TABLE OF CONTENTS
Microscopic Examination of Semen: Advanced Semen Evaluation in Veterinary Practice
Microscopic examination of semen refers to the detailed evaluation of semen under a microscope to assess sperm quality parameters that are not visible to the naked eye.
This examination provides insights into sperm motility, concentration, viability, morphology, and structural integrity, which are crucial for determining the fertility potential of the semen sample.
The following assessments are done during the microscopic examination of semen quality:
- Mass activity
- Individual motility
- Concentration of semen
- Live and dead sperm exam
- Acrosome integrity exam
- Sperm abnormality exam
- Biochemical evaluation of semen
1. Mass Activity
The collective movement of sperms or their wave motion is called as mass activity. It is estimated by keeping a semen drop on a warm glass slide and examining under low power microscope without putting cover slip.
Mass activity may be classified into five grade scale depending upon the wave motion and rate of sperm activity.
The evaluation depends upon the experience of the operator. 5 and 4th grade samples are acceptable. Others should be discarded.
2. Individual Motility
Motility is the most common and extensively used tool for estimating the semen quality. The movement of individual sperm is taken into consideration while estimating the motility.
To assess the individual motility diluted semen (diluted with physiological saline/3% sodium citrate/Tris buffer/Tris-egg yolk extender) is kept on a warm slide and covered with cover slip.
The slide is kept on the stage warmer of the phase contrast microscope and examined under high power.
The various types of motility observed may be:
- Progressive movement: Sperms with very rapid straight forward direction
- Circular movement: Sperms with movement in circular path
- Reverse movement: Sperms moving in reverse manner
- Oscillatory movement: Sperms with jerky movement
The progressively motile are sperms only taken into account while estimating the initial motility. The progressive sperms will cover a distance of 100-120µ in a second.
Based on progressive motility, the semen samples are graded as follows:
| Progressive Motility | Grade |
|---|---|
| 90-100% | Excellent |
| 70-80% | Good |
| 50-60% | Fair |
| 30-40% | Poor |
| 0-20% | Very Poor |
The semen collected after long period of time will have more dead sperms. The sperm with circular motility indicates cold shock to the sperms. The heat/thermal shock also affects the sperm motility.
A good semen sample should have an initial motility of 70%.
