The Relationships Between Milk Production and Some Blood Metabolites and Their Effects on Returning to Estrus in Lactating Holstein Dairy Cows

In this study, the relationships and correlations between milk production and some blood metabolites related to energy and protein balance and their effects were investigated on returning to estrus after AI in lactating Holstein dairy cows. Blood and milk samples were collected from sixty lactating Holstein dairy cows based on their reproductive status in 13-17 d post AI. BUN, MUN, glucose, triglyceride, cholesterol and BHBA were measured by enzymatic colorimetric method and blood progesterone concentration was measured by ELISA method. Between 18-25 d post AI, 27 cows returned to estrus (RE group), but 33 cows did not (NRE group). In RE group, there were significant correlations between DIM and Monthly Milk yield Record (MMR) (p< 0.05), BUN (p< 0.01) and glucose (p