Recent studies conducted in EU & USA revealed that extensive use of antibiotics in live stock (poultry, fish, pig, large animals) resulted in resistance development in microbes and also in formation of super bugs that are totally resistant to antibiotics.
Now antibiotic use in livestock in EU & USA is completely banned.
After this the EU researchers find their to solve the problems in herbal products obtained from natural sources mostly plant sources. While the researchers in USA find their in use of organic and inorganic acids.
Most commonly used organic acids are acetic acid, formic acid, propanoic acid etc. While the commonly used inorganic acid is phosphoric acid. Their continuous use show good results but they must be used regularly for long time.
Some researchers believe that to gain maximum results by these acids one has to treat his/her flock from the very beginning.
Other view is that these with very little quantity of antibiotics show excellent results in terms of
1. Lower disease occurance
2. High liveability
3. High weight gain
Currently experiments are undergoing before one can surely say that these are 100% safe and will not do any harm to humans as what was faced in shape of antibiotics.