1. Properly, because through famine your teats are destitute of milk for the nourishment of your poor children. Or rather,
2. Metaphorically, as the following words explain it,
for the pleasant and fruitful fields, which like teats yielded you plentiful and excellent nourishment, for which the land was said to flow with milk, Eze_20:6. And the earth being compared to the womb that bare us, Job_1:21, it is not strange if its fruitful fields be compared to the breasts which nourish us.