Postmolt performance of laying hens molted by high dietary zinc, low dietary sodium, and fasting: egg production and eggshell quality.

Single Comb White Leghorn (SCWL) hens, 65 weeks of age, were assigned to one of four dietary treatments: fasting to a body weight loss of 34% (FAST), administration of a diet containing less than or equal to 500 ppm sodium for 42 days (Lo Na), administration of a diet containing 20,000 ppm zinc for 10 days (Hi Zn), and a control (CON) diet. The hens were subjected to two photoperiod treatments, those receiving 17 hr (17-hr) of light per day throughout the 32-week experiment and those restricted to 8 hr of light per day for the first 42 days followed by a .5 hr/day increase until 17 hr was reached. Egg production and mortality were recorded daily. Feed consumption, feed conversion, and livability were determined weekly. Beginning on Day 56, eggs were collected at 28-day intervals for determination of egg weight, egg specific gravity, and shell weight. During the molt phase (1 to 6 weeks), the 17-hr light day significantly increased egg production, feed consumption, and decreased feed conversion (kg/doz) across all groups when compared with the 8-hr light/day treatments, but FAST treatments consumed identical amounts under both light treatments. From 7 to 32 weeks during the postmolt phase, egg production was significantly increased and feed conversion decreased by the FAST and Hi Zn treatments relative to CON, Lo Na treatment was intermediate. Feed consumption was significantly higher for the FAST treatment. Overall, there were not significant effects on egg production, feed consumption, and feed conversion.(ABSTRACT TRUNCATED AT 250 WORDS)