Abdul Azeez C.P.SHAKIR ARAFATH K.2020-07-232020-07-232018http://krishikosh.egranth.ac.in/handle/1/5810149705The present research work was undertaken to evaluate the occurrence of prolonged oestrus as a cause for infertility among crossbred cattle and to evaluate the efficacy of double prostaglandin injection protocol and Ovsynch protocol for the treatment of prolonged oestrus so as to formulate an effective therapeutic regimen to improve the conception rate of animals exhibiting prolonged oestrus. Animals exhibiting oestrus for more than 36 h were grouped into three with eight animals each. The first group was treated with the hormone PGF2α analogue as per double prostaglandin injection protocol. The cows in second group were treated with the Gonadotropin releasing hormone (GnRH) and PGF2α analogue as per Ovsynch protocol. The cows in third group were not subjected to any hormonal treatment and AI done with cryopreserved semen 12 h after the onset of oestrus at 24 h intervals till the end of the oestrus. Blood samples were collected on the days of prolonged oestrus, at the time of different treatment protocol and at the time of AI for serum progesterone estimation. Administration of PGF2α during luteal phase increased the per cent of animals exhibiting high intensity of oestrus among animals having prolonged oestrus and better oestrual characteristics of oestrual mucus were noticed in induced oestrus compared to spontaneous oestrus. Suprabasal progesterone levels during oestrus and suboptimal levels during luteal phase were noticed among prolonged oestrus cattle and the levels were significantly different from that of animals having normal duration of oestrus. Double prostaglandin injection and Ovsynch protocol were effective to correct the endocrine imbalance and conception rate was also better among the treatment groups compared to control group. It can be concluded that suprabasal progesterone levels during oestrus and luteal insufficiency in the luteal phase existed among animals exhibiting prolonged oestrus can be truncated by induction of oestrus by using PGF2 administration in the luteal phase followed by timely insemination improved conception rate.ennullThesis