Genetic analysis of emotional reactivity in sheep: effects of the genotypes of the lambs and of their dams

A total of 1347 weaned lambs from eight genotypes were tested over five consecutive years: Romanov (ROM) and Lacaune (LAC) pure breeds, the two F1 crossbreeds (RL and LR) and the offspring of ewes from these four genotypes sired with Berrichon-du-Cher rams (BCF). The lambs were individually exposed to three challenging tests involving novelty, human contact and social isolation. Ten synthetic variables were used to express social reactivity (i.e., active vs. passive strategy), exploratory activity and reactivity to humans. BCF crossbreds were more active (i.e., high bleats, locomotion and attempts to escape) than purebreds and F1. In contrast, ROM expressed more passive responses (i.e., low bleats and vigilance postures) than LAC and BCF crossbreds. In addition, ROM approached a motionless human less and had longer flight distances to an approaching human than did LAC and BCF crossbreds. When restrained, ROM, and to a lesser extent B×ROM and B×LR, avoided human contact more than did LAC, RL and B×LAC. Most of these differences were explained by direct additive genetic effects while maternal influences or heterosis effects were rarely significant. The highest heritability was for high bleats (h2 = 0.48). Females were more active and avoided human contact more than did males

Consequences of weaning piglets at 21 and 28 days on growth, behaviour and hormonal responses

International audienceA recent European Directive raised the minimum weaning age of piglets to 28 days, although weaning at 21 days is still allowed (but not necessarily practiced) in batch breeding conditions. The aim of the present study was to determine the consequences of weaning at 3 and 4 weeks on animal weight gain, behaviour and stress neuro-endocrine responses, compared to sow-reared piglets. Three groups of Large-White piglets were compared: six litters of seven to eight piglets weaned at 21 days (W21 group), six litters of seven to eight piglets weaned at 28 days (W28 group) and six litters of eight suckling piglets reared by the sow for 40 days (C group). Piglets were regularly weighed from birth to 75 days. Each weaned group was observed for 2 h/day for 7 days (between d − 1 and d + 12 after weaning) at the same time as the control group. The specific behavioural parameters assessed by direct observation were position, activity and social interaction. Urine was collected to measure glucocorticoid (cortisol and cortisone) and catecholamine (adrenaline and noradrenaline) levels. Compared to nursed piglets, weaning at 21 or 28 days induced a reduction in growth rate, as well as behavioural and hormonal changes. Early behavioural changes included an increase of vocalisations and of lying in litter cohesion; later changes included an increase of aggressive and nosing behaviour. Endocrine changes included a reduction in catecholamine (mainly noradrenaline) and cortisone levels in urine. Comparison of W21 and W28 showed that some of these changes were more intense and lasted longer with early weaning. Endocrine changes and certain behaviour (litter cohesion, vocalisations) could be related to food intake deficits, as measured by the greater reduction in growth rate in early-weaned animals. Changes in active behaviour (increase of aggressive and nosing behaviour) appeared earlier after weaning in the youngest animals. This study shows that weaning at 21 days has more negative consequences on growth rate and stress endocrine responses than weaning at 28 days. However, piglets weaned at both 21 and 28 days showed behavioural disturbances, but often with different kinetics

Evaluation de l'importance relative des changements d'environnement et/ou de groupe social au sevrage chez le porcelet : mesures comportementales, zootechniques et hormonales

National audienc

The role of familiarity in the development of social recognition by lambs

International audienceA series of experiments investigated the role of association and familiarity in the development of social recognition among lambs. In each experiment, lambs were tested successively with 2 different social partners. When separated from their mothers, lambs that were paired with a partner with which they had been housed for 17 or 5 days emitted fewer distress bleats than they did during tests with an unfamiliar lamb. However, this effect was only evident when the test with the unfamiliar partner preceded the test with the familiar partner. When lambs were first tested with an unfamiliar partner treated with the same artificial odorant that had previously been associated with members of their own group, they bleated more than they did during a second test with a partner whose odor was novel. This effect was not observed when the familiar- and novel-odor partners were encountered in the reverse order. Bleating frequencies by lambs paired with their twin did not differ reliably from those of lambs paired with a familiar non-twin. Nonetheless, there was a significant correlation between the number of bleats by twins that were tested together. Overall, the results indicate that lambs become familiar with and recognize individuals (twins and non-twins) as a result of direct association. Lambs also discriminate between novel scents and artificial odorants associated with their familiar agemates, but such odors neither mask nor substitute effectively for lambs' individually recognizable phenotypes. Bleating frequency increases with the novelty of the social partner and of the test situation, and is therefore markedly affected by repeated testing

Influence of housing and social changes on growth, behaviour and cortisol in piglets at weaning

The present experiment aimed at evaluating the relative effects of environmental and social changes on behaviour, growth and salivary cortisol of piglets at weaning. On Day 0, 26-day old piglets were weaned and allocated to one of four treatments: neither environmental nor social change (C), environmental change (E), social change (S), and both changes (SE). Overall, 6 replicates of 10-12 animals/pen/treatment were analysed. Piglets were video recorded during the first three days after weaning to observe social behaviour and general activity. Saliva was collected between 07:00 and 09:00 on Day 0 just before weaning (D0H7), on Day 1 (D1H7) and Day 2 (D2H7 and D2H16) to measure cortisol. Saliva cortisol did not change after weaning in C piglets but increased significantly at D1H7 in S and SE piglets, at D2H7 and D2H16 in E and SE piglets. Compared to C piglets, numerous behaviours were altered in SE piglets: more total lying (P<0.08), less lying on the belly, less environmental exploration, less playing, more fighting regardless the day, more lying awake inactive on Day 0 (P<0.05). Compared to C piglets, E piglets displayed more total lying but less environmental exploration whereas S piglets showed less lying on the belly but more fighting (P<0.05). Present results show that moving piglets to a new environment as well as mixing them with unfamiliar conspecifics at weaning have stressful effects which are additive

The role of familiarity in the development of social recognition by lambs

International audienceA series of experiments investigated the role of association and familiarity in the development of social recognition among lambs. In each experiment, lambs were tested successively with 2 different social partners. When separated from their mothers, lambs that were paired with a partner with which they had been housed for 17 or 5 days emitted fewer distress bleats than they did during tests with an unfamiliar lamb. However, this effect was only evident when the test with the unfamiliar partner preceded the test with the familiar partner. When lambs were first tested with an unfamiliar partner treated with the same artificial odorant that had previously been associated with members of their own group, they bleated more than they did during a second test with a partner whose odor was novel. This effect was not observed when the familiar- and novel-odor partners were encountered in the reverse order. Bleating frequencies by lambs paired with their twin did not differ reliably from those of lambs paired with a familiar non-twin. Nonetheless, there was a significant correlation between the number of bleats by twins that were tested together. Overall, the results indicate that lambs become familiar with and recognize individuals (twins and non-twins) as a result of direct association. Lambs also discriminate between novel scents and artificial odorants associated with their familiar agemates, but such odors neither mask nor substitute effectively for lambs' individually recognizable phenotypes. Bleating frequency increases with the novelty of the social partner and of the test situation, and is therefore markedly affected by repeated testing

Influence de la race sur le comportement d'ovins vis à vis de la présence humaine

National audienceEwe lambs from 2 breeds (Merinos d’Arles and Romanov) and their crossbreds, from Merinos ewes sired by Romanov rams, were observed during 5 individual tests. During the first 3 tests there were no other sheep in sight and animals were alone, with concentrate or with a human. During the last 2 tests, some penmates were in sight and the experimental animal was alone or with a human. Romanov animals were much more reactive than the M6rinos. They eliminated more, ate less and avoided the human more. For most of the criteria, crossbreds were closer to the Romanov than to the Merinos purebreds. This seemed to be due to genetic differences and not to direct maternal influence.Des agnelles de deux races (Mérinos d’Arles et Romanov) et des croisées issues de mères Mérinos saillies par des mâles Romanov ont été observées dans cinq épreuves individuelles. Pendant les trois premières épreuves il n’y avait pas de congénères en vue et les animaux étaient seuls, avec de l’aliment concentré ou avec un homme. Pendant les deux dernières épreuves, des congénères étaient visibles, dans un parc contigu, et les animaux étaient seuls ou avec un homme. Les agnelles de race Romanov ont été beaucoup plus réactives que celles de race Mérinos d’Arles. Elles déféquaient et urinaient plus fréquemment, mangeaient moins et évitaient plus l’homme. Pour la plupart des critères les croisées avaient des performances plus proches de celles des Romanov que de celles des Mérinos. Ces différences semblent être d’origine génétique plutôt que dues à la mère

Grouping piglets by sex at weaning reduces aggressive behaviour

International audienceThe aim of this work was to reduce aggressive behaviour when piglets are grouped at weaning. The experiment assessed whether it is better to group piglets by sex at weaning or to mix them in male–female groups. Large White piglets were weaned at 28 days and assigned to 4 conditions, with 6 groups of animals/condition: (L-MF) 4 males and 4 females reared together from birth, (A-M) 8 unfamiliar male piglets, (A-F) 8 unfamiliar female piglets, and (A-MF) 4 male and 4 female unfamiliar piglets. All groups were videotaped on days 28, 29, 31, 39 and 46 for 2 h. Aggressive interactions were quantified and scratches on each piglet were counted on days 27, 29 and 33. Feed consumption and piglets’ weights were quantified from birth to day 63. On days 27, 29 and 33, urine was collected between 7:00 and 8:00 for measurements of catecholamines and glucocorticoids. Fighting durations were longer in A-MF than in L-MF and both single-sex groups on day 29 (p < 0.05), and than in L-MF and A-F on day 28 (p < 0.05). Durations did not differ between L-MF and single-sex conditions. Fights were more severe and there were more scratches in the A-MF condition compared to the other three conditions. Conditions A-M and A-F did not differ. In the mixed-sex group, fights between two males tended to be more severe than fights between two females (p < 0.1) or than mixed-sex fights (p < 0.1); males initiated more aggression than females (p < 0.05). The presence of females seemed to increase males’ aggressive behaviour in mixed-sex groups. Growth and food intake were slightly affected by treatments but were similar between conditions on day 63. A rise of noradrenaline levels was observed after weaning for the unfamiliar piglets (p < 0.001). However, the grouping criterion by sex did not lead to changes in neuroendocrine activity. Grouping piglets by sex reduces aggressive behaviour at weaning and this should be taken into account in pig farms in order to improve animal welfare

Influence de la race sur le comportement d'ovins vis à vis de la présence humaine

National audienceEwe lambs from 2 breeds (Merinos d’Arles and Romanov) and their crossbreds, from Merinos ewes sired by Romanov rams, were observed during 5 individual tests. During the first 3 tests there were no other sheep in sight and animals were alone, with concentrate or with a human. During the last 2 tests, some penmates were in sight and the experimental animal was alone or with a human. Romanov animals were much more reactive than the M6rinos. They eliminated more, ate less and avoided the human more. For most of the criteria, crossbreds were closer to the Romanov than to the Merinos purebreds. This seemed to be due to genetic differences and not to direct maternal influence.Des agnelles de deux races (Mérinos d’Arles et Romanov) et des croisées issues de mères Mérinos saillies par des mâles Romanov ont été observées dans cinq épreuves individuelles. Pendant les trois premières épreuves il n’y avait pas de congénères en vue et les animaux étaient seuls, avec de l’aliment concentré ou avec un homme. Pendant les deux dernières épreuves, des congénères étaient visibles, dans un parc contigu, et les animaux étaient seuls ou avec un homme. Les agnelles de race Romanov ont été beaucoup plus réactives que celles de race Mérinos d’Arles. Elles déféquaient et urinaient plus fréquemment, mangeaient moins et évitaient plus l’homme. Pour la plupart des critères les croisées avaient des performances plus proches de celles des Romanov que de celles des Mérinos. Ces différences semblent être d’origine génétique plutôt que dues à la mère