Hello.
This is right. But "business administration" in your message indicates rather that of "department" or "course" in university. In this case "busyness administration" is rather "経営学" (keieigaku). You can say "my major study is /business/". But "busyness" in English has very wide meanings. And so, "ビジネス" in Japanese has very wide meanings and usages, and it is different from English "business". "私の専攻はビジネスです" (My major study is business) has almost no meanings in Japanese, or it has too wide meanings, thus it does not indicates the specified study. What you study in university is unsure in this case. In university, people study some science or technology. "ビジネス" is not science nor technology. "経営学", ”ビジネス管理” are a kind of science or technology. So you had better to say "My major study in university is "経営学" (or, ビジネス管理 etc.) rather "ビジネス". Cordially. _ mrd