Not surprisingly a-casein deficiency and the reduced concentration of casein proteins is accompanied by a reduction in the concentration of both calcium and phosphate in milk. The effect of a-casein deficiency in mice is similar to that reported for a aS1casein deficient goat breed (Cn0) in that total casein secretion is reduced by around 75% [18] . While there are no data available which suggest a critical growth delay in the offspring of aS1-Cn0 goats, it is unlikely that an allele that would have a nutritional impact similar to the inactivation of the a-casein in mice could have persisted in the natural environment. In addition, the Table 9 . Comparison regarding general health and behaviour between pups nursed by wild-type dams and pups nursed by acasein deficient dams. absence of a-casein does not appear to have a critical effect on calcium secretion in goats [17] . This indicates that there may be species (and maybe also strain-) specific differences in the assembly of casein micelles.