosters were randomly allocated to 6 groups and fed with different levels of organic and inorganic selenium. Treatments were included in the basal diet (control: CG), dietary supplementation of 0.15 (SeY0.15), 0.30 (SeY0.30), and 0.45 (SeY0.45) mg/kg selenium-enriched yeast (SeY), dietary supplementation of 0.30 mg/kg commercial organic selenium (Selemax), and dietary supplementation of 0.30 mg/kg sodium selenite (SS) as an inorganic source during 12 consecutive weeks. Ejaculated volume, semen quality attributes of the collected semen samples were evaluated every week.

To assess fertility, hatchability and the hatched chick quality, the semen samples collected during last 2 wk of the trial were used to artificial insemination of hens. In order to measure seminiferous tube diameter and seminiferous epithelium thickness, testicular histology was also performed at the end of the experiment. Sperm motility, plasma membrane functionality and integrity, and ejaculation volume were higher in the SeY0.45 group compared to the other groups (P < 0.05). Fertility and hatchability rate as well as seminiferous epithelium thickness and seminiferous tube diameter were improved in the SeY0.45 compared with CG, SeY0.15 and SS groups (P < 0.05). Also hatchelling quality from roosters with SeY0.45 was higher than CG and SS groups (P < 0.05). No significant differences were noted in embryonic mortality between groups (P > 0.05).

In conclusion, dietary supplementation of 0.45 mg SeY improved sperm quality and reproductive performance of aged broiler breeder roosters.

An Update on Semen Physiology, Technologies, and Selection Techniques for the Advancement of In Vitro Equine Embryo Production: Section II

Simple Summary

In order to improve fertilization and pregnancy rates within artificial insemination or in vitro fertilization techniques in horses, producers may choose to select the best sperm within an ejaculate. In this paper, we review conventional and novel methods of sperm selection.

Abstract

As the use of assisted reproductive technologies (ART) and in vitro embryo production (IVP) expand in the equine industry, it has become necessary to further our understanding of available semen selection techniques. This segment of our two-section review will focus on the selection of spermatozoa based on quality and sex for equine intracytoplasmic sperm injection (ICSI), as well as current and future developments in sperm sorting technologies. Ultimately, novel methods of semen selection will be assessed based on their efficacy in other species and their relevance and future application towards ARTs in the horse.

Fertilizing capacity of vitrified stallion sperm assessed utilizing heterologous IVF after different semen warming procedures

The aim of this study was to evaluate the fertilizing capacity of frozen or vitrified stallion sperm after assessing different warming procedures. In Experiment 1, different warming procedures were compared after sperm vitrification: immersion in extender at 43 °C (C), or in a water bath at 37 °C/30 s (W37), 43 °C/10 s (W43) or 60 °C/5 s (W60). With the W60 treatment, there were greater values (P < 0.05) for VCL (83.93 ± 3.6 μm/s) and ALH (3.00 ± 0.2 μm) than freezing and with the C group, and greater values (P < 0.001) for PM (35.33 ± 2.5 %) than with the W43 treatment. In Experiment 2, the fertilizing capacity of vitrified and frozen sperm was assessed utilizing heterologous IVF procedures, using cattle oocytes. Vitrification resulted in greater values (P < 0.05) than freezing for the number of bound sperm (1.36 ± 0.3 and 0.69 ± 0.2, respectively). There were no differences between frozen or vitrified sperm in pronuclear formation (26 hours post-insemination - hpi; 14.08 ± 4.2 % and 22.78 ± 4.8 %, respectively) or cleavage rate (32.77 ± 4.3 % and 39.66 ± 4.6 %, respectively). In conclusion, vitrified stallion sperm warmed in a water bath at 60 ºC had the capacity to penetrate cattle oocytes, leading to pronuclear formation and hybrid embryo cleavage after heterologous IVF.

Influence of sperm filtration and the addition of glycerol to UHT skimmed milk- and TEST-based extenders on the quality and fertilizing capacity of chilled ram sperm

The poor fertility of ram semen stored chilled for long periods has encouraged the development of protocols designed to improve the kinetic vigour and cervical barrier-crossing capacity of sperm. The present work evaluated the effect of sperm selection with Sephadex filtration and the supplementation of 2% glycerol (GLY) to extenders based on ultra-heat-treated skimmed milk (UHT) or Tris-Tes-Glucose (TEST) on ram sperm kinetic parameters, plasma membrane integrity, acrosome integrity, mitochondrial function and fertilizing ability, over long chilling times. The results showed that for non-filtered semen, values for progressive sperm motility (%PSM), straight line velocity (VSL, μm/s) and the percentage of sperm with an intact plasma membrane/intact acrosome/a high mitochondrial function index (%IPIAHM) at all times up to 96 h of chilling were higher when the UHT extender (P < 0.01) was used compared to TEST extender irrespective of the presence of GLY. When semen was previously filtered with Sephadex, the addition of GLY to the UHT extender improved total motility (%TM), the %PSM and the VSL at 96 h compared to all other treatments (P < 0.01). The best results of all were obtained with non-filtered semen and UHT either with or without GLY. Heterologous IVF using zona-intact bovine oocytes was used to assess the fertilizing capacity of non-filtered fresh (FS0), chilled-for-24 h (CS24) or chilled-for-48 h (CS48) ram semen diluted in UHT extender (GLY-free). Heterologous IVF showed that ram sperm, either FS0, CS24 or CS48, were equally capable of penetrating zona pellucida intact bovine oocytes, leading to pronuclear formation and hybrid embryo cleavage (46.3 ± 3.2; 48.8 ± 3.2; and 43.3 ± 3.5, respectively). No differences were seen with respect to fresh sperm in terms of sperm binding, penetration, polyspermy, pronucleus formation or cleavage rates (P > 0.05). In conclusion, neither Sephadex filtration nor addition of glycerol provided extra benefits to ram sperm chilled up to 96 h. Chilled, non-filtered sperm extended with UHT without GLY showed better sperm functionality than did similar sperm extended with TEST extenders. Indeed, sperm diluted in UHT extender, maintained fertilizing ability up to 48 h.

Heterologous murine and bovine IVF using bottlenose dolphin (Tursiops truncatus) spermatozoa

Assisted reproductive technologies are of great importance for increasing the genetic diversity in captive animals. The use of bovine or murine oocytes in heterologous IVF provides advantages compared to homologous IVF in nondomestic animals, such as the accessibility to oocytes and the availability of well-developed in vitro maturation systems. The aim of this study was to determine the heterologous IVF parameters using cryopreserved dolphin spermatozoa and zona-intact bovine or murine oocytes and to examine the nuclear chromatin status of the dolphin spermatozoa. All the processes involved in the fertilization including embryo cleavage were observed by confocal microscopy and hybrid embryo formation was confirmed by polymerase chain reaction. Heterologous bovine IVF showed no polyspermy, lower percentages of pronuclear formation, and a lower cleavage rate compared to homologous IVF group (34.8% vs. 89.3%). Heterologous murine IVF showed a lower cleavage rate than homologous IVF (9.6% vs. 77.1%). With respect to dolphin sperm chromatin, it was more stable, i.e. more resistant to EDTA-SDS decondensation than the bovine sperm chromatin. This study revealed the stability of the dolphin sperm chromatin and the ability of the dolphin spermatozoa to penetrate zona-intact bovine and murine oocytes, leading to hybrid embryo formation.

WITHDRAWN: Effects of various glycerol concentrations and thawing temperatures on CASA parameters and acrosomal integrity of frozen-thawed canine spermatozoa

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Ram Sperm Selection by a Dextran/Swim-Up Procedure Increases Fertilization Rates Following Intrauterine Insemination in Superovulated Ewes

The objective of this study was to compare the efficacy of 2 dextran/swim-up media to increase the sperm quality parameters and the maintenance of these parameters at 15 degrees C and 30 degrees C over 6 hours. Additionally, this study examined whether differences in sperm quality reflect different reproductive efficiencies following intrauterine insemination in superovulated ewes. The study involved 2 selected samples (SS) obtained by dextran/swim-up, performed either with (SS+) or without (SS-) capacitating compounds, and a control sample consisting of raw semen diluted in the same medium. The efficacies of the swim-up sperm selection procedures were similar in both media, and no significant differences were found among the evaluated parameters. Conversely, we found important differences between selected and control samples. Sperm motility, viability (as assessed by carboxifluorescein diacetate/propidium iodide [PI] staining), and mitochondrial activity (as assessed by rhodamine 123/PI) were significantly higher in the selected samples than in the control. Additionally, following incubation at 15 degrees C, the preservation of sperm quality was significantly better in the selected samples than in the control samples. After 6 hours of incubation at 15 degrees C, selected samples had a motility value of 46%, which was significantly (P < .001) higher than the value observed in control samples (27%). The percentage of viable cells observed after 6 hours of incubation at 15 degrees C was significantly (P < .0001) higher in selected samples than in the control samples. Furthermore, after 2 hours of incubation at 30 degrees C, swim-up samples had viability values that were significantly (P < .0001) higher than those of the control samples. SS+ and SS- samples did not differ significantly in spermatozoa yield, sperm quality, or survival. Differences between selected samples and controls were reflected in the fertilization rate obtained following intrauterine insemination in superovulated ewes that experienced a 52-hour interval between progestagen removal and artificial insemination. A restricted criterion for fertilization rate evaluation was established, and only the percentage of embryos recovered from the uterine horns 6 days after insemination was considered with respect to the total number of corpora lutea counted in the ovaries. The fertilization rate of SS- samples (50%) was significantly higher (P > .001) than those of the SS+ (2%) and control samples (5%).

Biological markers of boar fertility

The semen evaluation techniques used in most commercial artificial insemination centers, which includes sperm motility and morphology measurements, provides a very conservative estimate of the relative fertility of individual boars. As well, differences in relative boar fertility are masked by the widespread use of pooled semen for commercial artificial insemination (AI) in many countries. Furthermore, the relatively high sperm numbers used in commercial AI practice usually compensate for reduced fertility, as can be seen in some boars when lower numbers of sperm are used for AI. The increased efficiency of pork production should involve enhanced use of boars with strong reproductive efficiency and the highest genetic merit for important production traits. Given that the current measures of semen quality are not always indicative of fertility and reproductive performance in boars, accurate and predictive genetic and protein markers are still needed. Recently, significant efforts have been made to identify reliable markers that allow for the identification and exclusion of sires with reduced reproductive efficiency. This paper reviews the current status of proteomic and genomic markers of fertility in boars in relation to other livestock species.

Ability of Catalonian donkey sperm to penetrate zona pellucida-free bovine oocytes matured in vitro

An experiment was designed to study the interaction between fresh/frozen-thawed donkey spermatozoa and zona pellucida (ZP)-free bovine oocytes in an attempt to develop a model for assessing cryopreserved Catalonian donkey sperm function. Semen from five donkeys was collected using an artificial vagina. Sperm motility and viability were immediately assessed and the semen sample cryopreserved. Sperm viability and motility were then reassessed immediately after thawing. The motion characteristics of the fresh and frozen-thawed spermatozoa were determined using a computer-assisted sperm analysis system. In vitro-matured cow oocytes were inseminated with different percent live donkey sperm (high (>60%) or low (<40%) viability donkey sperm). After 18h of co-incubation, the oocytes were fixed, stained with 4',6-diamidino-2-phenylindole (DAPI) and examined for sperm penetration, the number of penetrated spermatozoa per oocyte, and male pronucleus formation. Frozen-thawed spermatozoa from high viability semen showed significantly lower VCL, VAP and mean ALH values than did high viability fresh spermatozoa. In contrast, frozen-thawed spermatozoa of low viability had significantly higher velocity values than fresh spermatozoa of low viability. A significant positive correlation (P<0.01) was detected between percentage fertilization and viability (r=0.84), and between percentage fertilization and certain CASA parameters (VAP, r=0.56; VCL, r=0.61 and mean ALH, r=0.68). Fresh or frozen-thawed high viability spermatozoa penetrated 90.1% and 85.4% of bovine oocytes respectively. Lower rates of penetration were observed for fresh and frozen-thawed low viability spermatozoa (34% and 22.5% respectively). The donkey spermatozoa were able to fuse with the oolema and even to decondense and form the male pronucleus (85-94%). Larger numbers of penetrated spermatozoa per oocyte were recorded when high viability sperm samples were used, whether fresh (3.02 vs. 1.12 for low viability sperm) or frozen-thawed (3.41 vs. 1.47). Consequently, low viability sperm samples showed higher percentages of monospermic penetration (91.17% and 61.97% for fresh and frozen-thawed sperm samples respectively). These findings suggest that bovine oocytes provide a useful model for assessing the penetration potential of frozen-thawed donkey sperm.

Identifying useable semen

The "predictors of useable semen" used in most commercial AI centers provide a very conservative estimate of the relative fertility of individual boars. Furthermore, the relatively high sperm numbers used in commercial AI practice (usually >3 x10(9) total sperm per dose of extended semen) usually compensate for reduced fertility, as can be demonstrated in some boars when lower numbers of sperm are used for AI. Differences in relative boar fertility are also masked by the widespread use of pooled semen for commercial AI in many countries. However, the need to continually improve the efficiency of pork production, suggests that commercial AI practice should involve increased use of boars with the highest genetic merit for important production traits. Necessarily, this must be linked to the use of fewer sperm per AI dose, fewer inseminations per sow bred, and hence more sows bred by these superior sires. In turn, this requires improved techniques for evaluating semen characteristics directly related to the fertilization process, such as IVM-IVF assays, analysis of seminal plasma protein markers, more discriminatory tests of sperm motility and morphology, with the goal of identifying high-index boars whose fertility is sustained when low numbers of sperm are used for AI. This paper reviews the current status of laboratory-based boar semen evaluation techniques that meet these criteria.

Computer automated motion analysis of crossbred bull spermatozoa and its relationship with in vitro fertility in zona-free hamster oocytes

The objective of this study was to determine the effective relationship between different motion characteristics of bull spermatozoa assessed by computer assisted semen analyzer (CASA) and in vitro fertilization percentage in zona-free hamster oocytes. A total of 64 frozen semen samples from 16 different crossbred bulls (Bos taurusxBos indicus) with four ejaculates from each bull were taken for analysis. Various motion characteristics of spermatozoa like progressive motility, path velocity, progressive velocity, beat cross frequency, straightness and linearity were recorded. Hypo-osmotic swelling test and sperm penetration bioassay were conducted to assess the membrane integrity and fertilization percentage of spermatozoa respectively. Significant positive correlation (P<0.01) was found between fertilization percentage and progressive motility (r=0.791) and between velocity parameters (VAP; r=0.612 and VSL; r=0.625) and fertilization percentage. Among different CASA variables, progressive motility alone contributed to 62.6% variation in the fertilization percentage. The velocity measurements (VAP and VSL) together with progressive motility and %HOS spermatozoa contributed to 66.1% of variation in fertilization percentage which was found to be significant (P<0.05).

Biometry of frozen–thawed sperm from eight breeds of Indian buffaloes (Bubalus bubalis)

Sperm morphometry, in combination with other objective traits, can be useful for developing a fertility index. The objective of the present study was to measure various biometric end points of frozen-thawed sperm from eight breeds of Indian buffaloes (Murrah, Surti, Tarai, Mehsana, Jaffrabadi, Bhadawari, Pandharpuri and Nili-Ravi). The sperm head of Pandharpuri buffaloes had the greatest length (10.21 microm), width (6.05 microm), area (52.31 microm(2)) and perimeter (31.86 microm). The ratio of sperm width to length was also greatest (0.61) in Pandharpuri as well as in two other breeds, viz. Nili-Ravi and Jaffrabadi. Murrah had the smallest sperm head width (4.75 microm), area (41.65 microm(2)) and perimeter (29.17 microm), but its sperm tail was longest (57.02 microm), along with that of Jaffrabadi buffaloes (56.96 microm). Based on mean values of sperm tail length, mid piece length and its width the eight buffalo breeds were categorized into three, four and five groups, respectively. Multivariate analysis and clustering put six breeds (Surti, Tarai, Mehsana, Jaffrabadi, Bhadawari and Nili-Ravi) in one cluster, whereas Murrah and Pandharpuri appeared as separate entities.

State of the art in farm animal sperm evaluation

Our ability to screen the structural and functional integrity of the spermatozoon in vitro has increased markedly over the past decades, but our capacity to estimate the fertility of a semen sample or of the sire from which it has been collected, especially in selected farm animal breeders, has not. The estimation of fertility is constrained by several factors (e.g. type of cell, analysis strength, sperm deposition strategies, recordings of fertility), including the fact that the ejaculate is composed of a diverse sperm population. Such cell heterogeneity is reflected not only in differences in the intactness of attributes needed for fertilisation, such as motility or morphology, but also in the relative ability of the spermatozoa to remain fertile over time, to sustain selection steps and responses to exogenous stimuli similar to those during sperm transport in the female genital tract, all of which account for innate variations in the fertilising ability among doses, ejaculates and sires. Determination of how large such a sperm population with competence for fertilisation and in-built ability to display these attributes under physiological signalling is would allow for a better estimation o f fertility, provided that th e particular s ire produces this sub-population in a repeatable manner. The value of these analyses is discussed in the present paper.

Can we increase the estimated value of semen assessment?

Estimating the fertility of a semen sample or of the male from where it has been collected by simple assessment of in vitro sperm characteristics is still difficult, owing to the variable correlations that laboratory results achieve with in vivo fertility. A major reason behind these variations is the fact that the ejaculate and the artificial insemination (AI)-doses it generates are composed of a diverse sperm population. Such heterogeneity is reflected both in differences of intactness of attributes needed for fertilization, such as motility or morphology, but also in the relative ability of spermatozoa to prevail fertile over time, handling and exposure to different stimuli, all of which account for innate variations in fertilizing ability among doses, ejaculates and sires. However, methods are already available to select sub-populations of intact spermatozoa which can be tested for their degree of competence for fertilization and whose estimated power is promising, allowing the elimination of cases of sub-fertility, particularly in bovine. Examples of these methods are the separation of viable spermatozoa by swim-up or discontinuous gradient centrifugation, followed by testing the ability of the selected spermatozoa to dose-response/time sustain capacitation and acrosome reaction induction. Finding how large a sperm population with non-compensated attributes for fertilization and ability to display and sustain stimuli is, perhaps by a quick screening of membrane integrity and stability by multi-parametric methods, would allow, provided the particular male produces this sub-population in a repeatable manner, for a better estimation of fertility.

Effect of egg yolk concentration on cryopreserving Spanish ibex (Capra pyrenaica) epididymal spermatozoa

Tris-egg yolk based diluents provide adequate cryoprotection for the sperm of most wild species in which they have been tested. The objective of the current study was to evaluate various Tris-based diluents containing different concentrations of egg yolk, for the fertilizing ability of epididymal spermatozoa of the Spanish ibex (Capra pyrenaica) after freezing and thawing. For this purpose, we used heterologous in vivo fertilization by intrauterine insemination of domestic goats (Capra hircus). In Experiment 1, a Tris-citric acid-glucose (TCG) diluent containing 6% (v/v) egg yolk and a TCG extender containing 20% egg yolk were compared. In Experiment 2, a TCG-6% egg yolk extender was compared with Triladyl-20% egg yolk. Diluted samples were cooled slowly to 5 degrees C over 1 h and equilibrated at that temperature for 2 h. At that point, aliquots of samples were loaded into 0.25 ml straws, and frozen in nitrogen vapor for 10 min. The fertility of spermatozoa frozen in TCG-6% egg yolk was higher (P<0.05) than for those extended with TCG-20% egg yolk, and tended to be higher than for those frozen with Triladyl-20% egg yolk. From the results of this study, the use of Tris-based extenders containing low concentrations of egg yolk (6%) is recommended for cryopreserving Spanish ibex epididymal spermatozoa.

Birth of live Spanish ibex (Capra pyrenaica hispanica) derived from artificial insemination with epididymal spermatozoa retrieved after death

As a consequence of increasing limitations to maintaining genetic variability in endangered wildlife species, methods of assisted reproduction widely used in domestic animals are being applied to nondomestic species. However, practical efforts have met limited success to date. The Spanish ibex (Capra pyrenaica hispanica) is a wild caprine originating exclusively in the mountains of Spain. This study was designed to evaluate the fertilizing capability of cryopreserved Spanish ibex epididymal spermatozoa recovered postmortem. For this purpose, we have previously evaluated the effect of time elapsed between death and sperm recovery on spermatic parameters, and the fertilization ability of frozen-thawed spermatozoa using heterologous in vivo fertilization by intrauterine insemination in domestic goat (Capra hircus). The time of death significantly affected most sperm quality parameters (motility, viability and intact acrosomes). The fertility obtained by heterologous artificial insemination was 18.7%, and only goats inseminated with spermatozoa recovered within 8h after death became pregnant. Our findings showed that heterologous in vivo fertilization is a useful method to evaluate the fertilizing capacity of sperm samples in rare or wild species. Sperm samples, with verified fertilization ability in the previous trial, were used to inseminate a total of six ibex females. Inseminations resulted in one pregnancy. The study demonstrated for the first time the feasibility of applying artificial insemination in Spanish ibex.

In vitro evaluation of the quality and fertilizing capacity of boar semen frozen in 0.25 ml straws

Twenty-two boar ejaculates were frozen in 0.25 ml straws using a controlled cooling rate, then evaluated in vitro in order to assess: (i) the extent to which a range of semen evaluation parameters accurately characterize sperm quality, (ii) the value of quality assessment in the characterization of long-term sperm survival and fertility and (iii) the suitability of the cryopreservation protocol used for yielding semen with good quality and fertilizing capacity. Motility with or without caffeine, plasma membrane integrity (PMI) evaluated with both propidium iodide (PI) and Hoechst 33258, and acrosome morphology were studied, the ejaculates being then classified into five quality groups. A thermoresistance test and a homologous in vitro fertilization test were applied to selected ejaculates of these groups. Caffeine-stimulated motility and PMI evaluated with PI provided better estimations of semen quality than the other tests of motility, PMI, or acrosome morphology, but this quality assessment could not reveal differences in fertilizing capacity or thermoresistance among ejaculates. Over 43% spermatozoa survived cryopreservation in 19 of the 22 ejaculates, with inter-boar and inter-ejaculate variability in the freezing success being observed. The fertilizing capacity, however, was seriously affected by the process regardless of the semen quality. It is concluded that caffeine-stimulated motility and PMI evaluated with PI give accurate information on sperm quality, but important aspects to the valuation of semen such as thermoresistance and fertilizing capacity are not revealed by this quality study. Moreover, the approach of selecting suitable protocols of cryopreservation does not appear to be sufficient for guaranteeing systematically good quality and fertilizing capacity in the frozen-thawed semen.

Concentração espermática e tempo de incubação na fecundação in vitro usando-se sêmen de touros da raça Guzerá

Estudou-se o efeito da concentração espermática e período de incubação e da interação dessas características sobre a fecundação in vitro (FIV) usando-se sêmen de touros Guzerá. Oócitos (n=1146) maturados in vitro foram divididos em tratamentos objetivando a FIV, em esquema fatorial 3×2×2 (três touros - A, B e C, duas concentrações espermáticas - 2 e 4×10(6) espermatozóides/ml e dois tempos de incubação 12 e 18 horas). Utilizaram-se espermatozóides viáveis obtidos por swin-up. A FIV foi realizada em meio fert-talp com heparina, em incubadora com 5% de CO2 e 95% de umidade, a 38,5°C. Após incubação, 50% dos oócitos foram fixados e corados para determinação das taxas de penetração, fecundação monoespermática e poliespermia. O restante foi co-cultivado com células da granulosa em meio CR2aa por oito dias, avaliando-se a taxa de clivagem e a produção de blastocisto. Houve maior taxa de penetração (P<0,05) na concentração de 4×10(6) espermatozóides/ml por 18 horas (64%), e não se observou diferença (P>0,05) entre os demais tratamentos. A taxa de poliespermia foi maior (P<0,05) na concentração espermática de 4×10(6), independente do tempo de incubação. Na concentração espermática mais alta, a taxa de poliespermia foi maior no tempo de incubação de 18 horas (P<0,05). O touro A apresentou menor (P<0,05) taxa de poliespermia em relação aos demais. Ainda, no touro A a taxa de clivagem foi maior (P<0,05) que no touro B, enquanto o C mostrou-se semelhante tanto ao A quanto ao B. O tempo de incubação, a concentração espermática e a interação das variáveis influenciaram as taxas de penetração e poliespermia, sem interferir na taxa de fecundação monoespermática e na produção de blastocistos.

Fertilizing Ability of Electro-Ejaculated Cryopreserved Semen in the Domestic Cat

Semen collection and AI in the cat are still not routine procedures. The correlation between semen quality and fertility under natural conditions is a relatively unknown field in the cat. In the present study, functional in vitro tests, such as the ability to bind and penetrate the zona pellucida or to fertilize in vitro, were used to determine fertilizing ability of sperm cryopreserved with a practical and efficient freezing protocol previously developed in our laboratory. Semen was collected by electroejaculation, evaluated for motility and diluted with Tris-glucose-citrate egg-yolk extender supplemented with Equex STM paste (0.5% v/v). After equilibration and loading into 0.25 ml straws, semen was frozen at 3.85 degrees C/min. Frozen-thawed semen was co-cultured with in vitro matured cat oocytes. Penetration rate was recorded 30 h after in vitro fertilization and cleaved zygotes were cultured in vitro until day 7. A correlation was found between sperm motility index (SMI) after thawing and semen fertilizing ability (p<0.05). In conclusion, it was demonstrated that the post-thaw motility quality, expressed as SMI, of spermatozoa frozen using the protocol mentioned above can be considered an index of the sperm ability to penetrate in vitro matured oocytes.

Functional significance of responsiveness to capacitating conditions in boar spermatozoa

New methods are needed for rapid and sensitive assessment of sperm function. As the ability to fertilize an oocyte is acquired during the capacitation process, assessments of sperm function have to be performed under fertilizing conditions. In this study, we monitored the dynamics of the temporal response of sperm from ejaculates of both fertile and subfertile boars to capacitating conditions in vitro (responsiveness) by following the changes in the response to calcium ionophore treatment and in [Ca(2+)](i). The differences between individual males were also investigated. Ionophore-induced changes and increased intracellular calcium ion content in boar spermatozoa were found to progress as a function of time during incubation under capacitating conditions. After primary kinetic analysis, 120 min was chosen as the point in time for assessment of responsiveness. Intra-boar variability in responsiveness parameters was relatively high (variation coefficient CV>30%), especially in the response to ionophore treatment, indicating that an isolated test may be inadequate for the evaluation of sperm function. Despite this high variability, there were markedly significant individual differences with respect to changes during capacitation, and there were significant correlations between conventional and responsiveness sperm parameters. The population of samples from subfertile boars, was found to be heterogeneous in regard to sperm responsiveness to capacitating conditions. There were two significantly different classes of subfertile boars ("low" and "high" responders), indicating that fertility may be associated with suboptimal rather than maximal response (both too rapid and too slow membrane changes). Therefore, criteria for quality judgement should include both the low and upper limits of responsiveness. The use of responsiveness parameters together with conventional spermatological parameters improved the prediction level of multiple regression models for farrowing rate and litter size. It can be concluded that the combination of sperm responsiveness parameters applied here is a suitable tool for the evaluation of sperm function.

Sperm survival and heterogeneity are correlated with fertility after intrauterine insemination in superovulated ewes

Efficient animal production involves accurate estimations of fertilizing ability. One key factor is the plasma membrane of the sperm cell, which is actively involved in the cascade of events before oocyte fusion. Many methods are used to analyze the characteristics of this membrane, including partition in aqueous two-phase systems which is an efficient method to analyze sperm surface changes accounting for loss of viability and different functional states. Centrifugal countercurrent distribution (CCCD) analysis can also be used in an aqueous two-phase system to determine the relationship between sperm parameters and in vivo fertility in ewes. In a previous work, we found a significant correlation between two post-CCCD parameters (heterogeneity and recovered viability) and field fertility when the same sample was used after cervical AI. The present study was intended to find out whether the control of several external factors that affect reproductive efficiency is able to increase the correlation coefficient between post-CCCD parameters and fertility. Thus, 90 Rasa aragonesa ewes were controlled on the same farm and received intrauterine inseminations using the same technical equipment. The fertilizing ability of the raw semen and sperm samples selected by a dextran/swim-up process was compared using a low number of spermatozoa per insemination (7 x 10(7)) to enhance possible fertility differences. A new post-CCCD parameter was considered; the loss of viability (LV) occurred during the CCCD process. This variable denotes the sperm surviving ability and corresponds to the difference between the total number of viable cells loaded and recovered after the CCCD run. The mean fertility of eight sperm control samples was 60% (range: 25-76%), and there was no significant correlation between standard parameters and in vivo fertility. LV ranged from 2 to 69% (average 27%) and was negatively correlated with fertility (r = -0.914, P < 0.01). Ejaculate heterogeneity (H) ranged from 20 to 47% and was positively, but not significantly, correlated with fertility (r = 0.391). A predictive equation for fertility was deduced by multiple analysis with a very high correlation coefficient (r = 0.967), and level of significance (P < 0.005): predictive fertility PF = 52.546 - 0.594 LV + 0.665 H. The mean fertility of 13 swim-up selected samples was 63% (range: 25-86%). Again, only parameters derived from the CCCD analysis were highly correlated with fertility, especially LV and H (P < 0.05).

Evaluation of fertility and infertility in natural service bulls

The potential fertility of bulls can be evaluated in the field by assessment of mating ability and physical examination. Both methods are useful for screening out low fertility bulls, although neither allows precise determination of the pregnancy rates that bulls actually achieve. Observations of coitus, libido testing and service capacity testing are the main methods of assessing mating ability in the field and, although not reliable for virgin bulls, are widely used for older bulls. Of the traits that are assessed during physical examination, those most closely correlated with fertility are scrotal circumference and the semen quality parameters of motility and morphology. Whilst these methods allow reasonable accuracy in determining the fertility potential of an individual bull, they do not take into account other managemental constraint to bulls' fertility. Although these are reasonable well understood for beef herds, the managemental factors that affect the performance of natural service sires in dairy herds are poorly understood.

Laboratory semen assessment and prediction of fertility: still utopia?

Finding a laboratory test reliable enough to predict the potential fertility of a given semen sample or a given sire for artificial insemination (AI) is still considered utopian, as indicated by the modest correlations seen between results obtained in vitro and field fertility. Male fertility is complex, and depends upon a heterogeneous population of spermatozoa interacting at various levels of the female genital tract, the vestments of the oocyte, and the oocyte itself. For this reason, laboratory assessment of semen must include the testing of most sperm attributes relevant for fertilization and embryo development, not only in individual spermatozoa but within a large sperm population as well. Strategies for the discovery of in vitro predictors of semen fertility require evaluations of low sperm doses for AI, so that differences in innate in vivo fertility can be accurately detected.

Fertility estimation: a review of past experience and future prospects

Fertility has many components and stages which require that males and females be functionally capable of carrying out all critical stages if each generational reproductive cycle is to be completed. To accomplish this, the male must produce and ejaculate normal fertile sperm. The female must produce, store and ovulate normal fertilizable oocytes. Furthermore, the female must provide a reproductive system compatible with sperm transport, capacitation, and fertilization of the oocytes, embryo and fetal development, and finally birth of healthy young. Reproductive success or failure at several of these points can be estimated quantitatively on a population basis, and in a few situations on an individual basis. It is important that fertility estimates be determined accurately and with precision to be most useful to researchers and managers of animal enterprises. Many studies have underestimated the biological relationship of fertility to other traits because the estimates lacked precision. Many in vitro manipulations of sperm in artificial insemination, of gametes in various assisted reproductive technologies, and of embryos in embryo transfer are utilized in animal breeding programs. Accurate estimation of reproductive efficiency of these in vitro procedures also is important. Conditions surrounding different sets of fertility estimates almost certainly will be different. These conditions should be described as precisely as possible, and appropriate controls included in all experiments. When possible, experiments should be replicated over time and place to determine the repeatability of the various criteria used to estimate fertility and reproductive efficiency. Advances in genomic information and molecular biology should facilitate characterizing more fully inherent potential fertility of animals at birth. In vitro tests will improve, and automated techniques will facilitate making multiple determinations possible on a large scale. Reliability of fertility estimates will increase, with the potential for enhanced animal reproductive performance through more accurate selection, genetic engineering, and enlightened animal care. Simultaneously, it is important to recognize that prediction of future fertility is more hazardous than estimating fertility, as a completely new set of circumstances may occur which are not predictable. Because fertility estimation may be applied under a myriad of conditions, principles and factors affecting fertility will be emphasized in this review as being more useful than a compilation of numerical examples.

Penetration in vitro of zona-free pig oocytes by homologous and heterologous spermatozoa

We examined the penetrability of pig, rat and bull spermatozoa into zona-free pig oocytes. Frozen-thawed boar spermatozoa penetrated into both zona-intact and zona-free oocytes with similar efficacy in a modified Tris-buffered medium (mTBM) supplemented with BSA and caffeine, but not in medium without caffeine. Rat epididymal spermatozoa did not readily penetrate into zona-free pig oocytes in mTBM with BSA. However, when a modified Krebs-Ringer bicarbonate solution was used, penetration rate varied with sperm concentrations at insemination: 79% of the oocytes were penetrated at 1.0 x 10(6) cells/ml, but very few at 0.1 x 10(6) and 10.0 x 10(6) cells/ml. In all oocytes penetrated, no activation was observed and the sperm nucleus was fully decondensed but did not transform into a male pronucleus. Frozen-thawed bull spermatozoa were also found to penetrate into zona-free pig oocytes in mTBM with BSA, caffeine and heparin: higher penetration rates were obtained with 1.0 x 106 and 10.0 x 10(6) spermatozoa/ml compared with 0.1 x 10(6) spermatozoa/ml. The penetration rate with 1.0 x 10(6) spermatozoa/ml was stable in five different bulls. All oocytes penetrated were activated and male pronuclear formation was observed in 57-79% of the penetrated oocytes. These results suggest that capacitation or the acrosome reaction is required for boar, rat, and possibly, bull spermatozoa to penetrate into zona-free pig oocytes. Bull spermatozoa can easily induce activation of pig oocytes and form male pronuclei, but rat spermatozoa cannot do so, indicating species differences in the ability of spermatozoa to activate pig oocytes and to transform to male pronuclei in the ooplasm.

Effect of precocious collection on semen output and quality in young Holstein bulls

Semen production units compete heavily with each other, so they tend to select and collect bulls at the earliest possible age, even before puberty, in order to reduce the interval between generations. This study is a retrospective analysis of the effect of precocious collection on semen quality in Holstein bulls. The semen parameters of early- and late-maturing bulls collected before and after 410 days of age, respectively, were compared over two periods, 1991-1995 and 1997-1999. These periods were defined in relation to the collection rhythms (three collections of two ejaculates at 15 days interval before 1996 and adaptation of the collection rhythms to individual physiological capacity after 1996) and the collection conditions. The effects of age, precocious collection and the interaction between age and precocious collection on mean semen parameters (volume of the ejaculate, sperm motility, percent of motile spermatozoa per ejaculate, total sperm concentration and mobile sperm concentration) measured on collections 1-6 (n = 358 for 1991-1995 and n = 121 for 1997-1999), 7-12 (n = 255 for 1991-1995 and n = 80 for 1997-1999) and 13-18 (n = 92 for 1991-1995 and n = 36 for 1997-1999) were studied by covariance analysis. The semen quality of bulls collected at the early age differed from that of bulls collected after 410 days of age for the first period when the collection rhythm was intense. No effect of precocious collection was evidenced for the second period, suggesting the importance of individual adaptation of the collection rhythm to sexual maturation in young bulls. Early collections at a semen production unit reduced the time needed to obtain the number of insemination straws required for the progeny-testing program by 40 days. Early sperm collection is, thus, of economic and technical interest in well managed semen production units.

Species-specific sperm-egg interaction affects the utility of a heterologous bovine in vitro fertilization system for evaluating antelope sperm

The purpose of this study was to evaluate cryopreserved fringe-eared (FE) oryx (Oryx gazella callotis) sperm function using a heterologous in vitro fertilization (IVF) system previously developed to study scimitar-horned (SH) oryx (Oryx dammah) spermatozoa. Semen was collected by electroejaculation from FE oryx (n = 2) and SH oryx (n = 2), evaluated immediately postcollection, and cryopreserved. Thawed spermatozoa were evaluated for motility, forward progression, and acrosomal status immediately post-thaw, after Percoll-separation, and 1, 2, 3, and 8 h after culture in IVF medium. In vitro-matured cow oocytes (n = 924) were inseminated with either domestic bull, FE, or SH oryx spermatozoa and after an 8-h coincubation period, half the oocytes were fixed and examined for sperm penetration, polyspermy, and male pronuclear formation. The remaining oocytes were placed into in vitro culture and evaluated for cleavage after 48 h. Overall, there were no between-species differences in sperm motility and acrosome integrity. However, an effect of time (P < 0.05) and a species-by-time interaction (P < 0.05) were detected for both parameters. Penetration, male pronuclear formation, and embryo cleavage were high (>90%, >85%, and >70%, respectively) for oocytes inseminated with domestic bull and SH oryx spermatozoa and did not differ (P > 0.05) between species. In contrast, very few oocytes (2.8%, 4 of 141) inseminated with FE oryx sperm were penetrated. Cleavage was rare (8.0%, 16 of 200) in oocytes inseminated with FE oryx spermatozoa and did not differ (P > 0.05) from that in parthenogenetic controls (4.2%, 3 of 72). Furthermore, FE oryx spermatozoa were incapable of penetrating zona-free cow oocytes. These results indicate that species-specific differences in gamete interaction may exist even between very closely related nondomestic bovids.

Assessment of in vitro fertility of deer spermatozoa by heterologous IVF with zona-free bovine oocytes

We have previously shown that the in vitro development of deer embryos differed according to the IVF conditions. The aim of the study was to use heterologous IVF with zona-free matured bovine oocytes to assess the in vitro fertility of 3 samples of deer semen (2 ejaculates from sika deer (Cervus nippon) and 1 pool of epididymal spermatozoa from red deer (Cervus elaphus)). The frozen/thawed semen samples were selected on Percoll gradient and resuspended in Tyrode modified medium supplemented with estrus sheep serum (0, 2, 20% v/v) or heparin (10 microg/mL). During 8 h of culture, the sperm motility index according to the post-insemination time (hpi) did not differ either between samples or between supplemented IVF media. In vitro matured zona-free bovine oocytes were inseminated in different IVF media with the semen samples. Penetration rates assessed at 15 hpi were optimal with 20% estrus sheep serum for sika deer ejaculates whereas 2% were sufficient to reach the maximum functionality of epididymal spermatozoa from red deer. The mean time of pronuclear formation was similar regardless of the semen sample. The precocity of the onset of the first S-phase in both pronuclei was characterized by Bromo-deoxy-Uridine exposures between 5 and 15 hpi in order to assess the developmental potential conferred by the semen sample (intrinsic value). As we previously observed in homologous IVF, this value seemed to be higher for the epididymal sperm sample.

Long-term preservation of chilled canine semen: effect of commercial and laboratory prepared extenders

The present study was conducted to evaluate chilled semen conservation over time in 3 commercial and 4 laboratory prepared extenders, including a new Tris-glucose extender. The beneficial effect of adding egg yolk to these media was also analyzed. The effects of these extenders on motility and acrosome reaction were characterized objectively using a computer-aided semen analyzer and the chlortetracycline staining, respectively. No significant differences were observed when comparing the different commercial extenders without egg yolk, but addition of egg yolk improved all motility parameters significantly (preservation of 50% of motility was observed at 3.2+/-1, 2.9+/-0.5, 2.3+/-0.5, 8.5+/-0.2, 5.4+/-1.1, 5.2+/-0.4 d, for Biladyl, green extender and fresh-phos extenders without and with egg yolk, respectively). Motility parameters were best preserved in egg yolk supplemented Biladyl extender with a mean percentage of 86.3+/-10.5 motile spermatozoa after 7 d at 4 degrees C. Efficacy of egg yolk-supplemented commercial extenders on sperm motility at 4 degrees C was (in decreasing order) as follows: Biladyl > green extender > fresh-phos. However, high quality motility and the percentage of motile spermatozoa were highest with some of the laboratory prepared extenders: a 50% conservation rate of motile spermatozoa was observed following the use of supplemented egg yolk extenders. These are classified in decreasing order as follows: Tris-glucose (13+/-1 d) > Tris-fructose (9.7+/-0.6) > EDTA (4.+/-0.6 d) > Tris-bes (3.6+/-1.1 d). A low concentration of motile spermatozoa was still observed in the Tris-glucose egg yolk extender 16 d after collection, clearly demonstrating the importance of the medium and the beneficial effect of egg yolk on sperm motility of 4 degrees C chilled semen. Similar effects of extender were observed for acrosome reactions. Egg yolk clearly had a protective effect reducing acrosome reactions significantly in all media tested as follows: the highest acrosome losses were observed in the fresh-phos and EDTA extenders without egg yolk; the lowest rate was observed with Tris-glucose supplemented egg yolk extender. In conclusion, at 4 degrees C, egg yolk extender best-protected sperm motility parameters. Differences in osmolarity between the extenders in terms of substrate related to sperm metabolic activity may explain the optimal results obtained using egg yolk-supplemented Tris-glucose extender, which preserved motility and acrosome integrity in chilled dog semen. These results indicated that good quality dog spermatozoa could be preserved for up to 10 d.