EFFECTS OF MILK PRODUCTION AND SOME BLOOD METABOLITES ON PREGNANCY STABILITY IN LACTATING HOLSTEIN DAIRY COWS.

In this experiment, relationships and correlations among some blood metabolites associated with energy and protein balance and their effects on pregnancy failure were investigated in lactating Holstein dairy cows. Blood and milk samples were collected from fifty-six lactating Holstein dairy cows based on their reproductive status (in 35-45 d post AI) and blood urea, milk urea, glucose, triglyceride, cholesterol and betahydroxy butyric acid were measured by enzymatic colorimetric and blood progesterone was measured by ELISA method. Cows at 56 to 63 day post Artificial Insemination, were divided in to two groups of Pregnant (PG; n=25) and Non-pregnant (NPG; n=31) by touché rectal pregnancy diagnosis. In NPG group, there were significant correlations among milk yield and some energy balance related metabolites (betahydroxy butyric acid and glucose) concentrations and correlations among milk yield and protein balance related metabolites (blood urea and milk urea) were significant in both NPG and PG groups. Furthermore, there were significant differences between means of monthly milk yield record, cholesterol, betahydroxy butyric acid and progesterone between two groups. In conclusion, although evidence exists for adverse effects of elevated circulating urea on fertility, pregnant cows were able to adapt to elevated circulating urea over several days. However fluctuating concentrations of metabolites in the early postpartum period may offer potential explanations for latent effects of early postpartum energy balance on subsequent fertility. Furthermore, in pregnant cows, the importance of progesterone and cholesterol as a precursor of ovarian steroidogenesis for pregnancy stability has been observed. [ABSTRACT FROM AUTHOR]