Hello Shruti,
For UG Programmes No university level entrance test is conducted for taking admission in Bihar agricultural university.

• Interested candidates must have appeared and passed     BCECE, conducted by Government of Bihar. Otherwise, should have appeared and qualified for All India Entrance Examination conducted by ICAR.
• 80% of the total seats are reserved for BCECE qualified candidates and 15% of the total seats for AIEE ICAR qualified candidates.
• Minimum Qualification Should have passed Class 12 or equivalent level.
• Stream Passed PCB/PCM/Agriculture

I'm also sharing the official website of BAU below.
http://www.bausabour.ac.in/
Hope it helps
All the best!