Evaluation of the open days and its relationship with hematobiochemical, milk and diet parameters in dairy Holstein cattle

Pregnancy open days (POD) and its relationship with diet, blood and milk parameters was assessed in high producer dairy cows to determine the indices could be affect on pregnancy rate. Following the estruses recording feed, blood and milk samples were prepared monthly up to the date of pregnancy in dairy cows. The visible estruses was from one to 6 and were 21.3%, 26.2%, 19.7%, 18.1%, 6.6% and 13.1%, respectively. The POD were varied from 2 to 11 months and were 11.5%, 21/3%, 9.8%, 1.6%, 11.5%, 9.8%, 11.5%, 3.3%, 9.8% and 9.8%, respectively. The differences among visible estruses and POD were statistically significant. Most cows revealed pregnancy after 3 months of calving. The overall mean for POD were 6 months. Approximately 50% of estruses were latent and have not been recognized. Mean values of urea, protein, calcium, magnesium, and phosphorus in diet, blood and milk during the POD were statistically significant difference among the groups . To realize the relationships between POD and biochemical parameters, POD classified into >120 and