Productive performance of naked neck, frizzle and dwarf laying hens under various natural climates and two nutritional treatments

Abstract

The productive performance of major genes for feather reduction (naked neck and frizzle) and body size reduction (dwarf) in a dual-purpose layer strain was evaluated in the subtropical coastal region of southeast Africa (Maputo, Mozambique). The experimental material consisted of eight different genetic groups, two diets (14.4 and 16.2% crude protein) and two climatic seasons. Birds were caged individually in a laying house with natural light and ventilation. Traits measured were: temperature and relative humidity, body weight, age at first egg, egg number and weight, feed intake and mortality. The following were calculated: persistence, egg mass, feed efficiency, feed conversion, biological efficiency (EMD/BW0.75) and productivity (EN/BW0.75). The main results show that: (1) none of the feather-reducing genes significantly improved egg production or feed efficiency, although the naked neck (Na) excelled in terms of biological efficiency and productivity; (2) the dwarf gene (dw) was associated with delayed sexual maturity, production of fewer and lighter eggs, higher persistence, better feed conversion and higher survivability; (3) elevated temperatures restrained voluntary feed intake, egg number and weight, and body weight gain; (4) the lower dietary protein content resulted in decreased body weight. It was concluded that the genes were not equally responsive to the environments, which offers the opportunity for selective breeding