Effects of Room Temperature Storage Duration on the Quality of Cauda Epididymal Spermatozoa Recovered from Red Sokoto Bucks

INTRODUCTION

Goat production contributes significantly to food security, income generation, and rural livelihoods in many developing countries, particularly in sub-Saharan Africa.^[1,2] Among indigenous goat breeds in Nigeria, the Red Sokoto goat is highly valued for its adaptability, reproductive efficiency, meat production, and premium-quality skin.^[3,4] The preservation and dissemination of superior genetic traits from outstanding breeding bucks are essential for improving herd productivity and maintaining valuable genetic resources.^[5] However, the sudden death, accidental slaughter, or loss of good breeding males often results in irreversible genetic loss, especially when semen has not been collected and preserved before death.^[6]

The epididymis serves as a storage site for mature spermatozoa that have completed their maturation process and acquired fertilizing capacity.^[7] Following the death of an animal, viable spermatozoa may remain within the cauda epididymis for varying periods depending on environmental conditions and storage duration.^[8,9] Recovery of epididymal spermatozoa from deceased animals has therefore emerged as an important reproductive biotechnology for the preservation of valuable genetic material. Such recovered spermatozoa can be utilized in artificial insemination, in vitro fertilization, and other assisted reproductive technologies.^[10]

Several studies have demonstrated the successful recovery and utilization of epididymal spermatozoa from different livestock species, including cattle, sheep, goats, horses, and wildlife species.^[8,10-13] The quality of recovered spermatozoa is influenced by factors such as postmortem interval, storage temperature, recovery technique, and handling procedures.^[14] Prolonged exposure of testes and epididymides to unfavorable environmental conditions may result in cellular degeneration, reduced membrane functionality, impaired motility, and loss of fertilizing ability.^[15] Consequently, determination of the period during which sperm quality remains acceptable after death is critical for effective germplasm rescue programs.

In tropical environments, where ambient temperatures are often high and refrigeration facilities may not be immediately available, testes obtained from slaughterhouses, or field situations are frequently maintained at room temperature before processing.^[16] Under such conditions, spermatozoa may undergo progressive deterioration due to metabolic exhaustion, oxidative stress, and structural damage. Understanding the effects of room temperature storage on epididymal sperm characteristics is therefore essential for the establishment of practical guidelines for sperm recovery and preservation under field conditions.

Despite the economic and genetic importance of the Red Sokoto goat, information on the postmortem survival of epididymal spermatozoa under room temperature storage remains limited. This study was conducted to evaluate the effects of different postmortem storage periods on the motility, concentration, viability, acrosomal integrity, plasma membrane integrity, and morphology of cauda epididymal spermatozoa recovered from Red Sokoto bucks. The findings are expected to provide valuable information for the conservation and utilization of genetic resources in this important indigenous goat breed.

MATERIAL AND METHODS

RESULTS

DISCUSSION

This study demonstrated that room temperature storage of testes-epididymides significantly influenced the quality of cauda epididymal spermatozoa recovered from Red Sokoto bucks. The reduction in sperm motility observed with increasing storage duration is consistent with previous reports in Red Sokoto goats, rams, and red deer.^[8,12,21] Sperm motility is highly dependent on adequate adenosine triphospate (ATP) production and intact mitochondrial function. Following death, the cessation of blood circulation deprives reproductive tissues of oxygen and nutrients, thus resulting in gradual depletion of intracellular energy reserves. Under room temperature conditions, sperm metabolism remains relatively active with increased ATP consumption, which leads to progressive loss of movement. Therefore, the complete absence of motility after 24 h might reflect severe metabolic exhaustion and irreversible cellular damage.

The lower sperm concentration recorded in stored samples compared with the immediately processed group may be attributed to postmortem degeneration of sperm cells within the epididymal environment. Similar observations have been reported in studies that evaluated delayed sperm recovery from epididymides of livestock species.^[9,13] Although sperm concentration is generally considered a stable characteristic, prolonged storage may increase cellular lysis and reduce the number of intact spermatozoa available for recovery. The absence of further reductions among the stored groups may suggest that most losses occurred during the early postmortem period.

Sperm viability remained relatively stable during the first 6 h of storage but declined markedly thereafter. This observation agrees with findings reported in goat and deer epididymal spermatozoa, where short-term storage maintained acceptable proportions of live cells while prolonged storage resulted in substantial mortality.^[8,21] The preservation of viability during the initial hours may be related to the protective microenvironment of the cauda epididymis, which contains antioxidants, proteins and osmotic regulators capable of supporting sperm survival.^[22] However, as the storage time increased, accumulation of reactive oxygen species and deterioration of cellular defense systems might have contributed to membrane destabilization and cell death.

In this study, acrosomal integrity showed a gradual decline with increasing storage duration, indicating progressive impairment of structures required for fertilization. Similar reductions have been documented in epididymal spermatozoa stored under postmortem conditions in domestic and wild animal species.^[9,14] The acrosomal membrane is particularly vulnerable to oxidative damage and enzymatic degradation. Loss of acrosomal integrity may compromise the ability of spermatozoa to undergo the acrosome reaction and penetrate the zona pellucida of the oocyte, thereby reducing fertilization potential even when some sperm cells remain viable.^[23]

The marked decline in plasma membrane integrity after 12 h and its complete loss after 24 h further confirms progressive structural deterioration of sperm cells in this study. Plasma membrane functionality is essential for maintenance of ionic balance, energy metabolism, and sperm–oocyte interactions.^[24] The observed deterioration may be associated with lipid peroxidation caused by oxidative stress, disruption of membrane phospholipids, and increased permeability resulting from prolonged exposure to elevated ambient temperatures. Similar mechanisms have been proposed by Tirpák et al.^[15] and De Toni et al.,^[16] who reported that thermal stress and oxidative damage are major contributors to impaired male reproductive cell function.

However, in this study, head and tail abnormalities were not significantly influenced by storage duration. This finding suggests that gross structural defects of these regions may be less sensitive indicators of postmortem deterioration than functional parameters such as motility, viability, and membrane integrity. Comparable observations have been reported in studies where sperm morphology remained relatively stable despite substantial declines in functional quality characteristics.^[13] The persistence of morphological appearance despite functional impairment, thus, demonstrates the importance of evaluating multiple sperm quality parameters when assessing reproductive potential.

On the contrary, the reduction in midpiece abnormalities observed after 24 h should be interpreted cautiously. Rather than indicating improved sperm quality, the decline might reflect preferential degeneration or disintegration of spermatozoa possessing damaged midpieces during prolonged storage. Severely compromised sperm cells may have fragmented or become unrecognizable during microscopic examination, thereby reducing the proportion of observable abnormalities. Similar methodological considerations have been noted in postmortem sperm studies involving prolonged storage periods.^[21,25]

From a practical perspective, the findings have important implications for germplasm conservation programs in tropical regions where immediate refrigeration may not be available. The maintenance of relatively high viability, acrosomal integrity, and plasma membrane integrity within 6 h of storage may suggest that valuable genetic material can still be salvaged from slaughtered or unexpectedly deceased Red Sokoto bucks during this period. However, the pronounced deterioration observed after 12 h might indicate that delays in sperm recovery should be minimized to maximize the likelihood of successful use in artificial insemination, in vitro fertilization, and other assisted reproductive technologies. These results provide useful baseline information for the development of field-oriented protocols for genetic resource conservation in indigenous Nigerian goat breeds.

CONCLUSION

Room temperature storage significantly affected the quality of cauda epididymal spermatozoa recovered from Red Sokoto bucks. Motility, viability, acrosomal integrity and plasma membrane integrity declined progressively as storage duration increased, whereas sperm morphology was largely unaffected. Acceptable sperm quality was maintained for up to 6 h after slaughter, but substantial deterioration occurred after 12 h, with complete loss of motility and viability by 24 h. Therefore, early recovery of epididymal spermatozoa is essential for effective genetic conservation and assisted reproductive applications.