Artificial selection to obtain cows yielding higher milk output represents
Option 1 : Stabilizing selection as it stabilizes this character in the population.
Option 2 : Disruptive as it splits the population into two, one yielding higher output and the other lower output.
Option 3 : Directional as it pushes the mean of the character in one direction.
Option 4 : Stabilizing followed by disruptive as it stabilizes the population to produce higher yielding cows.