Dairy farmers across the world have been artificially inseminating (AI) their cows since the early 20th century and have been using conventional and sexed semen since. The development of AI was driven by multiple factors, primarily farmers wanting to improve the genetics of their herd, enhance breeding efficiency and to control the spread of diseases.
Before adopting an AI approach, farmers would use a ‘natural breeding’ method, which saw cows mate with bulls without human intervention. This approach allowed for limited control over the genetics inherited by their animals as farmers would typically have to use whichever bulls were local to them.
The adoption of AI meant that farmers could use more superior genetics, from more distant locations.
What is conventional semen?
Conventional semen refers to the traditional form of semen which is taken from the bull and inserted into the cow.
Conventional semen is collected from a bull through an ejaculate obtained by either an artificial vagina or an electroejaculation procedure. The collected semen is then processed to remove seminal plasma and any debris, leaving behind a concentrated suspension of sperm cells in a nutrient medium.
Once processed, conventional semen can be diluted and packaged into individual straws or vials for storage and distribution. Each straw will usually contain a specific dose of sperm cells and a cryoprotective agent to preserve their viability during freezing and storage.
Conventional semen is used for insemination without any manipulation of the sex ratio of offspring.
When conventional semen is used, the resulting offspring will have a natural sex ratio, with approximately 50% being male and 50% being female.
What is sexed semen?
Sexed semen is a specialised type of semen which uses laboratory intervention to remove or sort the sperm cells based on their X or Y chromosomes.
This technology allows for sexed semen to carry a much larger likelihood to produce either a male or female offspring, depending on the desire of the farmer.
A dairy bull calf holds little value for the dairy farmer, due to their inability to produce milk, and lacking the desirable genetics for a strong beef animal. For this reason, dairy farmers would prefer to have only female offspring in the herd, making sexed semen a valuable asset.
It is important to note that sexed semen is not 100% accurate and usually results in a higher percentage of offspring of the desired sex rather than a guarantee.
The use of sexed semen provides breeders with the ability to strategically manage the genetic composition and population dynamics of their herds. It allows for targeted breeding programs, such as increasing the number of female replacements in a dairy herd or producing more male calves for beef production.
Sexed semen has slightly lower fertility rates compared to conventional semen. However, advancements in sexed technology have improved this over time.