Feed efficiency in the laying duck: appropriate measurements and genetic parameters.

The objective of this study was to characterize residual feed intake (RFI) in common laying ducks by a) adjusting position and duration of the measurement period and b) estimating genetic parameters of RFI. The feed intake (FI), BW, and egg mass laid (EML) were recorded for 64 I444 common ducks at the beginning (-35 wk of age) and the middle (41-48 wk of age) of the laying curve. Much feed wastage was observed at the beginning of the laying curve and led to biased FI data. However, when laying was well-established, weekly and fortnightly FI measurements were well correlated phenotypically (Rp from 0.84 to 0.92 and from 0.91 to 0.94, respectively for weekly and fortnightly FI) with the measurements over the whole 2-mo period. Regarding egg mass laid, phenotypic correlations between the one-week measurements and the measurements over the whole 2-mo period were more variable than those for FI, ranging from 0.74 to 0.94, and similar to whatever was the period of measurement. The RFI was investigated in a second experiment based on 384 common female ducks, for which FI, EML, BW, and BW gain were recorded at 39 wk of age. The RFI was determined by multiple regression of FI on metabolic BW and EML. Heritability values of FI and RFI were 0.34 and 0.24, respectively. In addition, if the heritability values obtained for BW (0.65) and BW gain (0.09) were consistent with studies in chickens, the very low EML estimates (0.06) were unexpected. The RFI was strongly genetically linked to FI (Rg = +0.89) but appeared to be independent from BW. Selection based on RFI should therefore reduce the FI of animals without clearly modifying the other components. Moreover, the correlated responses on reproductive traits seem favorable because lower RFI values increase the number of eggs produced per year as well as the hatchability and fertility rates.

Identification of different critical embryonic periods to modify egg incubation temperature in mule ducks.

Egg incubation of mule ducks, mainly used for fatty liver production, is one of the critical phases in this sector. Based on hatching rate, the best incubation parameters have already been well described for poultry, but the literature on ducks is lacking. In this study, we tested different incubation conditions by varying two important factors, temperature and relative humidity, in mule ducks. These variations were applied at different periods during embryogenesis in order to measure the impact of environmental disturbances on different zootechnical performances. The temperature was increased by 1.5 °C (16 h/24) and the relative humidity was set up to 65%, during 10 days. Six 10-day developmental windows were tested, from embryonic day 9 to embryonic day 14. Our results are in line with previous reports showing that increasing incubation temperature, even when relative humidity is adjusted, can have a negative impact on duck embryonic mortality up to 24.5% for the condition E10-E20 (P < 10-5). However, the hatchability can be maintained at the level of the control groups when these modifications are applied on the latest windows (from the 11th embryonic day). Sex ratio, hatching BW, and internal temperature are also sensitive to these incubation changes, and their modification could have a major impact on later zootechnical performance. These results should contribute to the development or embryonic temperature programming approaches, especially for the fatty liver production industry.