Pakistan Vet. J., 2008, 28(1): 5-8. 5 COMPARATIVE PRODUCTIVE PERFORMANCE AND EGG CHARACTERISTICS OF PULLETS AND SPENT LAYERS F. YASMEEN, S. MAHMOOD 1 , M. HASSAN, N. AKHTAR AND M. YASEEN 2 Department of Zoology, Government College University, Faisalabad; 1 Department of Poultry Science, 2 Department of Statistics, University of Agriculture, Faisalabad, Pakistan ABSTRACT Production performance and egg quality characteristics of pullets and spent layers were compared in this study. Forty birds, each from the flocks of pullets (24 weeks old) and spent layers (76 weeks old) were selected as experimental birds. The birds from each age group were divided into five replicates, each comprising of eight birds. All the experimental birds were fed a commercial layer ration @ 110g/bird/day for 12 weeks. The data on egg production, feed consumption, egg weight and egg quality characteristics viz. shell thickness, shell weight, breaking strength, albumen diameter, albumen weight and yolk weight were recorded. The data thus collected were utilized for calculation of FCR, Haugh unit and yolk index values. The results revealed that pullets produced more eggs and utilized their feed more efficiently than spent layers. However, egg weight in spent layers was higher than in their counterparts. Pullets also produced eggs with thicker shell and higher Haugh unit values when compared to the spent layers. Feed consumption and yolk index values remained unaffected due to the age. Pullets also had better egg quality characteristics than those of spent layers. Key words: Pullets, spent layers, egg production, FCR, egg characteristics. INTRODUCTION Commercial hybrids (layers and broilers) all over the world are being propagated for production of eggs and meat. The hybrid layers usually start laying at about 20 weeks of age and peak egg production is attained during the first production cycle. The average production rate of commercial layers usually remains very close to 0.9 eggs per day (Kekeocha, 1985). However, as the age increases, their egg production decreases. This situation is further aggravated during the second production cycle. Appetitive behaviour of hens is also affected during the later stage of production age. The climatic conditions have also been known to affect the production behaviour of the laying hens (Oluyemi and Roberts, 1979; Smith and Leclecq, 1990). In areas where climate is hot and humid, commercial hybrids produce an average of 180-200 eggs per year, while in more temperate climate, birds can produce between 250 and 300 eggs per year. The production cycle of eggs may also be influenced by many other factors such as breed, mortality rate, body weight, laying house lightening schedule, feed and culling (North and Bell, 1990). After one year of production, layers are culled and used for meat purpose without exploiting their full inherent potential, which can be exploited up to second production cycle (North and Bell, 1990). The factors like diseases and market rates usually reflect a miserable picture of annual flock replacement while rearing new pullets for profitable egg production. Moreover, keeping aged hens as such is uneconomical because of gradual decline in egg production with more erratic clutch cycles and poor feed efficiency in the relatively heavy layers. Therefore, pullets and spent layers must be managed effectively and efficiently in order to get maximum output and profitability (Kekeocha, 1985). However, very little research work has been conducted under local climatic conditions in Pakistan to exploit the production potential of spent layers. Therefore, this project was designed to compare the production performance of pullets and spent layers. The effect of age on various egg characteristics in these birds was also studied. MATERIALS AND METHODS Forty birds, each from a flock of pullets (24 weeks old) and spent layers (76 weeks old) were selected as experimental birds. The birds from each production cycle were divided into five replicates, each comprising eight birds. The experimental birds were kept in thoroughly cleaned and disinfected individual cages. They were offered a commercial layer ration (Table 1) at the rate of 110g/day/bird throughout the experimental period of 12 weeks. Fresh and clean water was made available throughout the experimental period. These