TRAPPC9 and mastitis: Although we reported the significant link of the selected SNPs in TRAPPC9 and CD4 genes milk production and mastitis resistance phenotypic traits, however, we recommend further in-depth studies to test the documented reported SNPs of TRAPPC9 and CD4 in a large Chinese Holstein population as well as in other different dairy breeds from various regions of the world by using our newly designed CCSC-I for the validation of its capability to improve milk production and mastitis resistance in dairy cattle.