Oaten Hay!!

Feeding lucerne hay together with lucerne pellets is not the ideal diet for our buns. Oat hay, like grass hay, has the right balance of fibre and nutrients (and very importantly is low in calcium), this is required for a rabbit healthy diet. Grass (meadow) hay is not a regularly stocked item. Also there is not the added issue of spreading unwanted weed seeds into your garden.
Oat hay can be found at your local Stockfeed supplier (anyone who supplies race horses will have oaten hay year round, most other stockists say they can only supply in spring) and try to encourage them to stock it for you (they can be persuaded when they know that you are able to buy it elsewhere!) and fellow rabbit owners in your area. If you only have one or two buns maybe ask a fellow rabbit friend to go halves in a bale. Your bunnies will thank you for this little extra effort!

The All-Important Hay
Edited by Irene King, Source HRS
In the wild, rabbits eat grasses, which in their dry form, is simply hay. Therefore our rabbits should be fed hay constantly and in abundance, and hay should be considered far more than just chewing entertainment. Hay provides invaluable fibre, vitamins, minerals, and protein, in a form that the rabbit's digestive tract needs for its good health.
But not all hays are the same. Lucerne, particularly the tasty leaf part, is higher than most hays in calcium and protein and when fed with calcium-rich feed (most pellets) it can cause extreme levels of calcium in the system. On a dry weight analysis, lucerne comes out among the highest in calcium content, and lower than most grass hays in fibre. Many experts advise against giving solely lucerne (also called alfalfa) hay to adult rabbits, particularly those not used for breeding as it contains 2-5x a rabbit’s daily requirement. An excess of calcium in rabbits can lead to urinary problems.
Grass hay, which comes in a variety of types depending on where you live, is a safer choice for older rabbits, especially those with urinary problems. Lower in calcium and protein and higher in fibre, it provides what the rabbit needs without excesses. In some cases, rabbits that have never eaten grass hay may rebel and hold out for lucerne. However, if pellets are rationed, the rabbit will be hungry enough to give in and eat the new hay. Lucerne can be fed as long as the pellets are reduced dramatically.
And not all pellets are the same. Some pellets are nothing more than extruded lucerne. If you must feed lucerne hay avoid lucerne pellets! Other pellets contain a variety of grains and additives. You should check the labels or ask your supplier.
As important as it is in the diet of a rabbit, hay is only one part of a sound nutritional program. The way we are accustomed to feeding our rabbits (unlimited pellets and occasional fresh vegetables) is not the healthiest feeding plan. By giving them the type of food they were meant to eat (i.e. hay and fresh vegetables) we can help them fight off some of the diseases that have killed domestic rabbits for many years. Whenever we return to the natural and reject the overly processed and chemically treated product we are taking a stand for our rabbit’s health.