Some positively selected genes were reported to be associated with lactation function and disease resistance, such as the butterfat rate [PPARGC1A (Weikard et al., 2005; Schennink et al., 2009)], milk production [B4GALT1 (Asadollahpour Nanaei et al., 2020; Valsalan et al., 2021)], immunity [IL2 (McCoard et al., 2019) and NFATC3 (Hu et al., 2018)], and mastitis resistance [ITSN2 (Miles and Huson, 2020)]. Here, IL2 is linked to mastitis.