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Background In mammals, the nutritional status experienced during embryonic development shapes key metabolic pathways and influences the health and phenotype of the future individual, a phenomenon known as nutritional programming. In farmed birds as well, the quantity and quality of feed offered to the dam can impact the phenotype of the offspring. We have previously reported that a 38% reduction in the intake of the methyl donor methionine in the diet of 30 female ducks during the growing and laying periods - from 10 to 51 weeks of age - reduced the body weight of their 180 mule ducklings compared to that of 190 ducklings from 30 control females. The maternal dietary methionine restriction also altered the hepatic energy metabolism studied in 30 of their ducklings. Thus, their plasma glucose and triglyceride concentrations were higher while their plasma free fatty acid level was lower than those measured in the plasma of 30 ducklings from the control group. The objective of this new study was to better understand how maternal dietary methionine restriction affected the livers of their newly hatched male and female ducklings by investigating the hepatic expression levels of 100 genes primarily targeting energy metabolism, amino acid transport, oxidative stress, apoptotic activity and susceptibility to liver injury. Results Sixteen of the genes studied were differentially expressed between the ducklings from the two groups. Maternal dietary methionine restriction affected the mRNA levels of genes involved in different pathways related to energy metabolism such as glycolysis, lipogenesis or electron transport. Moreover, the mRNA levels of the nuclear receptors PPARGC1B, PPARG and RXRA were also affected. Conclusions Our results show that the 38% reduction in methionine intake in the diet of female ducks during the growing and egg-laying periods impacted the liver transcriptome of their offspring, which may explain the previously observed differences in their liver energy metabolism. These changes in mRNA levels, together with the observed phenotypic data, suggest an early modulation in the establishment of metabolic pathways.

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.

International audience; Background The major prolificacy gene FecL was first described in the Lacaune sheep meat breed Ovi-Test in 1998. A few studies estimated the effect of this gene on prolificacy but little data is available. In 2010, the Ovi-Test cooperative started genotyping FecL in all of their replacement ewe lambs. Thanks to the large amount of genotyping data that is available now, gene effects on litter size and other relevant traits can be estimated more accurately.MethodsOur study included 5775 ewes genotyped since 2010 and 1025 sires genotyped since 2002. Performances and pedigrees were extracted from the French national database for genetic evaluation and research. Analysis of the effect of the gene on different traits was based on linear or threshold genetic animal models using the ASReml software.ResultsThe female population was composed of 71% homozygous wild type ewes (++), 27% heterozygous ewes for the FecL mutation (L+) and 2% homozygous mutant (LL) ewes. On average, L + ewes produced 0.5 more lambs per lambing than ++ ewes. The FecL gene not only affected the mean litter size but also its variability, which was lower for ++ than for L + ewes. Fertility after insemination was higher for L + ewes than for ++ ewes. Lambs from ++ dams were heavier (+300 g) than the lambs of L + dams and the mortality of twin lambs born from ++ dams was lower than those from L + dams. In addition, bias in estimated breeding values for prolificacy when ignoring the existence of this major gene was quantified.ConclusionsThe effect of the FecL gene on prolificacy was estimated more accurately and we show that this gene affects both the mean and the variability of litter size and other traits. This paper also shows that ignoring the existence of this major gene in genetic evaluation of prolificacy can lead to a large overestimation of polygenic breeding values.

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.

Les parametres genetiques de la taille de portee avec fecondation sur œstrus naturel ou sur œstrus induit (apres utilisation d'eponge vaginale impregnee de F.G.A., et injection de PMSG) ont ete analyses sur 9 110 agnelles Lacaune de 170 troupeaux laitiers. La prolificite sur œstrus induit (1,41) est tres significativement superieure a la prolificite sur œstrus naturel (1,18). Les effets de l'âge a la mise-bas et de l'epoque d'agnelage sur la prolificite ne sont pas significatifs. L'heritabilite de la prolificite, estimee par analyse de variance des demi-soeurs de pere, est significativement differente de zero (h2 = 0.064) pour la « prolificite induite », ce qui n'est pas le cas pour la « prolificite naturelle » (h2 = 0.032). La correlation genetique entre ces deux types de performances (rg = 0.33) laisse supposer que « prolificite naturelle » et « prolificite induite sont deux caracteres controles en partie par des genes differents. A la suite de ces resultats, nous presentons trois situations classiques d'utilisation des traitements hormonaux dans les structures francaises et nous indiquons leurs implications dans l'elaboration de schemas de selection sur les caracteres de reproduction.