Association between postpartum blood levels of glucose and urea and fertility of cross-bred dairy cows in Sudan

This study aimed to find correlations between blood glucose and urea levels and the duration of postpartum period (PPP), number of services per conception (S/C), open period (OP), conception rate (CR) to first service, and the overall CR in 80 multiparous cross-bred dairy cows. The two metabolites were measured 1, 4, 7, 10, and 13 weeks postpartum. The CR to first service and overall CR were 13.8% and 42.8%, respectively. Based on S/C, three groups were identified: Group 1 (G-1) (n = 11) consisting of cows that conceived from first service; G-2 (n = 46) representing cows that needed two inseminations to conceive; and G-3 (n = 23) consisting of repeat breeders (RB). G-1 represented 13.8%, with PPP and OP shorter than cows in G-2 and in G-3, and had blood glucose levels 17.5% and 27.9% higher than levels in G-2 and in G-3, respectively. Until the 7th week postpartum, blood levels of urea were higher in G-1 and lower in G-3. However, in the 10th and 13th weeks postpartum, results were reversed. The PPP, S/C, and OP were negatively correlated with blood glucose over the study period and with blood urea at the first seven weeks postpartum. However, these traits were positively correlated with blood urea measured at 10 and 13 weeks postpartum. It can be concluded that, from this study, maintaining high blood glucose until the 13th week postpartum, high blood urea during the first 7 weeks postpartum, and low blood urea during the 10th and 13th weeks postpartum were associated with good fertility in dairy cows.Keywords: Fertility, first service non-return cows, postpartum period, repeat breeders