Effetc of the type of the probiotic in broiler's diet on body growth, immune system organs and small intestine morphology in first week of growing

In order to compare the effect of two different types of probiotics on broiler’s body weights، organs of the immune system and small intestinal tissue during the first week of age، an experiment was carried out by 378 one-day old male broilers، which randomly assigned to three treatments and 6 replications with 21 male broilers in each replicate. Treatments included a control diet (without probiotic) and two experimental diets (a diet with Bacillus-based probiotic or acid lactic bacteria). At 3 and 7 days of age، after weighing all the broilers، one bird from each pen was slaughtered and weight of the immune organs، length and relative weight of different parts of small intestine were measured and morphological properties of jejunum were studied. During the first three days of age، length of jejunum to body weight ratio was higher in the bacillus-based probiotic group and relative length of ileum was higher in both groups fed different types of probiotic supplemented diets compared to the control group (P<0. 05). At 3 days of age، the average weight of broilers، which consumed bacillus-based probiotic was lower compared to the control group (P< 0. 05). However، microscopic morphological characteristics of jejunum at 3 and 7 days of age were not influenced by probiotic (P>0. 05). At the age of 7 days، the mean spleen weight of bacillus-based probitic group was higher than the control group (P<0. 05). Although positive effect of probiotics on growth performance of broilers after approximately three weeks of usage was reported by several researchers. However، based on the result of this study، fast effect of probiotics consumption on some parts of small intestine and growth of some immune system organs within the first week of age was observed and recorded. The initial effect of probiotics is different based on the type of bacteria in the probiotics.