Abstract :
Genotype by environment interactions (G
×
E) can form a potential source of inefficiency
in animal breeding if selection decisions are made without acknowledging their effects.
The presence of such interactions between two Scottish hill farms was investigated using
performance data collected from 18,459 Scottish Blackface lambs between 1997 and 2010.
Pedigree information was available for 27,548 animals. 30 out of 379 sires used during
this time period were used on both farms. Farm A is located on the East Coast of Scotland,
whereas Farm B is on the West Coast. The farms differ in a number of aspects including
annual rainfall, topography, vegetation, temperature and altitude ranges, with Farm B representing
a harsher environment overall. Traits studied were birth weight, 8-week weight
and weaning weight, ultrasound back-fat and muscle depths at weaning, carcass weight,
carcass fat grade and carcass conformation score. Genetic correlations were estimated for
each trait, between the two farms, with those significantly different from 1 (P < 0.05) indicating
the presence of G
×
E. The models used fitted relevant fixed effects as well as direct and
maternal genetic and permanent environmental random effects. Correlations estimated
were not significantly different from 1 for all traits apart from birth weight, which had a
correlation of 0.45 (s.e. 0.31). By taking G
×
E into account and comparing bivariate and univariate
analyses, the maximum selection response observed for birth weight was 0.0016 kg
per generation. Overall, the lack of G
×
E observed for the majority of traits studied suggest
that the common sire offspring have performed similarly across both farms. However, the
presence of G
×
E associated with birth weight may have implications for lambing associated
problems, or lamb survival, if sires produce lambs with unexpectedly high or low birth
weights.
