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Rapid Communication: Large exploitable genetic variability exists to shorten age at slaughter in cattle
Berry, D. P. Cromie, A. R. Judge, M. M.
Berry, D. P.
Cromie, A. R.
Judge, M. M.
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2017-10-01
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D. P. Berry, A. R. Cromie, M. M. Judge, Rapid Communication: Large exploitable genetic variability exists to shorten age at slaughter in cattle, Journal of Animal Science, Volume 95, Issue 10, October 2017, Pages 4526–4532, https://doi.org/10.2527/jas2017.2016
Abstract
Apprehension among consumers is
mounting on the efficiency by which cattle convert
feedstuffs into human edible protein and energy as well
as the consequential effects on the environment. Most
(genetic) studies that attempt to address these issues
have generally focused on efficiency metrics defined
over a certain time period of an animal’s life cycle, predominantly the period representing the linear phase of
growth. The age at which an animal reaches the carcass
specifications for slaughter, however, is also known to
vary between breeds; less is known on the extent of the
within-breed variability in age at slaughter. Therefore,
the objective of the present study was to quantify the
phenotypic and genetic variability in the age at which
cattle reach a predefined carcass weight and subcutaneous fat cover. A novel trait, labeled here as the deviation
in age at slaughter (DAGE), was represented by the
unexplained variability from a statistical model, with
age at slaughter as the dependent variable and with the
fixed effects, among others, of carcass weight and fat
score (scale 1 to 15 scored by video image analysis
of the carcass at slaughter). Variance components for
DAGE were estimated using either a 2-step approach
(i.e., the DAGE phenotype derived first and then variance components estimated) or a 1-step approach (i.e.,
variance components for age at slaughter estimated
directly in a mixed model that included the fixed effects
of, among others, carcass weight and carcass fat score
as well as a random direct additive genetic effect). The
raw phenotypic SD in DAGE was 44.2 d. The genetic SD and heritability for DAGE estimated using the
1-step or 2-step models varied from 14.2 to 15.1 d and
from 0.23 to 0.26 (SE 0.02), respectively. Assuming the
(genetic) variability in the number of days from birth to
reaching a desired carcass specifications can be exploited without any associated unfavorable repercussions,
considerable potential exists to improve not only the
(feed) efficiency of the animal and farm system but also
the environmental footprint of the system. The beauty
of the approach proposed, relative to strategies that
select directly for the feed intake complex and enteric
methane emissions, is that data on age at slaughter are
generally readily available. Of course, faster gains may
potentially be achieved if a dual objective of improving
animal efficiency per day coupled with reduced days to
slaughter was embarked on.