The Effects of Forced Molt Treatment on Selected Steroids in Hens1'2

ABSTRACT A study was conducted to determine the effects of an environmentally induced forced molt on concentrations of plasma progesterone (P), corticosteroids (CS), corticosterone binding globulin binding capacity (CBGgc), and liver corticosteroids (LCS) during early forced molt. Laying hens were placed into two environmental control chambers. In one chamber, control (C) hens were fed ad libitum and maintained on long photoperiods of 19 hr of light daily to maintain egg production. In the other chamber, early forced-molt (EM) hens were exposed to short photo-periods of 6 hr of light daily to decrease egg production. After 2 weeks of ad libitum feeding, feed was withdrawn from the EM hens for 2 days to initiate a molt. Feed was restored for 3 days to the EM hens before hens from both groups were sacrificed every 2 hr for 2 days. The EM hens had regressed ovaries, greater body weight losses, lower plasma P and CS hormone levels, lower nuclei free LCS levels, and lower CBGgc than C hens. Nuclear LCS levels were similar in EM and C hens. A single peak indicating a daily rhythm of plasma P was found only in C hens. Progesterone secretions appeared to be eposodic in EM hens. A daily rhythm with two peaks of plasma CS and nuclei-free LCS was found in the C hens. Nuclear LCS peaked thrice daily in C hens. A cascade of CS from the plasma to the liver cytosol and on to the liver nucleus was indicated. Plasma CS was negatively correlated with nuclei-free LCS. Two daily peaks of plasma CS occurred in EM hens. One peak exhibited a daily rhythm and the other did not. Daily rhythmic peaks in EM hens were less defined than in C hens. Force molt treatment in EM hens may have affected the loss of the LCS peaks as was found in the C hens. No daily rhythms of CBGgc were found in either hen group. (Key words: forced molt, corticosteroids, progesterone, daily rhythms