The use of antibiotics as growth promotors in food animals was banned by the EU years ago (think it was 2006 or 07) and had been discouraged in the UK long before that. They have never been used in that way for horses - what would be the point? Antibiotics are now only used therapeutically and the animal is withdrawn from the food chain for a specified period which is legally laid down.
As for gout, contrary to what used to be believed, it's not caused by excess food and drink consumption. It's caused by an excess of purines which are found in many foods, including herring, asparagus and mushrooms. Your body breaks purines down to form uric acid which turns into crystals in your joints, causing inflammation and pain. I know a vegetarian who has suffered with gout.
You state that the preservation of food by pickling has almost disappeared in the western diet - this is a good thing - pickling involves brining either with salt or soy or similar ingredients, thus raising the sodium intake to unhealthy levels causing hypertension and heart disease. Fine for a treat - I love the occasional pickled onion or red cabbage, but for a treat only. The pickling of vegetables has been replaced by freezing - much healthier.
And root veg are preserved throughout the winter nowadays - where do you think our carrots, potatoes, swedes etc come from - the farmers keep them in cool storage - just a development of the earth or sand clamps where our forebears would have stored them.
Not sure where you get your information from, but it seems very outdated to me.