Sperm motility and lactate production at different sperm concentrations

s / Journal of Equine Veterinary Science 34 (2014) 76 76 x106sperm/mL. Sperm recovery rate after centrifugation was lower in low concentration samples (p<0.001). Mean lactate concentration at T0 was the same in all three groups and directly correlated with raw semen volume (r1⁄40.5032; p1⁄40.0103). Lactate concentrations at T0 and T24 were not correlated. Compared to T0, lactate concentration was increased at T24when groupswere pooled, in C1, C4 and C8 groups separately, and lactate concentration was directly correlated with sperm concentration (r1⁄40.6080; p1⁄40.0002). At T24, lactate concentration was lower in C1 samples (p<0.001) when compared to lactate concentrations observed in higher sperm concentrations. In highly concentrated samples (C8), PTM was decreased after 8 hr but not PPM (p<0.01). After 24 hr, low concentration samples showed higher PTM and PPM (p<0.01). PTM and PPM after 24 hr were negatively correlated to lactate concentrations at T0 (r1⁄4-0.4568; p1⁄40.0217 and r1⁄4-0.4684; p1⁄40.0182). Concentrations of TM spermatozoa after 8 and 24 hr were correlated to lactate concentration at T24 (respectively, r1⁄40.5373; p1⁄40.0015 and r1⁄40.5320 and p1⁄40.0017). The same correlation was observed for the concentrations of PM spermatozoa after 8 and 24 hr (r1⁄40.5738; p1⁄40.0006 and r1⁄40.5579 and p1⁄40.0009, respectively). Concentration of NPM after 24 hr of storage was highly correlated to lactate concentration at T24 (r1⁄40.6767; p<0.0001). Fig. 1. Lactate concentration (mmol/L) according sperm concentration in samples and storage. Different letters in superscript indicate statistically different values. 4. Discussion Raw semen parameters are not associated with lactate concentration at T0, except the initial ejaculate volume. These data show that lactate concentration at T0 depends on collection conditions. It also shows that the negative effect of lactate on semen parameters is not observed immediately but during storage. In the present study, semen storage with high sperm concentration is rapidly deleterious for total motility, whereas progressive motility decreases between 8 and 24 hr. This delayed effect of high storage concentrations on progressive motility suggests that insemination with highly concentrated semen should not be performed later than 8 hr. Volume of the raw ejaculate is associated with lactate concentrations at T0 while raw semen concentration is not. Lactate concentration at T0 was negatively associated with progressive and total motility after 24 hr. This suggests that production and composition of seminal plasma could interfere with lactate concentration in raw semen and with its long-term conservation. Seminal plasma components should be studied to determine changes in metabolic products. A direct association between lactate concentration after 24 hr and total sperm concentration was observed, reflecting anaerobic metabolism by spermatozoa. Concentration of NPM spermatozoa was strongly correlated to lactate concentration after 24 hr of storage, suggesting an increased use of anaerobic glycolysis by the subpopulation of non-progressively motile spermatozoa. To conclude, lactate production is associated with total sperm concentration. It negatively affects preservation of total and progressive motility, showing an effect of by-products of anaerobic metabolism on long-term sperm storage. Moreover, our data show that non-progressively motile spermatozoa are highly associated with lactate concentration, and thus, anaerobic glycolysis. More studies are required to determine relative contributions of aerobiosis and anaerobiosis to sperm motility under different storage conditions.