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  • Title: NZ Frozen Sexed Semen Trial Results

  • Category:

  • Date: Friday, 7 December 2018


Frozen sexed semen remains available for LIC customers to purchase. Farmers may wish to continue using some frozen sexed semen across specific cows or sub-groups in their herd.For many years, dairy farmers have been excited about the possibility of using sexed semen to drive genetic gain within their herd. It makes sense; breeding more heifer calves from the best cows while joining lower end animals to other AI options such as beef opens up more opportunities.

However, farmers with block calving systems are also acutely aware of the contribution of a tight calving pattern and high 6-week in-calf rate to farm profitability. In block-calving systems, the risks of slower calving pattern must be weighed against the benefits of more AI heifer calves and increased rates of genetic gain.

Sexing Technologies, with its latest advances in the technology of sexing semen, was worthy of serious consideration. With all this in mind, LIC participated in a large trial with Sexing Technologies to assess the performance of the frozen sexed product in New Zealand commercial dairy farms. LIC hoped to see the technological improvements reflected in better non-return rates (NRR) for this product on-farm.

The trial

The blind trial, conducted in spring 2017 across nearly 100 New Zealand commercial spring-calving herds compared more than 12,000 straws of ‘control’ and ‘sexed’ straws. There was a good deal of anticipation and excitement about what the trial results would show.

The results clearly showed that there was still a substantial difference between frozen sexed and conventional frozen semen:

The frozen sexed semen was, on average, 13.3 % down on NRR compared to standard conventional frozen straws.

With getting cows in calf being one of the most important parts of any dairy farmer’s seasonal focus, the reproductive implications of a reduction in NRR by 13.3% is significant: These cows would remain in the dry paddock for at least three further weeks. 

Is there a place for frozen sexed semen?

Frozen sexed semen remains available for LIC customers to purchase. Farmers may wish to continue using some frozen sexed semen across specific cows or sub-groups in their herd.

A planned approach is recommended, to help mitigate any potential impact on the herd’s calving pattern.

Options include:

1. Yearling heifer joining - joining yearling heifers to sexed semen 2-3 weeks ahead of the herd. Their naturally higher average conception rates, along with joining the group well (2-3 weeks) ahead of the herd may help reduce calving pattern impacts.


- Feed budgets should allow for the extra earlier feed demand

- Bulls should be carefully chosen for suitability in yearling joining

- Heifers should be scanned early to identify those in-calf to AI and those in calf to run bulls

- Those in-calf to AI replacement sires should be calved separately to avoid mix-ups.

2.  Cows. Mate a select group of highly fertile early calving, high genetic merit cows to frozen sexed semen. Potentially do this ahead of the main herd joining start date to reduce the disadvantage for those that do not conceive. The same caveats around feed budgets apply.

Choose carefully:

Mate good cows to sexed semen; don’t waste a straw! Choose high merit, healthy, low somatic cell count cows. - Fertile cows: early-calved, young cows with no uterine infection and a cycle or two under their belt in the pre-mating period will be your best bet.

- Good cows: don’t waste a straw! Choose high merit, healthy, low somatic cell count cows. Interestingly, NZ farmers cull, on average, 6% of cows with pregnancies created from sexed semen for other reasons!

- On heat: Make sure she is on full standing heat; accurate heat detection helps conception rates. If you are unsure, use a conventional straw.

LIC continues to explore options as technology and the wider industry evolves. In the meantime, the product will continue to have a place for targeted use on some farms. It is encouraged that you assess the suitability of your herd, and discuss the impact of using sexed semen on your farm system with your professional advisor. 

Reproduction tips

A high 6-week in-calf rate delivers more days in milk and more AI heifers, with less intervention, in shorter overall AI mating periods. (Brownlie & McDougall, 2013).

- Aim to maximise your 6-week in-calf rate by getting cows cycling early, heat detected accurately, and AI for enough weeks to high-quality LIC bulls – that should provide plenty of choice of high quality AI replacement heifers

- If your 6-week in-calf rate is low, you should address the underlying issues and reap the benefits of improved 6-week in-calf rate. 

If you are interested in using sexed semen on your farm, please contact your LIC representative for more information.

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