Comparison of medium-heavy dwarf (dw) and normal layers using two feeds of different protein and energy levels

Abstract

One hundred and twenty-eight pullets issued from a medium heavy brown egg type population, either normal sized (DW) or dwarf (dw), were housed in individual cages at the age 16 weeks. Each genotype was divided into 2 groups, each receiving one of two commercialtype feeds, either having 15.7 % crude protein and 2650 kcal ME/kg, or 17.6 % crude protein and 2750 kcal ME/kg. Laying performance till the age 43 weeks was slightly decreased by the dw gene compared to Dw’ (about 5 % for egg number, 6-7 % for mean egg weight). The dwarf gene gave a gain in feed conversion with respect to egg production (respectively 20 % and 14 % at the ages of 27 and 41 weeks). With advancing age, there was a greater increase in mean body weight and mean egg weight increased relatively less for Dw⁺ than for dw hens when fed with the higher protein and energy level feed. At the end of the control period, there were less hens with deteriorated plumage among dwarf than among normal females. The poorer diet increased feed consumption, body weight and egg number, this effect tended to be more marked for normal than for dwarf females. « Pause » days were more frequent for Dw⁺ than for dw females on the richer diet. The effect of the dw gene on feed conversion showed little difference between the two diets, although decreased conversion by dw hens on the poorer diet was suggested in the second period of control.