Charles Ellicott Commentary Genesis 30:41-42

"And it came to pass, whensoever the stronger of the flock did conceive, that Jacob laid the rods before the eyes of the flock in the gutters, that they might conceive among the rods; but when the flock were feeble, he put them not in: so the feebler were Laban`s, and the stronger Jacob`s." — Genesis 30:41-42 (ASV)

The stronger cattle ... when the cattle were feeble. —The words for “strong” and “feeble” are literally bound and covered, so that evidently we have technical terms, which Onkelos and the Syriac explain as referring to the females at the two breeding seasons. The ewes in the spring, after the cold season, are bound, firmly knit together, and the lambs strong and healthy. The other word, covered, seems to mean seeking concealment, hiding away (Job 23:9); and therefore faint, its meaning in Psalm 61:2, Psalms 102:title (Authorised Version, overwhelmed), and Isaiah 57:16 (Authorised Version, fail). The autumn-born lambs are of no great value, and Jacob left them to the course of nature.