1688 S. de Paz Let. 23 Nov. in H. Ellis (1827) 2nd Ser. IV. 157 Though I can (to my sorrow) say why milk-asses are provided for.
1787 J. Beattie 57 Milk-cow, milk-ass, milch cow, milch ass.
1814 H. L. Stanhope Let. 28 Feb. in I. Bruce (1951) III. xix. 247 I..have a few Ewes, a little cow, & milk ass.