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There is an urgent need to evaluate and introduce alternatives for the unsustainable and traditional feed stuffs in poultry. This study evaluated the effects of graded replacement of soybean meal (SBM) by peanut meal (PNM) on egg production, egg quality, oxidative status, and yolk fatty acid profile in laying ducks. In total, 360 Longyan ducks aged 21 weeks were allocated to five treatments, each containing six replicates of 12 birds. Birds were fed the diets containing PNM replacing 0 (control), 25, 50, 75 or 100% of SBM for 16 weeks. With the increase of PNM level, egg production was improved (quadratic, P 0.05), egg weight and feed consumption were decreased, feed conversion ratio and egg mass were impaired at 100% PNM, and yolk colour was enhanced (quadratic, P 0.05). Plasma malondialdehyde concentration was increased at 100% PNM, while plasma glutathione concentration was decreased (quadratic, P 0.01) as PNM substitution increased. Total cholesterol content in yolk decreased (P 0.01) in response to increased PNM substitution. The contents of saturated fatty acids C20:0 and C22:0 in yolk increased (linear or quadratic, P 0.05) with increased PNM substitution, but the contents of saturated fatty acid C18:0, monounsaturated fatty acid C22:1, and polyunsaturated fatty acids C18:3n-3 and C22:6n-3 in yolk were decreased (linear, P 0.05) as PNM replacement increased. The contents in yolk of polyunsaturated fatty acid C18:2n-6, C20:2n-6, C20:3n-6, C20:4n-6, and total amount of polyunsaturated fatty acids increased with the highest contents obtained at 75% PNM substitution. The ratio between n-6 and n-3 increased (linear, P 0.05) as PNM substitution increased. The transcript abundance in liver of peroxisome proliferators-activated receptors γ and fatty acid synthase showed quadratic (P 0.05) responses with PNM replacement, with the highest expression of both genes being obtained with 75% substitution with PNM. Replacement of dietary SBM with 100% PNM decreased egg production and antioxidant capacity and increased the ratio of omega fatty acid in yolk between n-6 and n-3 in laying ducks. The obtained results indicate that PNM can be used to replace up to 75% of SBM in the diet of laying ducks without negative effects on the egg-laying production or egg quality. The regression model indicated that the maximal egg mass was obtained at no more than 67.6% replacement of SBM with PNM in the diet of laying ducks.

Optimizing the dietary calcium (Ca) level is essential to maximize the eggshell quality, egg production and bone formation in poultry. This study aimed to establish the Ca requirements of egg-type duck breeders from 23 to 57 weeks of age on egg production, eggshell, incubation, tibial, plasma and ovary-related indices, as well as the expression of matrix protein-related genes. Totally, 450 Longyan duck breeders aged 21 weeks of age were allotted randomly into five treatments, each with six replicates of 15 individually caged birds. The data collection started from 23 weeks of age and continued over the following 35 weeks. The five groups corresponded to five dietary treatments containing either 2.8%, 3.2%, 3.6%, 4.0% or 4.4% Ca. The tested dietary Ca levels increased (linear, P