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International audience; In sheep, the bond between the dam and her lambs is established during the first hours of a lamb's life. Genetic variability for behavioural reactivity of ewes assessed in an arena test performed 24 hr after lambing has already been reported. However, there is no evidence that this reactivity represents the ewe's maternal reactivity at lambing in outdoor conditions. The objective of this study was to investigate whether or not the behavioural reactivity of ewes in the arena test is genetically related to their maternal reactivity measured at lambing. A total of 935 Romane ewes were studied. The maternal reactivity of ewes at the outdoor lambing site was recorded in response to a human approach and to the handling of the lambs. Their behavioural reactivity was also recorded 24 hr post-lambing in the arena test that involved a separation from the litter and a human presence. Flight distance, aggressive reaction, time to restore contact with the litter, maternal behaviour scores and vocalizations recorded at the lambing site were heritable (0.12-0.34). All of these behaviours were genetically correlated with the behavioural reactivity in the arena test. The highest genetic correlations (from 0.60 to 0.90) were found amongst maternal behavioural scores, flight distance and high-pitched bleats. In conclusion, behavioural reactivity in the arena test can be used to assess early maternal reactivity in standardized conditions. Phenotyping of ewes' behavioural reactivity with a simplified arena test can be performed for genetic improvement in maternal behaviour in sheep.

In livestock, improving maternal reactivity towards the litter is an important issue in breeding strategies to promote production and animal welfare. As of yet, no studies have investigated the within-breed genetic variation of maternal reactivity in sheep. The objective of this study was to estimate the genetic parameters of maternal reac-tivity traits. A total of 1,095 primiparous and 1,441 multiparous Romane ewes were phenotyped 24hr postlambing using a behavioural test (arena test, AT) over a 10-year experimental period. The test consisted of three successive phases evaluating the ewe's attraction to her litter, reactivity to separation from her litter, and reactivity to a conflict between attraction to her litter and avoidance of a motionless human. The ewes were reared exclusively on rangelands (South of France) and lambed outdoors in the spring. High-pitched bleating and low-pitched bleating in the AT were mostly highly heritable (0.39‒0.46). Heritabilities were moderate for proximity to the litter in the presence of a human (0.27) and low for locomotion and vigilance in the AT (0.09‒0.15). The measurements of a given behaviour in the three phases of the AT were highly genetically correlated. Few genetic correlations were found between the different behavioural traits in the AT, the highest correlations being between high-pitched bleating and low-pitched bleating (−0.43 to −0.77). In conclusion, our find-ings demonstrate moderate-to-high heritability for maternal reactivity traits. These traits could be included in genetic selection schemes to enhance maternal attachment provided there is no unfavourable link with other production traits.

In sheep, social reactivity and reactivity to humans are relevant behavioral responses that are used to investigate the behavioral adaptation of farm animals to various rearing conditions. Such traits were previously reported as heritable and associated with several QTLs. However, few behavior-related genotype by environment (G × E) interactions have been reported to date. The experiment was performed on 2,989 male and female lambs issued from 30 sires. Every sire had progeny reared under both intensive and extensive conditions. After weaning, all lambs were individually exposed to two standardized behavioral tests. A broad range of behaviors including vocalizations, locomotion, localization, vigilance, and flight distance were assessed. Two complementary statistic approaches, with and without assumptions on the biological significance of behaviors, were performed to investigate social reactivity and reactivity to humans. G × E interactions were investigated based on the genetic correlations estimated for each factor or trait between farming conditions; those significantly different from 1 indicating a G × E. Environmental effects showed that social reactivity and reactivity to humans were higher in intensively reared lambs. The heritability of factors or traits used to measure social reactivity and reactivity to humans was similar in both rearing conditions. Estimated heritabilities were high for vocalizations in response to social isolation, moderate for locomotion and vigilance in response to social isolation, and low for both flight distance to an approaching human and proximity to a motionless human. No significant G × E interaction was found for vocalizations. G × E interactions were found for locomotion, vigilance and flight distance. Genetic correlations between both environments were low to moderate for vigilance, locomotion and flight distance. Vocalization in response to social isolation with or without human presence was identified as a robust trait and could be used to improve sheep sociability, independently of the environment. A G × E interaction was observed for behavioral reactivity to humans. Although moderate, the genetic correlation for this trait between intensive and extensive conditions could be used to select sires in the same environment by taking into account the G × E and to produce in different environments progenies that are less reactive to humans.

Gastrointestinal nematodes are one of the main health issues in sheep breeding. To identify loci affecting the resistance to Haemonchus contortus, a genome scan was carried out using 1,275 Romane × Martinik Black Belly backcross lambs. The entire population was challenged with Haemonchus contortus in 2 consecutive experimental infections, and fecal egg counts (FEC) and packed cell volumes were measured. A subgroup of 332 lambs with extreme FEC was necropsied to determine the total worm burden, length of female worms, sex ratio in the worm population, abomasal pH, and serum and mucosal G immunoglobulins (IgG) responses. Pepsinogen concentration was measured in another subset of 229 lambs. For QTL detection, 160 microsatellite markers were used as well as the Illumina OvineSNP50 BeadChip that provided 42,469 SNP markers after quality control. Linkage, association, and joint linkage and association analyses were performed with the QTLMAP software. Linkage disequilibrium (LD) was estimated within each pure breed, and association analyses were carried out either considering or not the breed origin of the haplotypes. Four QTL regions on sheep chromosomes (OAR)5, 12, 13, and 21 were identified as key players among many other QTL with small to moderate effects. A QTL on OAR21 affecting pepsinogen concentration exactly matched the pepsinogen (PGA5) locus. A 10-Mbp region affecting FEC after the 1st and 2nd infections was found on OAR12. The SNP markers outperformed microsatellites in the linkage analysis. Taking advantage of the LD helped to refine the locations of the QTL mapped on OAR5 and 13.

Quantitative trait loci (QTL) mapping for susceptibility to a Salmonella Abortusovis vaccinal strain was performed using an experimental design involving 30 Romane sheep sire families (1216 progenies). Nine QTL corresponding to bacterial load, weight variations and antibody response criteria were mapped on eight chromosomes, including the major histocompatibility complex area on chromosome 20. Surprisingly, none was found to be significant in the SLC11A1 region (formerly NRAMP1) that has been shown to influence Salmonella susceptibility in other species.

In this study, the potential association of PrP genotypes with health and productive traits was investigated. Data were recorded on animals of the INRA 401 breed from the Bourges-La Sapinière INRA experimental farm. The population consisted of 30 rams and 852 ewes, which produced 1310 lambs. The animals were categorized into three PrP genotype classes: ARR homozygous, ARR heterozygous, and animals without any ARR allele. Two analyses differing in the approach considered were carried out. Firstly, the potential association of the PrP genotype with disease (Salmonella resistance) and production (wool and carcass) traits was studied. The data used included 1042, 1043 and 1013 genotyped animals for the Salmonella resistance, wool and carcass traits, respectively. The different traits were analyzed using an animal model, where the PrP genotype effect was included as a fixed effect. Association analyses do not indicate any evidence of an effect of PrP genotypes on traits studied in this breed. Secondly, a quantitative trait loci (QTL) detection approach using the PRNP gene as a marker was applied on ovine chromosome 13. Interval mapping was used. Evidence for one QTL affecting mean fiber diameter was found at 25 cM from the PRNP gene. However, a linkage between PRNP and this QTL does not imply unfavorable linkage disequilibrium for PRNP selection purposes.

Two-dimensional electrophoresis was used to investigate the effects of a QTL for muscle hypertrophy on sarcoplasmic protein expression in ovine muscles. In the Belgian Texel breed, the QTL for muscle hypertrophy is localized in the myostatin-encoding gene. Based on microsatellite markers flanking the myostatin gene, we compared the hypertrophied genotype with the normal genotype. The average age of the sheep was 3 mo. Among the 4 muscles studied, in the hypertrophied genotype only the vastus medialis was normal, whereas the semimembranosus, tensor fasciae latae, and LM were hypertrophied. In the hypertrophied genotype, these muscles showed upregulation of enzymes involved in glycolytic metabolism together with oxidative metabolism in LM. Certain chaperone proteins, including glutathione S-transferase-Pi, heat shock protein-27, and heat shock cognate-70, were also more highly expressed, probably due to increased use of energetic pathways. Expression of the iron transport protein transferrin was increased. Alpha-1-antitrypsin was the only protein showing a similar pattern of expression (i.e., less expressed) in all 4 muscles of the hypertrophied genotype. It is suggested that transferrin and alpha-1-antitrypsin may interact to reinforce myogenic proliferative signaling.

International audience; In this review, we assess the current state of knowledge on domestication of the major livestock species. We present first some historical background on location and dates of domestication of livestock. The characteristics that favoured domestication are described, especially gregariousness, precocity of young and diet. We then describe the genetic processes involved during domestication, i.e. uncontrolled processes such as inbreeding and genetic drift, partially controlled processes such as relaxation of natural selection and natural selection in captivity and controlled processes such as active selection. Details are also given on how the resource allocation theory explains changes occurring during domestication. The methods used to assess the extent to which domestication has changed animals (comparisons of wild and domestic stocks, longitudinal analysis and molecular genetics) are also listed. Finally, major behavioural modifications observed during domestication are described, including relationships with humans and predators, and social, feeding, reproductive and maternal behaviours as well as morphological changes.

To compare the protection acquired by infection with Haemonchus contortus or Trichostrongylus colubriformis, successive cross infections with the two species were conducted in two genetically similar groups of 150 ewe lambs from 30 sires of INRA 401 breed. At 6 and 7.5 months of age, each group received two doses of 10 000 L3 separated by a treatment of one of the species, followed by a similar infection with the second species at 9 and 11.5 months. Faecal egg counts (FECs) were done 28 and 35 days after each dose. There were very high genetic correlation within and between species suggesting that the environmental conditions were very similar. The heritability of FEC of H. contortus ranged from 0.39 to 0.48 and the genetic correlations between FEC after the first and second infections with the same or different species were all near 1. Selection against this species could be done on the response to only one dose. For T. colubriformis, only the response to challenge infection had a similar heritability (0.47); the genetic correlations within and among species were also near one. These results will assist the selection of sheep resistant to nematode parasites.

International audience; Simulations were used to study the influence of model adequacy and data structure on the estimation of genetic parameters for traits governed by direct and maternal effects. To test model adequacy, several data sets were simulated according to different underlying genetic assumptions and analysed by comparing the correct and incorrect models. Results showed that omission of one of the random effects leads to an incorrect decomposition of the other components. If maternal genetic effects exist but are neglected, direct heritability is overestimated, and sometimes more than double. The bias depends on the value of the genetic correlation between direct and maternal effects. To study the influence of data structure on the estimation of genetic parameters, several populations were simulated, with different degrees of known paternity and different levels of genetic connectedness between flocks. Results showed that the lack of connectedness affects estimates when flocks have different genetic means because no distinction can be made between genetic and environmental differences between flocks. In this case, direct and maternal heritabilities are under-estimated, whereas maternal environmental effects are overestimated. The insufficiency of pedigree leads to biased estimates of genetic parameters.

The objective of this study was to show the existence of genetic variability in resistance of Creole goats to natural infection with intestinal nematodes. Four successive cohorts of male and female kids were reared from weaning during 9 months in intensive pangola pastures (stocking rate 1.4 t/ha, regrowth of 21 days, 300 kg N/ ha/year of fertilization). All cohorts considered, 203 offsprings from 13 bucks and 149 goats were used in the experiment. Animals were treated with an oral dose of ivermectin every seven weeks, from 3 to 11 months of age. They were sampled for fecal egg counts (FEC) and packed cell volume (PCV), 6 weeks after drenching, when 6 and 10 months old. Haemonchus contortus and Trichostrongylus colubriformis were the predominant species. Data of one cohort when 6 months of age and another one when 10 months old were not included in calculations because a self-cure occurred during a rainy season. Estimated means of FEC after square-root transformation were 1054 and 711 respectively for 6-month-old and 10-month-old kids. Phenotypic correlations between FEC and PCV were -0.46 (p < 0.001) and -0.29 (p < 0.01) when 6 and 10 months old, respectively. FEC repeatabilities estimated as variance ratio were 0.47 and 0.06 for within-age measures (data recorded at one week interval) and between age measures (6 vs. 10 months) respectively. No sire effect was significant for PCV. Sire effect on FEC was more significant when 6 months old (p < 0.03) than when 10 months old (p < 0.15). Further studies are now being carried out to confirm this genetic determinism of resistance to natural infection with strongyles in Creole goats.

Chantier qualité GA; International audience; The present study aimed to evaluate an experimental approach to individually assess social reactivity among sheep. INRA401 male lambs (n = 163) were reared together outdoors as part of a larger flock. Fifteen days after weaning the animals were individually exposed to an arena test of 2 phases (1-social attraction, 2-social isolation) during which proximity toward conspecifics and vocal and locomotor reactivity were measured. One day after the test their inter-individual distances were measured when grazing over a 2-h period in order to estimate their sociability on pasture. This was made using scan sampling recording the identity of the nearest neighbour for each individual, which led to the establishment of a sociability index. Overall, we found that high-pitched bleats recorded during the attraction phase (r = 0.22) and the isolation phase (r = 0.23) of the arena test as well as the locomo-tor activity measured during the isolation phase (r = 0.27) were positively correlated with the sociability index. Furthermore, the behaviour of lambs during the isolation phase of the arena test (i.e. vocal and locomotor agitation) appeared to be a significant predictor explaining 13% of the variance of the sociability on pasture. The behavioural reactivity measured through the arena test thus reflects at least to some extent the sociability of sheep. Those results are very encouraging as they suggest that the sociability of lambs could indeed be evaluated through a short experimental test, which is less time consuming than field ethological observations.

SUMMARY In the past, several studies have been performed to look for genes affecting traits of interest using microsatellite markers in sheep. Even if numerous chromosomal regions have been detected, few genes and causal mutations have been identified. The recent availability of high density SNP chip in sheep is a technological revolution for genomic researches and breeding selection. Firstly, genomic research in small ruminants will be boosted towards the identification of causative mutations underlying large genetic effects on sustainability traits, or the identification of very closely linked genetic markers that allow selecting genes in ovine breeding programmes. Secondly, such new molecular tools allow considering a new type of selection: the genomic selection. The principle of this selection is to use marker effects (without any information about the underlying genes) estimated within a part of the population which is phenotyped and genotyped (called the training population) and applying these effects to the rest of the genotyped population. However, the genomic selection might not always be a profitable strategy in sheep.

International audience; The slaughter period is very complex and may represent different types of stress for the animal. The way and extent animals react to these stress factors depend on their individual emotional reactivity. The objective of the present study was to determine in sheep relationships between reactivity profiles measured during rearing, plasma cortisol levels in blood collected at exsanguination, and metabolic activity in the post-mortem muscle. During the rearing period INRA401 lambs (n = 267) showed coherence in their responses to situations representing different contexts of novelty, social isolation and presence of man. Vigilance and high-pitched bleating were the most often occurring behaviours. Highest levels of these behaviours were observed during novelty and social isolation. Lambs with higher plasma cortisol levels at exsanguination produced meat with lower pH 3 h (r = −0.19, p = 0.003) and 24 h post-mortem (r = −0.13, p = 0.05). Multiple regression analysis found that more socially attracted lambs and lambs performing more high-pitched bleating had higher muscle temperature 3 h post-mortem (p < 0.001), explaining 23.5% of variability. More vigilant lambs had higher pH (r = 0.14, p = 0.02) 3 h post-mortem. Multiple regression including both cortisol and vigilance as explanatory variable was significant (p < 0.01) and explained 12.8% of variability of pH 3 h post-mortem. In the present study, slaughter day, that is, day-to-day variations in the slaughter context, explained 18.4% of the variability in cortisol levels and 25.0–72.7% of variability in post-mortem muscle measurements. When analyses were based on averages per category created according to cortisol levels at exsanguination, to reduce the variability due to slaughter days, behavioural traits (vigilance and social attractiveness of flock-mates) explained statistically about 50% of variability in cortisol levels at exsanguination, and pre-slaughter cortisol levels explained up to 50% of variability of ultimate pH. Relationships between post-mortem muscle metabolism and expressions of social distress and reactivity to novelty suggest that reactivity profile may predict stress reactions during slaughter period and that social disturbances and novel environment in the slaughterhouse may be major causes of stress.

A QTL for muscle hypertrophy has been identified in the Belgian Texel breed. A population of F2 and backcross lambs created from crosses of Belgian Texel rams with Romanov ewes was studied. Effects on carcass traits and muscle development of the Belgian Texel breed polygenes and Belgian Texel single QTL were compared. In both cases, carcass conformation and muscularity were improved. The Texel polygenic environment improved conformation mainly through changes in skeletal frame shape. Segments were shorter and bone weight lower. Muscles were more compact, shorter, and thicker. The single QTL affected muscle development. Thickness and weight of muscles were increased. Composition in myosin changed toward an increase of fast contractile type. The relative contribution of hind limb joint to carcass weight was increased. Differences in skeletal frame morphology among the three genotypes of the single QTL were small. Conformation scoring was mainly influenced by leg muscularity. Back and shoulder muscle development, which largely contributed to variability of muscularity, were less involved in the conformation scoring. Lastly, the QTL explains a small part of differences between these Belgian Texel and Romanov breeds for conformation or muscle development. A large part of genetic variability remains to be explored.

This experiment was conducted to assess the efficiency of selection on the basis of response to artificial challenges in order to breed sheep resistant to natural infection. A short-term divergent selection process was designed to estimate the genetic parameters of these two traits. Two flocks, including 100 Romanov ram lambs each, were challenged in 1990 when they were 6 months old. One flock received three artificial infections with 20 000 third-stage Teladorsagia circumcincta larvae, at intervals of 7 weeks. Faecal egg counts (FEC) were performed on Days 22, 25 and 28 post infection (p.i.) and the animals were drenched on Day 28 p.i. The other flock was grazed for 5 months on a pasture contaminated with the same species. Faecal samples were taken from the lambs at similar ages. About 5 rams with the lowest FEC and 5 with the highest FEC were selected in each flock and mated with unselected ewes. Their offspring (200 animals) were challenged in 1992, half in the same way as their sires, and the other half by the other method. Because of a drought in the summer of 1990, it was necessary to repeat part of the experiment, and in 1992 the 5 and 8 rams with the lowest and highest FEC, respectively, were selected from the offspring challenged on the pasture in 1992 and were mated with unselected ewes. Their progeny (about 80 animals) were challenged in 1994, half by natural infection, half by artificial infection. The mean FEC of the flock increased from the first to the third artificial infection. The natural infection was highly variable in different years, reflecting the difficulty of assessing resistance using this mode of challenge. Genetic parameters were estimated using animal models and REML solutions. The repeatabilities of the FEC following artificial and natural infection were 0.49 and 0.70 respectively within a period of one week, and 0.22 and 0.41 respectively for periods separated by intervals of 7 weeks; the heritabilities of the single egg count were 0.22 and 0.38 respectively. The genetic correlation was 0.87: the FEC recorded under natural or artificial infection appear to depend on the same genetic potential.

"Chantier qualité spécifique "Auteurs Externes" département de Génétique animale : uniquement liaison auteur au référentiel HR-Access "; International audience; An experimental population (1216 lambs from 30 sires) of the Inra401 sheep was created in an Inra flock to allow QTL detection for susceptibility to Salmonella infection, wool and carcass traits. The Inra401 is a sheep composite line developed from two breeds: Berrichon du Cher and Romanov. At 113 days of age on average, the lambs were inoculated intravenously with $10^{8}$ Salmonella abortusovis Rv6 (vaccinal strain). They were slaughtered 10 days after the inoculation. Several traits were measured at inoculation and/or slaughtering to estimate the genetic resistance of the lambs to Salmonella infection: specific IgM and IgG1 antibody titres, body weight loss, spleen and pre-scapular node weights and counts of viable Salmonella persisting in these organs. This paper presents a quantitative analysis of the genetic variability of the traits related to salmonellosis susceptibility. The heritabilities of the traits varied between 0.10 and 0.64 (significantly different from zero). Thus, in sheep as well as in other species, the determinism of resistance to Salmonella infection is under genetic control. Moreover, the correlations between the traits are in agreement with the known immune mechanisms. The genetic variability observed should help QTL detection.

Goat production is widespread in the tropics. Goats are very susceptible to gastrointestinal nematode infection, but there is less evidence of their genetic resistance. Genetic resistance of Creole goats to gastrointestinal nematodes has been studied at Guadeloupe in the French West Indies since 1995. The objective of this research was to investigate genetic variation for resistance to gastrointestinal nematode infection, in order to introduce this trait into breeding schemes. Genetic variability was assessed within a Creole experimental flock. Forty-nine sire groups were characterized at weaning and 55 during fattening after weaning. Kids were naturally infected, mainly by Haemonchus contortus and Trichostrongylus colubriformis. Fecal egg counts were determined once at weaning and every 6 and 7 wk after drenching during fattening. Blood samples were collected every 7 wk during fattening for determination of packed cell volume. Live weights were recorded at weaning and at the beginning and middle of every infection period during fattening. Genetic parameters were estimated using the REML for multivariate animal models. The heritability estimate for transformed fecal egg count was 0.37+/-0.06 at weaning. During fattening, it increased from 0.14+/-0.05 at 4 mo to 0.33+/-0.06 at 10 mo. Heritabilities of packed cell volume ranged from 0.10 to 0.33. At weaning, maternal heritability of fecal egg count reached 0.26 and direct heritability 0.20. After 6 mo of age, maternal effects were found to be unimportant for fecal egg count and packed cell volume. Live weights presented significant genetic variability. Genetic relationships between fecal egg counts and live weight in infected pastures were never significant. Genetic correlations between packed cell volume and live weight decreased from 0.47 to 0.10 from weaning to 10 mo of age. These results demonstrated the feasibility of breeding for improved resistance to nematodes in Creole kids.

An experimental population (1216 lambs from 30 sires) of INRA401 sheep was created to detect QTL controlling salmonellosis resistance, carcass traits and wool traits. INRA401 is a composite line developed from crosses between Berrichon du Cher and Romanov breeds. This paper describes a quantitative analysis of the genetic variability for carcass traits. Controlled traits included body and carcass weights, conformation score, carcass dimension, fat and skeleton measurements, surface area of longissimus dorsi. Using appropriate, fixed effect adjustments, genetic correlations and heritabilities were estimated from classical animal models. Heritabilities were found to be high in comparison to previous studies, indicating both a good standardisation of the environment and a high genetic variability in this newly created breed. On the whole the study shows that the data collected are promising in terms of QTL detection.

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.