Genesis 30:41-42

And it came to pass, whensoever the stronger cattle did conceive, that Jacob laid the rods before the eyes of the cattle in the gutters, that they might conceive among the rods.

Whensoever the stronger cattle did conceive. 'The sheep of those lands yean twice a year. In the autumn, when they have particularly rich pasture, then the stronger cattle did conceive;' accordingly, lambs which fall in February are the most esteemed. In the spring, when the pasturage is not so rich, and the sheep themselves are weakened by the damp and moisture, they do not conceive lambs of so good a quality. Jacob therefore took care to lay his rods in the gutters in the autumn, but did not do so in the spring' (Gerlach).