Data from: Suitability of traits related to aggression and handleability for integration into pig breeding programmes: genetic parameters and comparison between Gaussian and binary trait specifications

Changes in husbandry systems as well as consumers' increasing demands
for animal welfare lead to increasing importance of traits such as
handleability and aggressiveness in pigs. However, before using such novel
traits for selection decisions, information on genetic parameters for
these traits for the specific population is required. Therefore, weight
gain and behaviour-related traits were recorded in 1004 pigs (814 Pietrain
x German Landrace crossbred, 190 German Landrace purebred) at different
ages. Behaviour indicators and tests were assessed and conducted,
respectively under commercial farm conditions and included scoring of skin
lesions (twice) and behaviour during backtests (twice), injections (once),
handling (twice) and weighing (three times). Since behaviour scores often
exhibit suboptimal statistical properties for parametric analyses,
variance components were estimated using an animal model assuming a normal
(Gaussian, GA; all traits) and additionally a binary distribution of
variables (BI; using a logit-link function for all behaviour traits).
Heritabilities for behavioural traits ranged from 0.02 ± 0.04 (finishing
pig handling test; BI) to 0.36 ± 0.08 (backtest 2; GA) suggesting that
some of the traits are potentially useful for genetic selection (e.g.
finishing pig weighing test: h² (GA) = 0.20 ± 0.07). Only minor
differences were observed for results from binary and Gaussian analyses of
the same traits suggesting that either approach might yield valid results.
However, four-fold cross-validation using correlations between breeding
values of a sub-set of animals for the sample trait finishing pig weighing
score indicated slight superiority of the logit model (r = 0.85 ± 0.04 vs.
r = 0.77 ± 0.03) Generally, only weak to moderate associations were found
between behavioural reactions to the same test at different ages (rp ≤
0.11 for weighing at different ages; rp = 0.30 and but rg (GA) = 0.84 ±
0.11 for the backtests) as well as between reactions to different tests.
Therefore, for inclusion of behaviour traits into breeding programmes, and
considering high labour input required for some tests such as the
backtest, it is recommended to assess behaviour during situations that are
relevant and identical to practical conditions, while the use of indicator
traits generally does not appear to be a very promising alternative.