Effect of cervical and vaginal insemination with liquid semen stored at room temperature on fertility of goats

The effect of vaginal and cervical deposition of liquid semen stored at room temperature on the fertility of goats was tested in a field trial in which 217 Norwegian Dairy goats aged between 6 months and 7.5 years from 14 farms were inseminated after natural oestrous. Cervical insemination with 200 x 10(6) spermatozoa resulted in 25-day non-return and kidding rates of 87.0 and 78.0%, and vaginal insemination gave 85.5 and 74.3%, respectively. There was no significant difference between the cervical and vaginal inseminations (P = 0.59 for the 25-day non-return and P = 0.40 for the kidding rates). Farm had a significant effect on the 25-day non-return rate (P = 0.03) but not on the kidding rate (P = 0.07). There were no significant differences between the fertility rates for different bucks (P = 0.36 for the 25-day non-return and P = 0.15 for the kidding rates). Fertility results after vaginal insemination were encouragingly high. Vaginal insemination is a simple, less costly and time consuming technique compared to others, also bringing into focus the animal welfare aspects of the artificial insemination procedure. As the final goal is to establish a technique that could be applied similarly on a large scale by all farmers, vaginal insemination must be considered as a method that would simplify the use of liquid buck semen in Norway.     

The importance of porcine sperm parameters on fertility in vivo

It would be desirable to use semen parameters to predict the in vivo fertilizing capacity of a particular ejaculate. In animal production, an ejaculate is divided into multiple doses for artificial insemination (AI); therefore, it would be economically beneficial to know the functional quality (i.e., fertility) of the semen before it is inseminated. To identify a predictive assay of the fertilizing capacity of a porcine ejaculate, we performed 4 rapid assays of sperm quality (motility, viability, physiological status as assessed by chlortetracycline fluorescence, and ATP content) on samples from 9 ejaculates, before and after a thermal stress test (42.5 degrees C, 45 min). These parameters were subsequently correlated with in vivo fertility resulting from AI with 2 sperm doses, 3 x 10(9) or 0.3 x 10(9) motile cells in 70 mL (optimal or suboptimal sperm number per insemination, respectively) from these same ejaculates. No parameter was correlated to the fertility rates obtained after inseminating with the optimal semen doses, either before or after the thermal stress test (P > 0.05). However, with respect to the animals inseminated with the suboptimal semen dose, sperm motility (the percentage of motile spermatozoa as assessed visually by microscopy) prior to thermal stress was well-correlated to fertility rates (r = 0.783, P = 0.01). The percentage of spermatozoa displaying the chlortetracycline Pattern AR (acrosome reaction) was also statistically related to fertility (r = 0.05, P = 0.04), but the biological importance of this relationship is questionable given the small variation among ejaculates (range: 0 to 2%). No other sperm parameter was significantly related to fertility rates in this group (P > 0.05). These data, therefore, indicate that sperm motility is a useful indicator of sperm fertilizing capacity in vivo. Moreover, to identify a predictor of semen fertility it is critical that the number of spermatozoa used during insemination is sufficiently low to detect differences in sperm fertilizing efficiency.     

Seasonal variations of semen quality in male goats: study of sperm abnormalities

The type, frequency and seasonal variation of sperm abnormalities in male goats inhabiting in Mediterranean region were evaluated. Semen was collected twice a week with an artificial vagina from 9 10-month-old Murciano-Granadina male goats weighing 41 to 48 kg. Distal cytoplasmic droplets and acrosomal damage were the predominant abnormalities. Increase in age (10 to 27 months) did not reveal itself as a main effect on the occurrence of sperm abnormalities. All types of sperm abnormalities studied showed significant (P<0.01) seasonal variation. The poorest quality semen was collected during winter and spring. In spite of a seasonal variation in sperm quality, semen of Murciano-Granadina goats in the Mediterranean area is good all year long, since the proportion of abnormal spermatozoa was well within the accepted range for normal fertility.     

Artificial insemination of sheep: Effects on fertility of number of spermatozoa inseminated and of storage of diluted semen for up to 18 hours at 5°C

Ram semen was prepared in a buffered glucose-saline solution containing 3% (v/v) egg yolk so that insemination doses of 25 or 100 million spermatozoa in volumes of 50 or 250 μl could be given per ewe at artificial insemination (AI). Fertility was significantly reduced by dilution and, within the treatments of diluted semen, significantly higher lambing rates followed the use of doses of 100 million spermatozoa. The volume of the AI dose had no significant effect on fertility.Of 945 inseminations performed using diluted semen, 388 were with samples that had been cooled to 5°C and stored chilled for 5 or 18 hr. The mean lambing result of 40% for freshly diluted semen was significantly higher than 31.6% and 30.2% for samples stored chilled for 5 and 18 hr respectively. Ewes inseminated with doses of chilled semen containing 25 million spermatozoa had a low lambing rate of 21.3%. The presence of 7.5% glycerol (v/v) in the diluent did not significantly affect the fertility of chilled semen.     

Fertility of undiluted ram epididymal spermatozoa stored for several days at 4°C

In vitro preservation of the male gamete is a challenge in the development of artificial insemination techniques for domestic animals. Specific strategies and diluents have been developed for the preservation of the fertilizing ability of the semen for each species. However, the epididymal medium has been demonstrated to be the best sperm environment to maintain sperm viability over several days and weeks for mammals. The aims of this study were to evaluate the motility and in vivo fertility of ram epididymal spermatozoa when the semen was stored for up to 4 days at 4°C undiluted in epididymal plasma. The study was undertaken with two ovine breeds (Ile de France and Corriedale). The motility of epididymal spermatozoa was better preserved in the undiluted epididymal fluid than when epididymal spermatozoa were diluted in classic ovine extender such as skim milk. During storage, the decrease in the percentage of motile sperm was lower if the epididymal spermatozoa were collected immediately after epididymal sampling than 24 h after castration or animal death. The fertility obtained after cryopreservation of the stored sperm and subsequent intrauterine insemination ranged from 55% to 24% following 24 to 96-h sperm storage. There was a linear regression relationship between fertility and the number of motile sperm inseminated for both breeds. These results show that it is possible to keep epididymal sperm motile and fertile for several days without dilution. Such a method of sperm preservation could be a final possibility for animals of high genetic value or for endangered species when the collection of semen before death of the animal is not possible.     

Sources of variation in the reproductive performance of ewes inseminated with frozen-thawed ram semen by laparoscopy

Fertility data from 8 artificial insemination programs, involving more than 5000 ewes and 110 rams in 3 flocks, were analyzed to determine variation due to individual AI program and ram in the reproductive performance of ewes inseminated with frozen-thawed semen by laparoscopy. The semen had been previously frozen by commercial AI centers in either pellets or straws. Both AI program and individual ram affected the proportion of ewes pregnant and the number of fetuses per ewe inseminated, but not the number of fetuses per pregnant ewe. Semen samples from 97 of the rams used were analyzed on a Hamilton Thorn HTM 2000 image analyzer for sperm concentration, percentage of motile and progressively motile spermatozoa, mean progressive velocity, and mean linear index. The correlations between these traits and reproductive performance obtained after insemination were calculated. There was large variation in the quantity and quality of the frozen semen, but only the number of total and motile spermatozoa inseminated per ewe was correlated with fertility (0.25 and 0.26, respectively). Regression analysis showed that none of the traits measured were useful for predicting fertility.     

Improvement of rooster semen quality using coenzyme Q10 during cooling storage in the Lake extender

Sensitivity of rooster semen to stressful condition of cooling restricts the semen storage in commercial flocks for artificial insemination. This study was accomplished to investigate the effect of coenzyme Q10 (CoQ10) addition to the Lake extender during chilled-storage on the parameters of sperm quality and fertility performance. Roosters’ pooled semen samples were assigned into equal parts and diluted with Lake extender supplemented with different concentrations of CoQ10 (0, 1, 2, 5 and 10 μM CoQ10). Then, semen samples were cooled to 5 °C and stored over 48 h. Total and progressive motilities, abnormal morphology, viability, membrane functionality, lipid peroxidation (LPO) and mitochondria active potential of diluted sperm were evaluated at 0, 24 and 48 h of cooling storage. Fertility performance of cooled stored semen was examined at 24 h of cooling storage. Although CoQ10 did not affect sperm quality at the starting time of cooling storage (0 h), extender supplementation with 5 μM of CoQ10 showed higher (P ≤ 0.05) sperm total and progressive motilities, membrane functionality, viability and mitochondria active potential at 24 h as well as total motility, viability and membrane functionality at 48 h in contrast with other groups. Moreover, lipid peroxidation was lower (P ≤ 0.05) in semen samples diluted with 5 μM CoQ10 at 24 and 48 h compared to others. After artificial insemination with 24 h chilled-stored sperm, fertility efficiency was higher (P ≤ 0.05) in treatments contained 5 μM CoQ10 compared to the control group. According to the results, using optimum dose of CoQ10 could be helpful to save rooster semen against chilled storage structural and functional damages.     

Seminal traits, suitability for semen preservation and fertility in the native Portuguese horse breeds Puro Sangue Lusitano and Sorraia: Implications for stallion classification and assisted reproduction

The Puro Sangue Lusitano (PSL) is the major national breed of horse in Portugal, but no studies exist on its seminal characteristics, or on the possibility of conserving semen for future use. The aim of this study was to evaluate semen parameters, fertility and the aptness to semen preservation in Lusitano Stallions. In order to compare characteristics defined by a single or by multiple semen collections per stallion 152 ejaculates obtained from 152 Lusitano stallions presented at an annual breeding soundness examination as well as data related to 371 ejaculates obtained from 9 PSL were analyzed. These latter samples were also evaluated in terms of their possible use in assisted reproduction and were compared with 113 ejaculates obtained from 4 Sorraia horses, a rare and endangered Portuguese breed. The percentage of motile spermatozoa (PMS) was assessed after collection (AC), after semen dilution (AD) and at 24h of cool-storage. Mean values obtained for sperm motility and morphology and semen pH observed after semen collection differ significantly (P<0.05) between single collection/multiple stallions and multiple collections/limited stallions, and no age related effects were detected. Overall, Lusitano semen quality was comparable to that of related breeds, while Sorraia stallions had very poor semen quality. The response to cool-storage of diluted semen samples differed among stallions and breeds, and the best results for progressive motile sperm cells at 24h were in a range of 35-53% for PSL stallions and were lower for Sorraia stallions. Fertility rates obtained with artificial insemination (AI) averaged at 85% for PSL. With the exception of PMS AC, sperm vitality and semen pH no other seminal trait seemed to influence fertility rates in the Lusitano breed.     

Successful artificial insemination using semen frozen and stored by an ultrafreezer in the Majorera goat breed

The semen of five Majorera breed bucks was collected and processed to reach a final concentration of 200 × 10⁶ spermatozoa/straw in the extender containing 4% of glycerol and 12% of egg yolk. Two freezing techniques were assessed: (LN) straws were frozen and stored in liquid nitrogen, and (ULF) straws were frozen and stored in the ultra-low freezer at −152 °C. Semen quality (sperm motility, acrosome integrity and abnormal sperm cells percentages) was determined for different storage times (1, 30, 90 and 365 days of cryopreservation). Thereafter, 150 Majorera goats were assigned to four experimental groups: for groups LN-1 (n = 40) and LN-6 (n = 35), the goats were transcervically inseminated with frozen-thawed semen stored for 1 and 6 months in liquid nitrogen, respectively, while for groups ULF-1 (n = 40) and ULF-6 (n = 35), the goats were transcervically inseminated with frozen-thawed semen stored for 1 and 6 months in an ultra-low freezer at −152 °C, respectively. The pregnancy rate was determined by transabdominal ultrasound scanning; in addition, the kidding rate and prolificacy were recorded at parturition. In vitro results showed that the freezing protocol did not affect sperm quality with similar values for up to 1 year of cryopreservation. The kidding rates were not significantly different between experimental groups (43.6%, 38.5%, 42.8% and 40.0% for groups LN-1, ULF-1, LN-6 and ULF-6, respectively). In all experimental groups, the kidding rate and prolificacy were significantly higher (p < 0.01) in multiparous than in nulliparous goats. Therefore, the in vitro results and fertility trials confirmed the efficiency of the ULF technique for freezing and storage of goat semen.     

Effect of different diluents on goat semen fertility

Skim milk (SM) is considered to be the most widely employed extender for goat sperm used for artificial insemination (AI). However, the fertilizing life span of sperm stored in milk or milk-based extenders does not exceed 12h. Besides some seminal plasma components, such as a protein fraction from the goat bulbourethral gland secretion (SBUIII), interacts with some milk fractions and inhibits the spermatozoa motility. The aim of this study was to prolong the survival of buck semen and its fertility. Buck ejaculates were diluted to a final concentration of 100x10(6)spermatozoa/ml with three different diluents: SM, TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl) and TEMPOL+hyaluronic acid (TEMPOL+HA). At 7h from dilution 42 goats were inseminated with semen diluted with SM (short-term semen) while after storage for 24h, 44 and 45 goats were inseminated with semen diluted with TEMPOL and TEMPOL+HA (long-term storage), respectively. At day 50 from AI the percentages of pregnant goats were 71.4% (30/42) with SM, 61.4% (27/44) with TEMPOL and 48.8% (22/45) with TEMPOL+HA, with significant differences between SM and TEMPOL+HA. The kidding rate was 66.7% (28/42) with SM diluent, 61.4% (27/44) with TEMPOL and 48.8% (22/45) with TEMPOL+HA, without significant differences among treatment groups. In conclusion, it is possible to maintain good fertility in goats after AI with semen stored for 24h in TEMPOL.     

Quality and fertility of cooled-shipped stallion semen at the time of insemination

Stallion semen processing is far from standardized and differs substantially between AI centers. Suboptimal pregnancy rates in equine AI may primarily result from breeding with low quality semen not adequately processed for shipment. It was the aim of the study to evaluate quality and fertility of cooled-shipped equine semen provided for breeding of client mares by commercial semen collection centers in Europe. Cooled shipped semen (n = 201 doses) from 67 stallions and 36 different EU-approved semen collection centers was evaluated. At arrival, semen temperature was 9.8 ± 0.2 °C, mean sperm concentration of AI doses was 68 ± 3 x 10⁶/ml), mean total sperm count was 1.0 ± 0.1 x 10⁹, total motility averaged 83 ± 1% and morphological defects 45 ± 2%. A total of 86 mares were inseminated, overall per season-pregnancy rate in these mares was 67%. Sperm concentration significantly influenced semen motility and morphology at arrival of the shipped semen. Significant effects of month of the year on volume, sperm concentration and total sperm count of the insemination dose were found. The collection center significantly influenced all semen parameters evaluated. Semen doses used to inseminate mares that became pregnant had significantly higher total and progressive motility of spermatozoa and a significantly lower percentage of morphological semen defects than insemination doses used for mares failing to get pregnant. Results demonstrate that insemination with semen of better quality provides a higher chance to achieve pregnancy. Besides the use of stallions with good semen quality, appropriate semen processing is an important factor for satisfying results in artificial insemination with cooled-shipped horse semen.     

Sperm yield after single layer centrifugation with Androcoll-E is related to the potential fertility of the original ejaculate

Many attempts have been made to identify laboratory tests that are predictive of sperm fertility, both to improve the quality of stallion semen doses for artificial insemination (AI) and to identify potential breeding sires if no fertility data are available. Sperm quality at the stud is mostly evaluated by assessing subjective motility, although this parameter can be poorly indicative of fertility. Sperm morphology and chromatin integrity in Swedish stallions are correlated to pregnancy rate after AI. Because single layer centrifugation (SLC) selects for spermatozoa with normal morphology and good chromatin, retrospective analysis was carried out to investigate whether sperm yield after SLC is linked to potential fertility. Commercial semen doses for AI from 24 stallions (five stallions with four ejaculates each, 19 stallions with three ejaculates each; n = 77) obtained during the breeding season were cooled, and sent overnight to the Swedish University of Agricultural Sciences in an insulated box for evaluation, with other doses being sent to studs for commercial AI. On arrival at Swedish University of Agricultural Sciences, the semen was used for SLC and also for evaluation of sperm motility, membrane integrity, chromatin integrity, and morphology. The seasonal pregnancy rates for each stallion were available. The yield of progressively motile spermatozoa after SLC (calculated as a proportion of the initial load) was found to be highly correlated with pregnancy rate (r = 0.75; P < 0.001). Chromatin damage was highly negatively correlated with pregnancy rate (r = −0.69; P < 0.001). Pregnancy rate was also correlated with membrane integrity (r = 0.58; P < 0.01), progressive motility (r = 0.63; P < 0.01), and normal morphology (r = 0.45; P < 0.05). In conclusion, these preliminary results show that sperm yield after SLC is related to the potential fertility of the original ejaculate, and could be an alternative indicator of stallion fertility if breeding data are not available. Single layer centrifugation is fast (30 minutes) and does not require expensive equipment, whereas other assays require a flow cytometer and/or specialist skills. An additional option could be to transport semen doses to a laboratory for SLC if the stud personnel do not want to perform the procedure themselves.     

Effect of insemination dose on pregnancy rate in mares

Different insemination doses have been used for artificial insemination(AI) in horses. Since the insemination dose can affect the pregnancy rate, it is important to ensure that an adequate dose be used regardless of the type of inseminationprotocol used. The aim of this study was to find out if it is possible to decrease the insemination dose from 500 x 10(6) progressively motile spermatozoa to 300 x 10(6) progressively motile spermatozoa and still maintain an acceptable pregnancy rate when using extended fresh semen. Thirteen stallions of known fertility and a well-defined group of 64 mares were used in the study. The mares were randomly assigned to 1 of 2 insemination groups. Examination for pregnancy was performed by ultrasonography per rectum approximately 16 d after the last insemination. When using an insemination dose of 300 x 10(6) progressively motile spermatozoa the pregnancy rate per cycle was 75%. With an insemination dose of 500 x 10(6) progressively motile spermatozoa the pregnancy rate per cycle was 64%. There was no significant difference in the pregnancy rate between the 2 insemination doses (P = 0.341). We conclude that when using fresh extended semen it is unlikely that an insemination dose of 300 x 10(6) progressively motile spermatozoa would yield a lower pregnancy rate than a dose of 500 x 10(6) progressively motile spermatozoa if stallions with good quality semen are selected.     

Vaginal deposition of frozen-thawed semen in Norwegian Dairy goats: Comparison of single and double insemination with equal total number of spermatozoa

In a field trial, a total of 472 Norwegian Dairy goats showing natural estrus were artificially inseminated with frozen-thawed semen. The farmers themselves performed vaginal deposition of 400 × 10⁶ spermatozoa; one half of the does received two straws (200 × 10⁶ spermatozoa/straw) at the same time (single AI), while the other half received two straws (200 × 10⁶ spermatozoa/straw) 12 h apart (double AI). The commercially available extender Andromed^® was used for dilution. The does were housed at 15 different farms, and on average 31 does were inseminated per farm. Non return rates (NRR) and kidding rates after single insemination were 64.3% and 58.3%, respectively. Double inseminations resulted in a NRR of 62% and a kidding rate of 57%. No significant difference between single and double AI was seen in the study. This study indicates that single or double vaginal insemination with an equal total number of frozen-thawed spermatozoa (400 × 10⁶) can give acceptable fertility results in Norwegian Dairy goats. However, studies on reducing sperm numbers are called for to allow AI donor bucks to be used to their fullest potential.     

Relationship between thirty post-thaw spermatozoal characteristics and the field fertility of 11 high-use Australian dairy AI sires

This study determined the relationship between two measures of field fertility of 11 high-use Australian artificial insemination (AI) dairy bulls and thirty standard laboratory assessments of spermatozoal post-thaw viability.The two measures of field fertility used, conception rates (cCR) and non-return rates (cNRR), were both corrected for all major non-bull variables. Sperm viability assessments were conducted on semen collected within the same season as that used to derive the field fertility estimates. These assessments measured sperm concentration, motility, morphology and membrane integrity at thawing, after 2h incubation and after the swim-up sperm selection procedure. Derivations of these measures and in vitro embryo fertilizing and developmental capacity were also determined. The Genstat Statistical Package [Genstat 5 Release 4.2 Reference Manual, VSN International, Oxford, 2000] was used to conduct an analysis of variance on the viability parameters across semen straws and bulls, and to calculate the strength of correlation between each semen parameter, cNRR and cCR in a correlation matrix. Step forward multiple regression identified the combination of semen parameters that were most highly correlated with cCR and with cNRR.The sperm parameters identified as being most predictive of cCR were the percentage of morphologically normal sperm immediately post-thaw (zeroNorm), the number of morphologically normal sperm after the swim-up procedure (nSuNorm), and the rate of zygote cleavage in vitro (Clv); the predictive equation formed by these parameters accounted for 70% of variance. The predictive equation produced for cNRR contained the variables zeroNorm, the proportion of membrane intact sperm after 2h incubation at 37 degrees C (twoMem) and Clv and accounted for 76.5% of the variation. ZeroNorm was found to be consistent across straws and semen batches within-bull and the sperm parameter with the strongest individual predictive capacity for both cCR (P=0.1) and cNRR (P=0.001). Post-thaw sperm parameters can be used to predict field fertility of Australian dairy sires; the calculated predictive equations are particularly useful for identifying and monitoring bulls of very high and very low potential fertility within a group.     

Naturally and stimulated levels of reactive oxygen species in cooled stallion semen destined for artificial insemination

The decrease in foaling rates after artificial insemination with cooled semen warrants the search for new predictors of fertility. The objectives were to investigate levels of naturally occurring reactive oxygen species (ROS) in cooled, stored stallion semen doses for artificial insemination (AI), and their relationship with parameters of semen quality and with pregnancy rate. Semen was collected from warmblood stallions (n=15) and used to prepare commercial semen doses for AI. Sperm quality was evaluated after cooled transport to the laboratory overnight. The results were correlated with observed foaling and pregnancy rates. Hydroethidine and dichlorodihydrofluorescein diacetate were used as indicators for the ROS superoxide and hydrogen peroxide, respectively. Sperm morphology, motility, plasma membrane integrity and chromatin integrity were also evaluated. These variables were correlated with each other and with pregnancy rates. We found a high inter-individual variation in the ROS levels between stallions. The proportion of live, hydrogen peroxide-negative spermatozoa was correlated with progressive motility, whereas live hydrogen peroxide-negative spermatozoa and chromatin damage were negatively correlated, indicating that low levels of hydrogen peroxide were correlated with good chromatin integrity. The percentage of dead hydrogen peroxide-positive sperm was negatively related to the foaling rate. The negative relationships were stronger when combining results from both assays for ROS. These results for stored semen samples indicate that high individual variation exists for superoxide and hydrogen peroxide measurements, and that ROS status can influence sperm quality. Thus, ROS may be some of the factors influencing fertility. Moreover, combinations of ROS variables improved the correlation with fertility, indicating the usefulness of including these variables in a future model for prediction of the fertility of a semen sample.     

Methods for Cryopreservation of Guinea Fowl Sperm

Conservation of indigenous poultry species is an important part of the new Hungarian agricultural strategy. Semen cryopreservation is the most practical method for the long term storage of poultry genetic material. The objective was to compare four protocols for cryopreservation of guinea fowl sperm (slow and fast programmable, freezing in nitrogen vapor, and pellet) and three cryoprotectants (10% ethylene glycol, 6% dimethyl-formamide and 6% dimethyl-acetamide). The efficiency of the methods was examined by in vitro tests (subjective motility scoring, sperm concentration, morphological and live/dead sperm analysis with eosin-aniline staining). Thereafter, the two most promising methods were tested by artificial insemination of frozen-thawed semen (3 times a week for 3 weeks using 300 million spermatozoa/hen), followed by candling of incubated eggs, assessment of fertilization, embryonic death, and hatching rate. The survival rate of live, intact spermatozoa was greatest (p≤0.05) in pellet method and the slow programmable protocol (with 10% ethylene glycol) (28.6 and 23.5%). The two best protocols (based on in vitro assessment of post-thaw semen quality) were subsequently tested in vivo with artificial insemination. The pellet method yielded a 64% fertility rate compared to slow protocol with only 30% fertility. Regardless, both freezing protocols significantly increased embryonic deaths compared to the control group (16,7; 9,1 and 8,3%, respectively). During the 3-week in vivo trial, fertility increased and early embryonic death decreased over time. According to the results the guinea fowl sperm could tolerate the fast freezing in pellet better than the slower freezing rates and resulted acceptable fertility rate.     

Economics of selecting for sex: the most important genetic trait

Over 20,000 calves have resulted from artificial insemination (AI) of cattle with sexed, frozen/thawed sperm in the course of experimentation in several countries, and from commercial sales in the United Kingdom. This technology likely will become commercially available in many countries within a few years. Accuracy of the process is about 90% for either sex, and resulting calves appear to be no different from non-sexed controls in birthweight, mortality, rate of gain, and incidence of abnormalities. The main determinants of the extent of use of sexed sperm will be pregnancy rate and cost. Fertility of low doses (1.5 x 10(6)-2 x 10(6)) of sexed, frozen sperm for AI of heifers usually has been in the range of 70-80% of unsexed sperm at normal doses (10 x 10(6)-20 x 10(6) sperm) in well managed herds; it has been lower in poorly managed herds, and likely will be lower with lactating dairy cows. It is expected that fertility of sexed sperm will increase significantly due to very recent improvements in the hydrodynamics of the sexing process and potential improvements in cryopreservation procedures. It is unclear how sexed sperm will be priced; the cost of sexed sperm for cattle will likely be more than double the cost of unsexed sperm in most markets. The economic benefit of using sexed sperm also will depend on the baseline fertility of the herd since at lower fertility, it takes more doses of semen per calf produced. It is noted that for a small percentage of elite cattle, the economics of using sexed sperm do not depend primarily on increased production or efficiency of producing meat or milk, but rather on factors such as scarcity, tradition, cattle show winnings, and biosecurity during herd expansion. Until sorting efficiencies improve and costs decline, sales likely will be limited primarily to these niche markets. With near normal fertility and a premium for sexing in the range of US$ 10 per insemination dose, sexed sperm likely would become economically and environmentally beneficial for many, if not most populations of cattle being bred by AI.     

Regression analyses and motile sperm subpopulation structure study as improving tools in boar semen quality analysis

A precise estimation of the fertilizing ability of a boar ejaculate would be very useful to improve pig assisted reproduction results. For this purpose, we tested the mathematical combination of several parameters of the boar semen quality analysis, including the computer-assisted semen motility analysis (CASA), as a predictive fertility tool. The utilized mathematical relations among parameters were logistic and linear regressions. Two mathematical models obtained by logistic regression involving Osmotic Resistance Test (ORT Test), Hyperosmotic Resistance Test (HRT Test) and viability of fresh samples, showed a significant (P<0.05) correlation between semen characteristics and conception rate. However, none of the obtained models produced a significant correlation model between semen characteristics and prolificacy. The CASA analyses show that three separate subpopulations of spermatozoa with different motility characteristics coexist in boar ejaculates. There were significant (P<0.001) differences in the distribution of these subpopulations among boars, but no clear relationship between motile subpopulation structure and fertility was obtained. Our results support the belief that the predictive use of the results obtained in a standard boar semen quality analysis can reasonably be achieved by applying logistic correlation analyses among several function parameters of boar semen quality analysis and in vivo conception rates obtained after artificial insemination (AI).