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The sexed semen revolution starts here

Having double the amount of cells in every sexed semen straw means the Pratt family now has the confidence to use 4M on cows and heifers, safe in the knowledge conception rates will not be compromised. Traditionally, the Pratt family would have only used sexed semen on heifers, following concerns conception rates would drop off in less fertile cows on a more inconsistent diet.

However, that was at a time when they were reliant on using straws containing the usual two million sexed semen cells per straw. Since then, they have swapped to SexedULTRA 4M, in which every straw contains 4million sex-sorted sperm cells (see Q&A panel). As a result, conception rates have become more consistent, as James Pratt explains. “Until recently, we had mixed success with sexed semen,” he says. “We would have a run of nine in-calf heifers when we served 10, then five in-calf out of 10.

It was just a bit inconsistent. It did not seem as consistent as it does now.” James farms with his parents Alan and Edith and brother Richard at Studdah Farm, Bellerby, Leyburn. They run the Studdah herd of 130 pedigree Holsteins, yielding 9,811kg a cow a year at 4.31% fat and 3.19% protein. Cows calve year-round, with all replacements reared on farm.


Recently, the family decided to focus on producing more beef from the dairy herd in response to low milk and heifer prices. As a result, they were keen to breed replacements from their best animals and put the lower end to beef. To do so, they wanted to produce females from their top-end cows, as well as their heifers.

This was where 4M came in. James says: “There were trials to show SexedULTRA 4M had similar conception rates to rival conventional semen. So, if conception rates are similar, you have more chance to get heifers off your top cows and put beef on the bottom.” Now, about 50 cows are served to 4M and the remaining go to a three-sire British Blue semen straw; 50% of heifers are also served to 4M with the rest put to Aberdeen-Angus or used as embryo recipients. The best cows are selected based on classification data and the family’s knowledge, opting to breed for balanced type, quality udders, feet and legs, and positive milk, fat and protein.

In October, the business began genetically testing heifers with the view to using this knowledge to make more informed decisions on which heifers to breed replacements from, and to make faster genetic progress. This will help select embryo recipients when flushing cows to sexed semen.

The business is now achieving similar conception rates with sexed semen as they were with conventional. Cows are currently achieving 55% conception rate to first service with a 100-day in-calf rate of 68%. This figure includes beef semen and some overlap with using sexed semen straws with 2M cells. Of 10 heifers recently served to 4M, they achieved conception rates to first service of 80%.

The business also saw no effect on conception rates in cows during summer grazing. James says good conception rates from using the combination of 4M and the three-sire beef straw on cows has helped reduce calving interval from 395 days to 376 days between 2016 and 2017.

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