|Cheng, Heng wei|
Submitted to: Meeting Abstract
Publication Type: Abstract only
Publication Acceptance Date: 6/14/2002
Publication Date: 7/1/2002
Citation: CHENG, H., FREIRE, R. MORPHOLOGICAL AND PHYSIOLOGICAL RESPONSES TO INDUCED MOLTING IN LAYING HENS. MEETING ABSTRACT. 2002. P. 100. Interpretive Summary:
Technical Abstract: Induced molting in laying hens by feed withdrawal (FW) is a common practice in the U.S., which has led to public concern regarding their well-being, and there is a pressing need to evaluate physiological changes resulting from prolonged feed withdrawal (FW). A total of 168 hens from Hy-line W-92 line (65 wk of age) were divided into induced molting (IM) and control groups, including 24 hens used to monitor loss in body weight. IM hens were food deprived for eight days while kept on a 8h:16h (light:dark) lighting program, leading to a 30% loss in body weight (BW). Control hens had AD LIBITUM consumption of a laying ration. Physiological parameters were measured 3 days prior to food withdrawal (day 3 pre-FW), on days 1, 3, 5 and 8 (during FW), and 7 and 28 post-FW. Concentrations of corticosterone (CORT) were greater in IM hens than controls during the FW period (ANOVA, P<0.01), with a peak at day 1 of FW, and returned to control levels at the day 7 post FW. Interestingly, there was a biphasic increase in the concentration of dopamine, with peaks at day 1 and days 8 of FW (ANOVA, P<0.01). The concentration of norepinephrine was greater in IM hens than controls at day 1 of FW (ANOVA, P<0.05). There were no significant difference in epinephrine concentration between IM hens and controls (ANOVA, P>0.05). Both absolute and relative weight of the liver became less heavy in IM hens than control during FW (AVONA, P<0.05), which returned toward the control levels at days 7 post-FW. In contrast, both absolute and relative weight of the spleen became heavier at days 8 of FW (P<0.01). Relative weight of the adrenal gland (adrenal weight/BW) was heavier in IM hens than controls on days 5 and 8 during FW, and 7 days post-FW with a peak increase at 8 days FW (ANOVA, P<0.01), probably due to the loss in BW since absolute adrenal weight did not change in IM hens during the experiment. Results presented here suggest that the largest changes in physiological parameters occur shortly after food withdrawal, and each parameter has a unique pattern in response to molting. Differences in neuroendocrine response could be related to physical changes during and after food withdrawal, such as degradation and regression of the reproductive system, and feather loss and regrowth-out.