This study was conducted to investigate the effects of housing systems on the productivity and physiological response as stress indicators in White Leghorn chickens. The chickens subjected to the conventional cages had a significantly lower viability, hen-housed egg production, egg weight and body weight compared with those to the floor pens. However, the hens housed in the conventional cages had a shorter day of the first egg and a greater egg quality compared with those housed in the floor pens. In addition, this study was also investigated to identify biological markers for assessing the physiological response of chickens under stress conditions. As biological markers, the amount of telomeric DNA was analyzed by quantitative fluorescent in situ hybridization on the nuclei of cells. The DNA damage rate of lymphocytes was also quantified by the comet assay. The amount of telomeric DNA of the lymphocytes, kidney and spleen was significantly higher in the chickens under floor pens than those under conventional cages. The DNA damage also increased in chickens raised under conventional cages, as compared to the chickens under floor pens. As results, we conclude that the chickens housed in conventional cages have a greater stressful status than those housed in floor pens.(Key words : conventional cage, floor pen, production performance, telomere, DNA damage, stress, layer) † To whom correspondence should be addressed : shsohn@gntech.ac.kr

This work was carried out to investigate the performance of early laying period of large-type Korean native ducks. One hundred sixty eight ducks were used in this work and divided into A and B strains (6 replications/strain, 14 birds/replication). The days at first egg of A and B strains were the age of 154.5 and 154.7 days, egg weights were 69.1 g and 65.5 g, and body weights were 3,187 g and 3,105 g at the period of laying the first egg, respectively. The days at sexual maturity of A and B strains were the age of 175.8 and 171.5 days, egg weights were 75.2 g and 74.9 g, and body weights were 3,245 g and 3,225 g at the period of laying the first egg, respectively. There were no significant differences on the day of first egg, the day of sexual maturity, egg weight and body weight at first egg and the sexual maturity, average body weight, and daily feed intake between A and B strains (P>0.05). The day of the sexual maturity of B strain was earlier than that of A strain (P<0.05). However, weekly body weight was the highest at the age of 28 weeks (P<0.05), and weekly feed intake increased after 26 weeks old (P<0.05). Egg production (%) of B strain was higher than that of A strain at the age of 22～24 weeks (P<0.05), but there was no significant difference on egg production (%) the other weeks. A number of egg laid of B strain was higher than A strain at 22～24 weeks old (P<0.05). Feed conversion ratio of A and B strains were 10.7 and 6.53 at 24～24 weeks old, respectively, so feed conversion ratio of A strain was higher than that of B strain (P<0.05). Weekly feed conversion ratio wes the highest at 20～22 weeks old, and significantly decreased until 24～24 weeks old, but were lowly maintained from the age of 24 weeks to the age of 30 weeks. These results provided the basic data on the record of early laying period of large-type Korean native ducks.(Key words : Korean native ducks, large-type, early laying period, body weight, feed consumption ratio, laying performance)a First two authors equally contributed to this work.

This work was carried out to investigate the performance of large-type Korean native ducks at middle laying phase (30 to 50 weeks). A total of one hundred and sixty eight laying ducks were divided into A and B strains (6 replications/strain, 14 birds/replication and fed practical diet, for 20 weeks). There was no significant difference in body weight, daily feed intake and average egg weight. With increasing rearing period, mean body weight tended to be decreased and showed the lowest value (2,649 g) at 42 weeks of age (P<0.05). Similar trend was observed for weekly feed intake and average egg weight which decreased with passing weeks and was lowest (190.5 g and 83.8 g, respectively) at the age of 42~46 weeks (P<0.05). Daily egg production of B strain was higher than that of A strain at the age of 46~50 weeks (P<0.05). Weekly egg production of A and B strains commenced to decrease from the age of 42 weeks, however, B strain recovered at 46~50 weeks of age (P<0.05). At the age of 30∼38 weeks, the egg production in B strain was higher than A strain (P<0.05), whereas, there was no significant difference between both the strains during 38~50 week. Feed conversion ratio of A strain was higher than that of B strain at 46∼50 weeks of age (P<0.05). Weekly feed conversion was highest at the age of 42~46 weeks (P<0.05). In conclusion, the present results provides the basic information of the performance record of large-type Korean native ducks for the middle laying phase.(Key words : Korean Native Ducks, large-type, middle laying period, body weight, feed intake, laying performance, feed consumption ratio)