Sexed semen is finishing its first decade on the market, and has so far been an extremely successful product around the world. It has given dairy farmers the ability to select for females to maximize the value of each pregnancy, increasing the genetic potential of their herd and helping to improve their bottom line. At World Wide Sires, we strive to offer a complete line-up of bulls who can meet every customer’s sexed semen need, regardless of management style. However, getting the greatest return from this investment in your herd’s future requires paying special attention to both breeding and heifer management.
Using Sexed Semen
The process used to sort semen by the gender of the sperm involves advanced technology and lab work. Individual sperm are treated with dye and then separated based on the presence of an X or Y chromosome. For our gender-sorted product, at least 90% of the sperm in each dose of semen contains an X chromosome (females receive an X chromosome from the father, males receive a Y chromosome). Using sexed semen instead of conventional semen can increase the average genetic value of your herd simply by creating more heifers over the same period of time.
A side effect of this sorting process is that the sperm are subject to increased stress. Industry research by reproductive specialists, such as Mel DeJarnette at Select Sires/World Wide Sires, has shown a conception rate for sexed semen that is on average 80% of the rate for conventional semen. To maximize the conception rate of sexed semen, breeders should focus on two areas: proper semen handling and selecting the right animals to breed with sexed semen.
Sexed semen is packaged in 0.25 mL straws, which are more sensitive to temperature changes than 0.5 mL straws. Improper handling of doses can have a negative impact on sperm motility and decrease fertility. These smaller straws are especially sensitive to thermal shock, which can occur through touching the straw with a human hand or thawing at the wrong temperature. To avoid this, frozen semen should be handled with tweezers and thawed at 35⁰ to 37⁰ C for 45 seconds. The semen should be kept at human body temperature (the same range as thawing), either by using an AI syringe warmer or using the breeder’s own body heat, until breeding. Breeding should occur within 5 to 10 minutes of thawing for maximum conception.
In North America, sexed semen is recommended for use on virgin heifers, which traditionally have a higher conception rate than milking cows. This is in large part due to the decreased stress that heifers are under, since their bodies are not using energy for milk production. However, heifers may not be the ideal target for every herd.
When breeding Holstein heifers, the goal should be for them to calve at 560 kg (check for corresponding weight in crossbred heifers). Research has shown that this is the ideal weight to maximize production in the first lactation, and that a heifer weighing less than 400 kg is at a significant disadvantage because she will have to use more energy during her first lactation to finish growing to her mature body size. This advantage is lost when the heifer weighs more than 680 kg at calving, since overweight heifers tend to have more problems calving and are more susceptible to reproductive and nutritional disorders like fatty liver and ketosis.
The goal for Holstein heifer nutrition is to reach 300-330 kg of body weight by 14 months of age (225-275 kg for Jerseys and other small-framed breeds). This both maximizes first lactation production and minimizes feeding costs. However, this may not be a reasonable goal for all producers, in which case a different breeding strategy may be best.
Sexed Semen & Cows
Research with beef cattle has shown that sexed semen can achieve similar conception rates in both heifers and lactating cattle under low-stress conditions. For farmers with dual-purpose animals or late maturing heifers, using sexed semen on cows may be the best way to maximize the value of this product. Proper semen handling and breeding techniques must be used regardless of the age of the animal.
Tips for Maximizing Conception Rate
• Watch heifers for heat activity for 20 minutes at least twice a day.
• Use the AM-PM rule for breeding with sexed semen – breed 12 hours after observed heat.
• Use Sire Calving Ease (SCE) scores to avoid difficult births, especially with heifers – the lower the number the better!
• Protect the sperm from rapid temperature changes
• Avoid breeding during high stress periods, especially summer, when conception rates are already lower than normal.
Prepared by: Tyler Boyd, World Wide Sires
For more information contact
Amit Sachdev, India Consultant, World Wide Sires * E mail: firstname.lastname@example.org