Sexed semen may or may not give beef producers an advantage in maximizing their breeding program. It depends on the producer’s breeding goals.
Sexed semen technology has been available for more than a decade and is widely used in dairy operations for selecting heifers. However, the process of sexing semen is still tedious, making the sperm costly. The process also slightly hampers sperm in their ability to swim, so pregnancy rates related to sexed semen are about 10 percentage points lower than pregnancy rates with unsexed semen, for example 50 percent instead of 60 percent.
“Sexed semen is effective in increasing the percentage of heifer calves,” Seidel said, “which is why it works so well in a dairy operation. If a beef producer wants to expand a herd or sell replacements, sexed semen may be a good choice.”
In averages of thousands of animals, 49 percent of calves born are heifers. A few of those will be sterile freemartins. It isn’t unusual to have just 40 percent heifers from 100 consecutive calvings. Sexed semen can raise the ratio of heifers born to 90 percent, allowing for rapid herd expansion and decreasing risk of introducing disease through purchased animals.
Sexed semen typically costs between $15 and $20 more per straw. It is packaged in 0.25-ml straws, which requires a different insemination gun than the standard 0.5-ml straws.
“There’s a slight theoretical advantage in semen quality with use of the smaller straws,” Seidel said. “But they require more careful handling due to the larger surface to volume ratio compared with the larger straws. Three seconds is the absolute maximum time for moving the straws from one liquid nitrogen tank to another without damaging the sperm. The same is true for moving the straws from the tank to the thaw bath.”
Producers who want to increase selection intensity by choosing genetically superior dams of replacements may also benefit from using sexed semen.
“Without use of sexed semen, nearly half the females in a herd must be bred for herd replacement in order to maintain herd size,” Seidel said. “With sexed semen, only 25 percent of females would need to be bred for replacements. Sexed semen from superior males intensifies selection to an even greater degree, especially if a producer is selling breeding stock. The dams not needed for replacement matings could be bred to terminal cross sires, increasing overall income of the operation.”
First-calf heifer breeding programs may also benefit from use of sexed semen using sires that produce a low percentage of difficult births.
“The majority of dystocias are due to bull calves, which average about 5 pounds heavier in birth weight than heifer calves,” Seidel said. “A large study in New Zealand (1986) showed death losses from birth to weaning with first calf heifers were 10 percent for heifer calves and 18 percent for bull calves, mostly due to birthing difficulties. Using bulls that sire a low percentage of calves with difficult birth plus sexed semen to produce 90 percent heifer calves could decrease birthing issues substantially.
“An additional benefit is that these first calf heifers should be genetically superior to older cows in the herd, so resulting calves would be excellent replacements,” Seidel added. “In my opinion, this will be one of the most important uses of sexed semen, both in dairy and beef cattle production.”
Use of sexed semen is also valuable for in vitro fertilization (IVF), super ovulation and embryo transfer programs.
“The first calves produced with accurately sexed semen resulted from IVF,” Seidel said. “IVF requires many fewer sperm than artificial insemination. Accuracy of sexing sperm was 90 percent. With IVF or superovulation, a producer may want bull or heifer calves, depending on which sex was most valuable to their breeding objectives. Sexed semen would also be valuable in producing a large number of full brother bulls from genetically superior dams. Several companies provide IVF services using sexed semen. The semen from some bulls is more successful than others in IVF. One issue with this kind of program is cost.”
In superovulation programs, use of sexed semen reduces the number of embryos suitable for transfer by about 30 percent to 50 percent. However, nearly all donor cows receive embryos of the desired sex, reducing loss of time and resources in producing the “wrong” sex.
“It’s wise to consider that, in selecting the sex of cattle, we want to be cautious about saturating the market with either heifer or bull calves,” Seidel said. “We need to be careful about maintaining balance. It’s also good to consider that use of sexed semen in expansion plans can help reduce disease concerns.”