The response of laying hens to induced molt as affected by strain and age

Molt was induced in 502-d-old Lohmann, Hy-Line W-77, Yafa, and Yarkon strains of laying hens (Experiment 1), and at different ages during the 1st yr of production in the Lohmann strain (Experiment 2). The induced molt treatment included an 8-d feed withdrawal period followed by a 22-d rest period during which the birds received 60 or 70 g/d of a low-nutrient maintenance diet, in both experiments, respectively, and a reduced duration of daylight. In both experiments, induced molt resulted in an increase in postmolt egg production rate and a diminution of the rate of decline of production with age. The first eggs during the postmolt period were smaller than those of the unmolted birds but egg size increased rapidly to control levels. Egg breakage was markedly reduced by induced molt and its rate of increase with age was diminished. Postmolt feed intake was higher than that of the unmolted birds and body weights reached values higher than those of the controls. Those responses were not different among strains but the ranking among the strains in the molted group was similar to that of the unmolted controls, for all production traits. The postmolt rate of production approached that of first cycle peak and was not affected by treatment age. Shell quality as reflected by the percentage of breakage during the postmolt period was similar to that of the unmolted controls approximately 3 to 4 mo earlier.