Abstract :
[en] This study aimed to estimate genetic parameters
and identify genomic region(s) associated with selected
cheese-making properties (CMP) in Dual-Purpose
Belgian Blue (DPBB) cows. Edited data were 46,301
test-day records of milk yield, fat percentage, protein
percentage, casein percentage, milk calcium content
(CC), coagulation time (CT), curd firmness after 30
min from rennet addition (a30), and milk titratable
acidity (MTA) collected from 2014 to 2020 on 4,077
first-parity (26,027 test-day records), and 3,258 secondparity DPBB cows (20,274 test-day records) distributed
in 124 herds in the Walloon Region of Belgium. Data
of 28,266 SNP, located on 29 Bos taurus autosomes
(BTA) of 1,699 animals were used. Random regression
test-day models were used to estimate genetic parameters through the Bayesian Gibbs sampling method.
The SNP solutions were estimated using a single-step
genomic BLUP approach. The proportion of the total
additive genetic variance explained by windows of 25
consecutive SNPs (with an average size of ~2 Mb) was
calculated, and regions accounting for at least 1.0% of
the total additive genetic variance were used to search
for candidate genes. Heritability estimates for the included CMP ranged from 0.19 (CC) to 0.50 (MTA),
and 0.24 (CC) to 0.41 (MTA) in the first and second
parity, respectively. The genetic correlation estimated
between CT and a30 varied from −0.61 to −0.41 and
from −0.55 to −0.38 in the first and second lactations,
respectively. Negative genetic correlations were found
between CT and milk yield and composition, while those
estimated between curd firmness and milk composition
were positive. Genome-wide association analyses results
identified 4 genomic regions (BTA1, BTA3, BTA7, and
BTA11) associated with the considered CMP. The
identified genomic regions showed contrasting results
between parities and among the different stages of each
parity. It suggests that different sets of candidate genes
underlie the phenotypic expression of the considered
CMP between parities and lactation stages of each parity. The findings of this study can be used for future
implementation and use of genomic evaluation to improve the cheese-making traits in DPBB cows.
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