Manure and Docks

Helping a local farmer retrieve a group of 20+ frisky bullocks the other day, there was a lull in proceedings during which I commented to two locals on the huge concentration of docks in a neighbouring field that hasn't long been ploughed and re-sown.  Evidently, they tell me, dock seeds pass through bovine systems like tomatoes do through humans so, when slurry (cow manure without the straw) is sprayed on to fields, depending on the concentration of dock material fed as silage during winter, there's a likelihood that it can be full of seeds waiting for a new home to grow in.  Logically this can also apply to normal farmyard manure that we all value so highly>