Minimizing residual feed consumption by introducing dwarf and naked neck genes in laying chicken [electronic resouce].

Includes references.

An experiment was conducted to evaluate the effect of dwarf (dw) and naked neck (Na) genes in a single state or combination on feed efficiency and egg production parameters of laying hens under summer season of Egypt. Measurements related to efficiency of feed utilization for egg production were recorded between ages 20 and 40 weeks. Residual feed consumption (RFC) was estimated as the difference between observed feed consumption (OFC) and expected feed consumption (EFC) given by a multiple regression equation within feed consumption as dependent variable and egg mass, metabolic body weight (BW0.75) and weight gain as independent variables. The current results revealed that the dw gene significantly reduced body weight, total egg number, egg mass and feed intake in either normal or naked neck genotype. With respect to Na gene, the results showed that the presence of Na gene increased total egg number, egg mass and egg weight compared to normally feathered sibs, but the differences were not statistically significant. Moreover, the incorporated Na gene into dwarfed birds compensated the negative effect associated with dw gene on egg production parameters. The presence of dw gene in a single state or combined with Na gene significantly improved feed conversion ratio compared to normal type. Similar trend was observed for Na gene, but the difference was not statistically significant. Concerning eggshell quality, the presence of dwarf (dw) and naked neck (Na) genes improved eggshell quality. The results revealed that the equation calculated for Nanadwgenotype had a better rate of determination (R2=0.69) followed by nanadw- (R2=0.46), NanaDw- (R2=0.35) genotypes compared to nanaDw- sibs (R2=0.28). It was generally noticed that the observed values of feed intake were closely to expected values in Nanadw-, nanadw- and NanaDw- genotypes compared to nanaDw- sibs. This adjacency was reflected on RFC, where it was more consistent to zero line. Positive relationships between RFC and egg mass were observed in nanadw- and NanaDw- genotypes. However, these relationship were inverse in nanadw- and Nanadw- genotypes. Both observed feed consumption and feed conversion ratio was highly significant positive correlations with RFC in all genotypes. The relationships between RFC and yolk percentage were positive in all genotypes. In conclusion, the current results suggest the incorporation of dw and Na genes into laying chickens led to improved feed efficiency by minimizing residual feed consumption. The results also suggested that more consideration should be given the difference among various genetic stocks in their requirements for maintenance and egg production. Moreover, it is possible to use of residual feed consumption as selection criteria for improve feed efficiency.

Summary in Arabic.

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