Figure 1.

Brief overview of the dominant conditions studied. Glass-Eyed Albino (a–d) animals trace back to a mutant heifer born in 1994. Clinical features include white coat color (a), deafness, and “glass-eyes” (b). Partial phenotypic reversion consisting in heterochromia irides (c) or black spots on the ears (d) are sometimes observed. Dominant Red (e–h) is distinct from the traditional recessive red allele of the Melanocortin-1 receptor (MC1R^e) found in Holstein⁶⁶. It emerged in 1980 with the birth of a red mutant heifer (MC1R^D/D & DR^DR/+) from parents which were homozygous for the dominant black allele (MC1R^D/D & DR^+/+). In adulthood MC1R^D/D & DR^DR/+ dominant red animals (e,f) display substantial variations in colour ranging from a light brown which is close to the MC1R^e/e & DR^+/+ recessive red coat (g), to a dark brown close to MC1R^D/D & DR^+/+ dominant black coat (h). Neurocristopathy (NC) was observed in half of the progeny of a mildly affected Montbéliarde bull. Its main symptoms include hypotonia (i), lack of balance and coordination in the days following birth, facial abnormalities, heart defects and growth delay. Osteogenesis imperfecta type 2 (OI), is characterized by brittle bones that are prone to fracture (e.g. hind limbs in j). It has been reported in 29% of the progeny of an unaffected Fleckvieh bull. Bulldog (BD) calf syndrome is a lethal form of chondrodysplasia characterized by a generalized shortening of long bones (k,l). BD has been reported in 4% of crossbred calves from a Charolais bull (BD1, k), in 21% of purebred calves from a Holstein sire (BD2, l), and in an isolated case born from Holstein parents (BD3). Pictures e–h were generously provided by the breeding company Origenplus.