Analyse du déterminisme génétique de la caudophagie chez des femelles de la lignée Tai Zumu en fin d'engraissement

Cette étude porte sur la quantification des bases génétiques de la caudophagie chez des femelles Tai Zumu. Le phénotype mesuré est la présence de morsure(s) à la queue en fin d’engraissement, traduisant le fait que l’animal n’a pas su se défendre contre l’attaque de ses congénères. Les objectifs sont de 1/ comparer les performances de croissance et d’adiposité au contrôle à 100kg entre femelles indemnes et femelles mordues à la queue, 2/ quantifier la contribution d’effets génétiques sociaux, qui sont liés aux génotypes des partenaires de groupe, à la variation phénotypique du caractère ‘mordu’, et enfin 3/ estimer les effets de l’environnement sur l’expression génétique de ce caractère sous forme d’interactions génétique-environnement (GxE). La présence de morsure(s) a été enregistrée sur 33266 cochettes dans les trois élevages de sélection de la lignée. La prévalence variait entre 2,8% et 10,8% selon l’élevage. Ceux-ci diffèrent par les caractéristiques des groupes (ex. taille, nombre de mélanges) et le mode d’alimentation en engraissement. Les modèles d’analyse tenaient compte d’un effet génétique direct seul ou avec un effet génétique social. Les modèles ont été appliqués à la population globale des trois élevages et à chaque élevage séparément. Les effets génétiques sociaux contribuent à plus de 80% de la variance héritable. Leur prise en compte permet d’expliquer 40 à 80% de la variation phénotypique contre seulement 6 à 8% avec un modèle direct. Les différences entre élevages de classement des verrats connecteurs selon leurs valeurs génétiques, indiquent l’existence de fortes GxE puisque leurs corrélations de rang sont non différentes de 0. Bien que la part de variance génétique directe du caractère soit très faible, une sélection contre la caudophagie est possible. Inclure des effets génétiques sociaux permet de mieux quantifier la variation héritable et leur prise en compte dans les schémas augmenterait la réponse à la sélection contre ce comportement déviant.This study focusses on quantification of the genetic basis of tail-biting in Tai Zumu females. The phenotype under measure was the presence of tail bite(s) at the end of the fattening period, reflecting that the animal was unable to defend itself from groupmates’ attacks. The objectives were to (1) compare the growth and leanness performance at the monitoring at 100 kg between non-bitten females and bitten females; (2) quantify the contribution of social genetic effects, which depend on the genotypes of groupmates, to the phenotypic variation of the trait ‘bitten’; and (3) estimate the effect of the environment on the genetic expression of this trait as interactions between genetics and environment (GxE). The presence of tail bite(s) was recorded on 33,266 gilts from three nucleus herds. The prevalence of tail bites varied from 2.8% to 10.8% among herds that differed according to the groups’ characteristics (e.g., size, number of mixings) and feeding system during fattening. The models for analyses considered single direct genetic effects or also social genetic effects. Models were applied to the entire population including the three nucleus herds and to each herd taken separately. Social genetic effects contributed to more than 80% of total heritable variance, which equalled 40-80% of phenotypic variation, whereas only 6-8% was explained with a direct model. Differences in the ranking of connecting sires between herds according to their breeding values yielded rank correlations not different from zero, indicating strong GxE. Selection against tailbiting is possible even though the direct genetic contribution for this trait is low. Considering social genetic effects improves quantification of heritable variation, and accounting for them in breeding schemes would increase response to selection against this deviant behaviour

Genetics of tail-biting receipt in gilts from the Tai Zumu line

Tail-biting (TB) receipt was recorded at the end of the fattening period on 33,266 gilts of the Tai Zumu population, that were raised in groups of 6 to 20 females. This study aimed at quantifying the contribution of social genetic effects to TB receipt, and at assessing the importance of the environment on the genetic expression of this behaviour (GxE). Models for TB receipt included the fixed effects of number of group mates, (herd)-year-month, and the random effects of group, litter, and direct and social additive genetic effects. The model was applied to the complete gilt population and separately to 2 sub-populations, corresponding to 2 of the 3 nucleus herds raising that line, where TB receipt frequency differed and was high enough (>5%). TB receipt was analysed as a linear trait, following a normal distribution with the restricted likelihood methodology applied to an animal model. Social genetic effects contributed 81% to 93% of total heritable variance, which equalled 40 to 80% of phenotypic variation. The variance components varied between herds. The analysis of sire by environment interactions indicated re-ranking of sires between the 2 nucleus herds, according to both their direct and total breeding values

Towards the characterisation of animal robustness by dynamic energy allocation indicators in fattening pigs

International audienceThe objectives of this study were to investigate the possibility of characterising animalrobustness by using indicators based on the dynamics of energy allocation of the animal andto determine their genetic parameters. A total of 2 140 pigs, from the Piétrain NN Françaisline, were raised at the AXIOM boar testing station. This farm was equipped with automaticfeeding system, recording individual weight and feed intake at each visit. We used a dynamiclinear regression model to characterize the evolution of the allocation factor ( αt) betweencumulative net energy available, estimated from feed intake, and cumulative weight gainduring fattening period. The variance of α t, that could be interpreted as an indicator of theresponse of the animal to perturbations/stress, showed moderate heritability (0.27 ±0.08). Ourperspective is to further decompose the allocation factor into components to bettercharacterise the robustness phenoty

Disentangling the dynamics of energy allocation to provide a proxy of robustness in fattening pigs

International audienceAbstract Background There is a growing need to improve robustness characteristics in fattening pigs, but this trait is difficult to phenotype. Our first objective was to develop a robustness proxy on the basis of modelling of longitudinal energetic allocation coefficient to growth for fattening pigs. Consequently, the environmental variance of this allocation coefficient was considered as a proxy of robustness. The second objective was to estimate its genetic parameters and correlation with traits under selection as well with phenotypes routinely collected on farms. A total of 5848 pigs, from Piétrain NN paternal line, were tested at the AXIOM boar testing station (Azay-sur-Indre, France) from 2015 to 2022. This farm was equipped with automatic feeding system, recording individual weight and feed intake at each visit. We used a dynamic linear regression model to characterize the evolution of the allocation coefficient between cumulative net energy available, estimated from feed intake, and cumulative weight gain during fattening period. Longitudinal energetic allocation coefficients were analysed using a two-step approach, to estimate both its genetic variance and the genetic variance in the residual variance, trait LSR. Results The LSR trait, that could be interpreted as an indicator of the response of the animal to perturbations/stress, showed low heritability (0.05±0.01). The trait LSR had high favourable genetic correlations with average daily growth (−0.71±0.06) and unfavourable with feed conversion ratio (−0.76±0.06) and residual feed intake (−0.83±0.06). The analysis of the relationship between estimated breeding values (EBV) LSR quartiles and phenotypes routinely collected on farms shows the most favourable situation for animals from quartile with the weakest EBV LSR, i.e ., the most robust. Conclusions These results show that selection for robustness based on deviation from energetic allocation coefficient to growth can be considered in breeding programs for fattening pigs

Intérêt des performances de truies croisées pour la sélection en race pure de caractères de reproduction de la lignée maternelle Large-White

51. Journées de la Recherche Porcine, 5 et 6 février 2019, Paris, p. 309-314,Intérêt des performances de truies croisées pour la sélection en race pure de caractères de reproduction de la lignée maternelle Large-White. 51. Journées de la Recherche Porcin

Évaluation de la puberté de cochettes Landrace français et indentification de facteurs de variation

International audienceWhile insemination at first estrus is not recommended, most studies agree on the benefits of early puberty, both for reproductive performance and sow longevity. In the swine population in France, sexual maturity is expected at ca. 200 days of age. Although age at puberty is crucial information, it is not recorded on farms. Since selection for low boar taint influences male puberty, it raises questions about its potential side effects on female reproductive ability. This study was carried out as part of a project that assessed impacts of selection against boar taint on the reproduction of Landrace females. The sexual maturity of 1878 gilts at ca. 200 days of age was evaluated on five farms using quantitative plasma progesterone analysis in two blood samples taken 10 days apart. Cutoff values of 2.5 or 5.0 ng/mL gave similar estimates of 19% immature gilts, with a large variation among farms (8-49%). Insemination was not performed for 4% of gilts, 9% were re-inseminated during the first cycle and 15% did not farrow. The rate of earlyreproduction difficulties varied greatly among farms. The influence of immaturity at 200 days was generally low, with a large farm effect. Further investigation is required to analyze long-term effects of late puberty