I have 3 science subjects in hs (biology, physics and chemistry) can i eligible for OUAT?

Yes! You are eligible for OUAT since OUAT exam for B.Sc (Hons.) courses (such as Agriculture, Horticulture, Forestry, and Community Science) require a PCM or PCB at +2 level or equivalent exam. To qualify for BVSc, AH, and BFSc, applicants must have a +2 in PCM Science or an equivalent course with a minimum mark of 50%.