Document Type : Research Paper
Authors
- Maryam Rahbar 1
- Mehdi Behgar 2
- Mohammad Rasoul Khoshniyat 1
- Farahnaz Farahnaz Motamedi Sedeh 3
- Parvin Shawrang 3
1 Research Center of Nahadehaye Dami Jahed Co. (NDJ Co.), Karaj, Iran.
2 Nuclear Agriculture Research School, Nuclear Science & Technology Research Institute, P. O. Box: 31485–498, Karaj, Iran.
3 Nuclear Agriculture Research School, Nuclear Science & Technology Research Institute, Karaj, Iran
Abstract
ABSTRACT
Objective: Temperature-Humidity Index (THI) is used to study the effect of heat stress and is one of the critical factors in yield and infertility. This research was conducted to study the effect of THI on motility parameters and sperm motility velocity of Holstein bulls in different months and to study the internal correlation between these parameters.
Method: Meteorological data from the National Meteorological Organization were used to calculate THI. Semen collection and evaluation were carried out at Nahadehaye Dami Jahed (NDJ). Three Holstein bulls were used in this study. Diluted semen was then loaded into straws and frozen after cooling using a programmable freezer. The straws were immediately stored in liquid nitrogen and thawed in a water bath (37°C for 30 s) before evaluation. Sperm kinematic parameters were evaluated using CASA.
Results: The temperature-humidity index was lower in April than in other months and higher in July than in other months. The average temperature-humidity index in spring and summer was 64.00 and 70.67, respectively. Total motility, progressive motility, and slow motility were higher in May than in other months and lower in August than in other months. Among the sperm motility parameters, only beat cross frequency (BCF) and straightness (STR) showed significant differences in different months. BCF was higher in May compared to other months and lower in August compared to other months. However, STR was higher in July compared to other months and lower in August compared to other months. The temperature-humidity index had a significant negative correlation with progressive sperm motility. Regarding the relationship between motility parameters and sperm motility velocity, the results showed a significant positive correlation between total motility with progressive motility and curved line velocity (VCL). Progressive motility was also positively correlated with VCL and BCF. A significant positive correlation was observed between the sperm motility parameters. A positive correlation was observed between the average path velocity (VAP) and the VCL, straight line velocity (VSL), and BCF parameters. There was a positive correlation between the BCF parameter and the VCL and average path velocity (VAP) parameters.
Conclusions: The data show that mild heat stress leads to a decrease in sperm motility parameters and sperm velocity motility parameters. The negative correlation between temperature-humidity index and sperm progressive motility indicates the importance of heat stress on this important parameter. It is suggested that future studies should investigate the relationship between temperature-humidity index and sperm motility parameters with sperm fertility using regression models.
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