Disclosed herein are genomically modified livestock animals and methods to provide them that express the SLICK phenotype. The animals disclosed herein express a truncated allele for the prolactin receptor (PRLR) gene. When expressed, the livestock animals produce a PRLR that is missing up to the terminal 148 amino acid (aa) residues of the protein all ranges and values within the explicitly stated range are contemplated: e.g., from 148 to 69. Animals expressing SLICK have superior thermoregulatory ability compared to non-slick animals and experience a less drastic depression in milk yield during the summer.
