Congenital Sperm Cell Defects in Male Animals: Causes of Impotentia Generandi

Congenital sperm cell defects in male animals are a significant cause of Impotentia generandi. These defects originate during the developmental stages of spermatogenesis, often due to inherited genetic abnormalities or chromosomal anomalies.

Hereditary or congenital defects in sperm cells include:

1. Dag defect
2. Returned tail and narrow head defect
3. Knobbed acrosome defect
4. Corkscrew defect
5. Diadem defect
6. Pseudo-droplet defect
7. Decapitated sperm defect

1. Dag Defect

In Dag defect, up to 80 percent of the spermatozoa have strongly coiled, folded, disrupted, or split tails.

The fibers of the axial filament appear normal in the testis but become abnormal as the cells reach the cauda epididymis.

This defect is hereditary, and recovery has not been reported. Fertility is reduced, and affected animals may be sterile.

Confirmatory diagnosis is made using electron microscopy. The defect has been recorded in Danish Jersey bulls.

2. Returned Tails and Narrow Heads Defect

Returned tails and narrow heads defect is a genetic defect reported in jersey bulls with coiled or returned tails with a lowered motility rate.

3. Knobbed Acrosome Defect

The acrosomal cap is enlarged 6–8 times in the knobbed acrosome defect. Examination of an India ink smear reveals the presence of highly refractive cyst formation in the anterior part of the sperm head.

The motility of the affected sperm is usually not impaired. Affected bulls are sterile.

This hereditary defect is seen in bulls, boars, and dogs, but is most commonly observed in Friesian bulls and is caused by an autosomal recessive gene.

4. Corkscrew Defect

In the corkscrew defect, the midpiece of the affected sperm appears twisted like a corkscrew, in contrast to the normal cylindrical shape.

This abnormality is caused by an irregular distribution of the mitochondrial sheath, along with a high incidence of persistent proximal droplets in the affected sperm.

It is commonly observed in aged bulls of several exotic breeds. The defect results from progressive testicular degeneration, leading to a decline in sperm count.

Recovery from the corkscrew defect is rare.

5. Diadem Defect

In the diadem defect, affected sperm show a number of small red-colored spots located along the nuclear ring, resembling a row of pearls, a necklace, or a diadem.

This can be distinctly observed using eosin-nigrosin staining. The defect indicates disturbed spermiogenesis, and recovery is common.

The motility of individual affected sperm is not impaired; however, overall sperm motility in affected bulls is reduced.

6. Pseudo-droplet Defect

The pseudo-droplet defect is located in the center of the midpiece and appears as rounded, elongated, or irregularly thickened areas.

The midpiece is often bent at the site of the defect. This defect is sometimes mistaken for a protoplasmic droplet.

Some of the defective sperm are alive, but the fertility of the affected bull is reduced. This defect is common in Friesian bulls.

7. Decapitated Sperm Defect

In decapitated sperm defect, more than 50 percent of sperm show separation of loose heads and tails. Detached tails are bent around a distal droplet, and most of the tails exhibit active motility.

This defect is hereditary in nature, and affected bulls are sterile. It is mostly seen in the Guernsey breed.