Molecular markers, BM1500 and UMN2008, are associated with post-thaw motility of bull sperm

Determinant genetic markers of semen quality in livestock

The reproductive efficiency of livestock is crucial for agricultural productivity and economic sustainability. One critical factor in successful fertilization and the viability of offspring is the quality of semen. Poor semen quality, especially in frozen-thawed semen used in artificial insemination (AI) have been shown to influence conception outcomes, resulting a negative impact on livestock production. Recent advancements in genetic research have identified specific markers linked to semen quality traits in various livestock species, such as cattle, sheep, goats, pigs, buffalo, and equines. These genetic markers are essential in screening males for breeding suitability, which in turn enhances selective breeding programs. Understanding these markers is crucial for improving reproductive performance and increasing productivity in livestock populations. This review offers a comprehensive overview of the genetic markers associated with semen quality in key livestock. It explores the underlying genetic mechanisms and their practical implications in animal breeding and management. The review underscores the importance of integrating genetic insights into breeding strategies to optimize reproductive efficiency and ensure the sustainable development of livestock industries.

Canine Spermatozoa—Predictability of Cryotolerance

Simple Summary

Semen freezing in dogs is a field of growing interest. The international shipment of cryoconserved semen contributes to the avoidance of long travels and long-term storage of valuable gametes. However, the collection of one semen portion on average results in one to three doses for artificial insemination, which is a poor result in comparison to the outcome in large animals. The costs for the owners are therefore rather high. In individual dogs, the semen quality of raw semen is good; however, it could be suboptimal after thawing. To avoid costly freezing of these low-quality ejaculates, markers of freezability are useful. An abundance of markers are available for large animals, but not for dogs. This review provides an overview on markers for freezability of canine semen.

Abstract

Markers of freezability allow the selection of ejaculates of good freezability. So far, most investigations were conducted in boars, bulls, rams and horses, with high economic interests triggering the efforts. The progress in dogs is comparably slow. A critical evaluation of the methods requires consideration of practicability, with most labs not even possessing a computer assisted sperm analyser (CASA); furthermore, small canine ejaculates mostly do not allow the use of large semen volumes. In dogs, modern markers of freezability no longer assess single membrane constituents or seminal plasma components but comprise tests of cell functionality and adaptability, energy metabolism, cluster analyses of kinetic and morphometric parameters, as well as DNA intactness. Identification of the most efficient combination of tests seems useful. At present, examination by CASA combined with cluster analysis of kinetic subgroups, JC-1 staining and COMET assay or staining with toluidine blue seem most appropriate; however, cell volumetry and other functional tests deserve better attention. A better understanding of spermatozoa energy metabolism might reveal new markers. This review focuses on the requirements and markers of freezability of canine semen, highlighting potential future candidates.

Role of seminal MDA, ROS, and antioxidants in cryopreservation and their kinetics under the influence of ejaculatory abstinence in bovine semen

Despite many cryopreservation techniques in bovine semen, various stressors' detrimental effects remain a significant issue. The present study targeted to assess the role of semen quality parameters, sperm function tests, lipid peroxidation, reactive oxygen species (ROS), and different antioxidants in the cryopreservation of bovine semen. Further, the kinetics of lipid peroxidation, ROS, and antioxidants on repeated semen collection under short ejaculatory abstinence were studied. We designed a comparative study where bulls were grouped into good and low freezable semen groups (Freeze-groups) based on their post-thaw motility. All the bulls included had similar initial motility and qualified minimum standards for initial semen parameters viz. semen volume and sperm concentration. The present study detected a higher lipid peroxidation and ROS viz. superoxide anions (•O2-) and a lower total antioxidant capacity (TAC) in the low freeze-group compared to the good freeze-group. The ROS and antioxidants showed unique kinetics on repeated semen collection at short intervals, and no significant change was detected in semen volume, sperm motility, and sperm concentration. This study detected higher head abnormalities and poor acrosome integrity in the low freeze-groups. The present study results indicated that the sperm head might be the most vulnerable part of the sperm to cryopreservation stress. The present study finds significantly higher lipid peroxidation and ROS levels and reduced antioxidant capacity as the primary reasons for low cryopreservability. Further, repeated semen collection with a shorter or lack of abstinence does not impose any significant change in the semen volume and sperm concentration; moreover, it could be beneficial for higher antioxidant levels and lower lipid peroxidation levels. As seminal plasma has both inhibitory and stimulatory roles in sperm function and cryopreservation, identifying the critical role players of seminal plasma and identifying sperm related changes in cryopreservation could predict the cryopreservability potential of semen.

Marker-assisted selection vis-à-vis bull fertility: coming full circle-a review

Bull fertility is considered an indispensable trait, as far as farm economics is concerned since it is the successful conception in a cow that provides calf crop, along with the ensuing lactation. This ensures sustainability of a dairy farm. Traditionally, bull fertility did not receive much attention by the farm managers and breeding animals were solely evaluated based on phenotypic predictors, namely, sire conception rate and seminal parameters in bull. With the advent of the molecular era in animal breeding, attempts were made to unravel the genetic complexity of bull fertility by the identification of genetic markers related to the trait. Marker-Assisted Selection (MAS) is a methodology that aims at utilizing the genetic information at markers and selecting improved populations for important traits. Traditionally, MAS was pursued using a candidate gene approach for identifying markers related to genes that are already known to have a physiological function related to the trait but this approach had certain shortcomings like stringent criteria for significance testing. Now, with the availability of genome-wide data, the number of markers identified and variance explained in relation to bull fertility has gone up. So, this presents a unique opportunity to revisit MAS by selection based on the information of a large number of genome-wide markers and thus, improving the accuracy of selection.