If the battle of Normandy hadn't happened, they would've done it. They tested it in Scotland on sheep, and it worked, but they couldn't contain it. A sheep got blown off shore, spreading the disease. That's not why they shut it down, though. They shut it down because the war was basically over.

"The testing of anthrax as an animal elimination method was done on Gruinard Island, just off the coast of Scotland.[7][1] The location was chosen because of its small size, only 520 total acres,[8] and its lack of inhabitants, along with there being a nearby military base at Loch Ewe that served as a staging area. Original tests on the effectiveness of anthrax were conducted on the island in 1940 and 1941 with the bacteria being included in a bomb, which was dropped on 60 sheep that had been shipped to the island. The bomb itself contained a thick slurry of concentrated anthrax spores and was dropped from a Vickers Wellington bomber. This test proved more effective than expected, with all the sheep dying in days, but also infecting a number of farm animals on the mainland months afterwards. It was determined later that one of the buried sheep carcasses had become unearthed due to a major storm and washed ashore. Other tests continued until 1943 when the risk of infecting nearby populations became too great and the island was quarantined from all boat and plane traffic.[9] Because of the widespread contamination from the anthrax spores, the land remained closed until 1990.[10]

Operation Vegetarian was ready for deployment by spring of 1944 and plans were drafted for the cakes to be dropped in the summer when German cattle would be grazing openly in the fields. In order to entice the cattle into eating the linseed cakes, they needed to be dropped after the spring grass had been consumed and the amount of food left was limited. The raid and airdrops needed to be done in a single action and as quickly as possible to prevent the German military discovering what was being dropped. Fildes estimated that a flight path through Oldenburg and Hanover could be achieved in 18 minutes and cover 60 miles of cattle grazing land. But by the time the summer arrived, the Normandy Invasion had occurred and Allied troops were advancing across northern Europe, causing Operation Vegetarian to be abandoned.[4]"