I. Introduction
After the collection of the pig semen, the quality of the boar semen must first be assessed before the semen can be further processed to obtain high-quality semen. Before treating semen, choosing a method that can effectively screen semen is necessary to improve breeding performance on the farm. In the best case scenario, boar semen is evaluated before semen treatment to identify those inferior semen. For stored semen, the total number of active spermatozoa and the shape of the spermatozoa must be checked every day; this will ensure that semen used for artificial insemination is not contaminated. Therefore, the purpose of this article is to describe the method of assessing the quality of boar semen and to indicate which boar semen can enter the laboratory for further processing.
Second, the density
Four basic parameters should be tested when assessing the quality of boar semen: sperm density, vigor, shape, and acrosome integrity. Among them, the two basic parameters of sperm density and vigor are often used to select semen before semen treatment. The reason is that it takes the least amount of time to determine these two parameters and they can be used to calculate the dilution of the semen.
The determination of semen concentration or the total number of sperm is not only a component of the assessment of semen quality, but more importantly, it is used to monitor the health status and reproductive potential of boars; and it is also a major consideration in optimizing the genetic potential of individuals. Correctly assessing the quality of semen is not the only factor that increases the amount of ejaculation per boar and the efficiency of use of the barn. The purpose of the quality assessment of semen is to ensure that there are a sufficient number of viable sperm for artificial insemination.
Third, the vitality of sperm
The vitality of semen is an important aspect of semen assessment. A recent study showed that when sperm motility is less than 62.5% when evaluated and inseminated immediately after sperm retrieval (less than 24 h), the number of litter/litter rate will decline. However, since semen of commercial boars are rarely used within such a short period of time, the semen is generally treated before being transferred to the sow farm. After the semen is stored, its vigor will decrease. Therefore, when assessing boar semen, the minimum activity should be greater than 60%. Many boar stations have established screening criteria for sperm motility between 70 and 80%. The minimum activity of semen after laboratory treatment should be based on the planned storage time before use and the expected decrease in activity during this storage time. In addition, the breeding boar station must consider that the storage condition of the semen in the pig farm and the ability to handle the semen are poorer than that of the boar station. Considering the difference in semen transport between the boar station and the sow farm will help the boar station to select the initial viability acceptance level to ensure that the spermatozoa carrying the semen have a viability above 60.0%.
The method of visually estimating sperm motility by microscopy is the most widely used. Skills and experience have a certain influence on the accuracy of the results. In short, place a small dilution of semen on a warm slide (all dilutions of the semen must be standardized) and cover the coverslip. Diluting the sample to 400 times the objective lens is sufficient to observe all sperm cells, and the overall estimate comes from the observed sperm population. In this way, the experimenter should be trained first. This training first requires the experimenter to estimate the overall sperm motility, and then the experimenter uses a microscope to calculate the total number of sperm in 10 cells in 5 regions and the percentage of viable sperm to total sperm to verify total sperm motility.
Fourth, the appearance
The shape of sperm and the integrity of the acrosome also have an impact on the viability of the sperm. As far as the estimated semen quality is concerned, the evaluation of the sperm shape is more effective than the evaluation of sperm motility to reflect the semen quality. Both of these parameters and sperm motility are crucial in the assessment of semen quality. Together, they decide on semen collection and housing.
The sperm of the movement may not be normal in appearance; however, sperm with low exercise power may be fertilized. However, sperm without the acrosome cannot be fertilized. Assessing semen quality using these three parameters criteria is likely to underestimate the true fertilization capacity of semen and boar semen quality.
As with sperm motility, sperm appearance assessments indicate that when using artificial insemination, a percentage of normal sperm morphology is required to increase sow reproduction. The research data also showed that the appearance of this parameter was used for routine evaluation of sperm. If semen is used, seminal spermatozoa with less than 70% normal spermatozoa should be considered inferior semen. Since the percentage of normal spermatozoa will decrease during the storage period, and because there is a large difference between boar individuals. Therefore, when using long-term storage (>24 h) of semen; the percentage of sperm in the normal form of the semen to be processed initially exceeds 70%.
While examining sperm motility, sperm morphology can be roughly assessed. However, the ideal shape detection uses a microscope, which can distinguish the various parts of the sperm. Accurately assessing the shape of the sperm is calculated by counting the number of normal sperm heads, droplets, and tails, respectively. Pipette 1-2 drops of semen with 1:10 diluted with a diluent and observe with a microscope (400x or 1000x). The percentage of shape can be calculated directly. If semen cannot be detected immediately (
V. Acrosome integrity
The acrosomal membrane covers two thirds of the head of the sperm and contains the enzymes necessary to penetrate the oocyte. Assessment of acrosome integrity is time-consuming, requires more advanced microscopes, and requires skilled manipulation skills. Some studies have shown that acrosome integrity is more representative than sperm motility in assessing sperm quality. Acrosome integrity check is the same as sperm shape check. However, in the detection of single sperm cells, the slides should be placed under a microscope and the differences in sperm acrosome layers should be observed. Semen with an intact acrosome less than 51% is considered to be inferior semen, even if the fertilization rate of the semen may be at the same level. Acrosome integrity assessment uses the same principles as vitality and morphological assessment. When the semen is stored for a long period of time, the normal acrosome percentage is less than 51%. The semen rate of the semen may be very low. The assessment of vitality, appearance, or acrosome integrity does not completely estimate fecundity, but it is a basic manifestation of sperm viability. Compared with predicting litter size and conception rate of boar ejaculation capacity, the above-mentioned estimation method is to influence conception rate and litter size by eliminating inferior semen.
Use of colorants in appearance assessment
It is necessary to have a rough appearance to assess individual boar semen; however, regular and detailed testing may provide an effective quality monitoring method to ensure that the semen is roughly assessed to be consistent with the true appearance of the semen. Detailed evaluation of the appearance of the microscope is required, and staining of the sperm cells is sometimes required. Compared to the total shape detection, it detects a single sperm cell under a high power lens (1000x: oil immersion). For detailed shape detection, the head, middle and tail should be calculated separately. First, a blush stain (commercial shape stain) was mixed with semen in a 1:1 slide slide. This can fully distinguish the slight differences in the morphology of the sperm head. Normally, 100 total sperm cells are counted, and the percentage of normal sperm cells is calculated. Other staining agents used for visual inspection include: sperm staining with Williams stain, acroporus staining with naphthol yellow and erythromycin stain.
Appearance, color and smell
Although microscopic evaluation is the criterion for taking and setting boar semen; however, obvious visual and olfactory properties are a symbol of semen quality. Normal boar semen must have a considerable volume (>150 ml) and be milky like skim milk. Occasionally, semen contains a small amount of blood. This blood is usually from the urethra, giving the semen a slight yellowish color.
The collected semen must not have obvious odor. If it is, it may be a poor sanitary environment during semen collection; it may also be an irregular Boer sanitation process during semen collection. The scent that is emitted is likely to be a reflection of the foreskin fluid (urine), which is usually loaded with large amounts of bacteria and foreign contaminants. The use of antibiotics in semen dilutions can control the growth of pathogens during storage of semen and does not significantly reduce or prevent bacterial contamination during semen collection. Therefore, it is necessary to check whether the semen has any odor, and if it is found that the semen has an odor, it should be discarded. In addition, routine periodic insemination training should be available on most boars. Bacteria can multiply in poor environmental conditions and can be tested in the laboratory. Although semen used for insemination is almost inevitably accompanied by bacteria, there are few reports on the relationship between bacterial shape, content, and fertility. However, bacterial contamination is associated with decreased semen preservation time, semen agglutination, and uterine infectivity. Therefore, bacterial contamination in semen should be tested regularly to identify sources of contamination to reduce semen contamination. Table 2. Lists some of the more common bacteria found in boar semen and their possible origins.
Temperature stimulation and agglutination
Semen is not delivered directly to the laboratory after collection (ie between the barn and the laboratory or the repository), and it is important to consider the effects of temperature fluctuations on sperm. Rapid cooling can lead to cold shock of sperm. When viewed under a microscope, this phenomenon is obvious; some sperm tails are wrapped around the head curled or tightly hovering below the sperm head. By microscopic observation, a normal spermatozoon can normally exist in semen; however, when the temperature is less than 32[deg.] C., more than 10% of the tail curled sperm apparently shows a cold shock phenomenon. However, we should not discard these semen and should consider direct dilution with a diluent (because it is at the same temperature to prevent further damage).
A lot of data show that semen agglutination has a certain influence on fertility. The reason is that the sperm cells in the clot cannot move. Maybe it's because the sperm cells have been damaged or ejaculated when they pass through the testicles. Other causes of semen agglutination may include excessive temperature variations and bacterial contamination during transport.
When calculating sperm density, it is important to consider the actual degree of agglutination, even if there are few reports of semen clots affecting fertility. However, when diluting semen is measured with a spectrophotometer or sperm counts are calculated with a hemocytometer, the number of viable sperm may be underestimated. Observed under the microscope, sperm can sometimes be seen moving inside the clot; however, there is insufficient evidence that these sperm cells will separate after fertilization. Therefore, regardless of the physical appearance of the clot, the entire sperm count should be calibrated based on the percentage of semen clot present. The clots in semen may be related to the interaction of boars, boars and semen diluents, and semen management.
summary
The normal and minimum values ​​of the semen quality parameters. The most important thing is to remember the values ​​of the acrosomal parameters that are difficult to accurately detect and that are difficult to approximate. Sperm predisposition and specimen slides may significantly affect sperm counts. For example, the acrosome can only be seen when the sperm is lying flat on a microscope slide. We offer a method that is as good as any other assessment of the potential insemination ability of boar semen. Semen that meets one or more of the quality parameters in the assessment of boar semen quality does not completely guarantee the quality of semen. Due to the poor propagation of semen in the sow farm, the reduced reproductive performance ultimately comes down to the source of the semen.
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