Boar spermatozoa proteomic profile varies in sperm collected during the summer and winter

Proteomic Analysis of Differences in the Freezability of Porcine Sperm Identifies α-Amylase As a Key Protein

To investigate the mechanisms underlying the differences in the freezability of boar semen, Yorkshire boars with freezing-tolerant semen (YT, n = 3), Yorkshire boars with freezing-sensitive semen (YS, n = 3), Landrace boars with freezing-tolerant semen (LT, n = 3), and Landrace boars with freezing-sensitive semen (LS, n = 3) were selected for this study. Their sperm was subjected to protein extraction, followed by data-independent acquisition proteomics and functional bioinformatics analysis. A total of 3042 proteins were identified, of which 2810 were quantified. Some key KEGG pathways were enriched, such as starch and sucrose metabolism, carbohydrate digestion and absorption, mineral absorption, the HIF-1 signaling pathway, and the necroptosis pathways. Through PRM verification, we found that several proteins, such as α-amylase and epididymal sperm-binding protein 1, can be used as molecular markers of the freezing resistance of boar semen. Furthermore, we found that the addition of α-amylase to cryoprotective extender could significantly improve the post-thaw motility and quality of boar semen. In summary, this study revealed some molecular markers and potential molecular pathways contributing to the high or low freezability of boar sperm, identifying α-amylase as a key protein. This study is valuable for optimizing boar semen cryopreservation technology.

Ovine fertility by artificial insemination in the breeding season could be affected by intraseasonal variations in ram sperm proteomic profile

It is important to note that seasonality could affect ram reproductive parameters, and therefore, fertility results after artificial insemination. In this work, 1) we assessed fertility rates after cervical artificial insemination of 11,805 ewes at the beginning (June 21st to July 20th) and at the end (November 20th to December 21st) of the reproductive season in the Assaf breed for the last four years, and 2) we aimed to identify male factors influencing the different reproductive success obtained depending on the time at the mating season in which ovine artificial insemination was performed. For this purpose, we evaluated certain ram reproductive and ultrasonographical parameters as well as we performed a multiparametric and proteomic sperm analysis of 6-19 rams at two very distant points in the mating season (July as Early Breeding Season -EBS- and November as Late Breeding Season -LBS-). Rutinary assessments carried out in the ovine reproduction centers (testicular volume, libido, sperm production and mass motility) showed non-significant differences (P ≥ 0.05) between both studied times, as well as the ram ultrasonographic evaluation (Resistive and Pulsatility Index as Doppler parameters; and pixels mean gray level, and hypoechoic areas percentage and density as echotexture parameters). However, at level of sperm functionality, although sperm quality appeared non-significantly lower (P ≥ 0.05) in the EBS, we identified a significantly different (P < 0.05) sperm proteomic profile between the seasonality points. The following proteins were identified with the lowest abundance in the EBS with a fold change > 4, a P = 2.40e-07, and a q = 2.23e-06: Fibrous Sheath-Interacting Protein 2, Disintegrin and Metalloproteinase Domain-Containing Protein 20-like, Phosphoinositide-Specific Phospholipase C, Tektin 5, Armadillo Repeat-Containing Protein 12 Isoform X3, Solute Carrier Family 9B1, Radial Spoke Head Protein 3 Homolog, Pro-Interleukin-16, NADH Dehydrogenase [Ubiquinone] 1 Alpha Subcomplex Subunit 8, Testis, Prostate and Placenta-Expressed Protein, and Acyl Carrier Protein Mitochondrial. In conclusion, while our basic analyses on male and sperm quality showed similar results between the beginning and the end of the breeding season, on a proteomic level we detected a lower expression of sperm proteins linked to the energy metabolism, sperm-oocyte interactions, and flagellum structure in the EBS. Probably, this different protein expression could be related to the lower fertility rate of Assaf ewes after cervical artificial insemination at this time. More importantly, sperm proteins can be used as highly effective molecular markers in predicting sperm fertilization ability related to intraseasonal variations.

QTLs and Candidate Genes Associated with Semen Traits in Merino Sheep

Ram semen traits play a significant role in conception outcomes, which in turn may influence reproductive efficiency and the overall productivity and profitability of sheep enterprises. Since hundreds of ewes may be inseminated from a single ejaculate, it is important to evaluate semen quality prior to use in sheep breeding programs. Given that semen traits have been found to be heritable, genetic variation likely contributes to the variability observed in these traits. Identifying such genetic variants could provide novel insights into the molecular mechanisms underlying variability in semen traits. Therefore, this study aimed to identify quantitative trait loci (QTLs) associated with semen traits in Merino sheep. A genome-wide association study (GWAS) was undertaken using 4506 semen collection records from 246 Merino rams collected between January 2002 and May 2021. The R package RepeatABEL was used to perform a GWAS for semen volume, gross motility, concentration, and percent post-thaw motility. A total of 35 QTLs, located on 16 Ovis aries autosomes (OARs), were significantly associated with either of the four semen traits in this study. A total of 89, 95, 33, and 73 candidate genes were identified, via modified Bonferroni, within the QTLs significantly associated with volume, gross motility, concentration, and percent post-thaw motility, respectively. Among the candidate genes identified, SORD, SH2B1, and NT5E have been previously described to significantly influence spermatogenesis, spermatozoal motility, and high percent post-thaw motility, respectively. Several candidate genes identified could potentially influence ram semen traits based on existing evidence in the literature. As such, validation of these putative candidates may offer the potential to develop future strategies to improve sheep reproductive efficiency. Furthermore, Merino ram semen traits are lowly heritable (0.071-0.139), and thus may be improved by selective breeding.

Comparative assessment of reproductive capacity of boar-sires depending on the breed and season

The article highlights the results of the reproductive capacity of different breeds of boar sires in the farms of eastern, southern, and central regions of Ukraine in dynamics over three years are given. It represented the influence of the year's season on sperm quality by estimating the ejaculate volume, concentration, and motility of sperm of boars-sires of the different breeds and their hybrids. Data were also calculated on the culling of ejaculates of boar sires of various breeds for the years 2019–2021 in the dynamics. In a comparative aspect, the indicators were analyzed by the following genotypes: Large White, Ukrainian Meat, Landrace, Duroc, Yorkshire, and synthetic line Makster. The reproductive capacity of boars was within the limits of the indicators for the elite and first classes. However, specific differences were observed between boars of different breeds, which were constant and took place during the three studied years. The difference in the concentration of sperm in the ejaculates of the Ukrainian Meat breed gradually decreased starting from 2019 and was the smallest in 2021. The highest ejaculate volume was found in boars of the Ukrainian meat breed (310.9 ± 113.2 cm3), and the sperm concentration was the highest in boar sires of the Large White breed (215.7 ± 83.5 million/cm3). On the other side, hybrids of the Large White breed had low indicators compared to other groups of animals (Large White × Yorkshire – 184.2 ± 68.5 million/cm3, Large White × Makster – 189.0 ± 59.7 million/cm3). Sperm motility did not undergo significant breed differences: the average annual indicator of motility was 7.6 ± 0.09 points, and it was the highest in the winter period (8.6 ± 0.11 points), however, for the established variances; the dilution was used 1.65–3.58 times and a high percentage of unusable sperm (15.4–29.4 % of the total amount) was established in a large number of samples. According to the results of the annual analysis of the sperm production of boars, a high degree of culling of ejaculates was established for various reasons (high level of sperm agglutination (52.3–74.0 %), low concentration of germ cells (14.5–29.8 %), presence of foreign impurities (5,8–12.4 %). The highest percentage of culling was in summer (20.3 %). Thus, the obtained results showed the breed and seasonal characteristics of the reproductive capacity of breeding boars.

Effects of Heat Stress on Motion Characteristics and Metabolomic Profiles of Boar Spermatozoa

Heat stress (HS) commonly causes boar infertility and economic loss in the swine industry. The heat tolerance of boar semen presents obvious differences among individuals. However, whether heat stress affects motion characteristics and the metabolome profile in boar sperm remains unclear. In this study, the kinetic features of sperm from HS and non-HS (NHS) groups were detected by computer-assisted sperm analysis, and metabolomic profiling was performed by liquid chromatography−mass spectrometry. The results showed that heat stress significantly reduced sperm motility, average path distance (APD), straight-line velocity (VSL), straightness (STR), and linearity (LIN) (p < 0.05). A total of 528 and 194 metabolites in sperm were identified in the positive and negative ion modes, respectively. Lipids and lipid-like molecules, and organic acids and derivatives were major metabolic classes in the two modes. Furthermore, we separately identified 163 and 171 differential metabolites in the two modes between HS and NHS groups. Clustering analysis further revealed significant metabolic changes in sperm after heat stress. The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that differential metabolites in the two modes were enriched in glycerophospholipid, choline, and alanine, aspartate, and glutamate and lysine metabolism. Taken together, these results demonstrate that heat stress can alter the motion characteristics and metabolomic profiles of boar sperm.

Effect of Season and Parity on Reproduction Performance of Iberian Sows Bred with Duroc Semen

The Iberian pig is an autochthonous breed from the Iberian Peninsula highly valued for its meat. The sows are often bred as Iberian × Duroc crossings for increased efficiency. Since sow parity and season affect the reproductive performance, we evaluated two-year records from a commercial farrow-to-finish farm (live, stillborn, and mummified piglets after artificial insemination, AI). A total of 1293 Iberian sows were inseminated with semen from 57 boars (3024 AI). The effects of parity (gilts, 1, 2-4, 5-10, and >10 farrowings) and season were analyzed by linear mixed-effects models (LME). The data were fitted to cosinor models to investigate seasonal effects within parity groups. The effects of maximum daily temperature (MDT) and day length change (DLC) during spermatogenesis, pre-AI, and post-AI periods were analyzed with LME. The 2-4 group was the optimal one for parity. A seasonal effect was evident between spring-summer (lower fertility/prolificacy) and autumn-winter (higher). Cosinor showed that the seasonal drop in reproductive performance occurs earlier in Iberian sows than in other breeds, more evident in gilts. MDT negatively affected performance in all periods and DLC in spermatogenesis and pre-AI. These results are relevant for the improvement of Iberian sows' intensive farming.