Odour from Laying Hens Manure

Is there anyone willing to share experiences with treatments against bad odour from laying hen manure? I'm mostly interested in solutions that could be applied via feed or water. I've heard of some herbal and plant extracts that can be incorporated in the feed at small concentrations with certain antibiotic efficacy that could results in a significant reduction of bad odours from the manure as simultaneously helping to reduce the microbial contamination with E. Coli, Salmonella, etc.

I would appreciate to receive comments and experiences on this matter.