Abstract
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 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.
Highlights
Public concern about well-being of farm animals recently increased [1, 2] leading to considerable changes in pig production systems
A number of different housing systems commonly found in practice were included, and while it goes beyond the scope of the present study, to investigate the details of which factors affected pig’s behaviour to which extent, results highlight the importance of taking such factors into account when analysing behaviour traits
In Lesion score difference (LSD), which is thought to mainly reflect the effect of fights during mixing, differed between pigs housed in different systems, and were of biologically relevant magnitude, with higher LSD with pigs housed in the larger group during finishing
Summary
Public concern about well-being of farm animals recently increased [1, 2] leading to considerable changes in pig production systems. In response to this increasing public concern, laws including specific requirements for pig housing and welfare (e.g., group housing of pregnant sows or provision of enrichment items) have been passed (2008/120/EG). Herd sizes increase and new housing systems with higher levels of automation become more and more common [3, 4], leading to reduced human-animal contact and, as a consequence, less habituated animals when handling is necessary. The need for inherently calm and easy to handle pigs, with low levels of aggression further increases in order to reduce stress for the animals at handling or mixing procedures, and pig breeding companies consider changing their breeding goals towards a stronger focus on behaviour traits reflecting these characteristics
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