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Sexed semen use on dairy farms


Stephen Butler and Stephen Moore Teagasc, Animal & Grassland Research and Innovation Centre, Moorepark, discuss Sexed semen use on dairy farms including Maximizing fertility, Timing of AI, straw handling and more as part of the two-day Virtual Dairy Conference 2021 taking place today

Summary

  • In November 2021, Sexing Technologies established a semen-sorting lab located at Moorepark, with the service available to all Irish AI companies
  • Using sexed dairy semen in tandem with more conventional beef semen can transform the calf crop on dairy farms.

Why use sexed semen?

Increasing the dam-side selection pressure by breeding replacement females from only genetically superior heifers and cows in the herd could accelerate herd genetic gain by up to 15%. This also means there is scope to have a corresponding increase in beef semen usage (to produce crossbred beef calf offspring). For example, a typical herd using conventional dairy semen for the first half of the breeding season followed by beef semen or natural service beef bulls for the remainder of the breeding season could expect a calf crop with 27% female dairy calves, 27% male dairy calves and 46% beef cross calves. This is consistent with the current national statistics for calf birth registrations in Ireland. By using sexed semen instead of conventional dairy semen to generate replacement heifers and using more beef semen for all other mating events, the calf crop could be readily changed to 27% female dairy calves, 3% male dairy calves and 70% beef cross calves. In the long term, this altered calf crop is a more sustainable option for the dairy industry, markedly reducing the number of male dairy calves.

International trends

Internationally, the usage of sexed semen has steadily increased during the last decade, especially in systems with year-round calving. A survey of 3,200 US dairy farms (700,000 cows) reported reduced usage of conventional Holstein semen, replaced by parallel increases in both sexed Holstein semen and beef semen. Even more striking, a recent survey of UK breeding companies indicated that for the first time farmers are buying more sexed dairy semen than conventional semen. In 12 months to March 2020, sales of sexed semen in the UK made up 51.3% of all dairy semen sales, up from 31.9% the previous year, and only 17.9% in 2017. These rapid increases in the usage of both sexed dairy semen and conventional beef semen is likely due a combination of improving pregnancy rates with sexed semen, and greater scrutiny and monitoring of the welfare and fate of dairy breed bull calves.

Maximising fertility

Maximising conception rate with sexed semen requires careful animal selection, appropriate timing of AI, and attention to detail regarding straw handling.

Bull selection

It is not possible to predict which bulls will have good field fertility and which bulls will have poor field fertility after the sorting process. To mitigate the risk, use sexed semen from a large team of bulls (≥5).

Dam selection

Sexed semen use must be targeted towards the dams with the expected best fertility to maximise the likelihood of conception.

- Heifers

Have achieved the target live-weight for breed and BCS ≥3.25.

- Cows

  • Parity 1-4.
  • >50 days in milk on day of AI.
  • BCS ≥3.00.
  • Regularly cycling.
  • Free of postpartum disorders and uterine disease.

Timing of AI

When heifers/cows are being inseminated with sexed semen after observed heat, AI should be conducted 14-20 h after heat onset.

Fixed time AI is costly, but facilitates sexed semen usage on the best dams, and can be scheduled to be completed on the farm mating start date. This advances submission, and mitigates the risk of poor conception rates.

Straw Handling

  • Organise sexed straws into one goblet on the tank, and minimize the frequency that the goblet is lifted.
  • Change water in the thawing unit daily. Clean the thawing unit weekly.
  • Check that the temperature in the thawing unit is 35-37 °C.
  • Thaw a maximum of two sexed semen straws at a time.
  • Using a timer, thaw the straws for 45 seconds.
  • Load straws into pre-warmed AI guns.
  • Keep AI guns warm after loading straws, and ensure that inseminations are promptly completed (<5 minutes after loading).
  • Deposit semen in the uterine body. 

Due to updated Government guidelines the Teagasc National Dairy Conference has changed from an ‘in person’ event to being an online ‘virtual event’ only. 

The Dairy Conference 2021 is on Zoom over two days. Registration link below.

The complete Dairy Conference Proceedings will be published on www.teagasc.ie And the individual articles will be published on Teagasc Daily throughput the week. See more  at Dairy Conference