Proteome of follicular fluid from Murrah buffaloes (Bubalus bubalis): Normal cycling versus repeat-breeder females

Clinical evaluations have shown that repeat breeding is a major cause of infertility in buffaloes. The follicular fluid (FF) composition reflects directly metabolic status and fertility in females. Given this scenario, this study aimed to perform quantitative proteomic analysis of the FF collected from normal cycling (NC) and compared to repeat-breeder females. According to farm records, buffaloes were divided into two groups: normal cycling (NC, n = 7) and repeat-breeder (RB, n = 8) females. After estrus synchronization and using ultrasound-guided ovum pick-up, FF was aspirated from large follicles (> 8 mm). Posteriorly, proteins were identified by the shotgun method. A total of 119 proteins were identified and, among theses, three were uncharacterized and a protein (LOC123334375) was identified only in the NC group. The protein HP-25 homolog 2 was expressed only in RB females. The LFQ (label-free quantitation)-intensity of the proteins afamin (AFM), transthyretin (TTR), clotting factor IX (F9) and Xaa-Pro dipeptidase (PEPD) was significantly (P < 0.05) higher in RB than in NC females. In conclusion, the use of quantitative proteomics proved to be an important tool for the study of RB in buffaloes. The identification of HP-25 homolog 2 protein only in the RB females suggests that it can be used as a biomarker for this reproductive disorder. Additionally, an uncharacterized (LOC123334375) protein was identified only in normal cycling females and compensatory oxidative stress proteins were more expressed in repeat-breeders.