Safest way to transition from corn-fed to grass-fed?

My community has no shortage of cows. Practically every farm is a dairy farm, with the smattering of the occasional grass-fed beef herd. Those dairy cattle get little to no pasture, instead subsisting almost entirely on hay and corn. I know I can get a couple milch cows out here for a song, but I want to be sure before I switch them over to a pasture diet that the sudden transition won't have an ill effects. What's the safest way to make that transition?

And as a side topic, on the macro scale, we permies speak so often of a better possible future for farming. But one thing I wonder about is whether large-scale dairy farms could ever reasonably sustain their herds on pasture only. The reason being, if the cows need to be milked every day, is a roving paddock system effective when the cows need to be herded back to the stationary milkshed and all its immobile machinery? I want to think there's a solution out there, because I think the current system is unhealthy and unsustainable, so let me hear your thoughts!

A form of paddock shift used to be common in the midwest, but dairies were smaller.

As for adjusting a milk cow to pasture, it is fairly easy. You can feed them corn and hay while you milk them for a while, then slowly switch to your preferred milking ration.

You have to watch what they eat on pasture, at least initially, as they may eat too much overly rich stuff. We have to feed hay during milking year-round to make sure they get enough roughage. We still feed grain at milking, but mainly organic barley just to get them to eat extra mineral.

We have at least 4 dairies that I know of in South Carolina that have pasture fed cows. I don't want to advertise for them but a google search will turn up the pasture fed dairy cow farms in South Carolina.

I'm pretty sure that at least couple of them would be glad to share their knowledge with you if you contact them. A couple of local poultry farmers have been very helpful giving me advice on birds when I asked.

One of the pasture fed dairies here converted from modern conventional methods to pasture after his cows jumped the fence and got out into unsprayed fields and ate 'weeds'. He noticed the milk production went up when that happened and the rest is history. His place is 'relatively' large scale - but not large scale in the same way as the massive name brands that we see nation wide.

Personally I think that the elimination of large scale food production, going back to local sources of food, will create more sustainable communities and help eliminate food borne illnesses that we seem to see only in mass produced food.

EASY! Just buy cows that just got dried up and have a month or more until they calf. Keep them on hay and gradually reduce the feed intake. If you want to be really safe, reduce it by half a pound a day, but remember, that they need roughage when they eat grain, so if the pasture doesn't have tough roughage and just to be safe anyways, feed some course 1st cutting hay. Most farmers probably already have greatly reduced their feed ration during the dry period. It wouldn't be a bad idea to have free choice hay for the first year. The key is to keep the cows on mature grasses. I don't think corn would be such a bad thing for cows to be grazing either, mixed in with other pasture plants in the rotation.

New Zealand only practices rotational grazing, and Farms milking over 2,000 cows are not uncommon. New Zealand produces most of the worlds exported milk powder, so it can easily scale. Cows are milked twice a day, and normally have a fresh paddock after every milking.

To transition a cow from different feed types just add the new feed as part of the diet and gradually change it over a week 10 days. A cows gut is a bacterial digester, and different foods require different bacteria. You need to allow time for the bacteria specific to a type of feed to build up in numbers. That is all, the cow can do it easily by herself.

Keep them well fed before they get their pasture so they don't gorge themselves on grass and get bloat. You may have to off and on graze them while they are in the transition phase.

We have been 100% grass fed for almost 20 years, We transitioned many dairy cows (and sheep) from grain at the beginning of our farming adventures. Here is what we found it takes to do so with good results... Take the advise already given and take at least 10 days to reduce the feed, transitioning to REALLY top quality forage. Keep minerals and GOOD quality salt in front of them at all time. Please remember that it takes a minimum of one year to get a cow back into proper digestion after being fed grain. They will look bad for quite some time but use the condition of the coat as a guide rather than the body condition. Whether we transitioned cows or sheep we found this to be true. Also, depending on the breed, you can take them down to once a day milking to keep from pushing them too hard the first year. Our worst case took three years. She was giving 72lb of milk a milking and went down to 12 without grain. She gave us a healthy amount of milk for 10 years and gave us a beautiful calf every year until she died at 18 years of age.
I hope this helps.

Where are you, OP? Location, weather patterns, soils, etc. so heavily affect the outcome of your idea.

If your local cows are high production breeds, switching them over to a grass diet will guarantee a drop in production, and potentially shorten their productive life. It'd be like trying to feed an NFL linebacker on a desk worker's diet. Production dairies feed highly developed rations that aren't just corn and hay. The variety of forage, ensilage, dry roughage, grains, and supplements combine to a highly balanced and calculated ration.

On top of that, you could damage your fields as cows on wet ground is a death sentence to grass. They are heavy animals on relatively little hooves. You have to be very careful when you allow cows on pasture. In the US long term weather patterns are making for highly concentrated water events, less often. So you're looking at 1 week per month where you should not allow cows on the ground to save your land. Then you have cold winter months where you need to supplement your feed as the grass went into hibernation, and dry summers where the grass goes into hibernation. Maybe New Zealand has a better (more temperate year round) weather pattern allowing cows on the ground year round. And I'd be curious to see their milk prices and production levels. Powdered milk is the cheapest commodity level, so I'm guessing they're doing very low cost, low production levels.

Grass fed milk cows are totally doable, but I would recommend a smaller, lower production, higher value milk breed (Jersey's or some such), rather than a big high volume cow like an Holstein.

Most American farms could not make it as a grass-fed operation, because the general market price is too low for that. Grass-fed, organic, etc. feel-good labels have a limited saleability niche that can support the higher costs they require (land, fuel, etc aren't getting cheaper). Most people aren't willing to pay that premium. And to tell you the truth, there is a growing movement in industrial agriculture to be more "sustainable" to avoid another dust-bowl. Industrial scale monocultures are able to be put into rotations and cover crops that can both reinvigorate the soil and allow the continued use of highly efficient machineries.

Ok, to the person who said it takes ONE YEAR to make the transition in full... This is wrong. There are different types of bacteria in the rumen to digest different kinds of forage. You can make the transition from grain to grass in one day with a product called CornerPost made by Free Choice Enterprises, out of Wisconsin. The product has molasses, fish meal and a mixture of probiotics (bacteria) for a cow to properly digest grass. Because the animal was fed grain, the balance of bacteria is different, and it doesn't have the number of "Grass" bacteria it needs. Or you can do as recommended and make the transition over a number of days. Be careful taking advice from people who haven't actually done this.