Genetische Analyse von Verhaltensmerkmalen beim Schwein

Abstract

This thesis deals with different behaviour parameters in pigs, which were measured during different production periods. The aims of the thesis were to investigate traits that characterise agonistic behaviour as well as maternal behaviour in pigs. Furthermore, a genetic analysis of the investigated behavioural parameters had taken place in order to determine whether it is possible to include these behaviour traits in pig breeding programmes. Due to the changes that are currently taking place in the pig production (i.e. pregnant sows being kept in groups and increasing trends towards alternative housing systems of lactating sows) behaviour traits are gaining more and more importance. Reduced aggression among pigs kept in groups as well as better maternal behaviour in lactating sows will not only improve animals’ welfare and lead to reduced losses of piglets, but will also improve the profitability of pig production. The third chapter contains a review of tests that have been described to capture maternal characteristics in sows. Different test types have been developed to evaluate the aggressive and fearful behaviour towards humans. Tests have been developed to determine how sociable or anxious pigs react when coming into contact with people. In tests for lactating sows have been developed to assess the level of maternal care the sow shows towards her piglets through different kinds of separation between sow and piglets. The susceptibility of the sow towards the piglets has been assessed by acoustic signals (‘piglet scream test’) or by tactile stimuli. The tests described in the literature differ greatly regarding experimental setup and evaluation. In some studies very small numbers of pigs were tested. Therefore, genetic parameters in these studies are rare. However, behaviour tests seem suitable to help to genetically improve the behaviour of sows towards their offspring. Little is known about the correlation between maternal behaviour and other behaviour traits as well as production parameters. The purpose of the first trial (fourth chapter) was to determine how much the genetic parameters of agonistic behaviour differ when closely related animals were observed in two different surroundings. Data of 543 young Pietrain gilts (214 ± 12.2 days of age) had been collected, of which 302 pigs were housed on farm A, and 241 pigs housed on farm B. The housing conditions differ considerably between the two farms. The gilts were the offspring of 96 sires, with 64% of these having tested progeny on both farms. The behaviour of the pigs was observed for 30 minutes after the mixing of gilts from different rearing groups. The gilts from farm A showed less uni- and bilateral aggressions than those from farm B. The heritability for unilateral and bilateral aggression were of low magnitude for the pigs from farm A (h² = 0.11 ± 0.07 and h² = 0.04 ± 0.07, respectively). On farm B unilateral aggression had a heritability of h² = 0.29 ± 0.13 and bilateral aggression of h² = 0.33 ± 0.12. The genetic correlation between both traits examined on the two farms lie on a high level. Based on these values there seem to be no appreciable genotype x environment interactions. It can be fairly derived from these results that a genetic selection towards agonistic characteristics may be promising. The aim of the second test (fifth chapter) was to evaluate the suitability of behaviour tests on lactating sows in order to determine the sows’ maternal behaviour. Furthermore, their relationship with agonistic behaviour traits was calculated. Therefore, 798 Large White gilts were scored for agonistic behaviour at regrouping. The response of 848 Large White sows towards the separation from their 2,022 litters was observed at two different stages of lactation (i.e. within the first 2 to 12 hours after birth (SEPD1) and around day 10 after birth (SEPD10)). In addition, farrowing behaviour of the sows, rearing performance, the usability of the sows and udder quality were evaluated during lactation period. Low heritabilities were analysed for behaviour traits SEPD1 (h² = 0.03 ± 0.03) and SEPD10 (h² = 0.02 ± 0.03). For additional traits that were measured during lactation period low to moderate heritabilities could be estimated (h² = 0.03 ± 0.02 to h² = 0.19 ± 0.03). The heritability in gilts for unilateral and bilateral aggression was at a low (bilateral aggression) to moderate (unilateral aggression) level. No conclusion about the relationship between agonistic behaviour and maternal behaviour can be drawn due to high standard errors. To sum up, it seems to be possible and desirable to genetically alter these behaviour traits. These approaches may be used for the further integration of behaviour traits into pig breeding programmes.