Variance components of aggressive behavior in genetically highly connected Pietrain populations kept under two different housing conditions1

Abstract

Mixing of unfamiliar pigs is a standard management procedure in commercial pig production and is often associated with a period of intense and physically damaging aggression. Aggression is considered a problem for animal welfare and production. The objective of the present paper was to investigate the genetic background of aggressive behavior traits at mixing of unfamiliar gilts under 2 different housing conditions. Therefore, a total of 543 purebred Pietrain gilts, from 2 nucleus farms (farm A: n = 302; farm B: n = 241) of 1 breeding company, were tested at an average age of 214 d (SD 12.2 d) for aggressive behavior by 1 observer. Observations included the frequencies of aggressive attack and reciprocal fighting during mixing with unfamiliar gilts. On farm A 41% of the gilts were purebred Pietrains, whereas 59% were purebred Landrace or Duroc gilts. On the farm B 42% of the gilts were purebred Pietrains, and 58% purebred Large White gilts. The average size of the newly mixed groups of gilts was 28 animals on farm A and 18 animals on farm B. The Pietrain gilts from the 2 herds were genetically closely linked. They were the offspring of 96 sires, with 64% of these sires having tested progeny in both farms. There were clear differences in the housing of the animals between the 2 farms. The test pen on farm A had a solid concrete floor littered with wooden shavings and was equipped with a dry feeder. On farm B there was a partly slatted floor, and the gilts were fed by an electronic sow feeder. Mean space allowance was 2.6 m(2)/gilt on farm A and 3.9 m(2)/gilt on farm B. Although large interindividual differences existed, gilts from farm B performed numerically more aggressive attack (mean 1.12, SD 1.42 vs. mean 0.71, SD 1.20) and reciprocal fighting (mean 0.78, SD 0.98 vs. mean 0.44, SD 0.82) when compared with gilts from farm A. The heritabilities and additive genetic variances for behavioral traits were estimated with a linear animal model and were on a low level in farm A (h(2) = 0.11, SE = 0.07, and σ(2)a = 0.12 for aggressive attack and h(2) = 0.04, SE = 0.07, and σ(2)a = 0.02 for reciprocal fighting) and on a moderate level in farm B (h(2) = 0.29, SE = 0.13, and σ(2)a = 0.44 for aggressive attack and h(2) = 0.33, SE = 0.12, and σ(2)a = 0.27 for reciprocal fighting). For both aggressive attack and reciprocal fighting, genetic correlation of the same trait between farm A and farm B was 1.0. Therefore, aggressive behavior does not seem to be influenced by genotype × environment interactions. Under these circumstances aggressions in group housing can be reduced by genetic selection against aggressive behavior. Therewith, the welfare and health of sows will ultimately increase.

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

“…The heritabilities ranged from h 2 = 0.22 ± 0.07 [24] to h 2 = 0.43 ± 0.04 [39]. However, in the present study heritabilities for skin lesion scores were lower (LS1: h 2 = 0.14 ± 0.06; LS2: h 2 = 0.12 ± 0.07) and within the range of results found for direct observations of aggressive behaviour (attacks: h 2 = 0.11 ± 0.07 to h 2 = 0.29 ± 0.13 / reciprocal fights h 2 = 0.04 ± 0.07 to h 2 = 0.33 ± 0.07, [40]). Earlier results suggested that lesion scores recorded shortly after mixing mostly reflect the number of attacks received, but not of being an initiator of aggressive interactions [25].…”

Genetic associations between maternal traits and aggressive behaviour in Large White sows

“…The genetic correlation fell into range with genetic correlations between reciprocal aggression and the delivery of non-reciprocal aggression reported in other studies (Turner et al, 2008;D'Eath et al, 2009;Appel et al, 2013). A high positive genetic correlation was also found between SEPD1 and SEPD10, which indicates that these behaviour traits assessed at different points in time measured the same dimension of personality and therefore have a similar genetic background.…”

“…All agonistic encounters shown by the newly mixed gilts were recorded (adapted from Hellbrügge, 2007 and as described in Appel et al, 2013). Aggressive behaviour was subdivided into aggressive attacks (i.e.…”

“…For the trait FIGHT, the frequency of fights was documented for all of the involved gilts. Further information about the observed behaviour traits is presented in Appel et al (2013).…”

“…Most aggressive encounters lead to skin lesions, social stress and therewith a suppression of immunocompetence (Muirhead, 1983;Morrow-Tesch et al, 1994), reduced profitability, longevity and welfare of the animals (reviewed by Kongsted, 2004). For delivery of non-reciprocated bullying and reciprocated fighting, moderate heritabilities were found Appel et al, 2013). Therefore, selection against aggressiveness seems to be possible and may benefit the welfare of the animals (Turner et al, 2010;Tönepöhl, 2012).…”