The present study aimed to investigate the effect of Ovsynch estrus synchronization protocol on plasma Zn, Cu, Ca and P levels in cyclic Murrah buffaloes during summer and winter season. The buffaloes were categorized in to two groups: 1) summer (n = 20) and, 2) winter (n = 18). Estrus cycle of buffaloes were synchronized with Ovsynch protocol (Pursley et al. 1995) as per standard procedure followed by artificial insemination (AI) at 8 and 24hrs after second GnRH treatment. The blood samples were collected on the day of start of protocol (d0) and day of AI (dAI) for the estimation of minerals concentration. The pregnancy was confirmed through

sonography on day 45 post-AI. Levels of Zn were lower (P<0.05) in summer as compared to winter season (1.0 ± 0.1 vs. 1.5 ± 0.1 and 1.3 ± 0.1 vs. 1.9 ± 0.1 ppm, respectively) whereas Cu, Ca and P levels showed no seasonal variation. Pregnant and Non-pregnant buffaloes had significant lower (P<0.05) concentration of Zn on d0 and AI in summer as compared to winter season (0.9 ± 0.1 vs 1.6 ± 0.2 and 1.2 ± 0.2 vs. 1.7 ± 0.1ppm, respectively and1.1 ± 0.1 vs. 1.5 ± 0.1 ; 1.3 ± 0.1 vs. 1.6 ± 0.1 ppm, respectively). The pregnant and non-pregnant buffaloes exhibited similar mineral profiles in both seasons. In conclusion, plasma mineral concentrations remain lower during summer as compared to winter season in buffaloes that could be responsible for lower fertility in summer.