Comparison between the spermatic parameters of boars during the months of Summer and Winter

The present study aimed to evaluate the influence of the season of the year (temperature and humidity) comparing the spermatic parameters between summer and winter. Five boars were used aging from two to three years old, with weight of 250 to 300kg, from hybrid breed without physiologic alterations and with satisfactory reproductive performance. The ejaculate was collected by digital manipulation once a week of each boar. The evaluated spermatic parameters were the spermatic concentration using a sperm densimeter and Neubauer chamber, and the spermatic morphology. The weather temperature and humidity were measured during the summer and winter months of 2012 and 2013. After obtained the data those were subject of comparison between summer and winter using Student`s T test, at the significance level of 5%. The boars in this experiment represented the control of themselves, since they were used in both seasons (summer and winter) and years (2012 and 2013). The maximum and minimum temperatures during the summer were 29.3°C and 21.7°C, respectively, and for the winter were 28.1°C and 18°C, the mean temperature was 24.86±2.28°C at summer and 24.18±3.41°C (p=0.495).The humidity (%) in the summer was 82.25±10.76 and 81.66±0.75 at winter. Beside the numeric difference of temperature between the seasons analyzed were not found statistical difference (p>0.05). The spermatic concentration estimated with the sperm densimeter was statistically different from the calculated using the Neubauer chamber during winter (256.5±44.54a and 170.9±44.98b, respectively; p<0.001), probably due to a higher level of cellularity in the ejaculate during this season, leading it to a higher opacity. However at summer, no difference was found between the two techniques to achieve the spermatic concentration (243±57.98 by sperm densimeter and 237.9±56.25 by Neubauer chamber; p=0.844). That result reveals the importance of the manual evaluation because any change at the opacity of the ejaculate can be a factor to overestimate the spermatic concentration. The mean ejaculate volume were lower at summer than at winter (261.5±50.22b and 348.5±52.02a mL, respectivelly; p<0.001). The heat stress can cause a hormonal imbalance that could affect the seminal plasma production by the accessory glands (Scheid, Suinos & Cia, v.1, p.25-28, 2002). The major defects were found in higher incidence (p=0.009) at summer (20.1±15, 8%a) than winter (5.25±2.3%b), being higher than acceptable for the specie at summer (Hafez, Reproducao Animal, Ed. Manole, 2004). It was concluded, using these partial results, that the temperature elevation at summer had a negative influence in the sperm quality of the studied boars, showing a lower ejaculate volume, a lower sperm concentration and a higher presence of major defects during the summer season, also the importance of the Neubauer chamber to evaluate the sperm concentration.