The use of antibiotic growth promoters has been continued until about 10 years ago to ensure consistent production. However, its use has declined because of global concern about increasing antibiotic resistance, which leads to a problem in the treatment of infectious diseases in both animals and humans.
The mechanism of action of antibiotic growth promoters is based on inhibition of pathogenic microorganisms in the rumen and intestine, by adding them in small quantities in the food, in sub-therapeutic doses. This inhibition may also affect the nonpathogenic ruminal flora, altering microbial fermentation.
Use of antibiotic growth promoters in ruminants
There are numerous antibiotic growth promoters that are no longer used as an example in calves is flavophospholipol which was also widely used in other species such as turkeys, chickens or pigs.
In other animal species, such as pigs or poultry antibiotic growth promoters act in the intestine, while working in the rumen ruminants thus influence the intestinal or ruminal flora.
However, according to some authors it is expected that antibiotic growth promoters not only alter the ruminal environment, getting effect not only on the rumen and small intestine but also in the cecum and colon (Armstrong, 1984). It is also believed that monensin, increases the production of propionic acid and reduces energy loss due to the production of methane gas.
The use of antibiotic growth promoters increases average daily gain and improves the conversion rate in cattle.
Natural additives as an alternative to antibiotics as growth promoters
After the ban of antibiotic growth promoters in the European Union in 2006 have been investigated different alternatives of products based on natural extracts like garlic or yuca with inhibitory effects on pathogenic microorganisms. However, they should in further in vivo studies determine the extent of these natural products.
Many of these studies have good results in calves, with a decrease of diarrhea and improved production parameters (higher weight gain and lower conversion rate). Thus, they may represent a good alternative to antibiotic growth promoters, being especially useful in early stages.
There have also been improvements in ruminal homeostasis, increasing the production of volatile fatty acids and increasing microbial protein synthesis.
In any case, the use of natural additives must be accompanied by good management practices, health and good genetics to obtain the best possible result.