Within the circle of the Buddhists, Devadatta was the main pioneer for practice of Vegetarianism. Accompanied by his four conspiring monks, he strived for imposition of five extreme rules to the whole members of the Sangha, one of which was the rule to abstain absolutely from any food made of fish or meat. In response to this demand, the Gotama Buddha stated that the monks who felt comfortable, agreeable, and suitable to the rule may practice it. However, He rejected to validate and to apply the rule to all the monks compulsorily. From the discretion provided by the Gotama Buddha, it is very clear that Vegetarianism is actually not an official part of the Dhamma Vinaya.
Vegetarianism is an unrequired and unimportant practice.
In other words, whether Vegetarianism is practised or not, a person still has an opportunity and capacity to achieve the purity and the Real Freedom. The Gotama Buddha was repeatedly confronted with the problems of Vegetarianism. Then He told them an old-world tale. Once on a time, when Brahmadatta was king of Benares, the Bodhisatta was born as a brahmin. When he came of age he embraced the religious life.