PRESS RELEASE
4 March 2014
Female sexed semen has a higher value than previously thought
Using sexed female semen has gained significant momentum across the UK’s dairy herds
where the prospect of a valuable replacement heifer and the likelihood of an easy calving have
attracted many dairy farmers to this practice. But researchers from the USA have just
uncovered a further advantage to producing a heifer calf and revealed that the female calf’s
mother will produce significantly more milk than the cow producing a bull.
The trend is most pronounced of all in a first calf heifer which will give more milk in both her first and
second lactations if her first calf is female. If her second calf is also a heifer, the benefit accumulates,
and is worth 446kg of milk over the two lactations.
This is 2.7% more production than a cow which produced two bulls, and there is no difference
between the two in the quality of the milk.
And while the researchers – from Harvard and Kansas State Universities and from Dairy Records
Management Systems (a milk records organisation) – knew that the generally easier calving of a
heifer calf was likely to have a positive effect on subsequent production, they were able to prove
unequivocally that there was an additional cause.
Beginning their research with a remarkable 2.39 million lactation records from 1.49 million Holsteins,
they subsequently cut this dataset down to eliminate lactations which began with difficult calvings, and
even amongst this easy calving group, there was a positive effect on milk production of a female calf.
The mechanisms involved were not specifically identified but there was circumstantial evidence to
suggest the female foetus was exerting a hormonal influence on her dam.
Relating the group’s findings to the farm situation, the researchers said there were more compelling
reasons than before to use sexed female semen.
“Often in the USA, dairy farmers use sexed semen on heifers and one of the reasons for doing this is
to avoid dystocia,” said the first author of the research, Professor Katie Hinde. “But now we know
there’s also a production advantage to be gained, I’d say that if a heifer’s first calf is a bull, it’s worth
considering sexed semen for her second lactation.”
Here in the UK, cattle breeding company, Cogent - who pioneered the use of sexed semen and now
has one of the largest sexing facilities in the world at its Cheshire HQ - is delighted with the findings.
“Dairy farmers have been using sexed semen produced in Cheshire since 2000 and every year since
the facility opened, we have accumulated customers, fine-tuned the sexing procedures and improved
the outcomes,” says Innes Drummond, the company’s reproduction technologies manager. “Now we
have a product from which at least 90% of pregnancies will be female, and our customers are
increasingly benefitting from the sexed female advantage.
“These benefits include the production of a valuable heifer calf to become a herd replacement; the
easier calving of a generally smaller female calf and the chance of assisting with cash flow by
breeding the lower end of the dairy herd to a beef sire,” he says. “But now we know the mother of the
heifer calf will also give more milk, there’s an even more compelling reason to use sexed semen than
ever before.”
The research entitled ‘Holsteins Favor Heifers, Not Bulls: Biased Milk Production Programmed during
Pregnancy as a Function of Fetal Sex’ is published in the 3 February 2014 issue of the journal, PLOS
One at: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0086169
Ends
Images:
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AI Sexed Semen.jpg: Tom Woof from Cogent carries out an insemination using sexed semen.

Female calf in hutch.jpg: The mother of a heifer calf will yield significantly more milk than a cow
producing a bull.
Notes to editors

Cogent is the pioneering business behind sexed semen technology and supply and is the UK
market leader. It is wholly owned by the Grosvenor Estate, and from its headquarters on the
Grosvenor Estate in Cheshire, has established a market-leading reputation for its world-class UK
breeding programme.

Cogent's distinguished selection of high reliability UK proven bulls offers dairy and beef farmers
an unprecedented combination of production, type and value.

In 2011, Cogent acquired the business and marketing rights of World Wide Sires UK, the highlyregarded cattle-breeding business, and Dairy Daughters, the UK’s first direct supplier of Holstein
semen. These businesses remain a key part of the Cogent business, and Cogent remains the
exclusive supplier of WWS US products in the UK.

For more information, please contact Laura Andrews on 01244 622 069 or via email at
laura.andrews@cogentuk.com.
The text from this news release can be downloaded directly from the Agriculture/Livestock section of
the ABC (Agribusiness Communications Ltd)
Press Centre at www.abccomms.co.uk