In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: Oral bovine LF ( 30 , 100 , 300 mg / kg ) was given from day 8 to 14 in a reversal study .
### Output Text:
Oral bovine LF ( 30 , 100 , 300 mg / kg ) was given from day 8 to 14 in a reversal study . 