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What is the benefit of
crossbreeding with a Limousin sire?
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By: MANJO STIGLING (Limousin Breeders) & ILDINDE DU PLESSIS
(Biomedical Scientist)
WHY breed with Limousins?
Enhance your beef herd by investing in Limousin genetics and
leveraging the F94L muscling, or “profit” gene, found
predominantly in Limousin cattle.1 This genetic advantage
can help your herd achieve:
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Up to 19% more high-value cuts
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An 8% increase in retail yield
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6-11% greater tenderness
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All without additional feed
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No extra calving difficulty
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No reduced fertility
A key objective
of the Limousin Breeders’ Society of Southern Africa is to
make tools and sources of information available that will
enhance the breeding decisions of all users of Limousin
genetics.
The Myostatin
status of a bull, used in conjunction with wider information
such as Estimated Breeding Values (EBVs), enables informed
breeding decisions. This article explains what the role and
benefit is of Myostatin in using Limousin bulls for
crossbreeding.
What is the function of the myostatin gene?
The Myostatin
gene is a single gene that is present in the DNA of all
vertebrates. It is responsible
for producing the Myostatin protein, where ‘myo-’ means
muscle and ‘-statin’ means stop. This protein plays a key
role in regulating muscle growth and development, ensuring
balanced muscle formation and preventing excessive muscling.
A normally
functioning myostatin gene inhibits growth. A mutation in
this gene reduces its powers to switch off the
multiplication of muscle fibres, which can result in an
increase of the size or number of muscle fibers.
There are nine
well-documented variants of the myostatin gene in cattle5,
of which some are
breed-specific, and others are found across multiple
breeds4. Of these, six are “loss of function” mutations,
meaning they inactivate the myostatin gene causing muscular
“hypertrophy” (larger muscle fibres) and hyperplasia (more
muscle fibres).
To understand Myostatin information, it is important to know
the terms “homozygous”
and “heterozygous” animals. The Myostatin gene comes in a
pair, so each animal has two “copies” of the gene: one
inherited from its sire and one from its dam.
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An animal that has two identical copies of a gene is called
“homozygous,” and it will definitely pass this gene to its
offspring.
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On the other hand, an animal that has inherited only one
copy of the gene is referred to as “heterozygous” and may
pass the gene to its offspring.
The three main variants of Myostatin
Myostatin Variant F94L
The F94L gene causes a partial loss of function in the
myostatin protein and leads to an increase in the number of
muscle
fibers found in cattle that carry this gene. This results in
an increase of muscles, or “more meat,” and a higher
“meat-to-bone ratio”
without any
association with increased calving difficulty or lowered
fertility as seen with other myostatin variants.
Studies
indicate that 99% of all Limousin cattle carry at least one
copy of this variant. Due to its high prevalence, the
majority of animals within the breed are homozygous,
carrying two copies of the F94L gene.
The impact of the F94L gene in the Limousin breed is
considered a moderate increase in muscularity and
should not be mistaken
for the ‘double-muscling’ effect caused by
other Myostatin variants.
This genetic trait has played a significant role in shaping
the breed’s characteristics and is a key factor in its
commercial success.
Myostatin Variant nt821 and Q204X
The nt821 and Q204X mutations result in a complete loss of
function of the myostatin
protein7, leading to increased muscle fiber size in affected
animals2. Heterozygous carriers of these mutations tend to
exhibit greater loin depth, reduced fat content, and
improved conformation compared to non-carriers. However,
studies suggest that heterozygous animals with these genes
may also have a higher risk of calving difficulties and
lower milk yields.
The Limousin Breeder’s Society of Southern Africa prohibits
the import of Limousin genetics carrying the nt821, Q204X,
or any other less desirable myostatin variant. Anyone
purchasing Limousin cattle registered with the association
can be confident that their newly acquired animals will
carry the F94L gene and can rest assured that they will be
free of nt821 and Q204X.
What are the benefits of F94L?
1. Meat
Yield:
The carcasses
of homozygous F94L-carrying cattle have a dressing
percentage of 65-70%, significantly higher than that of
cattle lacking this trait. This increased yield results from
enhanced muscle mass, reduced body fat, lower bone density,
and smaller internal organs – yielding up to 19% more meat
than cattle lacking the gene.
Homozygous
animals demonstrate up to 19% increase in primal cut weights
and 8% improvement in overall retail beef yield. These
enhancements are achieved without additional feed input,
which translates into more feed efficient animals2. Meat
quality is also generally superior in these animals with
greater tenderness2, and reduced fat content5. Even
heterozygous animals, carrying a single copy of the F94L
gene, display these beneficial traits, albeit to a lesser
degree.
2. Feed
Efficiency:
Cattle that are
homozygous for this gene consume the same amount of feed as
those without it, yet produce significantly more beef. This
makes them highly feed-efficient, maximising meat production
without increased feed intake.
3. Meat
Quality:
F94L animals
produce higher quality meat, characterised by enhanced
tenderness, lower fat content, and a higher proportion of
polyunsaturated fats, contributing to a leaner and more
desirable product for certain markets.
A prime rib
section with higher fat content (intramuscularly and along
the outer edges) as well as a rougher texture, indicating
less compact muscle fibers. This composition results in a
lower overall meat yield per cut.
A leaner prime
rib section with lower fat content (intramuscularly and
along the outer edges) as well as a more uniform texture,
indicating more compact muscle fibers. This composition
results in a higher overall meat yield per cut.
What are the disadvantages of F94L?
There is no disadvantage to the F94L myostatin variant, such
as birth weight problems, calving difficulty, lack of
fertility, and milk yield, as are sometimes associated with
other myostatin variants such as nt821 and Q204X.
What is the benefit of crossbreeding?
When crossbreeding with Limousins, the progeny will inherit
one copy of the F94L gene and will typically show a 9.5%
increase in silverside and eye muscle area, a 4% higher
retail beef yield, a 3% improvement in loin muscle
tenderness, and a 5.5% increase in silverside tenderness.
This underscores the advantage of incorporating
Limousin
genetics into any beef herd to enhance meat quality and
yield.
Testing for Myostatin
Myostatin testing is now more accessible and affordable. The
Society recommends that breeders facilitate genetic
parentage confirmation through the Limousin Office, which
coordinates testing with the LRF. The Neogen GGP Bovine 100K
Genetic Test is conducted in Scotland. Breeders have the
option to request a parentage test only or a comprehensive
SNP test, which includes Myostatin testing.
How should myostatin information be used when buying a bull?
Knowing the genotypes of breeding stock helps stud and
commercial producers to select breeding animals for the best
possible outcomes. A myostatin genotype
provides
additional information that may assist in decision-making,
but should be considered alongside broader data, such as
Estimated Breeding Values (EBVs). EBVs integrate actual
performance data from the animal, its herd-mates, and its
relatives to predict genetic merit. This, combined with our
own assessment of type and pedigree, will support more
informed breeding decisions.
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