I am not one to freak out about properly applied pesticides. I am a state licensed chemical applicator. Me and my staff study these things and undergo regular training. There is much hysteria about pesticides and chemicals out there. Most is unfounded or based on shaky facts at best. I use Roundup as well as various selective herbicides around our chickens and ducks without issue. I don't spray it in their pen but that is mainly because weed control in there is unnecessary. Follow the label instructions and use as needed. These products exist to make our lives easier. If you don't like weeds you will have to apply some sort of pesticide to achieve decent results.