Liquid storage of ram semen for 96 h: Effects on kinematic parameters, membranes and DNA integrity, and ROS production

Exploring the full potential of sperm function with nanotechnology tools

Sperm quality is essential to guarantee the success of assisted reproduction. However, selecting high-quality sperm and maintaining it during (cryo)preservation for high efficiency remains challenging in livestock reproduction. A comprehensive understanding of sperm biology allows for better assessment of sperm quality, which could replace conventional sperm analyses used today to predict fertility with low accuracy. Omics approaches have revealed numerous biomarkers associated with various sperm phenotypic traits such as quality, survival during storage, freezability, and fertility. At the same time, nanotechnology is emerging as a new biotechnology with high potential for use in preparing sperm intended to improve reproduction in livestock. The unique physicochemical properties of nanoparticles make them exciting tools for targeting (e.g., sperm damage and sexing) and non-targeting bioapplications. Recent advances in sperm biology have led to the discovery of numerous biomarkers, making it possible to target specific subpopulations of spermatozoa within the ejaculate. In this review, we explore potential biomarkers associated with sperm phenotypes and highlight the benefits of combining these biomarkers with nanoparticles to further improve sperm preparation and technology.

Dietary supplementing South African indigenous rams with flaxseed oil and ascorbic acid improves cryopreserved semen quality and in vitro fertility

The purpose of this study was to evaluate how ascorbic acid with dietary flaxseed oil affects the quality and fertility of cryopreserved ram sperm in South African indigenous rams. Treatment diets were supplemented 60 days before semen collection to afford proper spermatogenesis, adaptation to the feed formulated and fed throughout the study. Semen was collected with the use of artificial vagina following dietary supplementation with five treatment diets (neg. cont. - negative control, pos. cont. - positive control, FLO - 5% Flaxseed oil, ASA - 4% Ascorbic acid, and FLO + ASA). Semen was then extended using tris-based extender and cryopreserved using the programmable freezer (CBS Freezer 2100 series, Laboratory consumables & chemical suppliers, America). Ovaries were collected from a neighbouring slaughter house and conveyed to the lab in 0.9% saline at 37 °C. Data (sperm parameters and in vitro fertility) was then exposed to the GLM (General Linear Model) in Minitab 17. Pearson's correlation coefficient was utilized to investigate the relationship between cryopreserved sperm quality and in vitro fertility. The student Least Significant Difference Test was used to separate the treatment means, and differences were accepted when the p-value was less than 0.05. The FLO + ASA group had higher (p < 0.05) progressive (36.33 ± 1.87), total (88.24 ± 2.24), rapid motility (27.52 ± 1.74), intact plasma membrane (75.67 ± 2.08), total fertilization (65.98 ± 7.39), and total cleavage (66.19 ± 6.50) when compared to other treatment groups. Total fertilization rate had a medium significant (p < 0.001) medium correlation with the progressive motility (r2 = 0.435), total motility (r2 = 0.447) and rapid motility (r2 = 0.409). In conclusion, dietary flaxseed and ascorbic acid (FLO + ASA) improves cryopreserved semen quality, in vitro fertilization rate, and the total cleavage rate. Noteworthy, the progressive, total and rapid motility play a crucial in the in vitro fertilization rate.

Effects of organic and inorganic selenium supplementation on frozen-thawed ram semen at two cooling periods

The aim of this study was to evaluate the effects of different selenium compounds on the sperm quality of cryopreserved ram semen. Ejaculates from four rams, collected using an artificial vagina heated to 38 °C, were individually evaluated. The approved ejaculates were pooled and diluted (1:1 v:v) in Tris-egg yolk extender (20%, v/v) and separated into two control groups, one cooled for 2 h and the other for 4 h. The pooled ejaculates at the two cooling periods were supplemented with two doses (0.5 and 1 μg/mL) of organic selenium (ORG), and inorganic selenium (SeNa), each. The samples were packed in 0.25 ml straws, at a concentration of 400 × 106 sperms/mL and stored in liquid nitrogen. The straws were thawed in a water bath at 37 °C for 20 s, and the samples were subjected to sperm kinetics evaluation by Computer Assisted Semen Analysis software. Sperm membrane integrity, acrosome morphology, and mitochondrial potential were assessed. In addition, oxidative stress markers reactive oxygen species (ROS), ferric reducing antioxidant power (FRAP), thiobarbituric acid reactive species (TBARS), and glutathione peroxidase (GPx) enzyme activity) were also evaluated. No significant improvement was observed in the ram semen quality at the two cooling times. Supplementation of the freezing extender with 0.5 μg/mL ORG, subjected to 4 h cooling period, increased the sperm motility when compared with the control group at the same cooling time. In addition, the 0.5 μg/mL SeNa group, under the 2 h cooling period, showed an increase in sperm motility when compared to the control group at the same cooling period. Considering the importance of sperm motility as a fertility parameter, our study indicates that supplementation with ORG and SeNa can help improve the total motility of the cryopreserved ram semen.

A systematic review on the prospects of X- and Y-sexed semen in ruminant livestock: implications for conservation, a South African perspective

South Africa is home to numerous indigenous and locally developed sheep (Nguni Pedi, Zulu, and Namaqua Afrikaner, Afrino, Africander, Bezuidenhout Africander, Damara, Dorper, Döhne Merino, Meat Master, South African Merino, South African Mutton Merino, Van Rooy, and Dorper), goat (SA veld, Tankwa, Imbuzi, Bantu, Boer, and Savanna) and cattle (Afrigus, Afrikaner, Bolowana, Bonsmara, Bovelder, Drakensberger, South African Angus, South African Dairy Swiss, South African Friesland, South African Red, and Veld Master) animals. These breeds require less veterinary service, feed, management efforts, provide income to rural and or poor owners. However, most of them are under extinction risks and some with unknown status hence, require immediate conservation intervention. To allow faster genetic progress on the endangered animals, it is important to generate productive animals while reducing wastages and this can be achieved through sex-sorted semen. Therefore, this systematic review is aimed to evaluate the prospects of X and Y-sexed semen in ruminant livestock and some solutions that can be used to address poor sex-sorted semen and its fertility. This review was incorporated through gathering and assessing relevant articles and through the data from the DAD-IS database. The keywords that were used to search articles online were pre-gender selection, indigenous ecotypes, fertility, flow cytometry, artificial insemination, conservation, and improving sexed semen. Following a careful review of all articles, PRISMA guidelines were used to find the articles that are suitable to address the aim of this review. Sex-sorted semen is a recently introduced technology gaining more attention from researchers particularly, in the conservation programs. Preselection of semen based on the sex chromosomes (X- and or Y-bearing chromosomes) is of paramount importance to obtain desired sex of the offspring and avoid animal wastage as much as possible. However, diverse factors can affect quality of semen of different animal species especially after sex-sorting. Flow cytometry is a common method used to select male and female sperm cells and discard dead and abnormal sperm cells during the process. Thus, sperm sexing is a good advanced reproductive technology (ART) however, it is associated with the production of oxidative stress (OS) and DNA fragmentation (SDF). These findings, therefore, necessitates more innovation studies to come up with a sexing technology that will protect sperm cell injuries during sorting in frozen-thawed.

The Effect of Adding Different Levels of Reduced Glutathione to Extender on the Quality of Cooled Ring-Necked Pheasant Semen

Aim: Artificial propagation of ring-necked pheasant through semen preservation is of significance, as this species is facing enormous threats in its natural habitat. Semen preservation inevitably induces oxidative stress, and exogenous antioxidants need to be investigated for the preservation of ring-necked pheasant semen. Therefore, the current study was conducted to investigate the role of glutathione (GSH) in extender on the liquid storage of ring-necked pheasant semen. Materials and Methods: Semen was collected from 10 sexually mature males, evaluated for sperm motility, and pooled. Pooled semen was aliquoted for dilution with Beltsville poultry semen extender (1:5) at 37°C having GSH levels of 0.0 mM (Control), 0.2, 0.4, 0.6, and 0.8 mM. Extended semen was gradually cooled to 4°C and stored in a refrigerator (4°C) for 48 hours. Semen quality, that is, sperm motility, membrane integrity, viability, acrosomal integrity, and DNA integrity, was assessed at 0, 2, 6, 24, and 48 hours. Results: Sperm motility (%), plasma membrane integrity (%), viability (%), and acrosomal integrity (%) were recorded higher (p < 0.05), whereas DNA fragmentation (%) was recorded lower in extender supplemented with 0.4 mM GSH up to 48 hours of storage compared with 0.2, 0.6, and 0.8 mM GSH concentrations and control. Conclusion: It is concluded that 0.4 mM GSH in extender improves sperm quality parameters of ring-necked pheasant during liquid storage up to 48 hours at 4°C.

Metabolomic analysis reveals spermatozoa and seminal plasma differences between Duroc and Liang guang Small-spotted pig

The Liang guang Small-spotted pig is a well-known Chinese indigenous pig that is valued for its exceptional meat quality. However, the Liang guang Small-spotted pig has a lower semen storage capacity, shorter storage time and worse semen quality compared to Duroc. Pig sperm used for artificial insemination (AI) loses part of vitality and quality when being stored in commercial solutions. Serious vitality losses and short shelf life of the semen are particularly prominent in Liang guang Small-spotted pig. In this study, the metabolites in seminal plasma and spermatozoa of Duroc and Liang guang Small-spotted pigs were identified using UHPLC-Q-TOF/MS technology. The findings indicated forty distinct metabolites concentrating on energy metabolic substrates and antioxidant capacity in Liang guang Small-spotted pig and Duroc seminal plasma, including D-Fructose, succinate, 2-dehydro-3-deoxy-d-gluconate, alanine betaine, citrate, carnitine, acetylcarnitine and so on. Seventeen different metabolites were explored, with a focus on glycerophospholipid metabolism in Liang guang Small-spotted pig and Duroc spermatozoa, primarily including glycerol 3-phosphate, acetylcarnitine, phosphatidylcholine (PC) 16:0/16:0, palmitoyl sphingomyelin, acetylcholine, choline, glycerophosphocholine, betaine, L-carnitine, creatinine and others. This study reveals the metabolite profile of spermatozoa and seminal plasma among different pig breeds and might be valuable for understanding the mechanisms that lead to sperm storage capacity. Metabolites involved in energy metabolism, antioxidant capacity and glycerophospholipid metabolism might be key to the poor sperm storage capacity in Liang guang Small-spotted pig.

The Addition of Opuntia ficus-indica Ethanolic Extract to a Skimmed Milk-Based Extender Impacts Ram Sperm Quality

Recently, researchers have focused on the use of natural antioxidants to improve semen quality as a key element for successful artificial insemination. In this context, the first aim of this study was to determine the antioxidant activity and composition (minerals, vitamins, and sugars) of Opuntia ficus-indica cladode ethanolic extract (ETHEX). A further purpose of the study was to investigate the effect of ETHEX supplementation on the quality of liquid ram semen extended with skim milk (SM) at 5°C. The antioxidant activity of ETHEX was studied using free radical 1, 1-diphenyl-2-picrylhydrazyl (DPPH•) assay. The mineral composition and the sugar and vitamin contents of ETHEX were determined using an inductively coupled plasma optical emission spectrometry (ICP-OES) and HPLC-DAD-RID analytical instruments. As a second part, semen was collected from five Boujaâd rams with an artificial vagina. The ejaculates with more than 70% motility were pooled, extended with skim milk (SM) extender without (control) or supplemented with 1-8% of ETHEX (37°C; 0.8 × 109 sperm/mL). Sperm quality parameters were assessed at 8, 24, 48, and 72 h. The results showed that ETHEX had a higher antioxidant activity compared to those of ascorbic acid and butylated hydroxytoluene (BHT). Furthermore, ETHEX contains a considerable amount of minerals, vitamins, and sugars. The inclusion of 1 or 2% ETHEX in SM increased the sperm motility, viability, and membrane integrity and decreased the abnormality of spontaneous and catalyzed lipids peroxidation (p < 0.05) up to 72 h. In addition, semen diluted with 1 and 2% ETHEX decreased the level of DNA fragmentation compared to the control group (p < 0.05). In conclusion, the ETHEX could be recommended to improve the quality of liquid ram spermatozoa. However, its effects on artificial insemination should be further studied.

Advances in sperm cryopreservation in farm animals: Cattle, horse, pig and sheep

Sperm cryopreservation is one of the most important procedures in the development of biotechnologies for assisted reproduction. In some farm animals, the use of cryopreserved sperm has so many benefits for which relevance has become more evident in recent decades. Values for post-thaw sperm quality, however, are variable among species and within individuals of the same species. There is no standardized methodology for each of the stages of the cryopreservation procedure (andrological examination, semen collection, dilution, centrifugation, resuspension of the pellet with the freezing medium, packaging, freezing and post-thaw sperm evaluation), which also contributes to differences among studies. Cryotolerance markers of sperm and seminal plasma (SP) have been evaluated for prediction of ejaculate freezability. In addition, in previous research, there has been a focus on supplementing cryopreservation media with different substances, such as enzymatic and non-enzymatic antioxidants. In most studies, inclusion of these substances have led to improved post-thaw sperm quality and fertilizing capacity as a result of minimizing the adverse effects on sperm structure and function. Another approach is the use of different cryoprotectants. The aim with this review article is to provide an update on sperm cryopreservation in farm animals. The main detrimental effects of cryopreservation are described, including the negative repercussion on reproductive performance. Furthermore, the potential use of molecular biomarkers to predict sperm cryotolerance is discussed, as well as the addition of substances that can mitigate the harmful impact of freezing and thawing on sperm.

Effect of fortification of extender with α-terpineol and rosemary essential oil on post-thaw ovine semsen quality

The goal of the present study was to assess the viability of the cryopreserved ovine (Ovis aries) semen, upon supplementation with α-terpineol and rosemary essential oil (Rosmarinus officinalis). The collection of the semen from six rams formed the pool, collected once a week during 7 weeks. The diluted semen was packed into straws (0.25 ml) and frozen in a TK 3000® device. Both α-terpineol and rosemary essential oil were added in the concentrations of 6.25, 12.5 and 25 μg/ml to the TRIS-yolk extender forming six experimental groups; the control group received only the TRIS-yolk extender. The samples were analyzed after thawing regarding motility and vigor, integrity of the plasmatic membrane, thermoresistance test (TT), mitochondrial membrane potential, acrosomal integrity and computer-assisted semen analysis (CASA). The levels of the thiobarbituric acid reactive substances were also analyzed. According to the results obtained with the addition of the concentrations of 6.25, 12.5 and 25 μg/ml of α-terpineol, significantly reduced the parameters assessed through CASA (VSL, LIN and WOB) and TT. Rosemary essential oil did not have deleterious effects on the spermatozoa and did not reduce the oxidative stress in the concentrations studied, although it presented absolute values higher than those of the control in several parameters. Alpha-terpineol in the concentrations studied was not able to reduce the oxidative stress and had toxic effect over the ovine spermatozoa.

Shielding effect of melatonin improves seminal quality and oxidative stress indices during chilled storage of ram semen

Supplementation of antioxidant to semen extender maintains seminal quality by reducing oxidative stress during preservation time period. The main aim of this study was to investigate the effect of different concentrations of melatonin supplementation on liquid storage of Magra ram semen. This study was performed on adult Magra ram (n = 8), and seminal ejaculates (48) were collected and evaluated for various macroscopic and microscopic seminal quality parameters for further processing. After preliminary evaluation, ejaculates of each collection session were mixed and divided into four equal aliquots. All the aliquots were diluted (1:10) with Tris-citric fructose egg yolk extender contained sans melatonin served as control, whereas the other three aliquots were supplemented with 0.5, 1 and 2 mM MLT which were grouped as MLT0.5, MLT1 and MLT2, respectively. Thereafter, the samples were stored at 4 ºC for 72 h, and various seminal parameters (individual sperm progressive motility, viability, abnormalities, plasma membrane functionality) along with oxidative stress parameters (total antioxidant capacity (TAC), malondialdehyde (MDA)) were evaluated at 0, 24, 48 and 72 h of preservation. The results indicated that the mean percent values for progressive sperm motility, viability, plasma membrane functionality and TAC were significantly higher (p < 0.05) in treated groups with the highest values in MLT1 group. Significantly lower (p < 0.05) percentage of total sperm abnormalities and MDA level was observed in treatment groups compared to control group. The results report that supplementation of 1 mM melatonin efficiently maintains the seminal quality and ameliorates oxidative stress during preservation at 4 ºC to 72 h.

Significance and Relevance of Spermatozoal RNAs to Male Fertility in Livestock

Livestock production contributes to a significant part of the economy in developing countries. Although artificial insemination techniques brought substantial improvements in reproductive efficiency, male infertility remains a leading challenge in livestock. Current strategies for the diagnosis of male infertility largely depend on the evaluation of semen parameters and fail to diagnose idiopathic infertility in most cases. Recent evidences show that spermatozoa contains a suit of RNA population whose profile differs between fertile and infertile males. Studies have also demonstrated the crucial roles of spermatozoal RNA (spRNA) in spermatogenesis, fertilization, and early embryonic development. Thus, the spRNA profile may serve as unique molecular signatures of fertile sperm and may play pivotal roles in the diagnosis and treatment of male fertility. This manuscript provides an update on various spRNA populations, including protein-coding and non-coding RNAs, in livestock species and their potential role in semen quality, particularly sperm motility, freezability, and fertility. The contribution of seminal plasma to the spRNA population is also discussed. Furthermore, we discussed the significance of rare non-coding RNAs (ncRNAs) such as long ncRNAs (lncRNAs) and circular RNAs (circRNAs) in spermatogenic events.

Impact of Oxidative Stress on Male Reproduction in Domestic and Wild Animals

Oxidative stress occurs when the levels of reactive oxygen species (ROS) overcome the antioxidant defenses of the organism, jeopardizing several biological functions, including reproduction. In the male reproductive system, oxidative stress not only impairs sperm fertility but also compromises offspring health and survival, inducing oxidative damage to lipids, proteins and nucleic acids. Although a clear link between oxidative stress and male fertility disorders has been demonstrated in humans and laboratory rodents, little information is available about the implications of impaired redox homeostasis in the male fertility of domestic and wild animals. Therefore, this review aims to provide an update regarding the intrinsic and extrinsic factors that are associated with oxidative stress in the male reproductive system and their impact on the reproductive performance of domestic and wild animals. The most recent strategies for palliating the detrimental effects of oxidative stress on male fertility are reviewed together with their potential economic and ecological implications in the livestock industry and biodiversity conservation.

Role of Antioxidants in Cooled Liquid Storage of Mammal Spermatozoa

Cooled preservation of semen is usually associated with artificial insemination and genetic improvement programs in livestock species. Several studies have reported an increase in reactive oxidative species and a decrease in antioxidant substances and sperm quality parameters during long-term semen storage at refrigerated temperatures. The supplementation of antioxidants in extenders before refrigeration could reduce this detrimental effect. Various antioxidants have been tested, both enzymatic, such as superoxide dismutase and catalase, and non-enzymatic, such as reduced glutathione, vitamins E and C and melatonin. However, the problem of oxidative stress in semen storage has not been fully resolved. The effects of antioxidants for semen-cooled storage have not been reviewed in depth. Therefore, the objective of the present study was to review the efficiency of the supplementation of antioxidants in the extender during cooled storage of semen in livestock species.

Exogenous catalase improves the goat seminal attributes at refrigeration temperature

The objective of the present study was to evaluate the potential benefit of catalase (CAT) on sperm functional parameters (motility, viability, membrane integrity and acrosomal integrity) during liquid storage of buck spermatozoa at 0 h, 24 h, 48 h, 72 h and 96 h. Semen samples from bucks were pooled to avoid individual effect and diluted with tris-egg yolk-fructose extender with catalase (0 U/ mL (control), 200 U/mL, 400 U/ mL, 600 U/ mL and 800 U/ mL) at a final concentration of 400 million/mL. No significant difference was observed between treatments at 24 h with respect to motility, viability and plasma membrane integrity. However, acrosome integrity of control was significantly higher as compared to other concentrations. Motility, viability, plasma membrane and acrosome integrity were observed significantly highest for CAT @ 600 U/mL in comparison to other concentrations at 48 h, 72 h and 96 h of liquid storage at refrigeration temperature. The seminal parameters declined with the progression of storage time and remained over 50% even after 72 h at refrigeration temperature in CAT @ 600 U/mL. It can be concluded that the addition of CAT @ 600 U/mL in semen diluent along with 20% egg yolk reduced the detrimental effects of cooling on motility, viability, plasma membrane and acrosome integrity.

Sperm DNA Integrity and Male Fertility in Farm Animals: A Review

The accurate prediction of male fertility is of major economic importance in the animal breeding industry. However, the results of conventional semen analysis do not always correlate with field fertility outcomes. There is evidence to indicate that mammalian fertilization and subsequent embryo development depend, in part, on the inherent integrity of the sperm DNA. Understanding the complex packaging of mammalian sperm chromatin and assessment of DNA integrity could potentially provide a benchmark in clinical infertility. In the era of assisted reproduction, especially when in-vitro fertilization or gamete intrafallopian transfer or intracytoplasmic sperm injection is used, assessment of sperm DNA integrity is important because spermatozoa are not subjected to the selection process occurring naturally in the female reproductive tract. Although sperm DNA integrity testing measures a significant biological parameter, its precise role in the infertility evaluation in farm animals remains unclear. In this review, the earlier findings on sperm DNA integrity in relation to male fertility are compiled and analyzed. Furthermore, the causes and consequences of sperm DNA damage are described, together with a review of advances in methods for detection of sperm DNA damage, and the prognostic value of sperm DNA quality on male fertility.

Mechanisms of ROS-induced mitochondria-dependent apoptosis underlying liquid storage of goat spermatozoa

Liquid storage of spermatozoa is important for artificial insemination and herd genetic breeding. However, the extended time of storage inducing the rapid decline in spermatozoa quality limits the development of this technology. The molecular mechanisms underlying liquid storage of spermatozoa remain largely unexplored. In this study, the effects of liquid storage on functional quality of spermatozoa were assessed in goat (Capra hircus). The time-dependent decline in spermatozoa motility showed a strong correlation with the significant increase in apoptosis. Moreover, apoptosis-related ultrastructural changes were observed, especially the defects in mitochondria. A significant decrease in mitochondrial membrane potential and changes in the expression of mitochondrial apoptosis-related proteins indicated mitochondrial dysfunction and mitochondrial apoptotic pathway activation. Notably, the abnormally high level of reactive oxygen species (ROS) caused by liquid storage resulted in oxidative damage to mitochondria and accelerated mitochondria-dependent apoptosis, as demonstrated by the addition of ROS scavenger N-acetylcysteine. Furthermore, critical differentially expressed proteins involved in mitochondria-dependent apoptosis and antioxidant defense were identified and profiled by quantitative proteomic analysis, facilitating the understanding of molecular regulation of ROS-induced mitochondria-dependent apoptosis. These outcomes provide insights into the mechanisms underlying liquid storage of goat spermatozoa and enhance the progress of semen storage technology.

Effect of three commercial extenders on sperm motility and fertility in liquid ram semen stored at 15 °C or 5 °C

The effect of different extenders on sperm motility and fertility was evaluated during liquid storage of ram semen at 5 °C and 15 °C. The semen was collected, pooled and diluted in three commercial extenders: Inra 96® (INRA) based on skimmed milk, Biladyl® A fraction (BIL) based on egg yolk, and Ovixcell® (OVIX) based on soybean lecithin. Then, sperm motility was evaluated at 0, 6, 24, 48, 72 and 96 h. In order to evaluate fertility, samples stored at 15 °C were used after dilution in INRA and OVIX. Results showed that progressive motility was significantly higher up to 72 h of storage in sperm samples maintained at 5 °C in comparison with 15 °C, similarly for each tested diluent. When samples were stored at 5 °C in OVIX, kinematic parameters such as velocity (except curvilinear velocity, VCL), trajectory [linearity (LIN), straightness (STR), wobble (WOB)], amplitude of lateral head displacement (ALH) and beat/cross frequency (BCF) were higher than in INRA and BIL. No significant differences in pregnancy rate were detected between INRA (62.6%) and OVIX (58.9%). In conclusion, liquid storage at 5 °C with OVIX extender is an interesting option since non-animal components are used, and this extender offers similar in vitro and in vivo efficacy as other extenders containing animal components.

Effect of addition of melatonin on liquid storage of ram semen at 4°C

Adding a certain amount of antioxidants to semen extender has been shown to improve semen quality. The aim of present study was to elucidate whether the supplementation of melatonin to the Tris-based extender (CTR) could enhance the quality of ram spermatozoa during storage at 4°C. Ram semen samples were collected and diluted with CTR extender containing different concentrations (0, 0.05 (M 0.05), 0.1 (M 0.1), 0.2 (M 0.2) or 0.4 (M 0.4) mM) of melatonin. Sperm routine indicators, mitochondrial activity, total antioxidant capacity (T-AOC) and malondialdehyde (MDA) content were analysed in control and melatonin treatment groups. The higher per cent of motility, plasma membrane integrity, mitochondrial activity and T-AOC activity was observed in M 0.05, M 0.1 and M 0.2 groups compared to control group at 5 days of storage (p < 0.05), while lower percentage of MDA content was observed among these groups (p < 0.05). In addition, there were no significant differences in acrosome integrity among the control and M 0.05, M 0.1 and M 0.2 groups during the experiment. The above results show that the addition of 0.05, 0.1, 0.2 mM of melatonin is beneficial to the preservation of ram semen during liquid storage at 4°C mainly through antioxidative stress.