AI Station Research Articles

Novel interpretation of sperm stress test and morphology for maturity assessment of young Norwegian Red bulls

The use of genomic selection significantly reduces the age of dairy bulls entering semen production compared to progeny testing. The study aimed to identify early indicators that could be used for screening bulls during their performance testing period and could give us insight into their future semen production performance, acceptance for the AI station, and prediction of their future fertility. The study population consisted of 142 young Norwegian Red bulls enrolled at the performance test station, followed until we received semen production data, semen doses, and, subsequently, non-return rates (NR56) from the AI station. A range of semen quality parameters were measured with computer-assisted sperm analysis and flow cytometry from ejaculates collected from 65 bulls (9–13 months). The population morphometry of normal spermatozoa was examined, showing that Norwegian Red bulls at 10 months of age have homogenous sperm morphometry. Norwegian Red bulls could be separated into 3 clusters according to their sperm's reaction patterns to stress test and cryopreservation. Results of semi-automated morphology assessment of young Norwegian Red bulls showed that 42% of bulls rejected for the AI station and 18% of bulls accepted had ejaculates with abnormal morphology scores. For the youngest age group at 10 months, the mean (SD) proportion of spermatozoa with normal morphology was 77.5% (10.6). Using novel interpretation of sperm stress test combined with sperm morphology analysis and consecutive cryopreservation at a young age allowed identification of the candidate's sperm quality status. This could help breeding companies introduce young bulls earlier to the AI stations.

Status and Constraints Evaluation of Artificial Insemination in Bishoftu and Its Environs

Efficiency of artificial insemination service might be lower due to various challenges including poor estrus detection, inefficiency of artificial insemination techniques, and distance from AI station, poor management system, inadequate nutrition and poor quality of semen. Failure of estrus detection and improper timing of insemination has been the most known problems of in diary animals. The intention of this study was to appraise the status, challenges and the outcome. AI service beneficiaries in and around bishoftu town. In this study, a total of 287 respondents (smallholder farmers, dairy farm, Animals health professionals and Artificial Insemination Techniques) were included through structured questionnaires survey and interviewed. In to this, Retrospective data study was included in the study to evaluate the status of AI service in the study site. As the result revealed that from 269 total farmer respondents 49.1% (132/269) had got AI service on time without any interruption while 50.9% (137/269) AI users couldn’t got service on time due to lack of input, unavailability of AITs and discontinuation of service on weekends and holidays with statistically significant among kebeles (p<0.05). Bellowing, clear mucous discharge from vagina, mounting, decrease production and feed intake, restlessness and nervousness, were found to be the most common estrus manifestation observed by diary owners as holidays, lack of appropriate collaboration and communication among stake holders, and repeat breeding. In case of repeat breeding, he maximum and minimum impression of AI users toward using AI repeatedly were 43.8% (Danbi) and 33.0% (Kality) respectively with statistically insignificant among respondents (p>0.05). Generally the questionnaire survey indicated that the application of assisted reproductive biotechnologies in the study area was at infant stage surrounded with challenge full so it requires urgent involvement of stakeholders before it aggravates.

30 Bull sperm kinetics after semen cryopreservation in extender containing propagermanium

There is a negative association between a plentiful production of oxygen reactive species and spermatozoa kinetics parameters. Thus, antioxidants have been added to the freezing medium to improve sperm quality due to their protective effect against membrane lipid peroxidation. Propagermanium (GE132) is an organometallic compound that has never been used in freezing medium despite its known antioxidant effect as a free radical scavenger. This study aimed to investigate the effects of different concentrations of GE132 added in a commercial freezing medium (CFM) on frozen-thawed sperm motion. Nine ejaculates of 3 Nellore bulls (3 replicates), collected by an artificial vagina, were evaluated, pooled, and divided into groups D (semen was diluted and kept at 33°C for 30min before cooling) and C (semen was cooled immediately after dilution). Both groups were submitted to the same experimental treatment, as follows: addition of 0, 500, and 1000µg mL−1 of GE132 in a CFM resulting in subgroups D0, D500, D1000, C0, C500, and C1000. The sperm samples were diluted to a final concentration of 30×106 spermatozoa per straw (0.25mL) and then cooled at 4°C for 5h before freezing. Sperm samples were assessed using a computer assisted sperm analyser at 5 and 60min post-thawing for total motility (TM;%), progressive motility (%), curvilinear velocity (μm s−1), velocity straight line (μm s−1), velocity average path (μm s−1), amplitude of the lateral head displacement (ALH; μm), beat cross frequency (Hz), linearity (LIN;%), and straightness (STR;%). Data were analysed using the R software package version 3.4.4 (2018; https://www.r-project.org/). An ANOVA was applied to assess statistical differences, and Tukey’s test was used to determine differences among subgroups. A significance level of P&amp;lt;0.05 was adopted. No significant differences (P&amp;gt;0.05) were observed among subgroups for all sperm parameters except for TM, in which C0 presented higher (P&amp;lt;0.05) value (68.72±3.36) than D0 (54.67±5.59), D5 (57.10±2.34), and C10 (54.20±2.73), with similar results between D10 (59.5±4.22) and C5 (59.52±4.64). There were significant differences within subgroups when comparing 5 and 60min post-thawing for TM, ALH, LIN, and STR. Total motility decreased 17.2 and 9.9% in C5 and C10, respectively. Similarly, values of ALH decreased 0.2, 0.4, and 0.2µm in D0, D5, and C5, respectively. However, the increase in LIN was 11% in D10, whereas the values for STR increased in D10 (10%), C5 (6.3%), and C10 (7.3%). The addition of GE132 to the CFM did not enhance all the sperm parameters after cryopreservation except for a slight improvement in ALH, LIN, and STR over time and TM among groups. The lack of additive effect could be due to the presence of antioxidants in the CFM; therefore, further investigation with fluorescent probes using flow cytometry and free-antioxidants freezing medium could lead to a new approach for bull sperm freezing. We acknowledge Tairana AI Station, Master Fertility, and Botupharma, Brazil.

Identification of genome regions determining semen quality in Holstein-Friesian bulls using information theory

Use of information theory can be an alternative statistical approach to detect genome regions and candidate genes that are associated with livestock traits. The aim of this study was to verify the validity of the SNPs effects on some semen quality variables of bulls using entropy analysis. Records from 288 Holstein-Friesian bulls from one AI station were included. The following semen quality variables were analyzed: CASA kinematic variables of sperm (total motility, average path velocity, straight line velocity, curvilinear velocity, amplitude of lateral head displacement, beat cross frequency, straightness, linearity), sperm membrane integrity (plazmolema, mitochondrial function), sperm ATP content. Molecular data included 48,192 SNPs. After filtering (call rate = 0.95 and MAF = 0.05), 34,794 SNPs were included in the entropy analysis. The entropy and conditional entropy were estimated for each SNP. Conditional entropy quantifies the remaining uncertainty about values of the variable with the knowledge of SNP. The most informative SNPs for each variable were determined. The computations were performed using the R statistical package. A majority of the loci had relatively small contributions. The most informative SNPs for all variables were mainly located on chromosomes: 3, 4, 5 and 16. The results from the study indicate that important genome regions and candidate genes that determine semen quality variables in bulls are located on a number of chromosomes. Some detected clusters of SNPs were located in RNA (U6 and 5S_rRNA) for all the variables for which analysis occurred. Associations between PARK2 as well GALNT13 genes and some semen characteristics were also detected.

8 Effect of Single Layer Centrifugation with Percoll Plus® of Fresh Bull Semen on Plasma Membrane Stability and Lipid Peroxidation After Cryopreservation

The discontinuous density gradient with Percoll® is routinely used for sperm selection before IVF in bovine in vitro embryo production. However, few studies have been addressed to investigate the use of this colloid in single layer centrifugation (SLC) before sperm freezing. Therefore, this study aimed to verify the effect of SLC with Percoll Plus® (PP; GE Healthcare, Uppsala, Sweden) before freezing on plasma membrane stability (PMS) and lipid peroxidation (LP) of frozen–thawed bull semen. Three Nellore bulls housed at the Artificial Insemination Station were used. The ejaculates, 6 of each bull, were collected by artificial vagina. On the day of each collection, semen was first assessed for sperm motility, concentration, and morphology. Then, the ejaculates were pooled and ~1 billion spermatozoa either diluted [D; 1:2 (v/v)] in freezing extender (without glycerol) or undiluted (UN) was placed on top of a 9-mL column of PP at concentrations of 70% or 90%, resulting in the 70D, 70UD, 90D, and 90UD treatment groups. After centrifugation at 839 × g for 13 min, except for the control group, the supernatant was removed and the pellet of spermatozoa was resuspended in freezing extender (plus glycerol) to a final concentration of 50 × 106 spermatozoa mL−1. Then, 0.5-mL straws were filled, cooled, and frozen. Sperm samples of each group and different days of collection were thawed in a water bath at 37°C for 30 s and diluted at 5 × 106 spermatozoa mL−1 in TALP-polyvinyl alcohol (PVA) plus Hoechst 342 (Sigma Co., St. Louis, MO, USA). Then, samples were stained for PMS with the association of MitoSoxRed (Molecular Probes Inc., Eugene, OR, USA) and YO-PRO-1 (Thermo Fisher Scientific, Hampton, NH, USA) and with C11-BODYPY (Thermo Fisher Scientific) for LP. The sperm samples were analysed by flow cytometer (BD LSR, Fortessa, Becton Dickinson, Mountain View, CA, USA), with the data analysed through use of BD FACSDIVATM software (version 6.1). Analysis of variance and Tukey’s test were used for statistical analysis with P &lt; 0.05 taken as significant. A lower percentage of cells displaying no destabilised membrane was found in 70D (27.6 ± 5.6) compared with the control group (43.1 ± 3.0), but no difference was observed among control group, 70UD (37.2 ± 5.1), 90UD (42.2 ± 7.5), and 90D (32.3 ± 6.5). There was a tendency (P = 0.08) for a higher proportion (P &lt; 0.05) of cells showing LP in control group (48.2 ± 5.7), 70D (48.3 ± 8.5), and 90D (44.43 ± 7.3) compared with the undiluted groups. Thus, spermatozoa selection using SLC with Percoll Plus® did not enhance membrane stability, but sperm LP might be diminished by using SLC with lesser dilution or concentration. It is suggested that lower generation of reactive oxygen species occurred when SLC with PP was used, indicating a possible protective effect on membrane phospholipids. Further studies, including anion superoxide, hydrogen peroxide, and mitochondrial membrane potential could elucidate these findings. This research was supported by FAPESP (grant #2015/20986-3), Tairana AI Station and Master Fertility, Brazil.

132 OVERVIEW OF FERTILITY TRAITS IN RUSSIAN HOLSTEIN BULLS USING GENOME-WIDE ASSOCIATION

Holsteins are the most widely distributed cattle breed in Russia. To achieve improvement of both milk production and fertility traits, principles were elaborated to use genomic approaches together with breeding strategies to develop a common breeding index. Combining semen-quality measures for sires with the cows’ reproduction records makes it possible to resolve the problems with decreased conception rates and semen production. Our objective was to search the genomic regions and associated markers for bulls’ fertility traits in Russian Holstein cattle. For the first step, 282 bulls were genotyped using the Bovine SNP50 BeadChip (Illumina Inc., San Diego, CA, USA). The data set originated from the Moscow AI station including records for semen volume (SV), sperm concentration (SC), average SV for multiple ejaculates collected from one sire (ASV), motility (Mt), and number of spermatozoa (NS). The data set consisted of 14,490 records, which varied between 10 and 328 per animal, with 104 sires in the data set. The average age of sires was 80.1 ± 0.3 months. For sires with own records, the deregressed estimated breeding values were calculated using BLUP AM, whereas for the sires without records direct genomic values (DGV) were calculated through GBLUP. The DGV values were used as the animal’s pseudo-phenotypes for a common data set. After quality check in Plink 1.07, 41,435 SNP were taken. Bonferroni correction test for detection of significant associations was applied as P &lt; 1.21 × 10−6. The values for the heritability were 0.322, 0.202, 0.366, 0.014, and 0.169 for SV, SC, ASV, Mt, and NS, respectively. The SNP with a direct significant effect on SV and ASV were identified: ARS-BFGL-NGS-100206 (P = 1.5 × 10−7), BTA-89872-no-rs (P = 6.0 × 10−8), ARS-BFGL-NGS-33119 (P = 2.7 × 10−7), Hapmap26947-BTA-133787 (P = 5.0 × 10−7), BTA-30092-no-rs (P = 9.8 × 10−7), ARS-BFGL-BAC-6515 (P = 1.0 × 10−7), and BTB-01625220 (P = 4.2 × 10−8). For SC and NS traits, the polymorphisms ARS-BFGL-NGS-57433 (P = 7.4 × 10−7) and ARS-BFGL-NGS-12662 (P = 5.1 × 10−7) were found. Two QTL for Mt including 11 SNP were detected on BTA1 (146.3–146.9 Mb) and BTA9 (76.9–77.1 Mb). The DGV effect of SNP (R2) ranged from 8.0 to 10.4% of additive genetic variance. The genes SOX5 (BTA12), PERP (BTA9), and EPT1 (BTA11) were associated with embryonic development, cell death, or apoptosis and synthesis of selenoproteins. Our results may be used to select donor cows for oocytes or embryo collection in the focus of genomic selection. Supported by the Federal Agency for Scientific Organizations #0600–2014–0007.6 and by the Russian Ministry of Education and Science #RFMEFI60414X0062.

Association between SOX5 Genotypes and Semen Quality in Polish Holstein-Friesian Bulls.

The aim of this study was to evaluate the effect of C/T missense mutation (SOX5) gene on selected parameters of non-frozen semen in Polish Holstein - Friesian bulls. Three hundred and sixty eight bulls were genotyped by the PCR-Rsa I technique. Semen was collected and evaluated by standardized procedure used in an AI station. Significant associations were found between SOX5 genotypes and sperm concentrations (p=0.020) and sperm motility (p=0.014). Bulls with TT genotype had the lowest values of both traits. Our results demonstrate that C/T missense mutation within the SOX5 gene is involved in bull sperm quality.

Effects of heat stress on semen characteristics of Holstein bulls estimated on a continuous phenotypic and genetic scale

Semen volume (SV), semen output (SO), semen motility (SM), number of semen doses per ejaculate (NSD) and semen concentration (SC) were analyzed on a phenotypic and quantitative genetic scale in dependency of the continuous environmental descriptor THI (=an index describing combinations of temperature with humidity). Longitudinal semen data included 10,341 observations from 562 Holstein sires kept on an AI station in the northwestern part of Germany. Statistical modeling was based on fixed and random regression methodology (RRM). In this context, the phenotypic and genetic trajectory of traits in dependency of THI was modeled by orthogonal polynomials, i.e. Legendre polynomials of order 3. A general heat stress threshold of THI=60 was identified, and indicating detrimental effects of heat stress beyond this threshold, especially on SV, SO, NSD, and SC. Least square means for semen productivity were generally higher for adult bulls, but compared to young bulls, adult bulls responded with stronger semen production losses for extremely high THI. The optimal environment for semen production was a THI in the range from 50 to 60. Detrimental impact of heat stress was reduced for bulls with longer intervals between consecutive semen collection dates. Heritabilities for semen traits were in a low to moderate range with the following maximal values: 0.18 for SV at THI 30, 0.29 for SM at THI 70, 0.26 for SO at THI 30, 0.26 for NSD at THI 58, and 0.27 for SC at THI 53. Genetic values of sires and additive genetic variances changed with alterations of THI, with highest genetic variances at the extreme ends of the continuous environmental descriptor. Genetic correlations in same traits from THI levels in great distance were lower than 0.80, and indicated genotype by environment interactions. Application of RRM allow to select sires according to THI specific breeding values, which implies an optimization of cow sire and bull sire selection for harsh environments.

Application of computer-assisted semen analysis to explain variations in pig fertility1

Sperm quality is often evaluated through computer-assisted semen analysis (CASA) and is an indicator of boar fertility. The aim of this research was to study the relationship between CASA motility parameters and fertility results in pigs. Insemination records and semen parameters from a total of 45,532 ejaculates collected over a 3-yr period were used. The statistical model for analysis of fertility data from these inseminations included factors related to sow productivity. The boar- and semen-related variance (direct boar effect) were corrected for the effects of individual boar, genetic line of the boar, age of the boar, days between ejaculations, number of sperm cells in an ejaculate, number of sperm cells in an insemination dose, and AI station. The remaining variance was analyzed if semen motility parameters had a significant effect. This analysis revealed significant (P < 0.05) effects of progressive motility, velocity curvilinear, and beat cross frequency on farrowing rate (FR). Total motility, velocity average path, velocity straight line, and amplitude of lateral head displacement affected (P < 0.05) total number of piglets born (TNB). Boar- and semen-related parameters explained 5.3% of the variation in FR and 5.9% of the variation in TNB. Motility parameters, measured by CASA, explained 9% of the boar- and semen-related variation in FR and 10% of the boar- and semen-related variation in TNB. Individual boar and genetic line of the boar affected (P < 0.0001) the variation in FR and TNB. No differences (P > 0.05) were observed between effects of AI stations on fertility outcome, underscoring the objectivity of the CASA system used. Motility parameters can be measured with CASA to assess sperm motility in an objective manner. On the basis of the motility pattern, CASA enables one to discriminate between the fertilizing capacity of ejaculates, although this depends on the genetic line of the boar used in AI stations.

Can external quality control improve pig AI efficiency?

External quality control programmes carried out by central laboratories have been long established in human andrology with the aim of enhancing the accuracy and reproducibility of semen assessment. Compared to human, demands on boar semen assessment in AI stations are more complex, with the need both to identify boars with poor ejaculate quality and to monitor individual boar differences for semen storage. Additionally, appropriate assessment serves as a control instrument to ensure the security and efficiency of semen processing. Despite current limitations regarding the ability of sperm assays to estimate the potential fertility of males, it is evident that boar fertility is related to certain conventional semen tests, e.g. sperm morphology. In central studies carried out on stored semen from 11 AI stations, flow cytometric assessment of plasma and acrosome membrane integrity proved to be more sensitive in detecting sperm damage associated with ageing and temperature stress as compared to light microscopy. Membrane integrity of stored semen differed between AI stations indicating significant influences of semen processing on sperm quality. Thus external control of semen quality in reference laboratories may be useful to monitor the efficiency of internal semen quality control in individual AI stations, to identify males with lower semen quality and/or poor response to semen storage, and to verify the precision of sperm counting. The possibility that central laboratories with sufficient resources may be able to identify functionally different responding sperm subpopulations for better estimation of fertility is discussed. Ideally, external quality control schemes for AI stations would comprise application of validated tests with high relevance for fertility (including bacterial status), analysis of semen processing on the AI station, and training courses for laboratory personnel.

Transmission of bovine viral diarrhoea virus through the semen of acutely infected bulls under field conditions

Epidemiological investigations implicated the semen of artificial insemination (ai) bulls as the only plausible source of infection with bovine viral diarrhoea virus (bvdv) in 10 Finnish dairy herds. The infection...

162 FREEZING OF SEMEN FROM ENDANGERED ASTURIANA DE LA MONTAÑA BULLS IN ZWITTERONIC LIPIDS-BASED EXTENDERS

This experiment was designed to test the efficacy of 2 different preparation protocols of zwitteronic soyabean-origin lipids for the production of lipidsglycerol liposomes for use in bull semen cryopreservation. Lipids liposomes were prepared at 10% concentration in Tris buffer by 1. highpressure homogenization (Panda 2K, Parma, Italy) and then 8% glycerol were added, extender-1 (E-1); Lipids were homogenized together with glycerol, extender-2 (E-2). Bioxcell extender (E-3) was used as control. Semen was collected 3 times from 3 endangered Asturiana de la Monta�a bulls by the means of an artificial vagina. Ejaculates with at least 70% motility were processed further by a standard freezing protocol used in our AI station. Semen was diluted at 37�C with each of the 4 extenders to a concentration of 92 � 106 spermatozoa per mL, cooled to 4�C over 4 h, aspirated into 0.25-mL plastic straws (IMV Technologies, Aigle, France), frozen in a bio-freezer (IMV Technologies) in 3 steps from 4 to –140�C, and then plunged into liquid N2. Straws were thawed in a water bath at 37�C for 30 s. Sperm motility was analyzed microscopically immediately after collection, after dilution, and after 4, 24, 48, and 72 h of storage at 4�C. Post-thaw semen progressive motility was assessed microscopically, and sperm movement characteristics were analyzed by computer-assisted semen analysis (CASA) (SCA�, Microptic, Barcelona, Spain). Data were compared between extenders and bulls by 2-way ANOVA; percentages were transformed by arcsine transformation before ANOVA. Total and progressive sperm motility at 0 h after dilution ranged from 90 to 70% and was not different between extenders and bulls. There was no difference between bulls in total and progressive motility after 24 h of cold storage; however, both were significantly greater (P &lt; 0.05) for Control (62.4 � 14.7 and 41.4 � 14.9) and E-1 (70.1 � 12 and 33.8 � 7.0) extenders than for the E-2 extender (22.5 � 17 and 1.2 � 1.3). Average post-thaw sperm motility was not different between bulls for either extender, but motility for Bioxcell (Control, 48.1 � 14.6%) and E-1 extenders (43.2 � 13.0%) were significantly greater (P &lt; 0.05) than for E-2 extender (18.7 � 8.8%). There were no differences between bulls for all kinematic semen parameters: curvilinear (VCL), straight line (VSL), average path (VAP) velocities, linearity (LIN) and straightness (STR), evaluated by CASA before and after freezing; however, all were lower (P &lt; 0.05) for the E-2 extender and not different between Control and E-1 extenders. Sperm movements derived from heads (VCL) and linearity of sperm(LIN), both closely related to field fertility, were in the range of 90.9 � 2.1 and 63.0 � 5.5 for E-3 (Control) extender; 99.1 � 3.4 and 49.4 � 3.5 for E-1; and 21.8 � 2.2 and 29.9 � 4.0 for E-2. In summary, zwitteronic soyabean lipid liposomes are an effective egg yolk substitute for the cryopreservation of Asturiana de la Monta�a bull semen; however, the homogenization protocol of the lipids-glycerol mixture must be improved.

Estrogen receptor gene (&amp;lt;i&amp;gt;ESR&amp;lt;/i&amp;gt;) and semen characteristics of boars

Abstract. Estrogen receptor gene (ESR) which is localized in the swine chromosome 1, has been recognized as a "candidate" gene of reproductive traits. The aim of this study was to determine the mutations in the ESR/AvaI (ESR1) and ESR/PvuII (ESR2) gene in boars kept at the AI Station and its effect on selected quantitative and qualitative characters of the semen. The study included 217 boars maintained at the AI Station. The ESR genotypes were determined with PCR-RFLP. Two alleles ESR1 were identified: A (109 and 76 bp), B (76, 62 and 47 bp) and also two alleles ESR2: C (120 bp), D (65 and 55 bp), with the frequencies: 0.79 (A), 0.21 (B), 0.83 (C) and 0.17 (D) respectively. In the studied population of boars, the genotype AA was detected with the frequency 0.69, AB-0.21, BB-0.10 of ESR1 and CC-0.72, CD-0.23, DD-0.05 of ESR2. The analysis showed statistically significant differences (P≤0,01) between boars carrying different ESR1 and ESR2 genotypes and all semen traits.

Estimation of Genetic Variation in Holstein Young Bulls of Iran AI Station Using Molecular Markers

Genetic profiles of Iranian Holstein young bulls at the national artificial insemination station were determined on the basis of individual genotypes at 13 ISAG's recommended microsatellites, the most useful markers of choice for parentage identification. In the present study a total of 119 individuals were genotyped at 13 microsatellite loci and for possible parent-offspring combinations. A high level of genetic variation was evident within the investigated individuals as assessed from various genetic diversity measures. The mean number of observed alleles per microsatellite marker was 9.15 and the number of effective alleles as usual was less than the observed values (4.03). The average observed and expected heterozygosity values were 0.612 and 0.898, respectively. The mean polymorphic information content (PIC) value (0.694) further reflected a high level of genetic variability. The average exclusion of probability (PE) of the 13 markers was 0.520, ranging from 0.389 to 0.788. The combined exclusion of probability was 0.999, when 13 microsatellite loci were used for analysis in the individual identification system. Inbreeding was calculated as the difference between observed and expected heterozygosity. Observed homozygosity was less than expected which reflects inbreeding of -3.7% indicating that there are genetic differences between bull-sires and bull-dams used to produce young bulls. The results obtained from this study demonstrate that the microsatellite DNA markers used in the present DNA typing are useful and sufficient for individual identification and parentage verification without accurate pedigree information. (Asian-Aust. J. Anim. Sci. 2006. Vol 19, No. 4 : 463-467)

Behaviour of boars in semen-processing centres

The behaviour of 78 boars in three different semen-processing centres was continuously recorded for 72 h per boar, with respect to boars' age, season, management system of the semen-processing centre (AI station) and size of boar pens. During each 24-h period of observation, the boars spent, on average, 81% of their time lying, equivalent to about 19.5 h per day. Most behavioural patterns were influenced by the AI station or by the semen-processing centre×season interaction. The percentages of active lying and active plus passive lying were significantly lower and the frequency of engagement with bedding was higher ( P<0.05) in one AI station compared with the other two stations. The circadian rhythm of lying behaviour and engagement with bedding was influenced by management factors, such as feeding and the provision of water and straw bedding. These differed between semen-processing centres. Pen size had only a significant influence on engagement with bedding.

A retrospective study on effects of storage time of liquid boar semen on reproductive performance in Norwegian swine

The objective of this retrospective field study was to determine the effects of storing, for up to 62 h, heterospermic and homospermic semen in the short-term extender Beltsville thawing solution (BTS), on reproductive performance in Norwegian swine of four different breed combinations. The study was based on fertility records after single or double inseminations with semen collected at an AI station in Norway from January 1998 to June 2001. Increasing the duration of storage of homospermic semen, but not heterospermic semen, from an interval of 4–14 h to an interval of 52–62 h, was associated with a 0.5 piglet reduction in litter size. There were differences in reproductive performance among breed combinations that appeared to be associated with duration of semen storage. In conclusion, prolonged semen storage decreased reproductive performance; the extent varied among breeds and was prevented by the use of heterospermic versus homospermic semen.

Estimation of genetic parameters of semen characteristics and reproductive traits in AI boars

(Co)variance components and further genetic parameters of boar semen characteristics and reproductive traits were estimated using the REML procedure applied to multi-trait animal models. The calculations were based on data from 210,733 ejaculates stemming from 2862 AI boars and collected from 1990 to 1997 in insemination stations for boars in the Czech Republic. Equal model equations for all traits included the AI station and the breed or breed combination as fixed effects, the interval between two collections for the boar as covariable and the animal and residual effects as random effects. The following heritabilities were estimated: semen volume 0.58, sperm concentration 0.49, progressive motion of spermatozoa 0.38, abnormal spermatozoa 0.34, number of total spermatozoa 0.42, number of insemination doses 0.40, number of piglets born alive 0.08, total number of piglets born 0.05 and conception rate 0.29. Heritabilities and genetic correlations were estimated on average values for each boar.

Effects of Trehalose and Sucrose, Osmolality of the Freezing Medium, and Cooling Rate on Viability and Intactness of Bull Sperm after Freezing and Thawing

The influence of the presence of trehalose or sucrose, the osmolality of the freezing medium, and the cooling rate on success of cryopreservation of bull sperm were investigated. Bull semen was frozen at four different cooling rates varying from 40 to 300°C/min in standard Tris–egg yolk medium and in hypertonic or isotonic media containing 0.2Mtrehalose or sucrose. Sperm motility, H33258 exclusion, and acrosome morphology were evaluated. In the hypertonic media the motility was almost completely inhibited, but could partly be restored by returning to isotonic conditions. Medium composition and cooling rate had significant effects, with a strong interaction of medium × cooling rate. The optimal cooling rate was found to be between 76 and 140°C/min. At the highest cooling rate, both the presence of the sugars and the high osmolality of the hypertonic media conferred significant protection against fast-cooling damage, sucrose being significantly better than trehalose. At all other cooling rates the medium differences were less pronounced, but the isotonic sugar media were generally superior to standard medium as to preservation of acrosome intactness and H33258 exclusion. This indicates that the isotonic sugar media could enable some improvement of cryopreservation of bull semen over the currently used Tris–egg yolk medium. Further improvement of sperm survival at the AI station should be possible by implementation of controlled rate freezing, using a cooling rate in the optimal range between 76 and 140°C/min.

Fundamentals and recent development in cryopreservation of bull and boar semen

Summary This paper describes some of the effects of cryopreservation on living sperm, and some recent results for bull and boar semen. During freezing and thawing of semen, the sperm can be damaged by the rapid and dramatic changes in the physicochemical conditions during cooling and ice formation. The rate and extent of these changes, and their impact on the cells, are strongly affected by the cooling rate and the medium composition. For many species, including humans and several farm animals, the optimal cooling rate has been determined, sometimes in combination with the cryoprotectant concentration. Recent results indicate that the cryopreservation of bull semen at the AI station could be improved by using controlled freezing at a cooling rate of about 100 °C/min, and by changing the composition of the freezing medium. An interaction between glycerol concentration and cooling rate has been described for boar semen. Current cryopreservation methods for boar semen based on an optimal combinations of these two factors allow consistent sperm survival in the frozen semen of AI boars, with acceptable variation among boars. The fertility results for semen processed in this fashion seem to be adequate for special applications, such as export, or long‐term storage.