The Tenderness Gene
DNA
Testing for Meat Tenderness in Cattle
Contact people: Chris
Morris and Neil Cullen
AgResearch Ruakura
Ruakura Research Centre
PB 3123, Hamilton
Tel 07.838.5417 or 5414
A
Project carried out by AgResearch under contract to Meat and Wool NZ
In
September 2003, Agritech Investments Ltd ( Now meat and Wool NZ) began
funding a 3-year contract with Ag-Research to study the DNA which codes for
four difficult-to-measure traits in New Zealand cattle, namely beef meat tenderness, retail beef
yield, resistance to facial eczema, and resistance to internal parasites.
The meat tenderness work centres around a gene called calpain-1. This is
involved in the breakdown of the muscle fibres at slaughter in the process of
converting muscle into meat, and its subsequent ageing. We have been testing
for particular genetic variants that are associated with increased meat
tenderness. Tenderness is an inherited trait in cattle, and estimates of its
heritability are generally low to medium in size. Not all the differences in
tenderness between like-treated Bos taurus animals are explained by
the genetic variants we have tested for. Selection for the calpain-1 tender
variant should be able to improve tenderness within your breed but it is
important to note that these results cannot be used to compare tenderness
between breeds because calpain-1 is one of many genes contributing to
tenderness, with other factors (stock management methods, carcass processing
and meat cooking methods) are important consideration for the final result on
the steak.
The
project is now releasing information
to New Zealand bull owners, on the results of this calpain-1 work on key
bulls.
Every
animal carries two copies of each gene. Calpain-1 is a gene found on cattle
chromosome 29, and is present with either the tender ( C ) or tough ( G )
variants in each copy to produce 3 combinations i.e ‘ CC ’ ‘ CG ’or ‘ GG
’genotypes. The results for each animal are scored as the number of C
(tender) copies of the gene.
e.g. 0 copies of the ‘ C ’ gene (‘GG’genotype)
= TOUGHEST
1 copy of the ‘ C ’ gene ( ‘CG’
genotype) = MODERATE TENDERNESS
2 COPIES OF THE ‘C’ GENE ( ‘CC’GENOTYPE) = MOST TENDER
There are
different frequencies for the ‘0’, ‘1’and the ‘2’ genotypes amongst the
breeds tested. Our research to date indicates that the advantage is in ageing
rate rather than final tenderness. Exports by
ship (if unfrozen’) will have reached final tenderness by the time the ship
reaches most markets regardless of genotype. Thus the main opportunity is for
beef sold as cuts on the local market or by air freight. The difference
between ‘0’score and a ‘2’ score is a about a 20% increase in the rate of
developing meat tenderness.
Initially we tested 11 of our stud sires as part of Chris Morris’
request for Angus breeders to take part in his
research project
(see
above).The C-allele frequency was 17 C alleles out of the 11 sires tested (= 22 alleles) or 77%
THIS COMPARES WITH 51%
of C ALLELES FOR THE REST OF THE 96 ANGUS BULLS TESTED
THE
FREQENCY OF THE CC GENOTYPE FOR THE BREED WAS 22%
Encouraged by the results
from our Sires, we decided to test all our 15 Month stud cattle. 98% of the
heifers
and 91% of the bulls had C
alleles. The frequency of the CC (or most tender) genotype in the 64 bulls
tested
was 60% For the 123 heifers
tested the result was a frequency of 51% for the CC genotype.
We will be aiming to mate a CC genotype bull
to CC genotype heifers this season. 100% of the resulting
progeny will carry a
double copy of the tenderness Gene.
Where to from here?
To increase the frequency of
occurrence of the CC genotype in any given herd of cattle, you need to use a
sire with the C allele
present. It works like this:—
Waimata Results
Bull Genotype CC
Bull Genotype CG
Dam Genotype CC
Dam Genotype CC
100% Of Progeny Will Have
CC Genotype
There is a 50% chance of progengy being CC & 50% chance they will be CG
25% Chance Calf will Be CC, 50% Chance
Calf will Be CG, 25% Chance Calf will Be GG
Bull Genotype CG
Dam GenotypeCG