Over the past decades there has been a substantial decline in the reproductive performance of high-producing dairy cows. The negative energy balance (NEB) early post partum and intake of a high-protein and high-energy diet, are known to cause hormonal and biochemical changes in these cows (Lopez –Gatius et al., 2001). Hence, metabolic and endocrine changes in early lactation allow enhanced mobilization of depot fat and skeletal muscle break down and favour partitioning of absorbed nutrients to the mammary gland to provide sufficient substrate for milk synthesis (Butler, 2002). Anoestrus, a common state during the post partum period in high-producing cows, has major economic implication since it increases the length of the calving interval. Beta hydroxybutric acid (BHBA) is caused by a negative energy balance, and typically is produced within 2 months after calving (Butler, 2002; Noordhuizen, 2003). Anoestrus is a failure to exhibit oestrus behaviour in cyclic cows that classified into the four groups, ovarian atrophy, persistent follicle, persistent corpus luteum and ovarian cyst (Waanga and Janowski, 2000). Therefore, the objective of this study was to investigate the relationships among milk production, glucose, urea nitrogen, phosphorus, BHBA, total protein and progesterone and length of the calving interval.