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Replacing fish meal and oil in trout diets with plant-derived ingredients is a contemporary challenge to move towards more sustainable aquaculture practices. However, such dietary replacement causes hepatic metabolic changes that have not yet been elucidated. Here, we aimed to decipher the effect of a 100% plant-based diet on the hepatic global DNA methylation landscape in trout and assess whether changes depend on fish genetic background. We analysed the global methylome and the expression of DNA (de)methylation-related genes of three isogenic lines that exhibit similar growth when fed a marine resource-based diet (M diet), but differ in their responses to a plant-based diet (V diet). Our results revealed that the V diet induced a decrease in 5-cytosine combined with an increase in 5-hydroxymethylcytosine in two of the three analysed lines. For one of these 2 affected lines, when fed the M diet but at the same feed intake of the V diet (MR), no methylome differences were highlighted between M and MR or between MR and V-fed trout whereas for the other affected line, M fed trout displayed a divergent methylome profile from MR and V fed fish. DNA (de)methylation-related genes were also affected by the V or MR diets. Our findings showed that the global hepatic methylome of trout is affected by a V diet, depending on genetic background. This latter effect seems to be due to either a decreased feed intake alone or combined with the effect of the dietary composition per se.

The Edible Ivorian Snails: Effects of Some Vegetables, Concentrated Diets and Dietary Calcium on the Growth of Archachatina ventricosa (Gould, 1850) in Indoor Rearing. Archachatina ventricosa (Gould) snails with 37.06 g body weight and 6.01 cm shell length were given two vegetable diets dialed with leaves of Lactuca sativa (Apiaceae) and Brassica oleracea (Brassicaceae) for R1, leaves of Laportea aestuans (Urticaceae) and Phaulopsis falcisepala (Acanthaceae) for R2 and four concentrated diets (RT, R3, R4 and R5) with variable calcium content (0.05%, 0.59%, 6.82%, 12.02%, 14.03% et 16.01% respectively) in order to determine the calcium content inducing the best growth and the cumulated mortality rate. This optimum calcium content was 16.01%. At higher calcium content, Archachatina ventricosa produced more shell than meat.

Evolution of genetic variability has been studied in six successive generation of a population originating from wild Helix aspersa. Short-term selection and domestication were of interest. In the first three no artificial selection was used, but in the next three a control line selected for greater adult weight was reared. A pedigree analysis was carried out. Results, the drop in the effective number of ancestors, were consistent with the theory of selection and the Bulmer effect.

Background: Rainbow trout is a significant fish farming species under temperate climates. Female reproduction traits play an important role in the economy of breeding companies with the sale of fertilized eggs. The objectives of this study are threefold: to estimate the genetic parameters of female reproduction traits, to determine the genetic architecture of these traits by the identification of quantitative trait loci (QTL), and to assess the expected efficiency of a pedigree-based selection (BLUP) or genomic selection for these traits. Results: A pedigreed population of 1343 trout were genotyped for 57,000 SNP markers and phenotyped for seven traits at 2 years of age: spawning date, female body weight before and after spawning, the spawn weight and the egg number of the spawn, the egg average weight and average diameter. Genetic parameters were estimated in multi-trait linear animal models. Heritability estimates were moderate, varying from 0.27 to 0.44. The female body weight was not genetically correlated to any of the reproduction traits. Spawn weight showed strong and favourable genetic correlation with the number of eggs in the spawn and individual egg size traits, but the egg number was uncorrelated to the egg size traits. The genome-wide association studies showed that all traits were very polygenic since less than 10% of the genetic variance was explained by the cumulative effects of the QTLs: for any trait, only 2 to 4 QTLs were detected that explained in-between 1 and 3% of the genetic variance. Genomic selection based on a reference population of only one thousand individuals related to candidates would improve the efficiency of BLUP selection from 16 to 37% depending on traits. Conclusions: Our genetic parameter estimates made unlikely the hypothesis that selection for growth could induce any indirect improvement for female reproduction traits. It is thus important to consider direct selection for spawn weight for improving egg production traits in rainbow trout breeding programs. Due to the low proportion of genetic variance explained by the few QTLs detected for each reproduction traits, marker assisted selection cannot be effective. However genomic selection would allow significant gains of accuracy compared to pedigree-based selection. [ABSTRACT FROM AUTHOR]