After Rachel had borne Joseph, Jacob wanted to go back to his own country. Laban didn’t want him to go as he learned by experience that God had blessed him for Jacob’s sake. He asked Jacob to name his wages.
Jacob made a deal with his uncle; “If you will do this thing for me, I will again feed and keep your flocks: Let me pass through all your flock today, removing from there all the speckled and spotted sheep, and all the brown ones among the lambs, and the spotted and speckled among the goats; and these shall be my wages.”
Laban liked the deal. He kept the white livestock. Coincidentlly, the meaning of Laban is “white.”
Giving Jacob’s livestock into the care of his sons, Laban put three days’ journey between himself and Jacob, and Jacob fed the rest of Laban’s flocks.
Jacob employed a selective breeding and animal husbandry method that God showed him in the next chapter, in Genesis 31:10-12.
Taking for himself rods of green poplar and of the almond and chestnut trees, he peeled white strips in them, and exposed the white which was in the rods. And the rods which he had peeled, he set before the flocks in the gutters, in the watering troughs where the flocks came to drink. But when the flocks were feeble, he did not put them in; so the feebler were Laban’s and the stronger Jacob’s.”
By using the plant rods and God’s help with genetics, Jacob selectively bred speckled, spotted and brown livestock from Laban’s flock, putting his own flocks by themselves.
How scientific was Jacob’s methodology? Here’s a good article about it from Answers in Genesis;
Research into botanical and herbal remedies over the past few decades has exonerated the methodologies which Jacob used with Laban’s flocks. Indeed, some of the same botanical specimens Jacob utilized are now being used to supplement livestock feed and are used as veterinary treatments on several diseases and conditions.Answers in Genesis: Jacob’s Odd “Breeding Program” of Genesis 30
It goes to show faith, knowledge and science can co-exist.