RESPONSES OF LAYING HENS TO FORCED MOLT PROCEDURES OF VARIABLE-LENGTHWITH OR WITHOUT LIGHT RESTRICTION

The importance of the length of the rest period and of photoperiod as components of the forced molt procedure was evaluated in 650- and 560- d-old Lohman hens. The procedure included an 8-d feed withdrawal phase and rest periods varying from 0 to 35 d, during which the birds were fed for maintenance only. In the first trial, forced molt was applied with or without omission of artificial illumination. The rest period v aried between 2 and 20 d. In the second trial, all treatments included omission of artificial illumination, and a variable rest period betwe en 0 and 35 d. Egg production ceased, after 4 to 5 d of feed withdrawa l and resumed 8 to 15 d after the end of the rest period, without any consistent response to its length. Forced molt stimulated egg producti on rate and diminished its age-dependent rate of decline, reduced the proportion of broken and shell-less eggs, and improved shell quality. Following wide oscillations proportional to the length of the rest per iod, egg weight stabilized at levels similar to that of the unmolted c ontrols. Feed intake was stimulated by forced molt to levels exceeding those of the control hens. Body weight increased during the postmolt period to levels slightly exceeding those of unmolted controls. Result s of one trial show that omission of artificial illumination was essen tial for the full expression of the molt responses. In the other trial , production rate and shell quality were improved and the percentage o f broken eggs was reduced when the length of the rest period was incre ased. Maximal improvements appears to have been reached with rests per iods of 14 to 21 d.