Sex-specific effects of a methionine-restricted maternal diet on liver transcript levels and fatty liver production in mule ducks

Sex-specific effects of maternal diet on offspring phenotypes have been reported in farm animals including in poultry. The present study was conducted in mule ducks, investigating the long-term effects of a methionine-restricted maternal diet on the production performance of the offspring of both sexes. Sixty female ducks were divided into two groups and fed either a control diet containing 4.0 g/kg of methionine or a restricted diet containing 2.5 g/kg of methionine. Next, 254 offspring were divided into four subgroups of 60-67 animals, according to maternal diet and sex. Their growth performance was recorded until 87 days of age. Then, plasma parameters were measured on these non-overfed ducks (NOFDs) at D87 and 60 of them were sacrificed, representing 15 males and 15 females in each maternal diet group. Carcass traits were recorded, and the liver transcript level of 170 genes mainly involved in energy or one-carbon metabolism was studied. The remaining 194 ducks were overfed during 12.5 days -until 100 days of age- for fatty liver production. Then, zootechnical traits and plasma parameters were measured on these 194 overfed ducks (OFDs), and the liver transcript level of the same 170 genes was studied. The results showed that the methionine-restricted maternal diet affected traits in NOFDs but in females only, with lower liver lipid and DM percentages (P-value = 0.006 and P-value = 0.004, respectively) and a lower plasma cholesterol level (P-value = 0.020). In OFDs, after the overfeeding period, fatty liver weight was reduced in both sexes by around 53 g, or almost 10% (P-value = 0.016 and 0.017 in females and males, respectively). Only females showed a tendency to lower liver lipid and DM percentages (P-value = 0.078 and P-value = 0.062, respectively) and their plasmatic aspartate aminotransferase activity was reduced (P-value = 0.025). In addition, 18 genes differentially expressed between maternal diet groups were identified in the liver of females only. All were up-regulated in the restricted group and involved in either energy or one-carbon metabolism. These findings showed that the methionine-restricted maternal diet had long-term effects on liver traits, impacting production performance in both sexes. Importantly, these effects were sex-specific, and robust enough to still be observed after the overfeeding period, despite the major reorganisation of metabolic pathways this implied.