Bacterial diversity in semen from stallions in three European countries evaluated by 16S sequencing.

The microbiome plays a significant role in shaping the health and functioning of the systems it inhabits. The seminal microbiome of stallions has implications for the health of the reproductive tract, sperm quality during preservation and antibiotic use in semen extenders. Diverse bacteria are present on the external genital tract and a mix of commensal microorganisms populates various parts of the reproductive tract, influencing the seminal bacterial content. Other sources of bacteria include the environment, semen collection equipment, and personnel. The bacterial load can adversely affect sperm quality and fertility, particularly in artificial insemination, where semen is extended and stored before use. Antibiotics are frequently used to inhibit bacterial growth, but their effectiveness varies depending on the bacterial strains present. The aim of this study was to assess the bacterial diversity in semen from 37 healthy stallions across three European nations (Germany, Portugal, and Sweden) using 16S sequencing. Semen samples were collected from individual stallions at three AI centers; DNA extraction, sequencing, and bioinformatic analysis were performed. Differences in bacterial diversity among the stallions were seen; although bacterial phyla were shared across the regions, differences were observed at the genus level. Climate, husbandry practices, and individual variability likely contribute to these differences. These findings underscore the importance of tailoring antibiotic strategies for semen preservation based on regional bacterial profiles. The study presents a comprehensive approach to understanding the intricacies of the stallion seminal microbiome and its potential implications for reproductive technologies and animal health.

Endocrine changes induced by GnRH immunisation and subsequent early re-stimulation of testicular function with a GnRH agonist in stallions.

CONTEXT: Resumption of testicular function after gonadotrophin-releasing hormone (GnRH) immunisation varies among individual animals and some stallions regain fertility only after a prolonged time. AIMS: This study evaluated endocrine effects of GnRH immunisation and early subsequent re-stimulation with a GnRH agonist. We hypothesised that GnRH agonist treatment advances resumption of normal endocrine function in GnRH-vaccinated stallions. METHODS: Shetland stallions were assigned to an experimental and a control group (n =6 each). Experimental stallions were GnRH-immunised twice, 4weeks apart. Each experimental stallion was hemicastrated together with an age-matched control animal when testosterone concentration decreased below 0.3ng/mL. Three weeks later, daily treatment with the GnRH agonist buserelin was initiated (4µg/day for 4weeks followed by 8µg/day). The remaining testicle was removed when testosterone concentration exceeded 0.5ng/mL in vaccinated stallions. Blood was collected for LH, FSH, oestradiol and anti-müllerian hormone (AMH) analyses, and testicular and epididymal tissue were conserved for real-time qPCR and histology. KEY RESULTS: GnRH vaccination reduced blood concentrations of LH and FSH, with a structural deterioration of testicular tissue and disruption of spermatogenesis. Daily buserelin treatment for approximately 60days partially restored gonadotropin secretion and induced a recovery of the functional organisation of the testicular tissue with effective spermatogenesis. CONCLUSIONS: Endocrine testicular function can be restored in GnRH-vaccinated stallions by daily low-dose buserelin treatment. The buserelin treatment protocol may potentially be improved regarding the dose, interval and duration. IMPLICATIONS: Daily buserelin treatment can be recommended for treatment of GnRH-vaccinated stallions with prolonged inhibition of testicular function.

Reduced bacterial load in stallion semen by modified single layer centrifugation or sperm washing.

The presence of bacteria poses a significant challenge to the quality of stallion semen used in artificial insemination. The bacterial content of insemination doses arises from various sources, such as the healthy stallion, environment, and collection equipment, and is implicated in fertility problems as well as reduced sperm quality during storage. The conventional approach of adding antibiotics to semen extenders raises concerns about antimicrobial resistance and potential negative effects on sperm characteristics, and may not be effective in inhibiting all bacteria. The objective of this study was to determine whether an innovative alternative to antibiotic usage - centrifugation through a single layer of a low density colloid (SLC) - could reduce the bacterial load in stallion semen, and to compare sperm characteristics in samples arising from this procedure, or simple extension of the ejaculate in semen extender, or from sperm washing, i.e. adding extender and then centrifuging the sample to allow the removal of most of the seminal plasma and extender. Eighteen semen samples were collected from six stallions. The semen samples were split and extended prior to washing or SLC, or received no further treatment other than extension. After preparation aliquots from each type of sample were sent for bacteriological examination; the remaining samples were stored for up to 72 h, with daily checks on sperm quality. The low density colloid SLC outperformed sperm washing or extension for bacterial reduction, effectively removing several bacterial species. The bacterial load in the samples was as follows: extended semen, 16 ± 6.7 × 105; washed, 5.8 ± 2.0 × 105; SLC, 2.3 ± 0.88 × 105, p < 0.0001. In addition, SLC completely removed some bacterial species, such as Staphylococcus xylosus. Although there is no selection for robust spermatozoa with the low density colloid, sperm motility, membrane integrity, and DNA fragmentation were not different to washed sperm samples. These findings suggest that SLC with a low density colloid offers a promising method for reducing bacterial contamination in stallion semen without resorting to antibiotics.

Short communication: Retrospective analysis of obligatory testing results for Equine virus arteritis reveals a decrease of its seroprevalence in stallions used for artificial insemination.

Equine viral arteritis (EVA) can induce a persistent carrier state in stallions which then shed the virus via semen. About 30 years ago, obligatory EVA testing of stallions used for artificial insemination (AI) was implemented in the European Union. Information on the efficacy of these regulations on the prevalence of EVA in stallions are not yet available. Therefore, we retrospectively analyzed results of serological and virus antigen testing for EVA in sires of different age and breed referred to Vetmeduni Vienna for semen preservation or veterinary diagnostic procedures between 2001 and 2021. For analysis, stallions were grouped by age (1-5, 6-8, 9-12, >12 years) and breed. The EVA antibody titer was determined by serum neutralization test and semen was analyzed for EVA virus by PCR and/or virus isolation test. Of 308 stallions tested, 14.9% (n = 46) were EVA seropositive and in 12 stallions EVA virus was detected in semen (26% of seropositive stallions). The incidence of seropositive stallions decreased over time (P < 0.05, χ2 test). Differences in the seroprevalence of EVA antibodies existed among stallion age groups (P < 0.01, Fisher's test) with the highest percentage of seropositive stallions being > 12 years old (43.5%). The EVA antibody titer increased with age (P < 0.01, Kruskal-Wallis test), potentially reflecting repeated virus challenge. In conclusion, analysis of monitoring results revealed a decrease of EVA seroprevalence and virus shedding in a European sire population. As monitoring for EVA was the only measure implemented Europe-wide, testing might be a major contributor to this development.

Protamine 2 and phospholipase C zeta 1 are possible biomarkers for the diagnosis of male subfertility in frozen-thawed stallion semen.

Subfertility is one of the main issues in horse breeding and the study of mRNAs in sperm might help in elucidating the reasons that lead to this diagnosis. The present study aims at assessing the differences in the expression of 10 potential candidate genes in stallions of different fertility. Frozen-thawed semen of 29 stallions was included. Each sample was classified into two groups according to pregnancy rates (PR) achieved with this semen: "good fertility" (GF; n = 17; PR ≥ 30 %) or "poor fertility" (PF; n = 12; PR <20 %). All stallions underwent a breeding soundness examination (BSE) before semen production and were only included into the semen cryopreservation program when raw semen characteristics at BSE met minimal requirements. Semen was cryopreserved following European Union regulations and all stallions met the respective health requirements. Each sample was assessed for concentration (NucleoCounter SP-100), motility (CASA), membrane functionality (SYBR-14/PI), mitochondrial membrane potential (JC-1), morphology (SpermacStain), acrosome integrity (SpermacStain), membrane integrity (HOS test) and chromatin integrity (Aniline blue). Sperm RNAs were extracted using the Direct-zol RNA Miniprep Kit (Zymo Research) and RT-qPCR was performed for each target gene. ACTB and RPL32 were included as reference genes (RGs) for normalization. For each variable of each group, mean, standard deviation and SEM were calculated. The difference in gene expression levels between the GF and PF group were analyzed using the Mann-Whitney U test and Spearman's rank correlation. Significant results were considered with p < 0.05. Sperm quality parameters did not differ significantly between the two groups except for concentration, that was significantly higher in GF (p = 0.043). In GF a positive correlation was identified for PRM1/PRM2 with r = +0.6, while PRM1/ACR (r = -0.495), PRM2/ZPBP (r = -0.645) and CRISP3/ACR (r = -0.551) were inversely correlated. In PF direct correlations were registered for PRM1/PRM2 (r = +0.629), PRM1/PRM3 (r = +0.657), PRM2/SPA17 (r = +0.685), SPA17/PLCZ1 (r = +0.786) and PRM3/ACR (r = +0.627). In the total sample (GF + PF), positive correlations were detected for PRM1/PRM2 (r = +0.625), PRM1/PRM3 (r = +0.368); PRM2/SPA17 (r = +0.465), SPA17/PLCZ1 (r = +0.637) and PLCZ1/ZAN (r = +0.587). Only two of the genes considered were differentially expressed in the 2 groups: PRM2 and PLCZ1, that were significantly (p < 0.05) overexpressed in the GF group. Stallions frozen-thawed semen with higher expression levels of PRM2 and PLCZ1 are more likely to belong to animals with a good pregnancy rate. Further studies are needed to investigate the role of sperm transcripts in male subfertility in stallions.

Abundance of Anti-Muellerian hormone in cat ovaries and correlation of its plasma concentration with animal age, weight and stage of the estrous cycle.

In female animals of different species, Anti-Müllerian hormone (AMH) is produced by follicular granulosa cells and has been associated with the ovarian follicle pool. Because concentration of AMH in plasma of ovary-intact female cats is apparently more variable than previously assumed, we have analysed AMH concentration in blood of cats (n = 93) presented for routine ovariectomy and assessed ovarian histology and AMH protein expression in the surgically removed ovaries. We hypothesised that AMH is synthesized only in preantral and small antral follicles and that plasma AMH concentration reflects the antral follicle count (AFC). Corpora lutea were detected in 35% of the female cats, whereas plasma progesterone concentration was ≥1 ng/mL in 57% of the cats. Follicular cysts were present in 15 cats (16%). Positive immunostaining for AMH protein was detected in close to all primordial and antral follicles, ovarian cysts, 70% of corpora lutea and 28% of atretic follicles. Concentration of AMH in plasma averaged 6.8 ± 0.5 ng/mL (range 1.3-21.7 ng/mL). The AFC increased with increasing AMH concentration with a moderate positive correlation between AFC and AMH (r = 0.286, p < 0.01). Plasma AMH concentration was not affected by season or cats' age, weight, stage of the estrous cycle and presence of follicular cysts. In conclusion, AMH protein is expressed in all endocrine structures of the cat ovary. While AMH is a marker for the presence of ovarian tissue, its usefulness to assess ovarian function in individual female cats is of limited value.

Low progesterone concentration in early pregnancy is detrimental to conceptus development and pregnancy outcome in horses.

High progesterone concentrations in the early luteal phase support pregnancy, whereas subphysiological progesterone concentrations delay embryonic development at least until placentation. In this study, fetal growth and development of pregnancy was investigated in pregnancies with prostaglandin F2α-induced low progesterone concentrations (PGF) in the early luteal phase and control pregnancies (CON) in the same mares (n = 12). Mares were inseminated and in PGF pregnancies received the prostaglandin F2α analogue cloprostenol (62.5 µg) on days 0-3 after ovulation to induce subphysiological progesterone concentrations; CON pregnancies remained untreated. Mares were assigned to PGF or CON treatments in alternating order and received the opposite treatment in the following year. Blood was collected and conceptus size determined repeatedly by transrectal (≤day 101) and transabdominal (>day 101) ultrasonography. After birth, foals were weighed, measured and submitted to a clinical examination. Treatment PGF resulted in fewer pregnancies than CON treatment. All foals born from CON pregnancies were healthy and mature, whereas 4/7 PGF pregnancies were either lost (one embryonic death, one abortion) or resulted in the birth of compromised foals (P = 0.018). Size of the conceptus (e.g., diameter day 49: PGF 6.6 ± 0.7, CON 7.7 ± 0.7 cm, P = 0.006) and embryo proper (e.g., crown rump length day 54; PGF 4.4 ± 0.8, CON 5.8 ± 0.6 cm, P = 0.015) differed between treatments. These size differences decreased over time and at birth PGF foals did not differ significantly from CON foals. In conclusion, reduced progesterone concentration in the early luteal phase leads to delayed conceptus growth beyond placentation and increased pregnancy loss.

Shipping duration and temperature influence the characteristics of cryopreserved horse semen stored in different shipping devices for up to 14 days.

This study aimed to investigate the effects of storing horse semen either in a dry shipper (≤ -150 °C) or on dry ice (≤ -78 °C) for up to 14 days. A total of 264 frozen semen straws from male horses (n = 8) stored in liquid nitrogen were transferred on day 0 (d0) to a dry shipper or a dry ice styrofoam box. On d1, d3, d7, d10, and d14, straws from the dry shipper and dry ice were returned to the liquid nitrogen container. Semen was evaluated by CASA for total (TMot), progressive motility (PMot) and sperm velocity parameters, by fluorescence microscopy for percentage of membrane-intact sperm (SYBR14/PI), high mitochondrial membrane potential (HMMP; JC1) and DNA fragmentation. Temperature inside the containers was monitored continuously. Until d7, no changes were observed in TMot, PMot, and membrane-intact spermatozoa. Thereafter, all three parameters decreased in semen stored on dry ice but not in a dry shipper (time p < 0.001, time x shipping device p < 0.001). The HMMP decreased continuously over time in both containers with a more pronounced decrease on dry ice compared to the dry shipper (shipping device p < 0.01, time p < 0.001, time x device p < 0.001). The DNA fragmentation increased on d10-14 on dry ice and d14 in the dry shipper (time p < 0.001, time x device p < 0.01). In conclusion, frozen horse semen can be safely stored for up to 7 days on dry ice. Sperm DNA integrity and HMMP, however, were adversely affected after 14 days in both shipping devices.

Double semen collection at a 1-h interval in dogs decreases the bacterial contamination of canine ejaculates.

Semen extenders usually contain antibiotics with the aim to minimize bacterial growth, but the indiscriminate use of antibiotics increases the emergence of multidrug-resistant bacteria. A limiting factor of semen processing in dogs is the low total sperm count that limits the number of insemination doses that can be obtained from one ejaculate. Therefore, two ejaculates collected at a short interval can be combined to increase the number of AI doses. In this study, semen was collected from dogs either once or the same dogs (n = 28) were submitted to dual semen collection 1 h apart. All ejaculates were submitted to bacteriological analysis. We hypothesized that bacterial contamination of semen is low but that a dual semen collection might increase contamination. A sample for bacteriological examination was taken from raw semen immediately after semen collection. Bacteria including mycoplasmas were isolated using conventional cultivation procedures and isolates were identified to the species level by matrix-assisted laser desorption ionization - time of flight (MALDI-ToF) mass spectrometry. In total, 22 bacterial species were identified in the 84 ejaculates with Mycoplasma cynos, Streptococcus canis and Canicola haemoglobinophilus being most frequent. Bacterial growth was sporadic in 16 and absent in 10 ejaculates. The overall bacterial growth was lower in the second than in the first ejaculate of dual semen collections (p < 0.05). The percentage of motile and membrane-intact spermatozoa in frozen-thawed ejaculates was not associated with the degree of bacterial contamination of raw semen. In conclusion, there was only limited microbial contamination in dog semen and the microorganisms isolated are considered part of the normal genital bacterial flora. Repeated semen collection reduced bacterial contamination in the second in comparison to the first ejaculate. The use of antibiotics in canine semen should be questioned.

Selection of frozen-thawed stallion semen by microfluidic technology.

The use of microfluidic technology is increasing in artificial reproduction technologies: With a small amount of semen, it allows for the selection of sperm with the best characteristics of kinetics, morphology and chromatin integrity. The ZyMot Multi (850 µl) is the most popular device of ZyMot Fertility Inc. To date, it was proven to be a valid instrument for sperm selection for in vitro fertilization and intracytoplasmic sperm injection in men. The aim of this study was to test the efficacy of the ZyMot Multi (850 µl) for stallion semen. Frozen-thawed semen from 15 stallions that were previously classified as being of 'good fertility' (GF; n = 8; pregnancy rate ≥ 40%) and 'poor fertility' (PF; n = 7; pregnancy rate < 20%), respectively, was used. Each ejaculate was assessed before and after microfluid recovery for kinetics (CASA), membrane integrity (MI) (SYBR14/PI), membrane functionality (MF) (HOS test), acrosome integrity (Spermac Stain Kit), morphology (Spermac stain kit), mitochondrial membrane potential (MMP) (JC-1) and chromatin integrity (aniline blue staining). Sperm concentration was reduced after sperm recovery in both groups, but more markedly in frozen-thawed semen of PF stallions (p < .05). Microfluid recovery increased total motility, MI, MF and MMP. While there was a significant increase in the percentage of progressively motile sperm after sperm microfluid recovery, there was a decrease in DAP, DSL, VAP, VSL, LIN, WOB and ALH (p < .05). A slight increase (p < .05) was detected in beat-cross frequency. The present results suggest that the ZyMot Multi (850 µl) device selects a specific sperm population from any stallion ejaculate with motile sperm and could therefore be a valid tool for in vitro testing with the aim to predict the fertility of frozen-thawed stallion semen.

Low plasma progesterone concentration during the early luteal phase delays endometrial development and the beginning of placentation in mares.

While detrimental effects of reduced plasma progesterone concentration in the early luteal phase on conceptus development in horses have recently been demonstrated, there is no information on associated effects on the endometrium, allantochorion (AC), and chorionic girdle (CG) in this species. We hypothesised that reduced early postovulatory progesterone concentration in pregnant horses is detrimental to endometrial function and development of the embryonic membranes and is an underlying cause of delayed conceptus development. After insemination and ovulation, mares (n = 11) were assigned to treatment (TREAT) or control (CON) during two pregnancies. In TREAT pregnancies, mares received a PGF2α analogue for four consecutive days starting on the day of ovulation with the aim to reduce progesterone secretion. Mares were left untreated in CON pregnancies and thus served as their own controls. Endometrial biopsies for analysis of histomorphology, epidermal growth factor (EGF) and EGF receptor (EGFR) mRNA and protein expression in the endometrium, AC, and CG as well as abundance of regulatory T lymphocytes (Tregs) were collected on day 34 of pregnancy. Histomorphometric analysis revealed a higher luminal endometrium and a higher CG epithelium in CON compared to TREAT pregnancies. Abundance of mRNA for EGF and EGFR was large in the endometrium, AC and CG but did not differ between TREAT and CON pregnancies. The number of endometrial regulatory T lymphocytes was reduced in TREAT compared to CON pregnancies, adding further aspects to the potentially detrimental effects of reduced progesterone concentrations on equine pregnancy.

Re-stimulation of testicular function in GnRH-vaccinated stallions by daily GnRH agonist treatment.

In stallions temporarily not intended for breeding, reversible suppression of testicular function by vaccination against GnRH can be of interest. In the present study, effects of GnRH agonist treatment on the resumption of testicular function after GnRH vaccination were investigated. Testis size, testosterone release, semen characteristics and behavior were evaluated. We hypothesized that GnRH agonist treatment would restore testicular function. Shetland stallions were assigned to an experimental and a control group (n = 6 each). Experimental stallions were GnRH-immunized twice, four weeks apart. Ejaculates for semen analysis and blood for analysis of testosterone concentration and GnRH antibody titers were collected. Each experimental stallion was hemicastrated together with an age-matched control animal when testosterone concentration decreased below 0.3 ng/mL. Three weeks thereafter, daily treatment with the GnRH agonist buserelin was initiated (4 µg/day for 4 weeks followed by 8 µg/day). The remaining testicle was removed when testosterone concentration exceeded 0.5 ng/mL in vaccinated stallions. Time from exposure to a mare until mounting increased in GnRH-vaccinated stallions and decreased with buserelin treatment. Total sperm count decreased after vaccination but increased only slightly in response to buserelin. Sperm motility and percentage of membrane-intact spermatozoa decreased after vaccination and returned to pre-vaccination values with buserelin treatment. Testosterone concentration and testis volume decreased after GnRH vaccination and started to increase with buserelin treatment. In conclusion, the downregulation of testicular function by GnRH vaccination can be counteracted with buserelin. This approach may be useful in GnRH-vaccinated stallions with prolonged suppression of testicular function.

An optimized workflow for microCT imaging of formalin-fixed and paraffin-embedded (FFPE) early equine embryos.

Here, we describe a workflow for high-detail microCT imaging of formalin-fixed and paraffin-embedded (FFPE) equine embryos recovered on Day 34 of pregnancy (E34), a period just before placenta formation. The presented imaging methods are suitable for large animals' embryos with intention to study morphological and developmental aspects, but more generally can be adopted for all kinds of FFPE tissue specimens. Microscopic 3D imaging techniques such as microCT are important tools for detecting and studying normal embryogenesis and developmental disorders. To date, microCT imaging of vertebrate embryos was mostly done on embryos that have been stained with an X-ray dense contrast agent. Here, we describe an alternative imaging procedure that allows to visualize embryo morphology and organ development in unstained FFPE embryos. Two aspects are critical for high-quality data acquisition: (i) a proper sample mounting leaving as little as possible paraffin around the sample and (ii) an image filtering pipeline that improves signal-to-noise ratio in these inherently low-contrast data sets. The presented workflow allows overview imaging of the whole embryo proper and can be used for determination of organ volumes and development. Furthermore, we show that high-resolution interior tomographies can provide virtual histology information from selected regions of interest. In addition, we demonstrate that microCT scanned embryos remain intact during the scanning procedure allowing for a subsequent investigation by routine histology and/or immunohistochemistry. This makes the presented workflow applicable also to archival paraffin-embedded material.

Suppression of reproductive behaviour and gonadal function in female horses-An update.

The behaviour of mares is often detrimental to their performance resulting in frequent demand for methods to suppress gonadal function. In addition, prevention of unintended reproduction especially in feral horse populations may require methods for suppression of gonadal function. Surgical ovariectomy is a safe method but not an acceptable approach in feral mares and undesired in mares where future breeding is considered. There are different approaches for artificial prolongation of the luteal phase resulting in transient inhibition of oestrus and ovulation. Among those, treatment with natural or synthetic progestogens is considered the most common and successful method. Whereas application of intrauterine devices may result in prolongation of luteal function in non-pregnant mares, intrauterine insertion of glass balls is no longer recommended because of complications in individual mares. There are several safer alternatives that may be of interest, especially for population control in free-roaming horses. Treatment with long-acting deslorelin implants inhibited ovulation and oestrus behaviour in mares for limited and variable time intervals in a dose-dependent manner. The effect of GnRH vaccines varies considerably among individual mares, is age dependent, and oestrus-like behaviour may still occur. Contraception via immunization against native porcine or recombinant zona pellucida antigen is successful, but immunocontraception is as much a result of ovarian inactivity as an antibody-based block to sperm-oocyte binding. In conclusion, several treatments for suppression of gonadal function in mares are available, but there are advantages and disadvantages associated that have to be considered. The treatment of choice will thus differ with regard to the demands.

Development of Foals Until One Year of Age When the Dam was Exposed to Blue Monochromatic Light Directed at One Eye During Late Pregnancy.

In horses, blue LED light directed at one eye of pregnant mares shortens gestation length and results in the birth of foals with lower wither heights, similar weight and reduced hair length compared to controls. In this study, we have therefore analysed postnatal development of foals born to either blue LED light-treated (n = 20) or control mares (n = 20). Size, weight and hair coat changes were determined for 1 year and heart rate, heart rate variability (HRV) and selected haematology parameters for 1 month. Haematocrit decreased (P < .001) and leukocyte and lymphocyte counts increased (P < .001) but none of the parameters differed between groups. Heart rate (P < .001) and HRV (P < .01) increased until day 6 but did not differ between groups, indicating that foals born to blue LED light-treated mares were mature and healthy. The guard hair was shorter in foals born to treated mares compared to control foals at birth (P < .001) but no differences in hair coat length were observed beyond the age of 2 months. At birth and 6 days thereafter, wither height (P < .01) and elbow to carpus distance (P < .05) of control foals were increased relative to foals born to blue LED light-treated mares. Height differences decreased over time and and for elbow-to-carpus distance there was a time x group interaction (P < .005) In conclusion, blue LED light treatment of pregnant mares is without detrimental effects on postnatal foal growth and development.

"Fine feathers make fine birds" - The mammalian sperm plasma membrane lipid composition and effects on assisted reproduction.

The sperm plasma membrane is important in modulating many sperm functions. The sperm membrane is composed of a complex mixture of lipids including phospholipids, glycolipids and sterols. There are differences of sperm membrane composition among mammalian species with two groups differing in the most abundant polyunsaturated fatty acid (PUFA), either docosahexaenoic (ω-3 PUFA) or docosapentaenoic acid (ω-6 PUFA). During testicular and epididymal maturation, composition of the sperm plasma membrane evolves with spermatozoa gaining the capacity for fertilization. The importance of fatty acid metabolism for complete spermatogenesis has been elucidated using gene knockout mice. During epididymal transit cholesterol content decreases and PUFA content increases, conferring more fluidity properties to the sperm membrane. The relatively lesser content of antioxidant enzymes and the relatively larger content of PUFA make the spermatozoa particularly susceptible to lipid peroxidation during sperm preservation. In numerous studies, there was adding of PUFA and antioxidants to the diet of animals or to semen extenders with the aim to improve sperm membrane integrity. This review highlights the current knowledge on the sperm membrane composition and effects on sperm function in mammalian domestic animals.

Effects of age, size and season on cryotolerance of dog semen - A retrospective analysis.

In a retrospective analysis of 508 ejaculates from 297 dogs, efficiency of semen cryopreservation and effects of age, season and dog size on characteristics of fresh and cryopreserved semen were evaluated. Volume of the sperm-rich ejaculate fraction increased to 10 years of age, decreased in 10 and 11-year old dogs (P < 0.001) but did not differ among seasons. Total sperm count was less in 10 and 11-year-old dogs (P < 0.001). The percentage of progressively motile, membrane-intact and morphologically normal spermatozoa before cryopreservation was least in 10 and 11-year-old dogs (P < 0.001). Cryopreservation resulted in less progressively motile spermatozoa (P < 0.001) with this being most pronounced in 10 and 11-year-old dogs (cryopreservation x age P = 0.004). The cryopreservation-induced decrease in morphologically normal spermatozoa (P < 0.001) was not affected by dog body weight. Number of cryopreserved AI doses differed among age groups (P < 0.001) and was less in 10 and 11-year-old dogs (median 1.5) compared with younger dogs (6-7 years, median 4.3). When ejaculates were grouped by a threshold of ≥ 35% progressively motile spermatozoa after freezing-thawing, 86.5% of all ejaculates were greater the threshold but this percentage decreased to 66% in 10 and 11-year-old dogs (P < 0.001). In conclusion, sperm cryotolerance is consistent for much of a dog´s lifespan but decreases after a certain age. Dog semen can be cryopreserved successfully throughout the year. Post-thaw semen characteristics were not different among cryopreserved ejaculates obtained from dogs differing in body weight.

Effects of blue monochromatic light directed at one eye of pregnant horse mares on gestation, parturition and foal maturity.

Blue light directed at 1 eye advances the equine ovulatory season but may also advance foaling. In this study, effects of blue LED light on pregnancy outcome were assessed. A total of 20 mares with singleton pregnancies were studied over 2 consecutive years in a cross-over design. In 1 year, mares received an extended photoperiod using 50 lux of blue LED light (468 nm) directed at a single eye from 08:00 until 23:00 daily via head-worn light masks starting mid-December and in the other year remained untreated as controls. Gestation was shorter in blue LED light-treated than in control pregnancies (median 333.0 vs 338.5 days, P = 0.036). Foals born to blue LED light-treated mares had lower wither heights (median 103.0 vs 104.5 cm, P = 0.023), similar weights (median 55.8 vs 54.8 kg, P = 0.732) and took less time to stand after birth than control foals (median 35.0 vs 53.5 min, P = 0.036). Foals born to blue LED light-treated mares had reduced hair length compared to controls (median 12.0 vs 20.0 mm, P = 0.009) and hair regrowth in treated mares was reduced (P = 0.036). In conclusion, blue LED light directed at 1 eye advanced foaling and influenced height and hair coat but not weight in foals.

Aspects of Breeding Stallion Management with Specific Focus on Animal Welfare.

Risk prevention is often counterproductive to stallions' living conditions when assessed under welfare aspects. In the wild, stallions live in social groups, but under domestic conditions, the majority of breeding stallions live in individual boxes with limited social contact. This stimulates aggressiveness and the incidence of stereotypic behavior. While racehorse stallions start their breeding career after having finished their performance career, riding horse stallions are often simultaneously used for breeding and performance. Training, performance, and the associated stress are unlikely to impair semen characteristics, but performing stallions may benefit from more opportunities for social contact. With regard to accommodation of stallions in single boxes, changes in the construction of the partition between them may help to improve social contact from merely visual to much more physical. This will help to reduce social isolation but requires careful observation if neighbors tend to either sympathize or fight with each other. Careful organization of the barn is thus of great importance. Under certain conditions, even keeping adult stallions in groups on spacious pastures is possible. Interestingly, the frequency of agonistic interactions usually decreases quickly and remains low after successful group integration. General changes in the husbandry of young stallions and at their transfer into the future career may help to produce stallions with better social skills and facilitate accommodation under improved welfare conditions.