Current status and advances in ram semen cryopreservation

Abstract

Ram semen cryopreservation contributes to genetic improvement through artificial insemination, eliminates geographical barriers in artificial insemination application and supports the preservation of endangered breeds thus the conservation of biodiversity. Sperm freezing process induces ultrastructural, biochemical and functional changes of spermatozoa. Especially, spermatozoa’s membranes and chromatin can be damaged, sperm membranes’ permeability is increased, hyper oxidation and formation of reactive oxygen species takes place, affecting fertilizing ability and subsequent early embryonic development. Aiming to improve ram frozen-thawed semen’s fertilizing capacity, many scientific investigations took place. Among them the composition of semen extenders, was a main point of interest. Semen preservation extenders regulate and support an environment of adequate pH and buffering capacity to protect spermatozoa from osmotic and cryogenic stress. Therefore, permeating (glycerol, dimethyl sulfoxide) and non-permeat ing (egg yolk, skimmed milk) cryoprotectants, sugars (glucose, lactose, trehalose, raffinose), salts (sodium citrate, citric acid) and antioxidants (amino acids, vitamins, enzymes) have been added and tested. Moreover, semen dilution rate, storage temperature, cooling rate and thawing protocol, are also some key factors that have been studied. The research results of this scientific topic are encouraging, not only about the freezing and thawing procedures, but also about the improvement of the additives’ properties. However, further research is needed to enhance the fertilizing ability of ram frozen-thawed semen, making its use practical in sheep reproductive management by the application of cervical artificial insemination.

Evaluation of Pregnancy Rate and Length of Pregnancy after Intracervical Insemination in Zwartbles Sheep

“…The artificial insemination is performed using fresh, chilled and diluted semen. Previously extracted doses stored in liquid nitrogen for a longer period of time are used only rarely, since this method of conservation leads to a rapid decrease of fertility of the insemination dose after its defrosting (Louda et al, 2001;Ntemka et al, 2018). A similar situation is reported with horses (Rečková and Filipčík, 2020).…”

The Re-Addition of Seminal Plasma after Thawing Does Not Improve Buck Sperm Quality Parameters

“…The use of frozen-thawed caprine semen for artificial insemination (AI) remains challenging due to its low fertility rate [ 1 ]. The fertilizing capacity of cryopreserved semen has been reported to be low due to the detrimental effect of freezing resulting in ultrastructural, functional, and biochemical damage as increased membrane permeability, hyper oxidation, and formation of reactive oxygen species and damages on the mitochondrial sheath and tail axoneme [ 2 ]. Traditionally, cryopreserving media contains widely used components such as egg yolk and glycerol, regarded as cryoprotectants, which help to minimise cryo-injuries during the freezing and thawing processes [ 3 ].…”

The Current Trends in Using Nanoparticles, Liposomes, and Exosomes for Semen Cryopreservation

“…However, the sperm freezing process induces ultrastructural, biochemical, and functional changes of spermatozoa. Especially, spermatozoa membranes and chromatin can be damaged, sperm membrane permeability is increased, and hyper oxidation and formation of reactive oxygen species takes place, affecting fertilizing ability and subsequent early embryonic development [1].…”