There are whole oats, and rolled oats that are used in horse feed. There is also crushed and ground oats. There is little nutritional difference between feeding whole and rolled oats, one study found. However, once the outer hull has been cracked (in rolled oats), the nutritious inside part starts to deteriorate as it is exposed to oxygen. Rolled oats can also be dustier that whole oats.
I also read that there are black oats and white oats. The black oats are usually grown in warmer climates, and are often preferred feed for horses, despite the fact that there is little difference between the white and black oats.
Good oats are plump, short,, round, hard, dry, floury if bitten, without odour, contain no bitter taste, with colour either pale yellow, or almost white or black. When bitten, they should break sharply across and if allowed to fall on a hard surface or be shaken in one's hand they should rattle. Good oats should smell slightly sweet and the kernels should bulge slightly through the husks and be uniform in size. The fatter the kernel is the heavier will be the weight of a bushel. Good oats should be beardless or nearly so and should be cleaned. They can be shaken to determine if there is any dust in them. White oats are more nutritious, as they have less husk than black oats. Crushed oats are more easily digested as digestive juices have greater access to the kernels and this leads to to a more perfect digestion. The kernels should merely be split as too much crushing will lose some of the flour. English and Canadian oats were the much preferred feed.
Taken from Modern Horse Management by Colonel R.S. Timmis
No not all oats are the same. There are a few different 'kinds' of oats, and then those that have been processed by way of: bruising, crimping, rolling, clipping and crushing (or doing nothing at all).
The oat 'varieties', I guess you could call them, that I know of off-hand are the plain whole oats, which are how we typically imagine oats complete with husks attached. This is how they are grown. They have the highest fibre levels of all oat grains.
Meanwhile, naked oats are not processed but have been grown to have loose husks that will shed off when harvested. This lowers fibre content but increases digestability. I believe they also have more protein.
In addition, quality varies from batch to batch. Good oats should be short, hard, dry and slightly round.
The elliments that make oats, in the most common term, not all the same are the factors that can make the answer to this question different with every oat.
Geography, heat, water, sun, wind, snow, frost, temperature, crop/soil management, planting and harvest all are factors. What may be optimum for Western oats in 2010 could easily be altered with a draught in 2011.