Determining the diagnostic value of calcium in prediction of reproductive performance of Holstein dairy cows

The reproductive performance of dairy cow is directly linked to uterine involution and resumption of ovarian cyclicity in the postpartum period. Many factors, such as negative energy balance, metabolic diseases and hormonal agents can affect reproductive performance in the postpartum period. Hypocalcemia through reduced Feed intake, reduced nutrient supply to the ovary and delayed return to normal uterus function has a potential role to reduce the reproductive performance of cows after parturition. The aims of this study were to examine the association of peripartum concentrations of calcium with reproductive performance and establish cow level critical threshold for calcium to predict conception to first service.

the study was conducted on 97 Holstein dairy cows. Serum concentrations of calcium were measured in all cows on day 10 prepartum, parturition, 1-2 days after parturition and on the weeks 1, 2, 4 and 6 postpartum. Based on Pregnancy success after the first insemination, the interval from calving to first insemination, the interval from calving to first pregnancy and number of services per conception, cows were divided to two, two, three and two groups respectively and differences of calcium concentration were evaluated among these groups. ROC analysis was applied to determine the critical calcium threshold at different times for predict pregnancy success after the first insemination.

the results showed that calcium concentration in pregnant cows with the first insemination was significantly higher than non-pregnant cow in the fourth week. Also, the cows that were became pregnant before 80 days after parturition had the significantly higher calcium concentration at 1-2 days and the fourth week after parturition than other cows. Based on results of ROC analysis, the calcium concentration at the fourth week after parturition (P=0/04) was appropriate to predict the pregnancy success after the first insemination. The optimum critical threshold that had the highest combined sensitivity (57/1%) and specificity (62/3%), for calcium in the fourth week was 9.05mg/dl. In the cows with success pregnancy before 80 days after parturition the calcium concentration was significantly higher than other cows (P=0/03).

the results of this study showed that there was a significant relationship between change in calcium concentration and reproductive performance indexes in the postpartum period. It seems that the monitoring of blood calcium concentration in the fourth week after parturition is a complementary index along with other reproductive performance indexes to evaluate the possibility of successful pregnancy after parturition Key words: calcium, postpartum, dairy cow, reproductive efficiency