**Author details**

**Figure 2.** Tandem mass spectra of multi-phosphopeptides: (A) di-phosphopeptide in αS1-casein, (B) tetra-phosphopeptide αS2-casein, and (C) tetra-phosphopeptide β-casein. The *y-* and *b-*ions are marked in each spectrum with losses of

phosphoric acid (neutral loss) probably owing to an in-source fragmentation.

158 Goat Science

Zohra Olumee-Shabon<sup>1</sup> \* and Jamie L. Boehmer2

