An investigation on the replacement of antibiotics by medicinal plants to control the infection of Escherichia Coli (E. coli) in broiler chickens
This study was done to determine the effects of garlic, mint and onion in feeding of the broiler chickens as a growth natural factor (GNF) instead of antibiotics. First, the antibacterial effects and minimum inhibitory concentration (MIC) of 0.5, 1, 2.5, 5, 10 and 20% concentrations of aqueous extracts of garlic (Allium sativum), mint (Mentha spp.) and onion (Allium cepa) on E. coli were determined in in vitro conditions. Results show that the minimum inhibitory concentration (MIC) of garlic extract was 0.5%. Distilled water, phenol phenicol and Floxacin were used as solvent and control. In the next step, the effects of adding garlic to the diet of broiler chickens were analyzed at farm. 300 day-old broilers (Arbor Acres Plus) were divided into groups of 60 birds each and randomly assigned to the five treatment diets. Each treatment has three replicates. These chickens were kept up to the age of 56 days (8 weeks), all under study and fed with the standard ration. According to the corrections, adding 8% garlic to the diet was equal to the minimum inhibitory concentration (MIC) in the lab. As a result, we used garlic itself instead of its aqueous extract in the diet. The different experimental groups did not receive any antibiotic and growth additives. The different experimental groups were as follows. The 1st group which was considered as the control group received feed without garlic. The 2nd group, one day in week, during breeding period received feed containing 8% garlic. The 3rd group, 2 days in week, during breeding period received feed containing 8% garlic. The 4th group, one day in week and in the 1st, 4th, 5th, 6th, 7th and 8th weeks, received feed containing 8% garlic. The 5th group, 2 days in week and in the 1st, 4th, 6th, 7th, and 8th weeks, received feed containing 8% garlic. During the conduct of the study, the performance of broiler chickens was recorded and then analyzed statistically. In the end, the results show that adding 8% of garlic to the feed of broiler chickens, in the probability level of 5% statistically did not have a significant effect on feed intake, body weight gain, feed conversion ratio, the mean of chicken’s weight, mortality percentage, dressing percentage, offal percentage, abdominal fat weight, weight of liver, spleen, pancreas, cecum, leg and breast and cecum and intestine size and taste (p>0.05), although, there was a little difference in the case of feed intake, weight gain, mortality percentage, intestine size and taste among different experimental groups. As a result, groups that consumed garlic showed a better performance.
Key words: Medicinal plants, aqueous extracts, garlic, mint, onion, antibiotic, E. coli, broiler chickens, performance.