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

PLoS One. 2018 Dec 28;13(12):e0204211. doi: 10.1371/journal.pone.0204211. eCollection 2018.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Female
  • Male
  • Models, Genetic*
  • Normal Distribution
  • Quantitative Trait, Heritable*
  • Selective Breeding*
  • Swine / genetics*

Associated data

  • Dryad/10.5061/dryad.f1j4s39

Grants and funding

The study was a part of the project “investigations of possibilities to integrate behaviour traits into pig breeding programmes” funded by the German Federal Ministry of Food, Agriculture and Consumer Protection (http://www.bmel.de/DE/Startseite/startseite_node.html) via the Federal Office for Agriculture and Food in the framework of the programme “innovation facilitation”, grant number: PGI-06.01-28-1-35.026-08. Funding was received by MG, BT and AA. BHZP GmbH (Bundes Hybrid Zucht Programm) provided support in the form of salary for author BV, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the 'author contributions' section. Furthermore, we acknowledge support by the German Research Foundation and the Open Access Publication Funds of the University of Göttingen.