HAPLOTYPES
- QUESTIONS AND ANSWERS
Haplotypes have been discovered that affect cattle fertility.
In order to avoid the devastation of failed conceptions or
early embryonic death, it is important that haplotypes and
their negative effects are understood. With haplotypes
becoming a hot topic within the cattle industry,
CIS Product Services Analyst Emma Eastham
addresses some of the common questions
that every farmer will want answers to
so that unnecessary cattle are not lost
What are haplotypes?
q The term “haplotype” refers to a group of single-nucleotide
polymorphism (SNP) markers that are located at nearby positions
on the chromosome and are usually inherited together.
q Haplotypes are passed on from both parents and whether
they cause harm or good depend on how these haplotypes are
arranged in the offspring.
Why do I need to know about them?
q Modern genomic tools have been used to identify thousands of
haplotypes on each chromosome; each has a positive, neutral or
negative association with production, conformation, health and
fertility.
q It is important to identify and understand which haplotypes
cause a negative effect in order to breed around them to ensure
that these effects are not passed on.
What are the negative effects of haplotypes?
q There are three haplotypes which have been discovered that
cause undesirable traits that impact on Holstein fertility. They are
known as HH1, HH2 and HH3. Animals can either be carriers (C) or
tested non-carriers (T).
q Reasons as to how these haplotypes impact fertility is unknown,
however it is thought that inheritance of the same haplotype
from each parent results in failed conception or early embryonic
death.
q Using semen from bulls with these haplotypes results in just
over 3% lower conception rate.
What are the chances of
haplotypes being passed on?
1. If both parents are carriers of an undesirable haplotype (e.g.
HH1C):
q There is a 25% chance that there will be an affected offspring
that would not survive to birth.
q There is a 50% chance that
X
R (Sire) r (Sire)
there will be a pregnancy that
would result in an offspring
R
RR
Rr
(Dam) (Free)
(Carrier) that would be a carrier (HH1C).
q There is a 25% chance that
r
Rr
rr
there will be one pregnancy
(Dam) (Carrier) (Death) that will result in one
unaffected offspring.
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THE JOURNAL APRIL 2012
2. If the dam is unknown, but the
grandsire and sire are both unaffected
carriers of an undesirable haplotype
(HH1C):
q There is a 12.5% chance that the
resulting embryo will not survive to
birth.
3. If the dam and the sire were carriers
of different haplotypes, e.g. if the dam
was HH1C and the sire was HH2C, the
following resulting offspring could be
expected:
q 25% non-carriers of both (HH1T and
HH2T).
q 25% carriers of one (HH1C).
q 25% carriers of the other (HH2C).
q 25% carriers of both (HH1C and
HH2C).
What can I do to avoid
breeding negative
haplotypes?
q The reaction to try and eliminate
every animal with an undesirable
haplotype is not necessary or practical.
q Breeders do not necessarily need to
avoid sires with these haplotypes nor
cull cows, heifers and calves that are
carriers.
q By eliminating those animals,
breeders are likely to do more harm
than good as it will lead to significant
economic losses in other important
and desirable traits.
q Computer programmes for mating
offer a simple and inexpensive solution
for avoiding further breeding of
undesirable haplotypes. With this in
mind, it is highly recommended that
these programmes are used.
q Holstein UK’s BullSelector and
WebMate are being enhanced so that
in the future our breeders will have
an option to exclude bulls and cows
which are carriers of these haplotypes.
How do I find out if my
cattle are carriers?
q Currently haplotypes impacting
fertility can be identified using the 6K
and 50K genomic tests.
q To request a genomic test from
Holstein USA, simply login to the
‘Members Section’ of the Holstein UK
website and choose the ‘Genomic’ tab.
You can then request a 6K or 50K test
for any female in your herd.
q An example of how these results
appear on a genomic test from
Holstein USA is illustrated below. From
this report it is clear that the animal
has been tested and is a non-carrier.
q Later this year Holstein UK will offer
a new service to members whereby
they can request UK genomic indexes
for their cows. It is expected that the
fertility haplotypes will be reported on
all tests at this time.
Further reading
Holstein USA
http://www.holsteinusa.com/pedigree_info/genetic_
codes_traits.html
Holstein USA – Interpreting and Utilising
New Holstein Genetic Information
http://www.holsteinusa.com/pdf/haplotype_details.pdf
Dr Kent A Weigel – Haplotypes Affecting Fertility and
their Impact on Dairy Cattle Breeding Programs
http://www.holsteinusa.com/pdf/haplotypes_affecting_
fertility_080511.pdf
THE JOURNAL APRIL 2012
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