Comparison of blood metabolites and GSH-Px, SOD, MDA levels as a predictor of pregnancy in primiparous cows after the Presynch-Ovsynch protocol
The reactive oxygen species level and antioxidants have determinative roles for gamete development, steroid synthesis and fertilization. The objective of the current study was to compare some metabolic and antioxidant parameters in primiparous cows with and without pregnancy after the presynch-ovsynch protocol in the postpartum period. Sixty dairy cows were allocated to two groups according to their pregnancy status after timed artificial insemination following the presynch-ovsynch protocol. Blood samples collected at the day of presynch-ovsynch protocol started, at AI and at pregnancy examination to determine glucose, urea, total protein, phosphorus and calcium, GSH-Px, SOD and MDA levels. Receiver operating characteristics (ROC) curves were used to determine the cow-level thresholds for the subsequently pregnant. Moreover, pairwise comparisons were made of the area under the curve (AUC) of ROC curves for the thresholds of GSH-Px, SOD and MDA for identifying the cows most likely to conceive. The biochemical metabolites were in physiological ranges. Serum glucose concentration was greater at the beginning of presynch-ovcsynch in cows that subsequently pregnant. An interaction noted between group x time for serum SOD, MDA and GSH-Px levels. The MDA concentration was lower before the synchronization protocol in cows that subsequently pregnant. Although GSH-Px concentration was greater, SOD was lower after the synchronization sampling time in cows that subsequently pregnant. MDA and SOD concentrations changed over time in cows that subsequently pregnant. MDA level at the beginning of synchronization was the best predictor for identifying the cows most likely to conceive with AUC values of 0.866. In conclusion, while presynchronization MDA and post synchronization SOD were lower, post synchronization GSH-Px were higher in pregnant cows. MDA level at the beginning of presynch-ovsynch was the only risk factor for pregnancy. Thus, MDA levels before the synchronization might be used as a biomarker for selecting the cows for presynch-ovsynch protocol.