Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2067/48816
Titolo: Genotype by environment interaction due to heat stress in Brown Swiss cattle
Autori: Landi, V.
Maggiiolino, A.
Cecchinato, A.
Mota, L.F.M.
Bernabucci, Umberto 
Rossoni, A.
De Palo, P.
Data pubblicazione: 2023
Due to its geographical position and a highly variable
orography, Italy is characterized by several climatic
areas and thus, by many different dairy cow farming
systems. Brown Swiss cattle, in this context, are a very
appreciated genetic resource for their adaptability and
low metabolic requirement. The significant heterogeneity
in farming systems may consist of genotype by environment
(G × E) interactions with neglected changes
in animals’ rank position. The objective of this study
was to investigate G × E for heat tolerance in Brown
Swiss cattle for several production traits (milk, fat,
and protein yield in kilograms; fat, protein, and cheese
yield in percentage) and 2 derivate traits (fat-corrected
milk and energy-corrected milk). We used the daily
maximum temperature-humidity index (THI) range,
calculated according to weather stations’ data from
2008 to 2018 in Italy, and 202,776 test-day records from
23,396 Brown Swiss cows from 639 herds. Two different
methodologies were applied to estimate the effect of the
environmental variable (THI) on genetic parameters:
(1) the reaction norm model, which uses a continuous
random covariate to estimate the animal additive effect,
and (2) the multitrait model, which splits each
production pattern as a distinct and correlated trait
according to the first (a thermal comfort condition),
third (a moderate heat stress condition), and fifth (a
severe heat stress condition) mean THI value quintile.
The results from the reaction norm model showed a descending
trend of the additive genetic effect until THI
reached the value of 80. Then we recorded an increase
with high extreme THI values (THI 90). Permanent environmental
variance at increasing THI values revealed
an opposite trend: The plot of heritability and the ratio of animal permanent environmental variance to phenotypic
variance showed that when the environmental
condition worsens, the additive genetic and permanent
environmental component for production traits play a
growing role. The negative additive genetic correlation
between slope and linear random coefficient indicates
no linear relationship between the production traits or
under heat stress conditions, except for milk yield and
protein yield. In tridimensional wireframe plots, the
extreme margin decreases until a minimum of ~0.90
of genetic correlation in the ECM trait, showing that
the magnitude of G × E interaction is greater than
the other traits. Genetic correlation values in Brown
Swiss suggest the possibility of moderate changes in
animals’ estimated breeding value in heat stress conditions.
Results indicated a moderate G × E interaction
but significant variability in sire response related to
their production level.
URI: http://hdl.handle.net/2067/48816
ISSN: 0022-0302
DOI: https://doi.org/10.3168/jds.2021-21551
Diritti: Attribution-NonCommercial-NoDerivatives 4.0 International
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