The study was undertaken to examine some blood parameters and minerals in serum in relation to estrus, conception and early pregnancy (on 28th day) in nulliparous heifers. Blood samples were obtained from 42 nulliparous heifers fed on TMR (Total Mixed Ration) on the day of AI and 28 days after AI. Serum was analyzed for BUN, blood glucose, Zinc, Cupper, and Selenium concentrations by Atomic absorbent spectroscopy. FSC (First Service Conception) rate, and pregnancy rate was 64.3% (27/42) and 66.6% (28/42) respectively. The pregnancy was confirmed and diagnosed on the 28th day by using ultrasound. There was noticeable increase in blood glucose, Zn, and ,Se levels in conceived or pregnant heifers (28/42) on both day of AI and 28th day After AI higher than their levels in non conceived, failed, or non pregnant heifers (14/42). While there was clear increase in BUN level in none conceived heifers in the day of AI (estrus) higher than its level in the conceived heifers. But there is decrease in Cu level in conceived heifers on both the day of AI and the 28th day after AI lower than its level in non conceived heifers. It is concluded that blood glucose, Zn, and Se are important for fertility and conception in nulliparous heifers, while increase of BUN and Cu during estrus are limiting the fertility and conception in heifers.