the real concern is in situations where contaminant got in the food chain which ends up with human consumption. there is neither suspicion that contaminant found its way into horse nor cattle feed, nor concern around that possibility with horses as very few are slated for human food. while thousands of other types of farms are on lock-down, so far there has not been any impact on horse movement or activities.
I doubt it will change. They have thus far shut down traffic and business for a number of farms and determined the source of contamination to be industrial fat that made it to pelletted food for chicken, porc and beef. Massive losses are thus far all on the closed down farmers as they have to run testing procedures in order to prove their products harmless.
Possibly there will be compensation paid at the end by the food plant/s who caused the mess in the first place but one can never know
Horsefeeds have thus far not been found to be concerned. Even if they would find dioxine in any horsefeeds it would be not likely that any horsefarms be shut down as there is little to no risk for horses to go into humane consumption in lower saxony. I could imagine they would stamp horses from concerned farms 'unconsumable' but that would probably be it as there is no contagious potential and the majority of sporthorses are stamped 'not for consumption' to begin with as otherwise they would have very limited access to treatment.
Possibly they will as the overboarding media response is already leading people to shut down their meat-consumption (again). It is sad what agricultural production has come to. Unfortunately with the structures being the way they are there aren't many farms that process in circles anymore (as in animal-produce fed with home-grown foods).
Trouble is each time some such 'scandal' shakes the earth around here the only response from consumers is to withhold from meat-consumption for a while and then go back to their normal shopping and eating routine until the next food-industry-gone-wrong scenario comes up. There is little to no thought given to the 'why' and 'how'. Instead even more paper-control systems are established so everybody will feel save seeing yet another 'quality-control' trademark out there.