Dietary methionine deficiency reduces laying performances of female common ducks and impacts traits of interest of their mule ducklings.

The effects of maternal nutrition on offspring phenotypes have been mainly documented over the past years in mammals, and are now studied in poultry as well. In the present study, we investigated the effects of a reduced level of dietary Methionine (Met) on laying performances of common laying ducks and their impacts on the phenotype of their mule ducklings. A total of 60 female laying ducks were divided into 2 dietary treatments at 10 wk of age. The restricted group received Met-restricted diets (R group) containing 0.25% of Met whereas the control group received control diets (C group) containing 0.40% of Met that meets Met requirements. The restriction was applied during the growing and laying periods, from 10 to 51 wk of age and a particular focus was put on female breeder traits that might be affected by the Met restriction. Plasma parameters of hepatic and lipid metabolisms were recorded in ducklings. Total weight (P < 0.001), albumen weight (P < 0.001) and albumen percentage of dry matter (P < 0.01) were decreased for eggs laid by female breeders from the R group. Both male and female ducklings from the R group of female breeders showed a reduced BW at hatching (P < 0.001) and a tendency to an increased proportional liver weight (P = 0.07). Finally, the maternal low dietary Met level modified plasma parameters in newborn ducklings regardless of sex: alkaline phosphatase (ALP) and alanine transaminase (ALT) activities were reduced (P = 0.07 and P = 0.002, respectively), levels of glucose (P = 0.03) and triglycerides (P = 0.01) were higher whereas level of free fatty acids decreased (P = 0.01). It was concluded that feeding female laying ducks with a restricted dietary Met content during the growing and laying periods has a negative effect on egg weight and composition. The ducklings that were restricted in nutrients during their early development, have a reduced BW, and altered lipid and hepatic metabolisms.

Impact of selection for residual feed intake on production traits and behavior of mule ducks.

A divergent selection experiment of Muscovy sires based on the residual feed intake (RFI) of their male mule progeny was initiated in 2009. Using electronic feeders, the aim of this study was to establish whether 3 generations of selection for RFI had an impact on feeding behavior traits and general behavior, and to examine its effect on liver and meat quality. Eighty mule ducks, issued from 8 Muscovy drakes per line with extreme RFI, were tested in a pen equipped with 4 electronic feeders. Feeding behaviors were recorded from 3 to 7 wk after hatching under ad libitum feeding conditions. Then animals were prepared for overfeeding with a 3-week period of restricted feeding, and overfed during 12 d before slaughter. The RFI was significantly lower in the low RFI line than in the high RFI line (-5.4 g/d, P = 0.0005) and daily feed intake was reduced both over the entire test period (-5 g/d, P = 0.049) and on a weekly basis (P = 0.006). Weekly and total feed conversion ratios were also significantly lower (-0.08, P = 0.03 and -0.06, P = 0.01, respectively). Low RFI ducks had more frequent meals, spent as much time eating as high RFI ducks, and their feeding rate was lower when analyzed at the wk level only. Additionally no significant correlation between feed efficiency and feeding behavior traits was evidenced, indicating only limited relationships between RFI and feeding patterns. Some differences in behavioral responses to stressors (open field test combined with a test measuring the response to human presence) suggested that a lower RFI is associated with less fearfulness. Selection for RFI had no effect on liver weight and quality and a slightly deleterious impact on meat quality (decreased drip loss and L*). Finally, low RFI animals had higher body weights after restricted feeding from wk 10 to wk 12 and after overfeeding than high RFI ducks. This suggests that selection for reduced RFI until 7 wk of age increases the feed efficiency up to slaughter.

Improving residual feed intake of mule progeny of Muscovy ducks: genetic parameters and responses to selection with emphasis on carcass composition and fatty liver quality.

In France, about 95% of the fatty liver production comes from mule ducks, an infertile hybrid cross between female common ducks (Anas platyrhynchos) and Muscovy drakes (Cairina moschata). As a hybrid, genetic improvement of the performance of mule ducks is achieved by selection of the parental populations. Feed represents two-thirds of the total costs of duck production; thus, the breeders' main concern is to improve the birds' feed efficiency without impairing their capacity to be overfed after the growing period. To obtain insight into this economically important trait, we designed a divergent selection experiment for Muscovy sires on the basis of the residual feed intake (RFI) of their male mule progeny. Residual feed intake represents the fraction of feed intake that cannot be explained by maintenance and production requirements. Data comprised records from generations 0 to 2 with 227 Muscovy sires of 2,016 mule ducks. Growth and fat deposition were measured individually for all mule ducks. Half-sib mule ducks were placed together in 1 small pen, and the feed consumption was recorded for each pen; all half-sibs therefore had the same feed intake estimates. Heritability of RFI was high (0.83 ± 0.42), and after 2 generations of selection, the differences between lines in terms of RFI (contrast of 9.13 g/d, representing 0.76 phenotypic standard deviation; P < 0.0001) and feed conversion ratio (contrast of 0.08, representing 0.28 phenotypic standard deviation; P = 0.0003) were marked. In regard to carcass traits, the low-RFI line (high-efficiency animals) had heavier legs (476 vs. 463 g; P < 0.0001) and magret muscles (268 vs. 262 g; P = 0.001) than the high-RFI line (low-efficiency animals). No differences were observed for either the liver weight or the melting rate between the 2 lines (P > 0.46). Selection on RFI thus improves the feed efficiency of animals without impairing their capacity to produce fatty liver.