Download Management Perspectives Polled or Scurred: Do You Know the

Management Perspectives
Polled or Scurred: Do You Know the Difference?
The popularity of polled
In other words, the abcattle breeding is a subsence of the polled gene
ject that needs no further
(i.e., horned) masks the
explanation – especially in
presence of the scur gene.
the Red & White breeders’
The polled gene is domicircle. Polled has been a
nant to the horned gene.
popular niche in Red &
The gene for scurs is exWhites for some time, and
pressed differently from
the majority of bloodlines
the genes for polled/
building the polled gene
horns. The way this gene
expansion trend still disis expressed depends on
play a strong Red base.
the sex of the animal. In
Not at all unexpected,
males, the scur gene is
or untypical when a single
dominant, meaning that
trait becomes the focus
scurs will be present if
of intense breeding, other
even only one copy of the
genetic-related discovergene is present. ThereScurs are small, loose, horny growths in the
ies happen. CV, BY, hapfore, it is more easily deskin where horns would normally develop,
lotypes and other undesirtected in the bull.
such as those visible on this bull. Scurs are
able traits have surfaced
In females, the gene is
determined by a different gene than polled.
in the Holstein breed, for
recessive, meaning that
example. Recently, with the intensity of breeding for the she must possess both genes for scurs in order for scurs to
polled gene, breeders have reported the increased incidents be present. If a cow possesses only one scur gene, she will
of animals with scurs. What does this mean? It is important not have scurs herself, but has a 50 percent chance of passto have an understanding if you are looking at breeding – ing the scur gene on to her calf.
and especially if marketing – polled animals.
Table A depicts the inheritance patterns and phenotypic exWhat are scurs?
pressions that can be expected in the various combinations
Scurs are small, loose, horny growths in the skin where of polled and scur gene inheritance. Genetic combinations of
horns would normally develop. Scurs can most easily be polled parents (PP as homozygous and Pp as heterozygous),
identified by touch; unlike horns, they are not attached to scurred parents (SS as homozygous, Ss as heterozygous and
the skeleton of the animal. Scurs can be wiggled and moved, ss as a non-carrier), and horned parents (pp) are represented.
regardless of age and size. The size and length of a scur
can vary rather significantly, Table A:
with the larger instances often seen in males, believed to
Genetic Makeup of
be influenced by the presence
Cows
Bulls
of testosterone.
Animal
Scurs have been common
in many beef cattle breeds
Polled with Scurs
Smooth Polled
PPSS
for decades. However, only
Possible to have scurs??
All male offspring polled with scurs
recently, logically due to the
focus on breeding polled catPolled with Scurs
PPSs
Smooth Polled
tle, has the gene even gained
Can sire polled offspring +/- scurs
awareness in dairy breeds.
What is the relationship
Smooth Polled
PPss
Smooth Polled
with the polled gene?
All offspring will be smooth polled
The gene that determines
Polled with Scurs
if an animal will have scurs
PpSS
Polled with Scurs
is not the same gene as that
Can sire smooth polled daughters.
which determines if it is
Polled with Scurs
polled. It is a common misPpSs
Smooth Polled
understanding that scurs are
Can sire polled offspring +/- scurs.
somehow a partial expression
Ppss
Smooth Polled
Smooth Polled
polled gene, but this is incorrect.
ppSS
Horned
Horned
The presence of the genetic
allele for scurs in cattle can
ppSs
Horned
Horned
only be seen in a polled anippss
Horned
Horned
mal, because horns will otherwise cover up the scurs1.
1 Long, C.R. (1978). “Inheritance of the horned, scurred and polled condition in cattle”. Journal of Heredity 69: 395-400.
by Ed Peck
Testing for polled should be considered
There are many reasons mistakes could happen in classifying a calf as polled or horned. The scur gene, human error,
poor judgment, and a varying degree of genetic influence
on horn growth strongly suggest testing for the polled gene
should be a mandatory when marketing or buying elite, highvalue polled animals. There currently are two different tests
available on the market, and the differences are important.
The Geneseek/Igenity test is the test available directly
through Neogen Corporation after the acquisition of the
Igenity brand. It is this test that is currently offered through
Holstein Association USA. This test is based on haplotypes,
meaning it tests several points along the chromosome to
evaluate the potential presence of the polled mutation, rather than testing for the mutation directly. Therefore, it is less
than 100 percent accurate, and should be considered as an
indicator of the likeliness the animal carries the polled mutation, but not a definitive confirmation.
In 2011, GeneControl out of Germany introduced a new
test based on the discovery that there are two different mutations that can cause the polled condition in cattle. To
cut through some of the scientific technicalities on what is
required to use the term “proven” in this area of genetics,
the new GeneControl test directly measures what scientists
regard as the causal mutations for polled. This means the
GeneControl test can be considered 100% accurate for the
two known types of polled. If there are more types of polled
yet to be discovered the GeneControl test of course will not
be any good for them.
Unfortunately, at this time, there is no test available for
testing an animal – male or female – for the scur gene.
Summary points to remember
1. Polled and scurred are different genes that interact to
give different phenotypes, generally classified as smooth
polled, polled with scurs or horned.
2. In order to have scurs an animal has to be polled. A
horned animal can carry the scurred gene, but the scur
itself will be hidden by the horn.
3. The scurred gene is considered to be dominant but is
heavily influenced by the sex of the animal. In order to
show the scurred phenotype males typically require only
one copy of the scurred gene while females typically require two copies.
4. It is expected that there are many genes other than
polled and scurred that influence horn shape and size
in smaller ways. These other genes are likely the reason
why there is a large amount of variation in scur shape
and size.
There is little doubt the demand for polled genetics will
continue to grow. Many predict it will become the way of
breeding all dairy cattle in the future, and it is hard to argue
the logic. For breeders and buyers involved in this rapidly
growing segment, it is very important to understand the genetic dynamics we know today, and will continue to learn
as bloodlines carrying the polled gene are both intensified
and expanded. Breeders should be prepared to answer the
questions buyers will want to know – and have a right to
ask. Buyers should most definitely ask the questions and
consider the knowledge and understanding they gain in their
investment risks.
Recent insights in the industry
Following are recent conclusions in the Red &
White industry that can help put some context
to the polled/scur situation:
• Clerinda Balti-Red-ET was initially marketed
as a polled bull, before the development of
the GeneControl test. Following numerous
reports of only horned calves from horned
dams, he was tested and confirmed to not
be a carrier of either of the two known polled
mutations. He has since been designed as
“Tested Free of Polled” by Holstein Canada
and his polled status has been rescinded
by Holstein Association USA. It remains unknown why Balti never grew horns as he was
not physically dehorned. More research is
needed to determine why Balti never grew
horns. He is believed to be a carrier of the
scur gene, which led to the confusion of
being polled. There is no genetic test for
scurs so this cannot be confirmed.
• Aggravation Lawn Boy P-Red is the most
common source of the polled gene in the
Holstein population. Lawn Boy is a proven
carrier of the polled gene, and also appears
to be a carrier of the scurred gene. Therefore, he can sire polled, polled/scurred,
scurred, or horned offspring.
• Sandy-Valley Colt P-Red-TW is a more recent, heavily influential polled sire. As a
Lawn Boy son himself, he too is a polled
carrier and also considered to be a carrier
of both the scurred gene.