Guess it depends how matured it was and well spread it is. But we used to graze our sheep with the chickens on a timeshare basis. Sheep mornings, chickens afternoons. Neither had any ill effects at all. The sheep ignored the chicken poo and ate around it until a downpour washed it in. The chickens ate the flies that landed on the sheep poo. So I would say with this heavy rain they can go on it straight away Foobar.