Browsing by Subject "Stallion"
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Item Analysis of estrone sulphate, testosterone, and cortisol concentrations around time of ejaculation and potential correlation to sexual behavior and sperm characteristics in stallions(2010-07-14) Seale, JenniferIn the stallion, inconsistent sexual behavior and variable semen quality are common. This reproductive variability has been attributed to differences in circulating hormone concentrations. In order to further examine this relationship, 7 miniature stallions were observed for sexual behavior and semen characteristics. Blood was also drawn from each stallion 15 min before mating (time -15), immediately following ejaculation (time 0) and at times following ejaculation (times +15, +30, and +60). Plasma was later analyzed for concentrations of testosterone (T), estrone sulphate (ES) and cortisol. Semen was evaluated for volume, sperm concentration and progressive motility. Sexual behavior was quantified by assigning a libido score to each stallion, recording reaction time and the number of jumps required for ejaculation. Upon statistical analysis, data revealed both ES and cortisol increased at the time of semen collection (P < 0.05), while T did not. Regression analysis revealed that ES and the ratio of ES to T at times -15, +30, and +60 were negatively correlated to libido scores. Additionally, a positive relationship was found between ES at times -15 and +60 and reaction time, as well as between cortisol at times -15, 0, and +15 and libido scores. No relationship was observed between T and sexual behavior. However, T at time -15 was positively correlated to progressive motility, and the ratio of ES/T at time -15 was negatively correlated to progressive motility. No other association was detected between ejaculate parameters and hormone concentrations. These results not only serve to enhance understanding of stallion hormone profiles, but also provide further insight into the hormonal control of sexual behavior and sperm production. This knowledge can be used to generate improved management techniques for stallions that are inconsistent in sexual behavior and sperm output.Item Effect of Density Gradient Centrifugation on Quality and Recovery Rate of Equine Sperm(2010-07-14) Edmond, Ann J.Density gradient centrifugation of sperm is a common assisted-reproduction procedure in humans used to improve semen quality. The technique allows sperm separation based on their isopycnic points. Sperm with morphologic abnormalities are often more buoyant, leading to their retention above centrifuged density gradients, with structurally normal sperm passing through the gradient. Three experiments were conducted to evaluate the effects of tube size, sperm number following centrifugation, and density gradient volume (height) on stallion sperm quality and recovery rate in sperm pellets following centrifugation. In all three experiments, equine semen was initially centrifuged to increase sperm concentration. In Experiment 1, one-mL aliquots were layered over EquiPure? Bottom Layer (1-Layer) or over-tiered EquiPure? Top and Bottom Layers (2-Layer). For Experiment 2, one-mL aliquots were layered over three different heights of EquiPure? Bottom Layer in 15-mL or 50-mL conical-bottom tubes. For Experiment 3, four different aliquots containing a sperm load of 1-4x were layered over a constant volume of EquiPure? Bottom Layer in 15-mL or 50-mL conical bottom tubes. The tubes were then centrifuged. Resulting sperm pellets were evaluated for morphologic quality, DNA integrity, motility and recovery rate. Sperm-EquiPure? centrifugation yielded improvements in motility, morphology and DNA integrity parameters (P<0.05), as compared to controls. The 1-Layer method resulted in a higher recovery rate than the 2-Layer method (P<0.05). Sperm processed in the 15-mL tubes yielded higher velocity and higher recovery rates than sperm processed in the 50-mL tubes (P<0.05). Within tube type, gradient volume did not impact parameters of semen quality or recovery rate. An increase in sperm number for density gradient centrifugation resulted in a decreased recovery rate (P<0.05) when 15-mL tubes were used.Item Gene Expression in the Stallion Testes(2011-08-08) Laughlin, Andy M.Understanding the genes that regulate spermatogenesis and steroidogenesis in the testis is critical for enhancement of stallion fertility. Stallion testicular samples were used to identify candidate genes by cDNA microarrays that simultaneously assessed expression levels of 9132 genes. First, gene expression was compared between light (spermatogenically active) and dark (spermatogenically inactive) testis tissue of 1.5-year-old horses (n = 3). Ninety-three genes were differentially expressed (35 light specific, 58 dark specific) in matched paired samples. Second, gene expression was compared between testicular tissue of two mature stallions, one with normal quality semen (fertile) and one with poor quality semen (subfertile). A total of 233 genes were differentially expressed (122 in fertile tissue, 111 in subfertile tissue). Of these, phosphodiesterase 3B (PDE3B), steroidogenic acute regulatory (StAR) protein, and outer dense fiber of sperm tails 2 (ODF2) mRNAs, were localized and quantified by in situ hybridization (ISH) in mature stallions and/or in unilateral cryptorchids. ISH revealed differences (P < 0.05) among mature stallions (n = 10) for PDE3B (localized to seminiferous tubules) and StAR protein (localized to interstitial spaces) mRNAs. A positive correlation coefficient (r = .556, p = .025) was found between StAR protein mRNA and plasma concentration of testosterone. Additionally, both gene products were evaluated in 1-year-old (n = 3) and 3-year-old (n = 3) unilateral cryptorchid stallions. Expression of both PDE3B and StAR protein gene was significantly higher in mature, descended testes compared to mature, retained testes and the descended and retained testes of immature, cryptorchid stallions. StAR protein gene demonstrated significantly higher expression in immature retained testes compared to immature descended testes. A precision-cut tissue slice (PCTS) in vitro culture system was evaluated as a potential tool to study equine testes function. Testes from immature stallions (n = 3) were cut into slices (mean slice weight = 13.85 +/- 0.20 mg; mean slice thickness = 515.00 +/- 2.33 ?m) and exposed to medium containing ovine luteinizing hormone (oLH) at concentrations of 0, 5, 50 and 500 ng/ml for 6 h at 32 degrees C. Medium content of testosterone and estradiol was increased 500% and 120%, respectively, by addition of oLH versus that observed for the testis tissue slices treated with 0 ng oLH (control). An oLH concentration-dependent increase in StAR protein mRNA in tissue slices was detected by in situ hybridization; whereas, differences for PDE3B and ODF2 mRNAs were not observed. Collectively, these results demonstrate that the stallion is an excellent model for studying male fertility due to the initiation of spermatogenesis, frequency of cryptorchidism, and routine castration providing useful tissue to use for studying gene expression.