the effects of using alfalfa-based molt diet compared with feed deprivation on blood parameters changes during molt period and post-molt performance of commercial laying hens

introduction: induced molting is a process that stimulates natural molting events. when birds return to full feed, a new plumage develops and the birds resume egg peroduction at a higher rate with better egg quality. induced molting extends the productive liffe of commercial chicken flocks and results in substantial reduction in the number of chickens needed to produce the nation's egg supply. however, molting induced by feed withdrawal (fw) case discomfort and stress in hens. stress causes a general deterioration of the well-being of chickens, usually involving a cascade of physiological adaptive responses that include changes in plasma levels of blood metabolites. the aim of the present study was determine the effects of alfalfa and feed deprivation on molt performance, some blood parameters changes during molt period and post-molt production of commercial laying hens. materials and methods: this experiment was carried out trough a completely randomized design with 108 of hy-line w-36 laying hens at the 74 week of age in 3 treatments and 6 replicates (with 6 birds in each replicate). the using treatments for 12 days molt period were included: 1- control group fed with layer ration (ff), 2- feed withdrawal group (fw), 3- group fed with 90% alfalfa and 10% layer ration (a90). blood sample was collected on day 0 (before any treatments began), 3, 6, 9 and 12 of molting period and serum concentration of triglyceride, cholesterol, glucose, calcium and uric acid were measured. at the end of this period, all hens return to the layer ration. egg production was monitored for 12 weeks after the end of the molting period. results and discussion: results indicated that, triglyceride, calcium and uric acid levels were generally lower in molted hens compared with nonmolted hens during the molt period. on days 3 and 6 of molting, ff hens exhibited higher blood triglyceride levels than fw and a90 hens. in addition, the triglyceride levels measured in the a90 hens were significantly lower (p<0.05) than those of the fw birds. similar results were observed on days 9 and 12 of molting period but no significant differences were found in triglyceride levels among hens molted by fw and a90 treatments. on days 3, 6, 9 and 12 of molting, serum uric acid from ff hens was significantly higher than other groups. on days 3, 6 and 12, fw hens had also higher levels of uric acid than a90 hens (p<0.05). plasma uric acid in fasted or feed restricted hens was related to protein catabolism from either dietary sources or interna protein stores during the molt period. the ff hens generally had higher levels of calcium in the blood compared with fw and a90 hens. on days 3, 6, 9 and 12 of molting, the ff hens exhibited higher (p<0.05) concentrations of calcium in blood than did the other treatments, and fw hens were the lowest (p<0.05) except when compared with a90 hens on 12 day of molting. calcium is mobilized from the bones and intestines and transported to the reproductive tract for deposition in the shell gland, and decrease levels of eggshell gland and intestine calbindin occure during molting. bone weight and density are known to decrease during a molt. alfalfa contains 1.3% calcium and can be suitable source of this substance during molting period. the cholestrol levels of a90 and fw groups were significantly higher (p<0.05) than the ff non molted hens on days 6, 9 and 12 of molting period. but the differences were shown in cholestrol levels of hens in fw and a90 groups were not significant. increases in serum cholestrol levels would be expected in molted hens, as the re-absorption of unovulated follicles during the process of molt increases the levels of circulating cholestrol fractions in the blood. in addition, failure to ovulate may also lead to an increase of an insoluble fraction of cholestrol, known as hdlr. the concentration of glucose was significantly lower in fw hens than other groups in early days of molting. on days 3 and 6 of molting, concentration of glucose were lower (p<0.05) in fw hens than in ff and a90 hens. decreases in glucose levels would be expected in molted hens, as the reduction of feed intake during the molt process. molted hens induced by alfalfa diet exhibited higher postmolt levels of egg production over a twelve week period than hens molted by feed withdrawal. the postmolt egg laid by hens molted by alfalfa were comparable quality to eggs from feed deprived hens. conclusion: in conclusion, the results of this experiment showed that the use of alfalfa for molt induction had favorable effects on some blood parameters during the molt period and improved the postmolt performance of hens.