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The search for the genetic determinism of prolificacy variability in sheep has evidenced several major mutations in genes playing a crucial role in the control of ovulation rate. In the Noire du Velay (NV) sheep population, a recent genetic study has evidenced the segregation of such a mutation named FecLL. However, based on litter size (LS) records of FecLL non-carrier ewes, the segregation of a second prolificacy major mutation was suspected in this population. In order to identify this mutation, we have combined case/control genome-wide association study with ovine 50k SNP chip genotyping, whole genome sequencing and functional analyses. A new single nucleotide polymorphism (OARX:50977717T>A, NC_019484) located on the X chromosome upstream of the BMP15 gene was evidenced highly associated with the prolificacy variability (P =1.93E-11). The variant allele was called FecXN and shown to segregate also in the Blanche du Massif Central (BMC) sheep population. In both NV and BMC, the FecXN allele frequency was estimated close to 0.10, and its effect on LS was estimated at +0.20 lamb per lambing at heterozygous state. Homozygous FecXN carrier ewes were fertile with increased prolificacy in contrast to numerous mutations affecting BMP15. At the molecular level, FecXN was shown to decrease BMP15 promoter activity and to impact BMP15 expression in oocyte. This regulatory action was proposed as the causal mechanism for the FecXN mutation to control ovulation rate and prolificacy in sheep.Author SummaryIn the genetic etiology of women infertility syndromes, a focus was done on the oocyte-expressed BMP15 and GDF9 genes harboring several mutations associated with ovarian dysfunctions. In sheep also, mutations in these two genes are known to affect the ovarian function leading to sterility or, on the opposite, increasing ovulation rate and litter size constituting the prolificacy trait genetically selected in this species. Through a genome-wide association study with the prolificacy phenotype conducted in the French Noire du Velay sheep breed, we describe a novel mutation located in the regulatory region upstream of the BMP15 gene on the X chromosome. This mutation increases litter size by +0.2 lamb per lambing at the heterozygous state, possibly through an inhibition of BMP15 expression within the oocyte. Our findings suggest a novel kind of BMP15 variant responsible for high prolificacy, in contrast to all other BMP15 variants described so far in the coding sequence.

International audience; The effects of maternal nutrition on offspring phenotypes have been mainly documented over the past years in mammals, and are now studied in poultry as well. In the present study, we investigated the effects of a reduced level of dietary Methionine (Met) on laying performances of common laying ducks and their impacts on the phenotype of their mule ducklings. A total of 60 female laying ducks were divided into 2 dietary treatments at 10 wk of age. The restricted group received Met-restricted diets (R group) containing 0.25% of Met whereas the control group received control diets (C group) containing 0.40% of Met that meets Met requirements. The restriction was applied during the growing and laying periods, from 10 to 51 wk of age and a particular focus was put on female breeder traits that might be affected by the Met restriction. Plasma parameters of hepatic and lipid metabolisms were recorded in ducklings. Total weight (P < 0.001), albumen weight (P < 0.001) and albumen percentage of dry matter (P < 0.01) were decreased for eggs laid by female breeders from the R group. Both male and female ducklings from the R group of female breeders showed a reduced BW at hatching (P < 0.001) and a tendency to an increased proportional liver weight (P = 0.07). Finally, the maternal low dietary Met level modified plasma parameters in newborn ducklings regardless of sex: alkaline phosphatase (ALP) and alanine transaminase (ALT) activities were reduced (P = 0.07 and P = 0.002, respectively), levels of glucose (P = 0.03) and triglycerides (P = 0.01) were higher whereas level of free fatty acids decreased (P = 0.01). It was concluded that feeding female laying ducks with a restricted dietary Met content during the growing and laying periods has a negative effect on egg weight and composition. The ducklings that were restricted in nutrients during their early development, have a reduced BW, and altered lipid and hepatic metabolisms.

For many decades, prolificacy has been selected in meat sheep breeds as a polygenic trait but with limited genetic gain. However, the discovery of major genes affecting prolificacy has changed the way of selection for some ovine breeds implementing gene-assisted selection as in the French Lacaune and Grivette meat breeds, or in the Spanish Rasa Aragonesa breed. Based on statistical analysis of litter size parameters from 34 French meat sheep populations, we suspected the segregation of a mutation in a major gene affecting prolificacy in the Noire du Velay and in the Mouton Vendéen breeds exhibiting a very high variability of the litter size. After the genotyping of mutations known to be present in French sheep breeds, we discovered the segregation of the FecLL mutation at the B4GALNT2 locus and the FecXGr mutation at the BMP15 locus in Noire du Velay and Mouton Vendéen, respectively. The frequency of ewes carrying FecLL in the Noire du Velay population was estimated at 21.2% and the Mouton Vendéen ewes carrying FecXGr at 10.3%. The estimated mutated allele effect of FecLL and FecXGron litter size at +0.4 and +0.3 lamb per lambing in Noire du Velay and Mouton Vendéen, respectively. Due to the fairly high frequency and the rather strong effect of the FecLL and FecXGr prolific alleles, specific management programmes including genotyping should be implemented for a breeding objective of prolificacy adapted to each of these breeds.

International audience; In the 1980s, Olkuska sheep went through a dramatic decline in population size, which resulted in a rapid increase in the inbreeding level. Implementation of conservation program led to enhancement of the number of flocks and resulted in establishment of flocks in regions far away from the center of origin of the breed. In this study, we analyzed genetic variation within this unique breed to better understand genetic structure and to support enhanced management strategies. The analysis of genetic diversity in Olkuska sheep was performed using two sources of information, pedigree and genomic data. Single nucleotide polymorphisms (SNP) data supported analysis of runs of homozygosity (ROH), inbreeding coefficient F-ROH, genomic inbreeding F-HOM, linkage disequilibrium and observed heterozygosity. On the basis of the pedigree data, inbreeding coefficient (F) and coancestry were calculated. Both sources of information provided similar results in regard to inbreeding level and showed significant differences between the Southern and the Central subpopulations of the breed. The average inbreeding coefficient (F) was 0.102 in the Southern subpopulation and 0.053 in the Central subpopulation. The average F-ROH in the Southern population was 0.124, and 0.082 in the Central population. The highest number of ROHs were observed on OAR1, OAR2 and OAR3. Most of ROHs were short (1-10 Mb). The pattern of ROHs detected in the study on Olkuska sheep is similar to other research findings cited in the paper. Significant differences between two subpopulations within the local breed which in the past went through a major decline in numbers, creates the threat of genetic diversity loss. Exchange of individuals between flocks located in the south and in the central Poland is strongly recommended.

Phenotype variability depends on genetics and environmental factors. Improving farm animal performances relies on genetic variability, but the possible improvement of selection schemes taking into account nongenetic transgenerational inheritance has become a topic of choice. Indeed, the parental diet may influence the adult phenotype of the offspring, and more and more studies suggest that information acquired from environmental exposures may be transmitted across generations. In this review, we focus on nongenetic inheritance of diet effects in birds, either as parental effect, that is, “nutritional programming,” or through the transmission of information across several generations, via “transgenerational epigenetic inheritance.” Compared to mammal models with regard to their closer proximity with humans, bird models have the added benefit to minimize maternal confounding effects by a direct manipulation of the egg content.

Polymorphisms in the gene encoding bone morphogenetic protein 15 (BMP15) have been associated with multiple ovulations in sheep. As BMP15 regulates inhibin expression in rodents, we assumed that the ovarian inhibin/activin system could mediate part of the effect of BMP15 mutations in the regulation of ovulation rate in sheep. To answer this question, we have studied the effects of two natural loss-of-function mutations of BMP15 on the expression of components of this system. The FecXR and the FecXGr mutations, when present respectively in Rasa Aragonesa ewes at the heterozygous state and in Grivette ewes at the homozygous state, were associated with a twofold increase in ovulation rate. There were only small differences between mutant and wild-type ewes for mRNA expression of INHA, INHBA, ACVR1B, ACVR2A, FST or TGFBR3 in granulosa cells and inhibin A or activin A concentrations in follicular fluid. Moreover, the effects of mutations differed between breeds. In cultures of granulosa cells from wild-type ewes, BMP15, acting alone or in synergy with GDF9, stimulated INHA, INHBA and FST expression, but inhibited the expression of TGFBR3. Activin A did not affect INHBA expression, but inhibited the expression of ACVR2A also. The complexity of the inhibin/activin system, including positive and antagonistic elements, and the differential regulation of these elements by BMP15 and activin can explain that the effects of BMP15 mutations differ when present in different genetic backgrounds. In conclusion, the ovarian inhibin/activin system is unlikely to participate in the increase of ovulation rate associated with BMP15 mutations in sheep.

International audience; AbstractBackground Classical genetic canalization models, which accommodate the mean and variance of a trait separately, provide a flexible approach to take heteroscedasticity for continuous traits into account. However, this model is not appropriate for discrete traits. The aim of this work was to propose heteroscedastic threshold models suitable for the genetic analysis of ordinal data.MethodsIn order to first fit the mean and variance of ordinal traits separately, we extended the classical threshold model (TM) for discrete data by introducing non-genetic and genetic factors of heterogeneity on the variance of its underlying variable, which leads to a homothetic threshold model HTM and its alternative parameterization HTM’ in which the thresholds of different individuals are linked by a homothetic-translation. Relaxing the constraint between the thresholds led us to propose an independent threshold model ITM that was more flexible than HTM’ but required the estimation of more parameters. TM, HTM and ITM models were applied to study 19,671 records on litter size in Romane sheep.ResultsBoth HTM and ITM were able to disentangle the link between the mean and variance that holds in the classical homoscedastic threshold model. The results obtained for the litter size of Romane ewes showed that the data was best fitted with HTM compared to ITM and TM. The correlations between the observed and predicted variances were equal to 0.6 and 0.2 for HTM and TM, respectively. These analyses showed the existence of a genetic component for the heterogeneity of litter size in sheep that was taken into account in HTM.ConclusionsHTM is the most suitable model to study the variability of litter size in sheep. It accommodates both the mean and variance separately while requiring the estimation of only a few parameters.

In mammals, litter size is a highly variable trait. Some species such as humans or cattle are monotocous, with one or sometimes two newborns per birth, whereas others, the polytocous species such as mice or pigs, are highly prolific and often produce a dozen newborns at each farrowing. In monotocous species, however, two or three newborns per birth may sometime be unwanted. In more polytocous species such as sheep or pigs, litter size is studied in order to increase livestock prolificacy. By contrast, twinning rates in humans or cattle may increase birth difficulties and health problems in the newborns. In this context, the aim of our review was to provide a clearer understanding of the genetic and physiological factors that control multiple births in low-ovulating mammalian species, with particular focus on three species: sheep, cattle, and humans, where knowledge of the ovulation rate in one may enlighten findings in the others. This article therefore reviews the phenotypic and genetic variability observed with respect to ovulation and twinning rates. It then presents the QTL and major genes that have been identified in each species. Finally, we draw a picture of the diversity of the physiological mechanisms underlying multiple ovulation. Although several major genes have been discovered in sheep, QTL detection methods in humans or cattle have suggested that the determinism of litter size is complex and probably involves several genes in order to explain variations in the number of ovulations.

Animals under environmental thermal stress conditions have reduced fertility due to impairment of some mechanisms involved in their reproductive performance that are different in males and females. As a consequence, the most sensitive periods of time and the magnitude of effect of temperature on fertility can differ between sexes. The objective of this study was to estimate separately the effect of temperature in different periods around the insemination time on male and on female fertility by using the product threshold model. This model assumes that an observed reproduction outcome is the result of the product of 2 unobserved variables corresponding to the unobserved fertilities of the 2 individuals involved in the mating. A total of 7,625 AI records from rabbits belonging to a line selected for growth rate and indoor daily temperature records were used. The average maximum daily temperature and the proportion of days in which the maximum temperature was greater than 25°C were used as temperature descriptors. These descriptors were calculated for several periods around the day of AI. In the case of males, 4 periods of time covered different stages of the spermatogenesis, the transit through the epididymus of the sperm, and the day of AI. For females, 5 periods of time covered the phases of preovulatory follicular maturation including day of AI and ovulation, fertilization and peri-implantational stage of the embryos, embryonic and early fetal periods of gestation, and finally, late gestation until birth. The effect of the different temperature descriptors was estimated in the corresponding male and female liabilities in a set of threshold product models. The temperature of the day of AI seems to be the most relevant temperature descriptor affecting male fertility because greater temperature records on the day of AI caused a decrease in male fertility (-6% in male fertility rate with respect to thermoneutrality). Departures from the thermal zone in temperature descriptors covering several periods before AI until early gestation had a negative effect on female fertility, with the pre- and peri-implantational period of the embryos being especially sensitive (from -5 to -6% in female fertility rate with respect to thermoneutrality). The latest period of gestation was unaffected by the temperature. Overall, magnitude and persistency of the temperatures reached in the conditions of this study do not seem to be great enough to have a large effect on male and female rabbit fertility.

A prolific allele named FecL(L) is known to segregate in the meat breed of the French Lacaune sheep on the basis of ovulation rate record. To gain more knowledge about the physiological effects of FecL(L), ewes homozygous for FecL(L) (L/L) were compared to wild-type ewes (+/+) for ovarian phenotype and reproductive endocrine profiles. At the ovarian level, the increased ovulation rate in L/L ewes was associated with an increased number of antral follicles of greater than 3 mm and with preovulatory follicles being, on average, 1 mm smaller. Intrafollicular estradiol and testosterone concentrations were not significantly different between the two genotypes. In contrast, L/L large follicles (>or=6 mm) had lower intrafollicular progesterone concentration. At the molecular level, expressions of ovarian markers, such as CYP19A1, CYP11A1, CYP17A1, LHR, and INHA, were not significantly different between the two genotypes. In contrast, FSHR and STAR mRNA levels increased in granulosa cells from L/L ewes. Plasma concentrations of estradiol, luteinizing hormone (LH), follicle-stimulating hormone (FSH), and progesterone measured across a synchronized estrous cycle revealed a significant increase in estradiol levels during the follicular phase, a precocious LH surge, and an increase in progesterone level during the luteal phase of L/L ewes compared to +/+ ewes. Circulating concentrations of FSH were not different between the two genotypes. The precocious LH surge was associated with an increase in frequency of LH pulsatility during the follicular phase. At the pituitary level, mRNA levels for LHB, FSHB, GNRHR, and ESR1 were not significantly different between the two genotypes. In contrast, ESR2 mRNA expression was decreased in L/L ewes compared to +/+ ewes. Based on ovarian phenotype and endocrine profiles, these findings suggest that the mutation in the FecL gene affects ovarian function in a different way compared to other known prolific mutations affecting the bone morphogenetic protein signaling system in the ovine species.

L’objectif de cet article est de définir et illustrer la notion de robustesse telle qu’elle est vue par les généticiens. Pour ces derniers, il existe deux concepts de robustesse. Le premier considère que la robustesse correspond à la capacité de survie de l’animal et au maintien d’un potentiel global de production dans des environnements stressants et fait notamment référence au rôle de l’axe corticotrope. Le second concept définit la robustesse comme le maintien d’un potentiel de production spécifique : dans ce cadre, un animal est dit robuste pour un caractère donné si ce caractère est stable dans des environnements variés, ce qui rejoint la notion d’interaction génotype-milieu et s’explique par différentes hypothèses génétiques (modèle de surdominance, modèle pléiotropique, modèle épistatique). La canalisation d’un caractère correspond alors à l’action de sélectionner pour diminuer la sensibilité aux variations environnementales. Cette canalisation est intéressante pour répondre, par exemple, aux attentes des producteurs (optimum de production), des transformateurs (homogénéité des productions) ou aux nouvelles contraintes environnementales (agriculture durable). La mise en pratique de cette dernière passe par différentes modélisations des interactions génotype-milieu ; la plus novatrice utilise les modèles dits structuraux qui considèrent une variabilité génétique de la variance du caractère considéré et pour lesquels des développements méthodologiques sont encore nécessaires. Différentes expériences de sélection canalisante ont été mises en place sur des animaux de rente avec plus ou moins de succès. A l’heure actuelle, seule la sélection canalisante sur l’homogénéité des poids des lapereaux à la naissance est pratiquée en routine, The objective of this article was to define and illustrate the meaning of robustness in the animal genetic context where this word pointsto two concepts. The first one considers that robustness is the ability to maintain a global production level in stressing environmentsand is mainly related to the role of the corticotrop axis. The second one defines the robustness as the ability to maintain the expressionof a given trait with a low variability in different environments. This concept refers to different genetic hypotheses and to theso-called «overdominance», «pleiotropic» and «epistatic» models, respectively.The canalisation of a trait is the selection to reduce its sensitivity to environmental variations; it is an interesting strategy to reach anoptimum production level, to homogenise production levels, to respond to the relaxation of environmental conditions (low input system)…Different genotype by environment interaction models can be used to canalise a trait. The most recent one is the structural model, which deals with the hypothesis that the expression of a trait is controlled by two sets of genes i. e. one set controlling the meanof the trait and the other set controlling the environmental variability of the trait. Several canalising selection experiments have beenperformed in farm animals but only canalisation for rabbit weight at birth is routinely used at the present time.

The phenotypic observation of some reproduction traits (e.g., insemination success, interval from lambing to insemination) is the result of environmental and genetic factors acting on 2 individuals: the male and female involved in a mating couple. In animal genetics, the main approach (called additive model) proposed for studying such traits assumes that the phenotype is linked to a purely additive combination, either on the observed scale for continuous traits or on some underlying scale for discrete traits, of environmental and genetic effects affecting the 2 individuals. Statistical models proposed for studying human fecundability generally consider reproduction outcomes as the product of hypothetical unobservable variables. Taking inspiration from these works, we propose a model (product threshold model) for studying a binary reproduction trait that supposes that the observed phenotype is the product of 2 unobserved phenotypes, 1 for each individual. We developed a Gibbs sampling algorithm for fitting a Bayesian product threshold model including additive genetic effects and showed by simulation that it is feasible and that it provides good estimates of the parameters. We showed that fitting an additive threshold model to data that are simulated under a product threshold model provides biased estimates, especially for individuals with high breeding values. A main advantage of the product threshold model is that, in contrast to the additive model, it provides distinct estimates of fixed effects affecting each of the 2 unobserved phenotypes.

International audience; The objective of this study was to evaluate genetic and non-genetic factors influencing characteristics of young buck semen production using a multivariate model that takes into account the longitudinal structure of data. Data were collected from 1989 to 2002 at two French A.I. centres. The data corresponded to 13151 and 9206 ejaculates of 758 Alpine and 535 Saanen bucks respectively, collected at the beginning of the first breeding season (September–December). The semen volume, the total number of spermatozoa, the concentration, the motility score of spermatozoa after freezing and the percentage of motile spermatozoa after freezing were registered for each ejaculate. Within-breed heritabilities and repeatabilities were estimated using a multivariate animal model using a power spatial covariance structure for environmental effect. For all characteristics and the two breeds, the main source of variation was the year–month interaction that interacted with the centre. We observed a decrease in years of motility score after freezing. Age and frequency of collection had a significant effect on semen volume and number of spermatozoa for both breeds, and on concentration of spermatozoa for the Alpine breed. No effect of these factors was found on the characteristics observed after freezing. Heritabilities for concentration, number of spermatozoa, semen volume, motility score after freezing and percentage of motile spermatozoa after freezing per ejaculate were respectively, 0.32, 0.15, 0.25, 0.12 and 0.05 for the Saanen breed and 0.34, 0.25, 0.29, 0.17 and 0.03 for the Alpine breed. Genetic correlations between volume and number of spermatozoa were respectively, 0.74 for the Alpine breed and 0.86 for the Saanen breed. Further study is required to compare the semen characteristics of young bucks with their mature production.

Bone morphogenetic protein 15 (BMP15) is a member of the transforming growth factor beta superfamily, is specifically expressed in oocytes and is essential for sheep prolificacy. Reported mutations in this gene cause increased ovulation rate and infertility in a dosage-sensitive manner. In this work, a new naturally occurring mutation in the BMP15 gene from the ovine Rasa Aragonesa breed is described. This mutation is a deletion of 17 bp that leads to an altered amino acid sequence and introduces a premature stop codon in the protein. Highly significant associations (P < 0.0001) were found between the estimated breeding value for prolificacy and the genotype of BMP15 in Rasa Aragonesa animals with high and low breeding values for this trait. As for other mutations in BMP15, this new mutation is associated with increased prolificacy and sterility in heterozygous and homozygous ewes respectively.

[EN] The aim of this preliminary experiment was to investigate the individual variability of the sexual receptivity of a rabbit doe in the presence of a buck (lordosis position, 0-1 variable). Twenty primiparous does maintained without reproduction were tested over 4 mo (3 tests per week at a 2- or 3-day interval) after their first kindling. Out of 48 tests, the receptivity rate was 52.5±50.0% on average and varied from 20.0 to 73.3% depending on the test day. The does were lactating at the beginning of the test period and a strong receptivity decrease was revealed at the peak of lactation. Receptivity did not vary according to the tester buck or to the test operator. The individual receptivity of does varied from 8.6 to 81.3%; three of them had a receptivity rate lower than 30% and four of them a receptivity rate greater than 70%. No relationship was revealed between average receptivity and body weight or body weight variations around first litter weaning. The repeatability of sexual receptivity of non-lactating does was 23.2%. Lowly receptive does had a shorter average oestrus time (4 tests) and a shorter dioestrus time (≤3 tests). The correlation between average receptivity and average oestrus time was 0.80. These results indicate a fairly high individual variability of the expression of rabbit sexual receptivity and of its duration, and justify the exploration of an eventual genetic origin in a subsequent experiment., The authors are grateful to P. Aymard, J.M. Bonnemère, Annette Debrusse, H. Girotto and D. Labatut, technicians at the PECTOUL Experimental Rabbit Farm at INRA in Toulouse, and to J. Ruesche and the SAGA IT team for their collaboration, and G. Wagman for her careful revision of the English.

[EN] Sexual receptivity of rabbit does at insemination greatly influences fertility and is generally induced by hormones or techniques known as “biostimulation”. Searching for more sustainable farming systems, an original alternative would be to utilise the genetic pathway to increase the does’receptivity. The purpose of the present study was to identify genetic and non-genetic factors that influence rabbit doe sexual receptivity, in the context of a divergent selection experiment over 1 generation. The experiment spanned 2 generations: the founder generation (G0) consisting of 140 rabbit does, and the G1 generation comprising 2 divergently selected lines (L and H lines) with 70 does each and 2 successive batches from each generation. The selection rate of the G0 females to form the G1 lines was 24/140. The selection tests consisted of 16 to 18 successive receptivity tests at the rate of 3 tests per week. On the basis of 4716 tests from 275 females, the average receptivity was 56.6±48.2%. A batch effect and a test operator effect were revealed. The contribution of females to the total variance was 20.0%, whereas that of bucks was only 1.1%. Throughout the experiment, 18.2% of does expressed a low receptivity (< 34%), 50.7% a medium one and 33.1% a high one (>66%). Some does were frequently receptive, whereas others were rarely receptive. The repeatability of sexual receptivity was approximately 20%. The results confirmed the high variability of sexual receptivity of non-lactating rabbit does maintained without any biostimulation or hormonal treatment. A lack of selection response on receptivity was observed. Accordingly, the heritability of receptivity was estimated at 0.01±0.02 from an animal model and at 0.02±0.03 from a sire and dam model. The heritability of the average receptivity of a doe was calculated as 0.04. In agreement with the low estimated heritability, the heritability determined was no different from zero. Nevertheless, the occurrence of pseudopregnancies due to uncontrolled ovulations and the presence of corpora lutea, as assessed by progesterone titrations, could have interfered with receptivity. Further studies would be necessary to confirm the low heritability of female rabbit receptivity., The authors are grateful to the Department of Animal Genetics of the National Institute of Agronomical Research for its financial contribution, to P. Aymard, J.M. Bonnemère, Annette Debrusse, H. Girotto and D. Labatut, technicians at the PECTOUL Experimental Rabbit Farm at INRA in Toulouse, to J. Ruesche, the IT team from SAGA for their collaboration and to G. Wagman for her careful linguistic revision.

The major challenge of animal phenotyping is to acquire systemic knowledge of farm animal robustness. This will allow responding to a double objective in terms of exploiting the variability of animal aptitudes: selection for major objectives in order to improve efficiency and robustness of genotypes and precision farming that exploits individual variability of animals for an improved resilience on the herd level or to improve the management for a specific genotype. Two major challenges of our knowledge exist which are interdependent and common to all animal breeding, and which must be met in order to improve animal robustness. The first is understanding andpredicting the compromise amongst vital functions. By this we mean understanding how priority changes are made under specific limited resources. The second is understanding and exploiting the temporal aspects of robustness during an animal’s life in order to allow the animal to maintain its level of performance under different environments without compromising its reproduction, health or welfare. Attaining these objectives requires accomplishing the following: i) defining complex phenotypes through the integration of data obtained on the molecular or tissular scales of an animal or of one of its functions; ii) developing high-throughput technologiesto characterize at a lower cost and the most precisely as possible the largest number of animals; iii) developing important data bases and reliable methods and computing tools necessary for the treatment of information for modeling and predictive biology., L’enjeu majeur du phénotypage animal est d’acquérir une connaissance systémique de la robustesse des animaux d’élevage pour répondre au mieux à une double finalité en termes d’exploitation de la variabilité des aptitudes animales : une sélection éclairée vers des objectifs majeurs pour améliorer l’efficience et la robustesse des génotypes, et un élevage de précision exploitant la variabilité individuelle des animaux pour gagner en résilience à l’échelle du troupeau, ou pour améliorer la conduite à génotype donné. Deux défis majeurs de connaissance, interdépendants et communs à toutes les filières animales, sont à relever pour améliorer la robustesse des animaux : i) comprendre et prédire les compromis entre fonctions vitales, c’est-à-dire les changements de priorités dans l’allocation de ressources limitées ; ii) comprendre et exploiter les aspects temporels de la robustesse au cours de la vie de l’animal pour lui permettre de maintenir son niveau de production dans une large gamme d’environnements sans pour autant compromettre sa reproduction, sa santé et son bien-être. Atteindre ces objectifs nécessite de lever les verrous techniques suivants : i) définir des phénotypes complexes à partir de l’intégration de données obtenues à différentes échelles moléculaires, tissulaires, de l’animal ou d’une de ses fonctions ; ii) mettre en oeuvre des technologies à haut débit pour caractériser à moindre coût et le plus précisément possible le plus grand nombre d’animaux ; iii) développer d’importantes bases de données, des méthodes et outils informatiques performants, nécessaires aux traitements des informations à des fins de modélisation et de biologie prédictive.

Chantier qualité GA; International audience; The "ram effect" has been an alternative method among many techniques to control the period of sexual activity in sheep. The objectives of this study were to (1) study the reproductive performances of the Barbarine breed in the spring, (2) to evaluate females' response to the ram effect, and estimate the phenotypic and genetic parameters of the females' response to the "ram effect". A total of 16,150 matings of 4201 ewes recorded during a period of ten years in seven flocks was used in this study. Among these ewes 1335 have known parents and were born from 199 sires and 1053 dams. Four cyclicity traits were analyzed: spontaneous, normal, short and not answer to the ram effect. The main results show that approximately 30% of the females were cyclic out of season and more than 60% became cyclic with the "ram effect". Flock, year and age at lambing had significant effects on the traits analyzed. A high negative phenotypic correlation of -0.75 was found between responses of normal cycles and responses of short cycle. The spontaneous ovarian activity in the spring was negatively correlated with the absence of response to a ram effect (r(g) = -0.44) and positively correlated to the response by a normal cycle (r(g) = 0.63). The correlation between responses with the normal cycle and short cycle was highly negative (r(g) = -0.88). For all variables, heritability was low (from 0.03 to 0.09) but significantly different from 0 and repeatability was slightly higher and varied from 0.06 to 0.1. These results indicate the great opportunity offered by the Barbarine breed for out of season breeding. (C) 2013 Elsevier B.V. All rights reserved.

Prolific sheep have proven to be a valuable model to identify genes and mutations implicated in female fertility. In the Lacaune sheep breed, large variation in litter size is genetically determined by the segregation of a fecundity major gene influencing ovulation rate, named FecL and its prolific allele FecLL. Our previous work localized FecL on sheep chromosome 11 within a locus of 1.1 Mb encompassing 20 genes. With the aim to identify the FecL gene, we developed a high throughput sequencing strategy of long-range PCR fragments spanning the locus of FecLL carrier and non-carrier ewes. Resulting informative markers defined a new 194.6 kb minimal interval. The reduced FecL locus contained only two genes, insulin-like growth factor 2 mRNA binding protein 1 (IGF2BP1) and beta-1,4-N-acetyl-galactosaminyl transferase 2 (B4GALNT2), and we identified two SNP in complete linkage disequilibrium with FecLL. B4GALNT2 appeared as the best positional and expressional candidate for FecL, since it showed an ectopic expression in the ovarian follicles of FecLL/FecLL ewes at mRNA and protein levels. In FecLL carrier ewes only, B4GALNT2 transferase activity was localized in granulosa cells and specifically glycosylated proteins were detected in granulosa cell extracts and follicular fluids. The identification of these glycoproteins by mass spectrometry revealed at least 10 proteins, including inhibin alpha and betaA subunits, as potential targets of B4GALNT2 activity. Specific ovarian protein glycosylation by B4GALNT2 is proposed as a new mechanism of ovulation rate regulation in sheep, and could contribute to open new fields of investigation to understand female infertility pathogenesis., Author Summary Prolific sheep have proven to be a valuable model to identify genes and mutations implicated in ovarian function and female fertility. Indeed, fecundity genes of the Bone Morphogenetic Protein (BMP) family discovered in sheep was evidenced as genetic candidates to explain female infertility pathologies. Studying French Lacaune sheep breed, we discovered another fecundity gene named B4GALNT2, encoding a glycosylation enzyme that is not related to the BMP family. The high prolificacy of Lacaune sheep was explained by overexpression of B4GALNT2 in the ovary leading to atypical glycosylation of inhibin, an important hormone regulating ovarian function. Our findings open promising fields of investigation to better understand female fertility disorders.

Background Successful achievement of early folliculogenesis is crucial for female reproductive function. The process is finely regulated by cell-cell interactions and by the coordinated expression of genes in both the oocyte and in granulosa cells. Despite many studies, little is known about the cell-specific gene expression driving early folliculogenesis. The very small size of these follicles and the mixture of types of follicles within the developing ovary make the experimental study of isolated follicular components very difficult. The recently developed laser capture microdissection (LCM) technique coupled with microarray experiments is a promising way to address the molecular profile of pure cell populations. However, one main challenge was to preserve the RNA quality during the isolation of single cells or groups of cells and also to obtain sufficient amounts of RNA. Using a new LCM method, we describe here the separate expression profiles of oocytes and follicular cells during the first stages of sheep folliculogenesis. Results We developed a new tissue fixation protocol ensuring efficient single cell capture and RNA integrity during the microdissection procedure. Enrichment in specific cell types was controlled by qRT-PCR analysis of known genes: six oocyte-specific genes (SOHLH2, MAEL, MATER, VASA, GDF9, BMP15) and three granulosa cell-specific genes (KL, GATA4, AMH). A global gene expression profile for each follicular compartment during early developmental stages was identified here for the first time, using a bovine Affymetrix chip. Most notably, the granulosa cell dataset is unique to date. The comparison of oocyte vs. follicular cell transcriptomes revealed 1050 transcripts specific to the granulosa cell and 759 specific to the oocyte. Functional analyses allowed the characterization of the three main cellular events involved in early folliculogenesis and confirmed the relevance and potential of LCM-derived RNA. Conclusions The ovary is a complex mixture of different cell types. Distinct cell populations need therefore to be analyzed for a better understanding of their potential interactions. LCM and microarray analysis allowed us to identify novel gene expression patterns in follicular cells at different stages and in oocyte populations.

Two models can be used for studying binary results of AI. The additive threshold model proposes an underlying variable as summing the environmental and genetic effects from the 2 individuals involved in the mating, and the product threshold model assumes that the conditional probability of AI success is the product of the probabilities of success of 2 unobserved binary phenotypes (one is the male fertility; the other is the female fertility). The purpose of this paper is to compare the predictive ability of the product and the additive threshold models for studying AI results and to compare results obtained with the 2 models in 3 different species cattle, sheep, and rabbits. Results showed that the predictive ability of the product model is similar to the additive model in sheep and rabbits but worst in cattle (percentage of wrong prediction = 42, 27, and 35% in the additive model; 43, 28, and 47% in the product model in sheep, rabbits, and cattle, respectively). Even when the 2 models have similar performance, they differed in their EBV (for instance, Pearson correlation between EBV predicted with the 2 models = 0.46 in sheep for male fertility). The product model can determine which sex is responsible for an AI failure. In sheep, the female was the responsible in 94% of the cases and male in 2% of them; in rabbits, the female was the responsible in 54% of the cases and the male in 39% of them. Different estimates of probabilities for male and female fertility success obtained with the product model in the 3 species suggest that male and female fertilities behave differently depending on the species and the uniqueness of the data sets. Although product model seems to provide additional information in the fertility process, further research is needed to understand the worst performance of the product model in cattle. © 2011 American Society of Animal Science. All rights reserved.

Spontaneous ovulatory activity (SOA) in spring has been used to study the out-of-season breeding ability of Merinos d’Arles (MA) ewes. Within this breed, an association was found between more intense seasonality and genotype 2/2 at a MnlI restriction site (allele 2 for its absence v. 1 for its presence) in Exon II of the MT1 receptor gene. This study was designed to ascertain whether this association results in a direct effect of the MT1 genotype on the expression of seasonality in MA ewes. In the first year of the study, genotyping of 314 MA ewes at locus MnlI was carried out and resulted in frequencies of 43.0%, 44.9% and 12.1% for genotypes 1/1, 1/2 and 2/2, respectively. The SOA of these ewes was determined in early April of two consecutive years by assaying plasma progesterone concentrations in two blood samples taken 9 days apart. Groups of 30 ewes of each homozygous genotype (1/1 and 2/2) were identified from this population and their SOA was followed by taking blood samples at regular intervals between January and mid-April of the second and third year of the study. In the second year, groups of ewes were managed together on rangelands, whereas in the third year each group was split into two subgroups given differential feed levels. The results clearly showed that genotype had no significant effect on SOA during the 2- to 3-month period preceding the introduction of rams for spring mating. In the second year of the study, in which the experimental procedure allowed a fair comparison of the fertility of ewes in spring mating, fertility was similar for both genotypes. The reciprocity of the association was not demonstrated and the MnlI polymorphic site could not be used as a genetic marker of selection for out-of-season breeding ability, at least not in the MA breed. The percentage of cycling ewes significantly decreased between January and April, and older ewes (5 or 6 years old depending on the year of the study) were more cyclic than younger ones (2 and 3 years old, respectively). The differential feeding level of ewes from early February did not significantly affect their SOA during the time period studied in the third year of the study.

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; In the Lacaune sheep population, two major loci influencing ovulation rate are segregating: FecX and FecL. The FecXL mutation is a non-conservative substitution (p.Cys53Tyr) in BMP15 that prevents the processing of the protein. Using a statistical approach, FecL has been shown to be an autosomal major gene. A full genome scan localized the FecL locus on sheep chromosome 11. Fine mapping reduced the interval containing FecL to markers BM17132 and FAM117A, corresponding to a synteny block of 1.1 megabases on human chromosome 17, which encompasses 20 genes. The expression of 16 genes from this interval was observed in tissues of the reproductive axis, but expression was not affected in homozygous FecLL females. In this interval, a unique haplotype was associated with the FecLL mutation. This particular haplotype could be predicted by the DLX3:c.*803A > G SNP in the 3' UTR sequence of the DLX3 gene. This SNP provided accurate classification of animals (99.5%) as carriers or non-carriers of the mutation and therefore maybe useful in marker assisted selection. A synergistic action of FecLL and FecXL mutations on both ovulation rate and litter size was demonstrated. Until now, all the Fec genes identified in sheep belong to the bone morphogenetic protein (BMP) system. Based on the human orthologous region, none of the 20 genes in the FecL region corresponds to known molecules in the BMP system. The identification of the FecLL mutation could lead to the discovery of a new pathway involved in the regulation of ovulation rate.

Artificial inseminations (n = 678 168) recorded during 5 years in five French artificial insemination (AI) centres (2 'Lacaune', 1 'Manech tête rousse', 1 'Manech tête noire' and 1 'Basco béarnaise') were analysed to determine environmental and genetic factors affecting the insemination results. Analyses within centre-breed were performed using a linear model, which jointly estimates male and female fertility. This model combined four categories of data: the environmental effects related to the female, those related to the male, the non-sex-specific effects and finally the pedigree data of these males and females. After selection, the environmental female effects considered were age, synchronisation (0/1) on the previous year, total number of synchronisations during the female reproductive life, time interval between previous lambing and insemination, already dry or still lactating (0/1) when inseminated, and milk quantity produced during the previous year expressed as quartiles intra herd * year. The environmental male effects were motility and concentration of the semen. The non-sex-specific effects were the inseminator, the interaction herd * year nested within the inseminator, considered as random effects and the interaction year * season considered as a fixed effect. The main variation factors of AI success were relative to non-sex-specific effects and to female effects. Heritability estimates varied from 0.001 to 0.005 for male fertility and from 0.040 to 0.078 for female fertility. Repeatability estimates varied from 0.007 to 0.015 for male fertility and from 0.104 to 0.136 for female fertility. These parameters indicate that genetic improvement of AI results through a classical polygenic selection would be difficult. Moreover, in spite of the large quantity of variation factors fitted by the joint model, a very large residual variance remained unexplained.

A divergent selection experiment based on the homogeneity of birth weight in rabbit was carried out at the INRA experimental farm of Auzeville. The two lines were created by selecting breeding does and bucks from the female strain AGP22 bred at the Grimaud Freres Selection company for environmental variability of birth weight. This involved a new model incorporating a genotypic value for the mean and a genotypic value for the environmental variance. There was a selection response with a significant difference in the within-litter standard deviation of birth weight between the lines after four generations of selection (6.93 g vs. 8.13 g). The mortality of kits at birth and from birth to weaning was lower in the “homogeneous” line than in the “heterogeneous” line (16.6% vs. 18.6% and 17.7% vs. 32.7%, respectively). The litter size at weaning was higher in the “homogeneous” line (7.22 vs. 5.39). The selection on the homogeneity of birth weight had no significant influence on the other traits. It was concluded that selection for reduced environmental variance of birth weight improved young rabbit survival without reducing the mean of birth weight.

Genetic mutations with major effects on ovulation rate and litter size in sheep were recently identified in three genes belonging to the TGFβ superfamily pathway: the bone morphogenetic protein 15 (BMP15, also known as GDF9b), growth differentiation factor 9 (GDF9), and BMP receptor type IB (also known as activin-like kinase 6). Homozygous BMP15 or GDF9 mutations raise female sterility due to a failure of normal ovarian follicle development, whereas heterozygous animals for BMP15 or GDF9 as well as heterozygous and homozygous animals for BMP receptor type IB show increased ovulation rates. In the present work, a new naturally occurring mutation in the BMP15 gene in the high prolific Lacaune sheep breed is described. The identified variant is a C53Y missense nonconservative substitution leading to the aminoacidic change of a cysteine with a tyrosine in the mature peptide of the protein. As for other mutations found in the same gene, this is associated with an increased ovulation rate and sterility in heterozygous and homozygous animals, respectively. Further in vitro studies showed that the C53Y mutation was responsible for the impairment of the maturation process of the BMP15 protein, resulting in a defective secretion of both the precursor and mature peptide. Overall, our findings confirm the essential role of the BMP15 factor in the ovarian folliculogenesis and control of ovulation rate in sheep.

Ovarian folliculogenesis in mammals from the constitution of primordial follicles up to ovulation is a reasonably well understood mechanism. Nevertheless, underlying mechanisms that determine the number of ovulating follicles were enigmatic until the identification of the fecundity genes affecting ovulation rate in sheep, bone morphogenetic protein-15 (BMP-15), growth and differentiation factor-9 (GDF-9) and BMP receptor-1B (BMPR-1B). In this review, we focus on the use of these sheep genetic models for understanding the role of the BMP system as an intra-ovarian regulator of follicular growth and maturation, and finally, ovulation rate.

The litter size in Suffolk and Texel-sheep was analysed using REML and Bayesian methods. Litters born after hormonal induced oestrus and after natural oestrus were treated as different traits in order to estimate the genetic correlation between the traits. Explanatory variables were the age of the ewe at lambing, period of lambing, a year*flock-effect, a permanent environmental effect associated with the ewe, and the additive genetic effect. The heritability estimates for litter size ranged from 0.06 to 0.13 using REML in bi-variate linear models. Transformation of the estimates to the underlying scale resulted in heritability estimates from 0.12 to 0.17. Posterior means of the heritability of litter size in the Bayesian approach with bi-variate threshold models varied from 0.05 to 0.18. REML estimates of the genetic correlations between the two types of litter size ranged from 0.57 to 0.64 in the Suffolk and from 0.75 to 0.81 in the Texel. The posterior means of the genetic correlation (Bayesian analysis) were 0.40 and 0.44 for the Suffolk and 0.56 and 0.75 for the Texel in the sire and animal model respectively. A bivariate threshold model seems appropriate for the genetic evaluation of prolificacy in the breeds concerned. ispartof: Genetics, selection, evolution. : GSE vol:36 issue:5 pages:543-62 ispartof: location:France status: published

DOI:10.1051/gse:2002036; International audience; Organising the breeding plan of a seasonally breeding species, such as sheep, presents a challenge to farmers and the industry as a whole, since both economical and biological considerations need to be carefully balanced. Understanding the breeding activity of individual animals becomes a prerequisite for a successful breeding program. This study set out to investigate the sources of variation and the genetic profile of the spontaneous, out-of-season ovulatory activity of ewes of the Chios dairy sheep breed in Greece. The definition of the trait was based on blood progesterone levels, measured before exposing the ewes to rams, which marks the onset of the usual breeding season. Data were 707 records, taken over two consecutive years, of 435 ewes kept at the Agricultural Research Station of Chalkidiki in northern Greece. When all available pedigree was included, the total number of animals involved was 1068. On average, 29% of all ewes exhibited spontaneous, out-of-season ovulatory activity, with no substantial variation between the years. Significant sources of systematic variation were the ewe age and live weight, and the month of previous lambing. Older, heavier ewes, that had lambed early the previous autumn, exhibited more frequent activity. Heritability estimates were 0.216 ($\pm 0.084$) with a linear and 0.291 with a threshold model. The latter better accounts for the categorical nature of the trait. The linear model repeatability was 0.230 ($\pm 0.095$). The results obtained in this study support the notion that spontaneous out-of-season ovulatory activity can be considered in the development of a breeding plan for the Chios sheep breed.

International audience; Classical selection for increasing prolificacy in sheep leads to a concomitant increase in its variability, even though the objective of the breeder is to maximise the frequency of an intermediate litter size rather than the frequency of high litter sizes. For instance, in the Lacaune sheep breed raised in semi-intensive conditions, ewes lambing twins represent the economic optimum. Data for this breed, obtained from the national recording scheme, were analysed. Variance components were estimated in an infinitesimal model involving genes controlling the mean level as well as its environmental variability. Large heritability was found for the mean prolificacy, but a high potential for increasing the percentage of twins at lambing while reducing the environmental variability of prolificacy is also suspected. Quantification of the response to such a canalising selection was achieved.

The genetic parameters of spontaneous spring ovulatory activity were investigated in the Mérinos d’Arles breed under the usual pastoral and transhumant management conditions of this breed in southeastern France. Ovulatory activity was determined by assaying the plasma progesterone concentration in two blood samples taken 8-10 days apart. The data set consisted of 1 887 ovulatory activity performance measurements in 1995, 1996 and 1997 on 933 ewes, daughters of 176 rams. The effects of the ’physiological status’ (hoggets, adult ewes with or without lambing in the previous autumn), age and live weight just before the mating period were found to be highly significant. They were included in the linear animal model and the threshold sire model used to estimate genetic parameters. On average, 27.9 % of ewes exhibited ovulatory activity in April. Age and live weight just before the mating period had a marked positive effect on ovulatory activity. A difference of about 8-9 % was observed between extreme classes for these factors. The heritability and repeatability estimated through the linear model were 0.20 (standard error: 0.04) and 0.30 (0.07), respectively. When using the threshold model, the heritability was 0.37. These values led us to conclude that a genetic approach for improving spontaneous spring ovulatory activity should be further developed. Nevertheless, further studies are necessary to determine all the implications of such selection., Les paramètres génétiques de l’activité ovulatoire spontanée au printemps ont été estimés en race Mérinos d’Arles dans le système d’élevage pastoral traditionnel (transhumance estivale) du sud-est de la France. Le dosage de la progestérone plasmatique dans deux prélèvements sanguins effectués à 8-10 j d’intervalle a permis de déterminer l’activité ovulatoire des brebis. 1887 performances d’activité ovulatoire ont été enregistrées en 1995, 1996 et 1997, sur 933 brebis issues de 176 béliers. Le «statut physiologique » (antenaises, brebis adultes avec ou sans mise bas à l’automne précédent), l’âge et le poids au moment de la lutte des brebis ont des effets très significatifs sur l’activité ovulatoire. Ils ont été pris en compte dans le modèle animal linéaire et le modèle père à seuil utilisés pour estimer les paramètres génétiques. En moyenne, 27,9 % des brebis présentaient une activité ovulatoire en avril. L’âge et le poids au moment de la lutte ont un net effet positif sur l’activité ovulatoire. Une différence de 8-9 % a été observée entre les classes extrêmes pour ces facteurs. L’héritabilité et la répétabilité estimées avec le modèle linéaire sont de 0,20 (erreur standard : 0,04) et de 0,30 (0,07), respectivement. L’héritabilité calculée avec le modèle à seuil est de 0,37. En conclusion, compte tenu de ces valeurs, l’approche génétique visant à améliorer l’activité ovulatoire spontanée au printemps mérite d’être poursuivie. Néanmoins, d’autres études sont nécessaires pour connaître toutes les implications que supposent une telle sélection.

The present study was conducted to assess the degree of genetic determination of the variability in the mean nocturnal plasma concentration of melatonin in sheep. Three hundred twelve ewes born from 18 males and with known genealogy were sampled at the summer and the winter solstices. The nocturnal plasma melatonin concentration was defined as the mean of four plasma samples taken at hourly intervals in the middle of the night (2200–0200). Identity of the father ( P < 0.001) and the solstice ( P < 0.05) were significant. Melatonin concentrations varied considerably among individuals [338.4 ± 197.5 (SD) pg/ml; range 26.6–981.3 pg/ml] and between rams regarding the melatonin concentrations of their daughters (range from 202.9 to 456.3 pg/ml). Inheritance was analyzed by a statistical model that allows discrimination of genetic effects from nongenetic effects and that estimates repeatability and heritability coefficients. Both the repeatability coefficient between solstices (0.60) and heritability coefficient [0.45 ± 0.07 (SE)] were high. These results demonstrate that the variability in plasma melatonin concentration in ewes is under strong genetic control.

We investigated whether the genetic difference in plasma melatonin concentration in ewes was due to differences in the synthesis pathway from the pineal gland or in the catabolism of the hormone. Two groups of ewes [9 low (L) and 10 high (H)] were selected according to the breeding value of their mean nighttime plasma melatonin concentrations estimated at winter and summer solstices. In response to an identical dose of melatonin administered intravenously at 9:00 AM, no differences between groups were observed for any of the kinetic parameters: clearance rate, steady-state volume of distribution, terminal half-lives, and mean residence times. In the second experiment, two series of frequent blood samples were performed, one in the middle of the dark phase with samples taken every 5 min, and the other over 24 h with hourly samples. Highly significant differences between groups in nocturnal melatonin production rate were observed (L: 25.7 ± 2.8 vs. H: 63.1 ± 8.9 μg ⋅ kg−1⋅ h−1, P < 0.01). Thus the genetic differences in plasma melatonin concentrations in ewes originate in the synthesis pathway of the melatonin from the pineal gland rather than from differences in the catabolism of the hormone.

Some sheep breeds are naturally prolific, and they are very informative for the studies of reproductive genetics and physiology. Major genes increasing litter size (LS) and ovulation rate (OR) were suspected in the French Grivette and the Polish Olkuska sheep populations, respectively. To identify genetic variants responsible for the highly prolific phenotype in these two breeds, genome-wide association studies (GWAS) followed by complementary genetic and functional analyses were performed. Highly prolific ewes (cases) and normal prolific ewes (controls) from each breed were genotyped using the Illumina OvineSNP50 Genotyping Beadchip. In both populations, an X chromosome region, close to the BMP15 gene, harbored clusters of markers with suggestive evidence of association at significance levels between 1E−05 and 1E−07. The BMP15 candidate gene was then sequenced, and two novel non-conservative mutations called FecXGr and FecXO were identified in the Grivette and Olkuska breeds, respectively. The two mutations were associated with the highly prolific phenotype (pFecXGr = 5.98E−06 and pFecXO = 2.55E−08). Homozygous ewes for the mutated allele showed a significantly increased prolificacy (FecXGr/FecXGr, LS = 2.50±0.65 versus FecX+/FecXGr, LS = 1.93±0.42, p, Author Summary Although causes altering reproductive function and leading to several fertility syndromes in women are various, a clear association between mutations in some members of the TGFβ family (BMP15 and GDF9) and abnormal ovarian phenotype has established the importance of these factors for normal female fertility. Some sheep breeds are naturally prolific since they carry major genes affecting ovulation rate and litter size. These species are therefore unique informative models for the study of reproductive genetics and physiology. Through a GWAS conducted in two sheep breeds using highly prolific ewes as cases and normal prolific ewes as controls, we identified an X chromosome locus close to the BMP15 gene in both breeds. Two novel non-conservative BMP15 mutations, one in each population, located in very well conserved domains of the protein were associated with the phenotype at heterozygous and homozygous status. Moreover, we showed that both mutations altered the BMP15 signaling activity, suggesting a novel kind of BMP15 variant responsible for an atypical high prolificacy, in contrast to all other BMP15 variants described so far. Our findings suggest an additional role of the BMP15 protein in folliculogenesis and could contribute to a better understanding of the pathogenesis of women′s fertility disorders.

The objectives of this work were to examine the usefulness of measuring ovulation rate (OR) in order to improve genetic progress of litter size (LS) in sheep and to study different selection criteria combining OR and prenatal survival (ES) performance. Responses to selection for 5 generations within a population of 20 male and 600 female parents were compared using Monte-Carlo simulation techniques with 50 replicates per selection method. Two breeds with low (Merino) and medium (Lacaune) prolificacy were considered. Records were generated according to a bivariate threshold model for OR and ES. Heritabilities of OR and ES in the underlying scale were assumed constant over breeds and equal to 0.35 and 0.11, respectively, with a genetic correlation of -0.40 between these traits. Four methods of genetic evaluation were compared: univariate best linear unbiased prediction (BLUP) using LS records only (b-LS); univariate BLUP on OR records (b-OR); bivariate BLUP using OR and LS records (b-ORLS); and a maximum a posteriori predictor of a generalised linear model whereby OR was analysed as a continuous trait and ES as a binary threshold trait (t-ORES). Response in LS was very similar with b-LS, b-ORLS and t-ORES, whereas it was significantly lower with b-OR. Response in OR was maximum with b-OR and minimum with b-LS. In contrast, response in ES was maximum with b-LS. This study raised the question as to why selection based on indices combining information from both OR and ES did not perform better than selection using LS only., Cet article discute l’intérêt du taux d’ovulation (OR) pour accroître le progrès génétique sur la taille de portée (LS) et étudie à cet effet divers critères de sélection combinant OR et le taux de survie embryonnaire (ES). On a examiné par simulation les réponses à la sélection en 5 générations dans une population de 20 et 600 reproducteurs mâles et femelles avec 50 réplications par méthode. On a considéré 2 races, de prolificité faible (Mérinos) et moyenne (Lacaune). Les performances ont été générées à partir d’un modèle bicaractère à seuils. Les héritabilitiés d’OR et ES ont été supposées constantes sur l’échelle sous-jacente dans les 2 races et prises égales respectivement à 0,35 et 0,11 avec une corrélation génétique entre ces 2 caractères de - 0,40. Quatre méthodes d’évaluation génétiques ont été comparées : i) Blup unicaractère basé sur LS (b-LS) ; ii) Blup unicaractère basé sur OR (b-OR) ; iii) Blup bicaractère basé sur OR et LS (b-ORLS) ; iv) Prédicteur du maximum a posteriori bicaractère d’un modèle linéaire généralisé où OR est traité comme un caractère continu et ES comme un caractère à seuils (t-ORES). Les réponses observées étaient très voisines avec b-LS, b-ORLS et t-ORES, alors que b-OR donne une réponse significativement inférieure. La réponse sur OR était maximum avec b-OR et minimum avec b-LS, tandis que la réponse sur ES était maximum avec b-LS. Cette étude pose la question de savoir pourquoi la sélection basée sur des indices combinant OR et ES ne donne pas de résultats significativement supérieurs à la sélection sur LS.

The ovulatory response of ewes from breeds that differ widely in prolificacy (Ile-de-France, ++ Booroola Merino, Romanov, F+ Booroola Merino and F+ Booroola Romanov with adult ovulation rates of about 1.5, 1.2, 3, 3 and 3.5 respectively) to 750 IU of hCG given at different physiological stages (before puberty, during anestrus or during the luteal phase) was compared. In all except one experiment, hCG induced ovulation in 73 to 98% of the lambs, indicating that follicles sensitive to LH were present at all stages studied. Ranking of the breeds according to hCG-induced ovulation rate in prepuberal lambs was similar to that based on adult ovulation rate. Furthermore, hCG induced more ovulations in prepuberal F+ than in ++ lambs (3.7 +/- 1.4 vs 1.7 +/- .8 at 4.5 mo of age) as well as in anestrous ewes (F + at 3.1 +/- 1.8 vs ++ at 1.6 +/- .7). Within ewes, the correlation between hCG-induced ovulation rate and mature ovulation rate was positive in nonprolific breeds but not significant in prolific breeds. We conclude that 1) the number of hCG-induced ovulations can be used to identify sheep that are carriers of the Booroola gene and 2) the mechanisms responsible for a number of large ovulatory follicles typical of a breed are present at stages (prepuberal, anestrus, luteal phase) other than the follicular phase.

International audience; The gene encoding the MT1 melatonin receptor in sheep has a restriction fragment length polymorphism (RFLP) site to the MnlI enzyme whose incidence is associated to the expression of seasonality in several breeds. The aim of this study was to examine the relationship between this genetic marker and the physiological effects of MT1 receptor gene polymorphism on several seasonal functions in Île-de-France ewes. The study was performed using 12 pairs of half-sib adult Île-de-France ewes. Within each pair, ewes were selected on the basis of their genotype at the MnlI RFLP site: group +/+ and -/- (presence and absence of MnlI restriction site, respectively). No difference in the dates of the beginning, the end or the length of the breeding season was observed between groups during the two-year study. The seasonal changes in prolactin secretion were not different between groups. Similarly, wool growth rate and primary follicle activity, measured for one year, varied with the time of the year in the same way in the two groups. Our study therefore failed to show any relationship between MT1 polymorphism and reproductive seasonality in Île-de-France ewes. This suggests that the influence of this polymorphism on the regulation of seasonal function is dependent upon the breed and/or environmental conditions. The MT1 polymorphism can explain only a small part of the genetic variability of seasonal functions and the implication of other genes must be investigated.

A bivariate threshold model for ovulation rate and embryonic survival was developed and the genetic relationships in the observed scale among ovulation rate, embryonic survival, and litter size were derived. This model was applied to data of nulliparous Lacaune sheep. Heritabilities assumed were .30, .05, and .12 for ovulation rate, embryonic survival, and litter size, respectively. Three values for genetic correlation between ovulation rate and embryonic survival were considered: -.78, -.30, and 0. Three criteria to increase litter size were studied: a linear index combining ovulation rate and embryonic survival, ovulation rate, and litter size. The linear index used gave an increasing weight to embryonic survival with higher ovulation rates. A selection scheme was simulated to test predications of response for the different criteria. A nucleus of 10 sires and 300 dams was simulated. Females were selected according to their own performance (mean of three records) and males according to their dam's performance. Selection was continued for six discrete generations. Response with an index was better than direct selection only in the short term, whereas this superiority was not maintained in the last generations of selection. Indirect selection on ovulation rate was clearly inferior to both index and direct selection. In the situation analyzed here, litter size seems to be close to the optimum 'natural index' combining ovulation rate and embryonic survival.

This study was conducted to determine the origin of the high variability in the mean nocturnal plasma melatonin concentration (MC) in sheep. Two extreme groups of 25 lambs each [low (L) and high (H)] were obtained by calculating their genetic value on the basis of the MC of their parents. The MC of lambs was significantly higher in the H group than in the L group (L: 189.7 ± 24.4 vs. H: 344.1 ± 33.0 pg/ml, P < 0.001). Within each group, 13 lambs were slaughtered during the day (D) and 12 lambs during the night (N). Pineal weight was significantly higher in the H group than in the L group (L: 83.5 ± 6.7 vs. H: 119.1 ± 9.2 mg, P < 0.01) but did not differ between D and N. The amount of melatonin released in vitro per milligram of pineal gland, the arylalkylamine N-acetyltransferase (AANAT) activity, the AANAT protein content, and the level of AANAT mRNA differed significantly between D and N but not with genetic group. Hydroxyindole O-methyltransferase activity did not differ significantly between D and N or between genetic groups. Therefore, the genetic difference in MC between the two groups of lambs was attributed to a difference in pineal size, not in enzymatic activity of the pinealocytes.

Canalising selection is handled by a heteroscedastic model involving a genotypic value for the mean and a genotypic value for the log variance, associated with a single phenotypic value. A selection objective is proposed as the expected squared deviation of the phenotype from the optimum, of a progeny of any candidate for selection. Indices and approximate expressions of parent-offspring regression are derived. Simulations are performed to check the accuracy of the analytical approximation. Examples of fat to protein ratio in goat milk yield and muscle pH data in pig breeding are provided in order to investigate the ability of these populations to be canalised towards an economic optimum, Le problème de la sélection canalisante est traité grâce à un modèle hétéroscédastique mettant en jeu une valeur génétique pour la moyenne et une valeur génétique pour le logarithme de la variance, toutes deux associées à une seule valeur phénotypique. Pour un objectif de sélection visant à minimiser l’espérance des carrés des différences entre le phénotype et l’optimum, pour un descendant d’un candidat à la sélection, des index sont estimés et des expressions approchées de la régression parent-descendant sont calculées. La précision de ces expressions analytiques est mesurée à l’aide de simulations. Afin d’appréhender la capacité de ces populations à être canalisées vers un optimum économique, des exemples sont donnés : le rapport entre matière grasse et matière protéique du lait de chèvre, et le pH d’un muscle chez le porc

Avec l’arrivée de données de génotypage à haut débit, il est maintenant possible d’estimer la valeur génétique d’animaux candidats à la sélection dès leur naissance, sans attendre la collecte de phénotypes. La sélection génomique bouleverse complètement les perspectivesen amélioration génétique. Elle nécessite la constitution d’une population de référence formée d’animaux génotypés (jusqu’à récemment, il s’agissait principalement de mâles) et ayant des performances précises, par exemple la performance moyenne de leurs filles. Les évaluations génomiques consistent à prédire les phénotypes dans cette population de référence comme la somme des effets des marqueurs moléculaires. Le problème méthodologique principal est que le nombre d’effets à estimer est typiquement beaucoup plus élevé que le nombre de phénotypes disponibles. Nous décrivons les idées générales de diverses familles de méthodes proposées : BLUP génomique basé sur une parenté entre individus calculée à partir des marqueurs, méthodes Bayésiennes plus flexibles mais aussi plus coûteuses, méthodes de sélection de variables, méthode en une seule étape qui combine évaluation génétique nationale et évaluation génomique. La précision des évaluations génomiques est faite par validation croisée chez les animaux les plus jeunes de la population de référence. La taille de la population de référence, la manière de prendre en compte les QTL à effet fort et le degré d’apparentement entre candidats à la sélection et animaux de la population de référence ont un impact non négligeable sur l’efficacité desméthodes de sélection génomique., With the advent of high throughput genotyping, it is now possible to estimate breeding values of selection candidates at birthwithout waiting for phenotypic data collection. Genomic selection is deeply changing future prospects in genetic improvement. Itrequires the creation of a reference population made of genotyped animals (generally males) with precise phenotypes, such as averagedaughter performances. Genomic evaluations consist in predicting phenotypes in this reference population as the sum of molecularmarker effects. The main methodological challenge is the large number of effects to estimate, usually much larger than thenumber of available phenotypes. We briefly describe the various families of proposed methods: genomic BLUP based on relationships computed from marker information, Bayesian methods which are more flexible but more tedious, variable selection methods and asingle step method which combines national genetic evaluation and genomic evaluation. The precision of genomic selection is donevia cross validation among the youngest animals of the reference population. The size of the reference population, the way QTL withlarge effects are modeled, the relationship between selection candidates and the reference population have a significant impact on theefficiency of genomic selection methods.