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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; Selection for feed efficiency is questioned as reducing the ability of farm animals to face stress and overcome challenges. The hypothalamic-pituitary-adrenocortical (HPA) axis activity, measured by the cortisol level in plasma after ACTH injection, has been proposed as an indicator of robustness. The objectives of this study were to evaluate (1) if a modified cortisol level in pigs alters their feed efficiency and their production performance; and (2) if alternative dietary resources would affect these responses. Parallel trials including divergent lines for plasma cortisol 1 hour after ACTH injection and divergent lines for residual feed intake (RFI) were run during growth with a conventional diet and a diet with high fibres, low energy and low protein content. Selection for higher or lower plasma cortisol levels after stimulation of the adrenal gland did not impact growth and feed intake traits, but it had a significant impact on body composition and carcass yield, with improved composition in the high cortisol animals. The two lines had similar responses to an alternative diet, with decreased growth rate and feed intake, and increased feed conversion ratio. On the other hand, lines selected for divergent RFI had different responses to the alternative diet, the more efficient line having a more reduced growth rate with the diet with lower energy and AA contents. However, in terms of FCR it remained more efficient. The initial hypothesis of decreased efficiency associated to increased cortisol was not validated. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant no. 633531.

National audience; An unfavourable relationship between responses to stress and feed efficiency has been proposed. Parallel trials were run, including divergent lines for residual feed intake and divergent lines for plasma cortisol response 1 h after ACTH injection. At 6 weeks of age, 48 pigs from each of the four lines were injected with ACTH. Plasma cortisol was measured before injection, and 1 h and 4 h later. Growth rate, feed intake, feed efficiency, body composition and meat quality were measured during the growing-finishing period on the same pigs fed either a conventional diet (9.7 MJ net energy (NE) and 160 g crude protein/kg) or a diet with an increased proportion of dietary fibres to dilute NE and digestible amino acids (AA) by 10%. Comparison of the lines selected for feed efficiency showed that the response to ACTH was slightly stronger, and lasted longer, in the more efficient line (P < 0.05). During the feed challenge, the growth rate of the most efficient line decreased more with the diet with lower NE and AA contents than that of the less efficient line (P < 0.06). However, in terms of feed efficiency, the more efficient line remained more efficient. On the other hand, comparison of the 'response to ACTH' lines showed no difference for growth and feed intake during the growth period, but a higher carcass yield and a leaner body composition of animals with higher plasma cortisol after ACTH injection. Thus, the initial hypothesis of a negative association between feed efficiency and the HPA axis activity is not supported.; Une relation défavorable entre réponse au stress et efficacité alimentaire est souvent mise en avant. Deux lignées divergentes pour l’efficacité alimentaire, et deux lignées divergentes pour la réponse en cortisol plasmatique à une injection d’ACTH, indicateur de l’activité de l’axe corticotrope, ont été testées en parallèle. A 6 semaines d’âge, 48 porcs par lignée ont reçu une injection d’ACTH. Le cortisol plasmatique a été mesuré avant injection, 1 h et 4 h après injection. La vitesse de croissance, l’ingestion, l’efficacité alimentaire, la composition de carcasse et la qualité de la viande ont été enregistrées. La moitié des animaux a reçu un aliment croissance conventionnel (9,7 MJ d’énergie nette (EN) et 160 g de protéines brutes/kg), et l’autre moitié a été soumise à un challenge alimentaire avec un aliment contenant des fibres alimentaires pour diluer l’EN et les acides aminés digestibles dans une proportion de 10%. La réponse à l’ACTH a été légèrement plus forte, et prolongée dans le temps, dans la lignée la plus efficace (P < 0,05). La vitesse de croissance et l’ingéré de la lignée plus efficace soumise à un régime fibreux ont été plus diminués que ceux des porcs moins efficaces (P < 0,06), mais l’avantage d’efficacité alimentaire a été maintenu. D’autre part, la comparaison des lignées « réponse à l’ACTH » ne montre pas de différence pour les caractères de croissance et d’ingestion pendant la période de croissance, quel que soit l’aliment, mais montre une composition corporelle plus maigre des porcs ayant une concentration de cortisol plasmatique plus élevée. Ainsi, contrairement à l’hypothèse initiale, la sélection pour une meilleure efficacité alimentaire n’affecte pas négativement la réponse à l’ACTH, et la diminution de l’activité de l’axe corticotrope n’est pas favorablement corrélée aux performances.

International audience; Mutations in the FecL locus are associated with large variation in ovulation rate and litter size in the French Lacaune sheep breed. It has been shown that the B4GALNT2 gene within the FecL locus is most likely responsible for the high fecundity in the French breed. In this study, we have highlighted the segregation of the FecLL mutation within the B4GALNT2 gene in North African sheep breeds and notably in the highly prolific D'man breed. Genotyping of a sample of 183 Tunisian D'man individuals revealed a high frequency (0.65) of the prolific allele FecLLwhich was attributed to the adoption of a decades‐old breeding strategy based on the selection of ewe lambs born from large litter size. Homozygous LL ewes showed a significantly increased litter size compared to heterozygous and non‐carrier ewes (FecLL/FecLL = 2.47 ± 0.09 vs. FecLL/FecL+ = 2.23 ± 0.09, p < 0.05 and FecL+/FecL+ = 1.93 ± 0.18, p < 0.01). The presence of the FecLLpolymorphism in both D'man and Lacaune breeds argues for an ancestral origin of this mutation and brings an answer to the old question of the genetic determinism of the extreme prolificacy of the D'man ewes. The results of this study can help to establish planned genotype‐based mating allowing both higher profit for the breeders and an optimal management of the FecLL mutation in D'man sheep populations.

International audience; Weaning is a stress every piglet has to face. It is a main cause of antibiotic uses due to digestive disorders. In this study, response to weaning was analyzed in pigs from two lines divergently selected for residual feed intake (RFI) during growth. A total of 132 pigs from each line, housed per line and diet in conventional postweaning units of 12 castrated males and 12 females, were fed either a conventional control (two successive diets) or a complex (three successive diets) dietary sequence during the postweaning period (4 to 10 wk of age). BWs were recorded at weaning (days 0 and 28 of age), days 1, 2, 6, 12, 19, 26, and 42 (10 wk of age), and at 23 wk of age. Feces texture was examined before weaning (day −1), at day 1, 2, 6, 12, and 19. Feed intake was recorded at pen level from days 0 to 42 after weaning, and individually thereafter. Plasma was collected after blood samplings at days −1, 6, 19, and 42 on half of the piglets: all piglets of a given sex in each pen were sampled, to achieve a balanced number across factors. Pigs of the low RFI (LRFI) line were heavier at weaning, had greater glucose concentration, and lower levels of diarrhea at days 1 and 2 than pigs from the high RFI (HRFI) line (P < 0.01). At day 42, there was no BW difference between lines, and G:F ratio did not differ between lines (P = 0.40). The LRFI pigs had lower feed intake and growth rate from day 0 to day 19 (P < 0.005), and greater plasma concentration of non-esterified fatty acid (P < 0.001), indicating an increased mobilization of body lipids and proteins immediately after weaning compared with HRFI pigs. They also had greater levels of diarrhea at day 6 (22% for LRFI vs. 14% for HRFI, P = 0.002), but the concentration of plasma haptoglobin did not indicate acute inflammation. The complex diet sequence improved feed intake and growth, and reduced diarrhea, mainly in the LRFI line (P < 0.001). To conclude, pigs from the LRFI line were more negatively affected by weaning stress, but managed to recover afterwards. The complex diet sequence ameliorated some of the negative effects that weaning had on the LRFI pigs, but limited effects of nursery period feeding sequence on growth performance were observed during the growing-finishing period.

International audience; The aim of this experiment was to evaluate the significance of neonatal environment on feed efficiency. For that purpose, rabbits from a line selected for residual feed intake (RFI) during 10 generations (G10 kits) were cross-fostered with non-selected control does (i.e., G0 line), and reciprocally. In parallel, sibs were fostered by mothers from their original line. Nine hundred animals were raised in individual (N = 456) or collective (N = 320) cages. Traits analysed in this study were body weight at 32 days and at 63 days, average daily gain (ADG), feed intake between weaning and 63 days (FI), feed conversion ratio (FCR) and RFI. The maternal environment offered by does from the line selected for RFI deteriorated the FCR of the kits, independently of their line of origin, during fattening (+0.08 +/- 0.02) compared to FCR of kits nursed by G0 does. The line, the type of housing and the batch were significant effects for all the measured traits: G10 kits were lighter than their G0 counterparts at 32 days (-82.9 +/- 9 g, p < 0.0001) and at 63 days (-161 +/- 16 g, p < 0.0001). They also had a lower ADG (-2.36 +/- 0.36 g/day, p < 0.0001), RFI (-521 +/- 24 g/day, p < 0.0001) and a lower FI (-855 +/- 31 g, p < 0.0001), resulting in a more desirable feed efficiency (FCR: -0.35 +/- 0.02). There was no significant difference in the contrast of G10 and G0 performances between collective and individual/digestive cages (p > 0.22): -2.35 g/day versus 2.94 g/day for ADG, -0.39 versus -0.40 for FCR, -577 g versus -565 g for RFI and -879 g versus -859 g for FI, respectively). Thus, no genotype-by-environment (housing) interaction is expected at the commercial level, that is, no re-ranking of the animals due to collective housing.

National audience

To get insights into selection criteria for feed efficiency, 2 rabbit lines have been created: the ConsoResidual line was selected for residual feed intake (RFI) with ad libitum feeding and the ADGrestrict line was selected for ADG under restricted feeding. The aim of the present study was to evaluate the impact on carcass and meat quality of the genetic selections. This comparison was performed using 2 different feeding strategies corresponding to the selection design. Carcass and meat quality traits were recorded for the 3 lines (ConsoResidual, ADGrestrict, and an unselected control [generation 0 {G0}]) in the 2 feeding systems (ad libitum and restricted) for 163 animals. Concerning the line effect, the BW at 63 d old was higher for the ADGrestrict line compared with the G0 and ConsoResidual lines ( < 0.0001). There was no line effect on the gastrointestinal tract. The rabbits did not exhibit a different carcass yield but showed different carcass traits. Indeed, the ConsoResidual rabbits had a higher hind leg yield ( < 0.0001) but no difference in the meat-to-bone ratio of the hind leg. On the contrary, the ADGrestrict line had a higher proportion of forelegs plus thoracic cage ( = 0.03). We also found lower perirenal ( < 0.0001) and scapular fat yields ( < 0.0001) in ConsoResidual rabbits. The ADGrestrict line had an intermediate perirenal fat yield compared with the other 2 lines. The G0 line always exhibited higher fat yields. Concerning meat quality, the ConsoResidual rabbits showed a lower ultimate pH ( < 0.0001) and higher water loss (drip and cooking loss; < 0.002) compared with the G0 and ADGrestrict rabbits. The feeding level had a strong effect on the gastrointestinal tract ( = 0.0004) and the carcass yield ( = 0.001). The latter was decreased in restricted rabbits. The effects of feeding strategy on meat quality were detrimental in the case of restricted feeding. Even if the ultimate pH was slightly higher in restricted rabbits ( = 0.0002), the carcass chilling loss ( = 0.0005) and the drip loss during 6 d ( < 0.0001) were higher. The selection on ADG with restricted access to feed seems to be less adversely correlated with carcass traits and meat quality traits but it leads to an increase in the live weight of the rabbits. Adversely, the selection on RFI, without affecting growth rate, would not modify age at slaughter because growth rate is not affected, but it might induce detrimental effects on meat quality.

To get insights into selection criteria for feed efficiency, 2 rabbit lines have been created: the ConsoResidual line was selected for residual feed intake (RFI) with ad libitum feeding and the ADGrestrict line was selected for ADG under restricted feeding (-20% of voluntary intake). The first objective of this study was to evaluate, after 9 generations of selection, the direct and correlated responses to selection on production traits in the 2 lines for traits recorded during growth. Second, applying the 2 feeding conditions used for selection to both selected lines plus the control unselected line (generation 0, G0) in a 2 × 3 factorial trial, the line performances were compared and the gut microbiota of the lines was characterized. The correlated responses in feed conversion ratio (FCR) were remarkably equivalent in both selected lines (-2.74 genetic σ) but correlated responses in other traits were notably different. In the ConsoResidual line, selection for decreased RFI resulted in a small negative correlated response in BW at 63 d old (BW63) and in a null response in ADG. In the ADGrestrict line, on the contrary, the correlated response in BW63 was substantial (+1.59 σ). The 2 selected lines had a FCR reduced by 0.2 point compared with the G0 line, and the same difference was found in both feeding regimens ( < 0.001). Indeed, selection on ADG would lead to heavier animals with no significant reduction of feed costs, whereas selection on RFI leads to lower feed costs and no increase of animal BW under ad libitum feeding. Altogether, our results do not suggest any genotype × environment interaction in the response to feeding regimens. The intestinal microbial communities from efficient rabbits differed from their unselected counterparts in terms of fermentation end products and microbial phylotypes, suggesting a central role of these microbes in the better feed efficiency of the rabbits.

Mutations in the FecL locus are associated with large variation in ovulation rate and litter size in the French Lacaune sheep breed. It has been shown that the B4GALNT2 gene within the FecL locus is most likely responsible for the high fecundity in the French breed. In this study, we have highlighted the segregation of the FecL

Selection for feed efficiency is questioned as reducing the ability of farm animals to face stress and overcome challenges. The hypothalamic-pituitary-adrenocortical (HPA) axis activity, measured by the cortisol level in plasma after ACTH injection, has been proposed as an indicator of robustness. The objectives of this study were to evaluate 1. if a modified cortisol level in pigs alters their feed efficiency and their production performance, 2. if alternative dietary resources would affect these responses. Parallel trials including divergent lines for plasma cortisol 1 hour after ACTH injection and divergent lines for residual feed intake (RFI) were run during growth with a conventional diet and a diet with high fibres, low energy and low protein content. Selection for higher or lower plasma cortisol levels after stimulation of the adrenal gland did not impact growth and feed intake traits, but it had a significant impact on body composition and carcass yield, with improved composition in the high cortisol animals. The two lines had similar responses to an alternative diet, with decreased growth rate and feed intake, and increased feed conversion ratio. On the other hand, lines selected for divergent RFI had different responses to the alternative diet, the more efficient line having a more reduced growth rate with the diet with lower energy and AA contents. However, in terms of FCR it remained more efficient. The initial hypothesis of decreased efficiency associated to increased cortisol was not validated.

Weaning is a stress every piglet has to face. It is a main cause of antibiotic uses due to digestive disorders. In this study, response to weaning was analyzed in pigs from two lines divergently selected for residual feed intake (RFI) during growth. A total of 132 pigs from each line, housed per line and diet in conventional postweaning units of 12 castrated males and 12 females, were fed either a conventional control (two successive diets) or a complex (three successive diets) dietary sequence during the postweaning period (4 to 10 wk of age). BWs were recorded at weaning (days 0 and 28 of age), days 1, 2, 6, 12, 19, 26, and 42 (10 wk of age), and at 23 wk of age. Feces texture was examined before weaning (day −1), at day 1, 2, 6, 12, and 19. Feed intake was recorded at pen level from days 0 to 42 after weaning, and individually thereafter. Plasma was collected after blood samplings at days −1, 6, 19, and 42 on half of the piglets: all piglets of a given sex in each pen were sampled, to achieve a balanced number across factors. Pigs of the low RFI (LRFI) line were heavier at weaning, had greater glucose concentration, and lower levels of diarrhea at days 1 and 2 than pigs from the high RFI (HRFI) line (P < 0.01). At day 42, there was no BW difference between lines, and G:F ratio did not differ between lines (P = 0.40). The LRFI pigs had lower feed intake and growth rate from day 0 to day 19 (P < 0.005), and greater plasma concentration of non-esterified fatty acid (P < 0.001), indicating an increased mobilization of body lipids and proteins immediately after weaning compared with HRFI pigs. They also had greater levels of diarrhea at day 6 (22% for LRFI vs. 14% for HRFI, P = 0.002), but the concentration of plasma haptoglobin did not indicate acute inflammation. The complex diet sequence improved feed intake and growth, and reduced diarrhea, mainly in the LRFI line (P < 0.001). To conclude, pigs from the LRFI line were more negatively affected by weaning stress, but managed to recover afterwards. The complex diet sequence ameliorated some of the negative effects that weaning had on the LRFI pigs, but limited effects of nursery period feeding sequence on growth performance were observed during the growing-finishing period.

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.

Session : Génétique Participation à cette étude : Plateforme d'Infectiologie Expérimentale (PFIE) UE 1277 - Nouzilly Centre Inra Val de LoireSession : GénétiqueParticipation à cette étude : Plateforme d'Infectiologie Expérimentale (PFIE) UE 1277 - Nouzilly Centre Inra Val de Loire; La pasteurellose est la première cause de mortalité des femelles en élevage cunicole. Le projet RELAPA (Génomique pour la REsistance génétique des LApins à la PAsteurellose) a pour objectif de mettre en évidence des régions du génome associées à la réponse à la pasteurellose. Pour ce faire, 955 lapins ont été inoculés à 6 semaines d’âge avec une souche de Pasteurella multocida pyogène et suivis pendant 14 jours. La réponse des animaux était très variable, avec 7% de lapins résistants (sans aucun symptôme de pasteurellose et sans Pasteurella multocida détectée dans les organes) et 11% d’animaux très sensibles (morts ou euthanasiés pendant l’essai avec des Pasteurella multocida détectées). L’effet du père sur les caractères mesurés est très significatif, ce qui laisse présager l’existence d’une variabilité génétique importante dans la résistance à la pasteurellose.

The aim of this study was to compare the energy balance and dynamic of body reserves in rabbit females divergently selected for longevity. One hundred and twenty-nine females from a high longevity line (HL) and 131 females of a low longevity line (LL) were studied from the 1st to the 3rd kindling. Litter size and weight and female body weight were measured at kindling (1st, 2nd and 3rd), insemination (2nd and 3rd) and at weaning (1st and 2nd). The total body electric conductivity (TOBEC) method was used to estimate the body reserves in all females at artificial insemination and at weaning, and at kindling in females that achieved parturition. Energy balance between the 11th and the 21th d of lactation was also calculated for these females. No significant difference was found for fertility or for the number of offspring born alive and weaned. However, the total number of offspring born was higher in the LL line than in the HL line at the 2nd parturition (+1.12±0.46 g; Pnd artificial insemination (+107.0±29 g; P=0.049), leading to a similar weight between the lines at the 2nd artificial insemination. There was no significant difference between lines for estimated energy used for growth between the 11th and the 21th d of lactation, or for estimated milk production (2365±30 g in HL line vs. 2398±30 g in LL line), estimated using the weight gain of the kits between the 11th and 21st d of lactation, for feed intake measured during this period (351±5 g/d in HL line vs. 359±5 g/d in LL line) or for energy balance (–6.11±0.3 MJ in HL line vs. –6.30±0.3 MJ in LL line). However, body energy content was higher in HL females than in LL (+2.72±0.64 MJ; P=0.001). In conclusion, selection for higher functional longevity results in a better ability of females to use body reserves in their early reproductive life.

Improvement of feed efficiency can be achieved by genetic selection directly on feed to BW gain ratio or for alternative traits. In the present study, 2 different traits were explored in the growing rabbit and their heritability and genetic correlations with traits recorded between weaning (30 d) and 63 d of age: i) residual feed intake (RFI), to select animals having low ad libitum feed intake independently from their production level, and ii) ADG under restricted feeding (ADGR; with a restriction level of 80% compared with ad libitum feeding of a control group), to select animals having high growth rate despite limited feed intake. To study these traits, 2 rabbit lines were established named i) ConsoResidual line and ii) ADGrestrict line. Under ad libitum or restricted feeding, it comes to select animals that waste less energy for maintenance, metabolism, or activity and retain more for tissue deposition. The selection process was similar in both lines. Data comprised records from generations 0 to 6 for about 1,800 rabbits per line measured for their BW at weaning and 63 d of age (BW63) and their individual feed consumption. Under ad libitum feeding, the heritability estimates were moderate for RFI (0.16 ± 0.05), ADG (0.19 ± 0.05), and feed conversion ratio (FCR; 0.22 ± 0.05). The high genetic correlation estimated between RFI and FCR (0.96 ± 0.03) was in accordance with the literature. The genetic correlation between RFI and ADG traits was not significant. Thus, selection for low RFI with ad libitum feeding was confirmed as a potential trait to improve FCR and reduce feed intake, with little effect on ADG. To our knowledge, there is no previous selection experiment on growing rabbits with restricted feeding. Our heritability estimates for ADGR and feed conversion ratio under restricted feeding (FCRR) were moderate (0.22 ± 0.06 and 0.23 ± 0.07, respectively) and had very high negative genetic correlation. Both selection criteria were found with high and favorable genetic correlations with feed efficiency recorded under each feeding regimen. However, their different genetic correlations with BW at weaning and at 63 d of age (BW63R; respectively, 0.85 and 0.17 for RFI and -0.25 and 0.81 for ADGR) suggested different impacts on major production traits that need further analyses to decipher the relative advantages of the 2 selection criteria, together with interactions between genotypes and feeding regimen.

With the development of automatic self-feeders and electronic identification, automated, repeated measurements of individual feed intake (FI) and BW are becoming available in more species. Consequently, genetic models for longitudinal data need to be applied to study FI or related traits. To handle this type of data, several flexible mixed-model approaches exist such as character process (CPr), structured antedependence (SAD), or random regression (RR) models. The objective of this study was to compare how these different approaches estimate both the covariance structure between successive measurements of FI and genetic parameters and their ability to predict future performances in 3 species (rabbits, ducks, and pigs). Results were consistent between species. It was found that the SAD and CPr models fit the data better than the RR models. Estimations of genetic and phenotypic correlation matrices were quite consistent between SAD and CPr models, whereas correlations estimated with the RR model were not. Structured antedependence and CPr models provided, as expected and in accordance with previous studies, a decrease of the correlations with the time interval between measurements. The changes in heritability with time showed the same trend for the SAD and RR models but not for the CPr model. Our results show that, in comparison with the CPr model, the SAD and RR models have the advantage of providing stable predictions of future phenotypes 1 wk forward whatever the number of observations used to estimate the parameters. Therefore, to study repeated measurements of FI, the SAD approach seems to be very appropriate in terms of genetic selection and real-time managements of animals.

This study reports a functional characterization of a limited segment (QTL) of sheep chromosome 12 associated with resistance to the abomasal nematode Haemonchus contortus. The first objective was to validate the identified QTL through the comparison of genetically susceptible (N) and resistant (R) sheep produced from Martinik × Romane back-cross sheep. The R and N genotype groups were then experimentally infected with 10 000 H. contortus larvae and measured for FEC (every three days from 18 to 30 days post-challenge), haematocrit, worm burden and fertility. Significant differences in FEC and haematocrit drop were found between R and N sheep. In addition, the female worms recovered from R sheep were less fecund. The second step of the characterization was to investigate functional mechanisms associated with the QTL, thanks to a gene expression analysis performed on the abomasal mucosa and the abomasal lymph node. The gene expression level of a candidate gene lying within the QTL region (PAPP-A2) was measured. In addition, putative interactions between the chromosome segment under study and the top ten differentially expressed genes between resistant MBB and susceptible RMN sheep highlighted in a previous microarray experiment were investigated. We found an induction of Th-2 related cytokine genes expression in the abomasal mucosa of R sheep. Down-regulation of the PAPP-A2 gene expression was observed between naïve and challenged sheep although no differential expression was recorded between challenged R and N sheep. The genotyping of this limited region should contribute to the ability to predict the intrinsic resistance level of sheep.

International audience; A consequence of increasing litter size in sheep is that a portion of the lambs have to be reared artificially. Detailed information about the pattern of milk consumption of artificially reared lambs would help improve their management. The purpose of this study is to describe the individual and group feeding behaviour of 94 Romane artificially reared lambs from 5 to 28 days of age using an electronic automatic lamb feeder. Animals were located in four pens of 8 to 15 lambs of similar age with one teat per pen. They were fed ad libitum. In our experimental situation (group rearing, continuous lightning) on average a lamb made 1.4 +/- 0.7 visits to the teat per meal and 9.5 +/- 3 meals per day. Mean meal duration was 247 +/- 158 s and the mean daily time spent feeding was 38 +/- 25 min. The mean quantity of milk intake was 176 +/- 132 ml per meal and 1.68 +/- 0.8 l per day. With age, the number of daily meals and their duration decreased while the quantity of milk consumed per meal and per day increased. Females tended to make more visits to the teat per meal and perform more meals per day but their milk consumption per meal was lower. The feed conversion ratio was 1.36 +/- 0.2. Synchrony in feeding (group meal) was estimated as the percentage of lambs that wanted to access the teat within the same short period (relative group meal size). On average 65% of lambs in the pen wanted to access the teat within the same period, but for 35% of group meals the relative group meal size was >90%. There was no consistency in the order in which lambs accessed the teat during a group meal. Our evaluation suggested that electronic automatic lamb feeders are tools that can provide, on a large scale, data describing the feeding behaviour of artificially reared lambs. It is then possible to study factors influencing these traits in order to improve the outcome of artificially reared lambs.

Susceptibility to scrapie is mainly controlled by point mutations at the PRNP locus. However, additional quantitative trait loci (QTL) have been identified across the genome including a region in OAR18. The gene which encodes the inducible form of the cytoplasmic Hsp90 chaperone (HSP90AA1) maps within this region and seems to be associated with the resistance/susceptibility to scrapie in sheep. Here, we have analyzed several polymorphisms which were previously described in the ovine HSP90AA1 5' flanking region and in intron 10 in two naturally scrapie infected Romanov sheep populations. First, we have studied 58 ARQ/VRQ animals pertaining to the sire family where the QTL influencing scrapie incubation period in OAR18 was detected. We have found a significant association between polymorphisms localized at -660 and -528 in the HSP90AA1 5' flanking region and the scrapie incubation period. These two polymorphisms have also been studied in a second sample constituted by 62 VRQ/ VRQ sheep showing an extreme incubation period. Results are concordant with the first dataset. Finally, we have studied the HSP90AA1 expression in scrapie and control animals (N=41) with different HSP90AA1 genotypes by real time PCR on blood samples. The HSP90AA1 expression rate was equivalent in CC -600AA-528 and CG-600AG-528 scrapie resistant animals (ARR/ARR) and was higher in their CC-600AA-528 than in their CG-600AG-528 scrapie susceptible counterparts (VRQ/VRQ). Our results support the hypothesis that the ovine HSP90AA1 gene acts as a modulator of scrapie susceptibility, contributing to the observed differences in the incubation period of scrapie infected animals with the same PRNP genotype. © Cell Stress Society International 2009.

National audience

International audience; Background: The pre-weaning growth of lambs, an important component of meat production, depends on maternal and direct effects. These effects cannot be observed directly and models used to study pre-weaning growth assume that they are additive. However, it is reasonable to suggest that the influence of direct effects on growth may differ depending on the value of maternal effects i.e. an interaction may exist between the two components. Methods: To test this hypothesis, an experiment was carried out in Romane sheep in order to obtain observations of maternal phenotypic effects (milk yield and milk quality) and pre-weaning growth of the lambs. The experiment consisted of mating ewes that had markedly different maternal genetic effects with rams that contributed very different genetic effects in four replicates of a 3 x 2 factorial plan. Milk yield was measured using the lamb suckling weight differential technique and milk composition (fat and protein contents) was determined by infrared spectroscopy at 15, 21 and 35 days after lambing. Lambs were weighed at birth and then at 15, 21 and 35 days. An interaction between genotype (of the lamb) and environment (milk yield and quality) for average daily gain was tested using a restricted likelihood ratio test, comparing a linear reaction norm model (interaction model) to a classical additive model (no interaction model). Results: A total of 1284 weights of 442 lambs born from 166 different ewes were analysed. On average, the ewes produced 2.3 +/- 0.8 L milk per day. The average protein and fat contents were 50 +/- 4 g/L and 60 +/- 18 g/L, respectively. The mean 0-35 day average daily gain was 207 +/- 46 g/d. Results of the restricted likelihood ratio tests did not highlight any significant interactions between the genotype of the lambs and milk production of the ewe. Conclusions: Our results support the hypothesis of additivity of maternal and direct effects on growth that is currently applied in genetic evaluation models.