Investigation on the effect of dietary zataria multiflora boiss extract supplementation and its using times on performance, carcass characteristics and gut microbial populations in broiler chickens

In this experiment, 336 one-day-old boiler chicks (Ross strain) were allocated to 7 dietary treatments in a completely randomized design throughout the 42 d experimental period. Each dietary treatment consisted of 4 replicates with 12 chicks in each. The dietary treatments were: 1) basal diet, BD [control group, without Zataria multiflora extract (ZME)], 2 and 3) BD+0.5 and 1% of ZME for 42 days, 4and5) BD+ 0.5 and 1% of ZME in the two last week of rearing period, and 6and7) BD+ 0.5 and 1%of ZME in the last week of rearing period. Feed intake (FI), weight gain and feed conversion ratio (FCR) were recorded at the end of each growth phase. At day 42, two birds per replicate were slaughtered to investigate the effects of dietary treatments on carcass efficiency and carcass parts. On days 21 and 42, digesta samples from ileum of slaughtered chicks were taken for bacterial analyses. Adding ZME to the diets at the levels of 0.5 and 1%significantly (P<0.05) reduced FI (97.78 and 99.67 g) compared to the control group (101.06 g). ZME at the level of 1% for the entire period of experiment improved FCR (1.53 vs. 1.68) compared to the control group (P<0.05). Effect of ZME and its using times on the relative weights of carcass components were not significant (P>0.05). The use of 1% of the extract for 42 days resulted in a significant increase in the relative weight of the thymus (0.7 vs. 0.55%, P<0.05). ZME at the levels of 0.5 and 1% reduced E. coli (5.57 and 5.34 vs. 6.16) and increased Lactobacillus (6.67 and 6.78 vs. 6.22) populations during the first 21 days and the entire period of the experiment (P<0.05). According to the results of this study, dietary inclusion of ZME at 1 % for 42 days significantly improved feed conversion ratio and gut microbial populations in broiler chickens (P<0.05).