BACKROUND: The use of feed withdrawal method for molt induction can be caused physiological stress and negatively affected the immunological response of hens. OBJECTIVES: The aim of the present study was to survey of hormonal changes and immunological response in hens fed by alfalfa molt diet during the molt period. METHODS: In this experiment 108 Hy-line (W36) laying hens aged 74 weeks in a completely randomized design with 3 treatments and 6 replicates were used. 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). Performance of birds was monitored for 12 weeks after the end of the molting period. RESULTS: Total circulating leukocyte were generally lower in FW hens group compared with the other groups during the initial stage of molt (P<0.05). On d 3 and 6 of molt, heterophil to lymphocyte ratio were incresed in molted hens and FW hens had higher levels than other groups. On d 3 of molt, plasma corticosterone was generally incresed in molted hens and FW hen higher level than A90 hens (P<0.05). Plasma T3 was significantly decreased in molted hens than nonmolted hens during the molt period (P<0.05). Plasma T4 was significantly increased in molted hens than nonmolted hens during the molt period (P<0.05). On d 6 and 9 of molt, concentrations of T4 were higher in FW hens than in the A90 hens (P<0.05). Date of reentry and days return to 50% and 80% egg production were significantly lower in A90 groups than in the FW groups (P<0.05). CONCLUSIONS: The results showed that, A90 diet can limit physiological stress and improve the performance of immunological response that accompany feed withdrawal method during an induced molt.

BACKGROUND: The use of feed withdrawal for molt induction can negatively affected the structure and microbial environment of intestine and lead to greater intestinal colonization by salmonella infection. OBJECTIVES: The aim of the present experiment was to determine the effects of alfalfa as a high fiber ingredient for molt induction on intestinal morphometric characteristics and performance of commercial laying hens. METHODS: In this experiment 108 Hy-line (W36) laying hens aged 74 weeks in a completely randomized design with 3 treatments and 6 replicates were used. 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). Performance of birds was monitored for 12 weeks after the end of the molting period. RESULTS: Feed withdrawal hens had lowest villus height in all three regions of the intestine (p<0.05).The highest average of deudenal crypt depths was observed in FW hens. In all three regions of the intestine, the lowest amounts of villus index and villus surface was observed in FW hens (p<0.05). In all three regions of the intestine, the highest and lowest average of goblet cells was seen in the A90 and FW hens respectively. The highest mean of post molt egg mass was observed in FW hens (p<0.05). The best FCR was seen in the A90 group. CONCLUSIONS: The use of alfalfa-riched feed for molt induction of laying hens results in improvement of morphometric characteristic of intestine and post molt performance.