Abstract: Antibiotics was a common veterinary drug used in livestock production, whose addition dosage in feed was large and metabolite rate was low. It passed out from the body mainly through feces. The environments might therefore be exposed to these antibiotics due to the application of animal manure into agricultural land or open storage of untreated manure. The fate and effects of the antibiotics applied in agricultural fields are partly governed by absorption characteristics of the antibiotics. Thus, laboratory studies were conducted to characterize the absorption abilities of four typical antibiotic compounds, oxytetracycline (C22H24N2O9HCl), tylosin(C46H77NO17), enrofloxacin (C19H22FN3O3) and sulfadimidine (C12H14N4O2S), using pig and poultry manures. The results showed that adsorption behaviors were related to species of antibiotics. Oxytetracycline, tylosin, and enrofloxacin were more strongly adsorbed onto manures and colloidal materials than sulfadimidine. Poultry manure had greater capacity to adsorb antibiotics than pig manure. The absorption of the antibiotics to colloidal materials isolated from animal manures was higher than corresponding animal manures. Our experimental results showed that when animal manures were stacked around the farm or were applied into agricultural land, the absorption of sulfadimidine and manures was weaker, and the loss risk with soluble form was larger; however, the loss risk with soluble form of oxytetracycline, tylosin, and enrofloxacin was smaller and they could be washed away with the soil surface runoff in colloid combination state．

Key words: antibiotics, absorption, animal manure, environmental risk