Arabian Stallions Research Articles

Arap aygırlarında spermatolojik parametrelerin sezonun farklı dönemlerine göre değişimlerinin değerlendirilmesi

In this study, determining of the variations on spermatological characteristics of Arabian stallion semen in the different periods of the breeding season is aimed. The periods have been described as the beginning of the season (BS: 15th February – 15th March), mid-season (MS: 15th April – 15th May), and end of the season (ES: 30th May – 30th June). A total of 7 Arabian stallions that were 5-10 years old, with body condition scores between 3-3.5 and without any problems in terms of general and reproductive health, were enrolled in the study. In total, three semen samples were collected from each stallion, once in each period. Then, these samples were evaluated in terms of volume, concentration, total motility (TMOT), progressive motility (PMOT), viability, high mitochondrial membrane potential (HMMP), acrosome integrity (AI), capacitation index (Ci), and lipid peroxidation (LPO) parameters, which were analyzed by computer assisted sperm analysis and flowcytometry devices. As a result, the differences in volume, concentration, TMOT, and PMOT between the BS, MS, and ES periods were statistically insignificant (p>0.05). The lowest viability values were determined in the BS period (p

The optimum concentration of soya-lecithin for replacing egg yolk in INRA-82-modified semen extenders improved the cryopreserved semen quality and DNA integrity of Arabian stallions

The cryopreservation of stallion spermatozoa varies greatly between animals. Different equine semen extender supplements were invented to maximize the post-thaw semen quality. Soy lecithin is one of those additives that contain plant origin phospholipids used to replace egg yolk to minimize disease transmission. This study aimed to determine which concentrations of soy lecithin can replace egg-yolk in modified INRA-82 semen extenders for the cryopreservation of horse semen. Semen was collected from six Arabian stallions and extended with modified INRA-82 semen extender supplemented with 0.0, 1.25, 2.50, and 5.0% soya lecithin. Frozen-thawed sperm motility was measured at 0, 1, 2, and 3 h. Viability index, sperm plasma membrane integrity (SPMI), and acrosome integrity in addition to the comet assay non-fragmented DNA, head DNA, tail DNA, tail length, and tail moment were statistically analyzed. The addition of 2.5% soya lecithin had the highest post-thaw sperm motility at 0, 1, 2 h (P < 0.001) and 3 h (P < 0.0001), the optimum viability index (P < 0.0001), SPMI (P < 0.05), acrosome integrity (P < 0.0001), non-fragmented DNA (P < 0.01), DNA in the comet head (P < 0.05), minimum DNA in the comet tail (P < 0.05), shortest comet tail length (P < 0.0001), and lowest comet tail moment (P < 0.01). Soy lecithin at concentrations other than 2.5% deteriorated all post-thaw semen parameters. Soy lecithin (2.5%) can replace egg yolk in the modified INRA-82 semen extender for the cryopreservation of good-quality stallion semen.

Between Purity and Pragmatism: The Politics of Purebred Breeding and Racing of the Orlov Trotter in Imperial Russia, 1880–1915

Towards the end of the nineteenth century, trotting racing had become a popular urban pastime in imperial Russia, largely due to the Imperial St. Petersburg Society of Trotting Horse Breeding. Founded in 1860, this semi-state organization ran tri-annual racing events, managed the totalizator – a pari-mutuel betting system – and invested in nationwide breeding programmes. It notably championed the Orlov Trotter, a famous Russian horse breed originating from crossbreeding between Dutch, English, and Mecklenburg mares and Arabian stallions. Building on recent scholarly ideas that the evolution of horse breeds is a nuanced and complex journey rather than a straightforward process, this study explores the intricate politics of equestrian breeding and racing, focusing on the Society’s failed efforts to recast the Orlov Trotter as a purebred. International competition, especially from American trotters, and local urban politics intensified after the totalizator’s 1880s introduction. This led to financial dilemmas and ethical concerns around gambling. In response, the Society pivoted to support purebred breeding, adopting nationalist rhetoric to preserve the ‘pure Russian horse’, and gaining broader support. By 1915, once the Society stabilized financially, it reverted to advocating crossbreeding, rejecting the idea of breed purity.

Modulatory effects of ergothioneine on behavioural responses of Arabian stallions following a 2,000 m race during the rainy and hot-dry seasons in a tropical environment

Abstract Experiments were performed to determine the effects of ergothioneine (ERG) on behavioural responses of stallions to exercise during hot-dry and rainy seasons. Eighteen healthy stallions were divided into three groups of six horses each. Group I (ERG + Exercise) was treated with ERG before exercise, group II was treated after exercise (Exercise + ERG), and group III (Exercise only) was not treated but subject to exercise. The stallions were subjected to a race of 2,000 m at maximum speed. The time spent standing by the horses in the ERG + Exercise and Exercise + ERG groups (1430.31 ± 30.73 s/30 min and 1403.32 ± 32.43 s/30 min, respectively) were higher (P < 0.0001) than the time spent standing in the Exercise-only group (1033.26 ± 21.19 s/30 min). The number of times the stallions bit their cribs per 30 min in the ERG + Exercise (0.38 ± 0.02/30 min) and Exercise + ERG (0.67 ± 0.0530 min) groups was lower (P < 0.0001) than that recorded in the Exercise-only group (3.51 ± 1.7730 min). It was concluded that ERG modulates behavioural responses to exercise in stallions, and the agent may be beneficial in alleviating exercise-induced stress responses and improving the welfare of horses post-exercise.

Reproductive Performance of Tunisian Arabian Stallions: A Study on the Variance and Estimation of Heritability.

A consistently high level of stallion fertility plays an economically important role in modern horse breeding. To better understand the factors affecting variation in stallion fertility, we have performed a statistical analysis study on some breeding factors: year of breeding, stud farm, age of the stallion, number of covered mares per stallion, reproduction methods, and age of the mare. This work was conducted on 94 purebred Arabian stallions in four different regions of Tunisia. The results showed an increase in the number of stallions during the study period, ranging from 11.33% in 2011 to 13.29% in 2018. Sidi Thabet's stud farm contained the highest number of purebred Arabian stallions. The majority of stallions were between 15 and 21 years old and had covered 1 to 20 mares; 95.19% of stallions were used in natural mating (Nat); 50.36% had low fertility, 17.69% had medium fertility, and 32.3% had excellent fertility according to fertility standards. Depending on the year and stud, there was a variation in fertility per cycle (FERPCE) and end-of-season fertility (FERPSE) of the stallions. The highest average FERPCE and FERPSE values were obtained using artificial insemination with fresh semen (AIF). Analysis of FERPCE and FERPSE showed that the model used in our study explained 40.21% of total variability observations for FERPCE and 42.1% for FERPSE. The used statistical model showed that the breeding year, the stud, the age of the stallion, the number of covered mares by stallions and the method of reproduction significantly affected both FERPCE and FERPSE (with p = 0.001). Low to moderate heritability estimations for FERPCE (hs2 = 0.08) and FERPSE (hes2 = 0.36) were obtained.

Molecular docking and experimental validation of the effect of ergothioneine on heat shock protein-70 following endurance exercise by Arabian stallions

BackgroundExercise-induced oxidative stress is a challenge in equine sports. This study aims at determining the effects of ergothioneine on heat shock protein-70 (HSP-70) following the stress of an endurance exercise of 30 km by Arabian stallions. Molecular docking was also done to investigate the interaction between the ligand ergothioneine and heat shock protein-70 using sulfogalactosylceramide and sulfogalactoglycerolipid as standards.The study involved a total of 18 clinically healthy stallions, with an average age of 6.7 ± 2.4 years and an average weight of 411.54 ± 12.46 kg. Only clinically healthy stallions were selected as subjects. The stallions were divided into two groups of nine stallions each. Group I (ERGX) was administered ergothioneine at a dose of 0.02 mg/kg once daily orally for four weeks while group II (ERGN) was not administered ergothioneine. The activities of the antioxidant enzymes superoxide dismutase, catalase, and glutathione peroxidase were determined in the two groups before and post-exercise. The concentrations of malondialdehyde and HSP-70 were also determined.ResultsThe results obtained showed that the activities of the antioxidant enzymes and concentration of HSP-70 were higher (P < 0.05) in the ERGX group compared to the ERGN group. The concentration of malondialdehyde was however lower in the ERGX group. Following molecular docking, ergothioneine and the selected standards have common amino acids at the site of interaction with the target protein (HSP-70) suggesting that ergothioneine may have a modulatory effect on the synthesis of HSP-70.ConclusionThe results obtained indicated that ergothioneine modulated the synthesis of HSP-70 and the biomarkers of oxidative stress. It was therefore concluded that ergothioneine may be beneficial to horses subjected to endurance exercise.

Ultrasonographic & biochemical analysis of thyroid bio-architecture for further pharmacological intervention in adult Arabian stallions & mares

Based on the growing attention to the Arabian horses with a lack of records regarding their normal physiological parameters, which are critically vital for disease diagnosis &convenient drug administration, we give great attention to their thyroid gland normalcy. The thyroid gland is one of the key players in regulating many physiological processes. Therefore, we tackled thyroid biology & morphology in 14 Arabian stallions & 18 Arabian mares from the beginning of March to the middle of April on animals from 4 to 19 years old. First, the blood samples taken from their jugular vein were used for hematological profile, lipid profile, glucose-coagulation axis & thyroid profile. Moreover, thyroid gland dimensions & volume were estimated using ultrasonography. Noteworthy, Arabian mares have significantly higher MCH & relative eosinophils than Arabian stallions, while Arabian stallions have significantly higher glucose levels than Arabian Mares. Interestingly, this study found that Arabian horses have a high level of Total T4 & low level of platelets count compared to other horses. These results pointed to the deiodinase inhibitors as a possible target therapy for hyperthyroidism & thyroid cancer in Arabian horses, making surgery a second option. Also, these results refer to the caution required before giving Arabian horses high plasma protein bounded drugs, especially anticoagulants. Also, sonographic results showed that the left lobe is larger than the right lobe in both genders, & the lobes volume is larger in Arabian horses compared to others. These results would guide the veterinarian during diagnosis & thyroidectomy.

Genotypic study of Tunisian Arabian stallions

Diversity of Arabian stallions distributed throughout the territory of Tunisia has been evaluated. Seventeen microsatellite markers were used for the determination of genetic variation. A total of 95 alleles were detected in the 50 stallions studied. The number of alleles per locus ranged from 2 to 9 with an average of 5.6. The observed mean number of genetically diverse alleles (Na) was 5.6 (0.44). The mean number of expected alleles (Ne) was 3.42 (0.28). The average expected and observed heterozygosity was approximately 0.675 (0.026) and 0.593 (0.044), respectively. Principal component analysis showed the presence of 2 subpopulations in the studied sample set. These findings demonstrate the potential of microsatellites as a tool for designing and controlling animal breeds. Results show that the population under study has sufficient levels of genetic variations, which can be used as a foundation for developing plans for species conservation and long-term sustainability.

Relation of seminal plasma trace mineral in the Arabian stallion’s semen with the semen characteristics and subsequent fertility

BackgroundSeminal plasma contains several microelements like Zn, Fe, Se, and Cu that affect sperm motility and male fertility. Biochemical evaluation of seminal plasma trace elements is important for assessing fertility and diagnosing male infertility. AimsThe present study was designed to evaluate the effect of seminal fluid trace elements on sperm parameters and fertility in Arabian horses. MethodsNinety-four ejaculates from 25 Arabian stallions (4–27 years old) were used to investigate the effect of seminal fluid trace elements on semen parameters and fertility. Data divided according to season, stallion age, and fertility of stallions. The concentrations of Zn, Fe, Se, Cu, Cr and Mo were determined using an atomic absorption spectrophotometer. Percentage stallion fertility estimated by mares that conceived on their first cycle. Data were analyzed by ANOVA using SPSS statistical software program (2013), version 22.0. ResultsThere was a significant effect of season on semen volume, pH, Fe, Se, Cu, Cr, and Mo. Stallion age had a significant effect on pH, sperm motility, concentration, total motile sperm count, sperm abnormalities, Zn, and Fe. Sperm motility was higher (P < 0.05) and sperm abnormalities were lower (P < 0.05) in group IV (>70% fertility) than in group I (infertile) and group II (<50% fertility). Sperm abnormalities were low in group IV and high in groups I and II. Seminal plasma Zn and Cu levels were higher (P < 0.05) in groups III (50_70% fertility) and IV than in group I. Fe levels were lower (P < 0.05) in group IV than in groups I, II, and III. Seminal plasma Mo concentrations were higher (P < 0.05) in group III than in group I. ConclusionsHigh seminal plasma concentrations of Zn, Se, Cu, and Mo and low Fe concentrations are associated with improved stallions' semen parameters and fertility.

СРАВНИТЕЛЬНЫЙ АНАЛИЗ БИОХИМИЧЕСКИХ ПОКАЗАТЕЛЕЙ СПЕРМОПЛАЗМЫ ЖЕРЕБЦОВ С НОРМАЛЬНОЙ И НИЗКОЙ ПРОГРЕССИВНОЙ ПОДВИЖНОСТЬЮ СПЕРМАТОЗОИДОВ ПОСЛЕ КРИОКОНСЕРВАЦИИ

The aim of this work was to perform a comparative analysis of the biochemical parameters of spermoplasm of stallions with normal and low sperm progressive motility after cryopreservation. Seminal plasma of 34 Arabian stallions was collected during the breeding season (February-May). The activity of H+-ATPase was determined on the SF-2000 spectrophotometer (OKB Spectrum LLC, Russia), the activity of alkaline phosphatase (ALP), creatine kinase (СK), alanine aminotransferase (ALT), aspartate aminotransferase (AST), α-amylase (AA), lactate dehydrogenase (LDH), as well as the concentration of triacylglycerin (TAG), glucose and fructose - on a biochemical analyzer AU 680 (Beckman Coulter, USA), cytochrome oxidase activity, lactate and citrate concentration - on a semiautomatic analyzer Stat Fax 1904+ (Awareness Technology Inc, USA). The succinate content was determined on an IF analyzer StatFax 3200 (Awareness Technology Inc, USA). Statistical analysis was carried out using the Statistica 10 program and the nonparametric Mann-Whitney U-test. It was found that in the spermoplasm of stallions with low progressive sperm motility after freezing-thawing, the activity of ALT (p=0.012), AST (p=0.012), LDH (p=0.017) and H+-ATPase (p=0.037) is statistically significantly higher than in the spermoplasm of stallions with normal progressive sperm motility after cryopreservation. The results obtained may be associated with damage to the cytoplasmic and mitochondrial membranes of spermatozoa, which leads to a drop in ATP synthesis. The latter may be accompanied by a decrease in progressive motility in spermatozoa after cryopreservation. The research was supported by the grant of the Russian Science Foundation No. 20-16-00101.

Ergothioneine Modulates Biomarkers of Oxidative Stress, Biochemical Profiles and Rectal Temperatures of Arabian Stallions Following Exercise in A Hot-Humid Environment

These experiments were performed to determine the effect of ergothioneine (EGT) and environmental parameters on some physiological profiles of Arabian stallions following an 1800 m race in a hot-humid environment. Twelve stallions having a mean weight of 401 ± 7.33 kg and aged 5.28 ± 1.14 years were used as subjects. They were divided into two groups of treated stallions (n = 6) and untreated stallions (n = 6). Group I which was the experimental group was administered with EGT (0.5 mg/kg orally)every week for two months while group II which served as controls was not treated. The temperature and the relative humidity of the experimental site were determined for six days and on the day of the experiment. The temperature-humidity index (THI) was also calculated. Vital parameters and some biochemical parameters of all stallions were determined before the commencement, immediately after, and one hour after the exercise. Some biomarkers of oxidative stress and serum biochemical parameters (aspartate aminotransferase, creatinine and lactate dehydrogenase) of the stallions were also determined.The biochemical parameters were higher (P &lt; 0.05) in the untreated group than in the treated group. The results obtained showed that EGT lowered the rectal temperature and modulated biomarkers of oxidative stress and biochemical profiles.

Influence of the concentrations of essential and toxic elements in the blood serum on the indicators of sperm quality in Arabian purebred stallions

Analysis of trace elements in blood serum can be an important tool for monitoring micronutrient supply in stallions in order to maintain reproductive health. In this regard, the purpose of this study was to determine the relationship between the concentrations of macro- and microelements in the blood serum of stud stallions with the qualitative characteristics of fresh sperm and sperm after cryopreservation and thawing. The studies were carried out on purebred Arabian stallions (n=50). As a biomaterial for studies, we used blood serum, fresh and thawed sperm after cryopreservation. The elemental composition of seminal plasma was determined by 25 chemical elements Co, Cr, Cu, Fe, I, Mn, Se, Zn Ca, K, Mg, P, B, Li, Si, V Na, Ni, Sn, Hg, Sr, Al, As, Cd, Pb) by ICP-DRC-MS methods. It was found that the concentrations of Mg and Co in the blood serum positively correlate with the qualitative characteristics of the sperm of Arabian purebred stallions. Wherein, the optimal range of concentrations of Mg in the blood serum, typical for stallions with relatively high indicators of sperm quality, is 22.64 to 27.05 μg/g; Co – 0.001 to 0.0015 μg/g.

Black Fungi in Arabian Horses: Scanning Electron Microscopy Study of Cutaneous Equine Mucormycosis Caused by Mucor indicus for the First Time in Eastern Province, Saudi Arabia

Four Arabian mares and two Arabian stallions had been admitted to a University Veterinary Medicine Teaching Hospital because of a mass in its right nasal cavity. Horses numbered from 1 to 6. All infections in horses occur in the area of the nostrils. Horse 1 was an Arabian mare of 5-year-old 390kg and had a mass (3.5x3.5 cm in diameter) in its right nasal cavity. Horse 2 was an Arabian mare of 7-year-old 370.0kg and had a mass (4.0x5.5 cm in diameter) in its right nasal cavity. Horse 3 was an Arabian mare of 6.3-year-old 379kg and has a mass (9.0x4.0 cm in diameter) in its right nasal cavity. Horse 4 was an Arabian mare of 5.8-year-old 395.3kg and had a mass (5.0x5.5 cm in diameter) in its right nasal cavity. Horse 5 was an Arabian stallion of 8.2-year-old 421kg and had a mass (4.0x5.5 cm in diameter) in its right nasal cavity. Horse 6 was an Arabian stallion of 7-year-old 471kg and had a mass (4.0x5.5 cm in diameter) in its right nasal cavity. Endoscopic examination of upper respiratory tract revealed a mass that blocked most of the right nasal passage. The mass covered by a bulky pile of ulcerated granulation tissue exuding thick serosanguinous fluid. A specimen of mucor indicus was isolated from a polypes sample and its identity confirmed through LSU rRNA sequence analysis. Microbiological examination showed abundant fungal growth and the strain corresponded to mucor indicus. On histological examination, the dermis and subcutaneous tissue showed the presence of mucor indicus. Mucor indicus confirmed by scanning electron microscopy and light microscopy. Clinical recovery occurred 3 weeks after administration of amphotericin B (40.0 mg/kg body weight/day). The current study concluded that mucor indicus was verified in eastern province of Saudi Arabia for the first time.

PSXV-13 The activity of thiol cathepsins in seminal plasma of stallions with different percentages of viable sperm after freezing-thawing

Abstract The aim of this work was to study the activity of cathepsins B, L and H in the seminal plasma of stallions with normal (&amp;gt;25%, n = 11) and low (&amp;lt; 25%, n = 13) percentage of viable sperm after freezing-thawing. Sperm of 24 Arabian stallions aged from 5 to 20 years (12.1 ± 4.8 years on average) was collected during the breeding season (February-May). The activity of cathepsins in spermoplasm was studied by the spectrofluorometric method (System 3 Scanning Spectrofluorometry, Optical technology devices, inc. Elmstord, New York, 10523) by Barrett&amp;Kirschke. The viability of the sperm was determined after its freezing-thawing. Sperm smears were eosin stained and live:dead-ratio was examined using an Olympus BX41 phase contrast microscope (Olympus Corporation, Japan). The significance of differences in the studied groups was determined using the Mann-Whitney U-test. There were no significant differences in the activity of catepsins B and L in the spermoplasm of stallions with normal and low percentages of viable spermatozoa after freezing-thawing. It was found that in the group of stallions with a normal percentage of viable spermatozoa after freezing-thawing, the activity of cathepsin H in the spermoplasm was significantly higher than in the group with a low percentage of viable spermatozoa (P = 0.0219). Free radicals formed during freezing-thawing of sperm can damage cell membranes, leading to loss of sperm viability. Thiol cathepsins are involved in the degradation of oxidatively modified proteins and, apparently, it is cathepsin H that is most actively involved in this process in the sperm of stallions. We assume that the low activity of cathepsin H in the seminal plasma of stallions with a low percentage of viable spermatozoa indicates a high involvement of this enzyme in the protection of sperm membranes from oxidative damage. The research was supported by the Russian Science Foundation grant No. 20-16-00101.

Measurement of the reproductive efficiency of Arabian stallions intended for AI in Algeria

The aim of this study was to determine the reproductive efficiency of Arabian stallions presented at CNIAAG and selected for an artificial insemination (AI) program. Ten Arabian stallions between 8 and 15 years of age were subjected to an analysis of the reproductive parameters. Assessment of sexual behaviour, testicular measurements and appreciation of semen quality collected with the help of artificial vagina was done. There was a significant correlation between the sexual behaviour, the spermatic parameters and the testicular parameters, especially between the number of mounts with the motility and the daily sperm ejaculated (DSP) (r=0.99). The testicular volume total and mounts was highly correlated to the average volume of ejaculate (73.33 ± 60.27 ml) and total Sperm concentration (billions) (r=0.99) which allowed us to produce 38 straws intended for the preservation. Based on the results, it is concluded that there is a positive correlation between (TSW) and motility, the various measurements of testis size were highly correlated with each other; and consequently to predict the fertility of the stallions from the testicular measurements.

Haematological profiles and erythrocyte fragility of Arabian stallions subjected to a 2000-m maximal race following administration of ergothioneine

Haematological profiles and erythrocyte fragility of Arabian stallions subjected to a 2000-m maximal race following administration of ergothioneine

Effects of Spermine and Spermidine supplemented extenders on post-thaw Spermatological Parameters in Stallion Semen Cryopreservation

In this study, the effects of polyamines, Spermine and Spermidine, on long-term preservation and post-thaw spermatological parameters were evaluated. Moreover, determination of the most suitable polyamine and its dose that can be added to standard extenders were aimed. Four adult Arabian stallions were used in the study. Five ejaculates were collected from each of four stallions via artificial vagina two days interval. Each ejaculate was divided into 13 aliquots. INRA96 (95,5%), egg yolk (2%), and glycerol (2,5%) were used as a control extender. Extenders of experimental groups were prepared with different doses of Spermine and Spermidine (0,1 mg/ml; 0,2 mg/ml; 0,4 mg/ml; 1 mg/ml; 2 mg/ml; 4 mg/ml). Stallion semen that were cryopreserved with Control and experimental extenders were evaluated in terms of Total Motility, Progressive Motility, Plasma Membrane Integrity, Capacitation Index, Acrosome Integrity and DNA Fragmentation Index. At the end of the evaluations, it was determined that 0,2 mg/ml Spermine and 0,4 mg/ml Spermidine showed better Total Motility and Progressive Motility, numerically. On the other hand, it was observed that 4 mg/ml Spermine and Spermidine had the lowest statistically significant values (p < 0,001). While statistically similar differences were obtained between groups in terms of the Plasma Membrane and Acrosome Integrity, it was determined that all experimental groups had lower and statistically significant values in terms of Capacitation and DNA Fragmentation Index (p < 0,001). As result, it was observed that the stallion semen cryopreservation success can be increased by the addition of 1–2 mg/ml Spermine that had effective protection on Capacitation and DNA Fragmentation Index without damaging other spermatological properties.

Effects of Adding Cysteine or Ascorbic Acid on the Quality of Frozen Semen from Arabian Stallions

Effects of Adding Cysteine or Ascorbic Acid on the Quality of Frozen Semen from Arabian Stallions

Monthly Evaluation of Testicular Biometry and Sexual Behavior With Respect to Seminal Aspects of Arabian Stallions Under Subtropical Conditions in Kuwait

Monthly Evaluation of Testicular Biometry and Sexual Behavior With Respect to Seminal Aspects of Arabian Stallions Under Subtropical Conditions in Kuwait

Modulatory effects of melatonin on erythrocyte indices in Arabian stallions following a 30-km sub-maximal exercise

Experiments were performed to determine the effects of melatonin on erythrocytes indices in Arabian stallions following a sub-maximal exercise of 30 km. Twelve, apparently, healthy stallions of average age 6.3 ± 4.4 years and mean weight 403.44 ± 12.46 kg were used. They were divided into two groups of six stallions each. The stallions in MT which was the experimental group were administered with melatonin before exercise while stallions in the second group (NT) which served as the control were not administered with melatonin. Erythrocyte count in the MT group was higher (p = 0.023) than the count obtained in the NT group. Packed cell volume of NT group was lower (p = 0.038) than the value obtained in the MT group post-exercise. Haemoglobin concentration of the MT group was higher (p = 0.041) than the value obtained in the NT group after exercise. The values of mean corpuscular volume, mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration of the MT group were higher than the corresponding values recorded in the NT group (p = 0.033, 0.029 and 0.025 respectively). It was concluded that melatonin enhanced erythrocytes indices in the stallions studied.