Semen characteristics, freezability, and application of motility-based protein markers (proAKAP4) in assessing the suitability of superior Bali bulls (Bos sondaicus) at the Regional AI Center

The use of molecular markers in selecting superior bulls, including Bali bulls, for the AI program will significantly increase reproductive efficiency and affect the economic aspects of several countries, especially in the livestock industry sector. Motility-based protein markers, proAKAP4, as one of the molecular markers that have recently been developed in the breeding industry, are expected to be applied and used at AI centers in Indonesia to optimize the use of superior Bali bulls, which are also supported by various semen and freezability characteristics. Using all Bali bulls from the Regional AI center in one of the provinces in Indonesia, this study divided the bulls into motility grade A and motility grade B groups. The collected semen is tested using various methods based on the literature, including fresh and frozen semen and sperm freezability. The proAKAP4 was quantified using the Bull 4MID® Kit with ELISA. The characteristics of fresh semen were significantly different (P < 0.05) except for sperm abnormalities (P > 0.05). The frozen semen characteristics were significantly different (P < 0.05) regarding plasma membrane integrity, DNA fragmentation, and several kinematic parameters. There was no significant difference (P > 0.05) in the freezability characteristics of Bali bull sperm. ProAKAP4 was significantly (P < 0.05) more abundant in the motility grade B bull group and was closely correlated (P < 0.05) with progressive motility and sperm viability. Motility-based protein markers, proAKAP4, can be applied to bulls at the Regional AI Center, with quantification results showing that half of the bull population used in research does not meet the fitness standards for superior bulls.