Playing devils advocate here, or rather just the messenger, but a quick google search resulted in a theist claiming to have a possible answer.
http://www.biblestudymanuals.net/gen30.htm
GEN 30:25-43
JACOB’S ‘SCHEME’ TO MULTIPLY SPOTTED SHEEP - DOES IT CONTRADICT TRUE SCIENCE?
I) INTRODUCTION
A) [Gen 30:25-43]:
(v. 25) "After Rachel gave birth to Joseph, Jacob said to Laban, 'Send me on my way so I can go back to my own homeland.
(v. 26) Give me my wives and children, for whom I have served you, and I will be on my way. You know how much work I’ve done for you.'
(v. 27) But Laban said to him, 'If I have found favor in your eyes, please stay. I have learned by divination that the LORD has blessed me because of you.'
(v. 28) He added, 'Name your wages, and I will pay them.'
(v. 29) Jacob said to him, 'You know how I have worked for you and how your livestock has fared under my care.
(v. 30) The little you had before I came has increased greatly, and the LORD has blessed you wherever I have been. But now, when may I do something for my own household?'
(v. 31) ‘What shall I give you?’ he asked. ‘Don’t give me anything,’ Jacob replied. 'But if you will do this one thing for me, I will go on tending your flocks and watching over them:
(v. 32) Let me go through all your flocks today and remove from them every speckled or spotted sheep, every dark-colored lamb and every spotted or speckled goat. They will be my wages.
(v. 33) And my honesty will testify for me in the future, whenever you check on the wages you have paid me. Any goat in my possession that is not speckled or spotted, or any lamb that is not dark-colored, will be considered stolen.'
(v. 34) ‘Agreed,’ said Laban. 'Let it be as you have said.'
(v. 35) That same day he removed all the male goats that were streaked or spotted, and all the speckled or spotted female goats (all that had white on them) and all the dark-colored lambs, and he placed them in the care of his sons.
(v. 36) Then he put a three-day journey between himself and Jacob, while Jacob continued to tend the rest of Laban’s flocks.
(v. 37) Jacob, however, took fresh-cut branches from poplar, almond and plane trees and made white stripes on them by peeling the bark and exposing the white inner wood of the branches.
(v. 38) Then he placed the peeled branches in all the watering troughs, so that they would be directly in front of the flocks when they came to drink. When the flocks were in heat and came to drink,
(v. 39) they mated in front of the branches. And they bore young that were streaked or speckled or spotted.
(v. 40) Jacob set apart the young of the flock by themselves, but made the rest face the streaked and dark-colored animals that belonged to Laban. Thus he made separate flocks for himself and did not put them with Laban’s animals.
(v. 41) Whenever the stronger females were in heat, Jacob would place the branches in the troughs in front of the animals so they would mate near the branches,
(v. 42) but if the animals were weak, he would not place them there. So the weak animals went to Laban and the strong ones to Jacob.
(v. 43) In this way the man grew exceedingly prosperous and came to own large flocks, and maidservants and menservants, and camels and donkeys."
B) FARRELL TILL’S POINT OF VIEW CLAIMING THAT THE BIBLE IS FULL OF ERRORS POINTING TO THIS PARTICULAR PASSAGE AS AN EXAMPLE
[ http://www.manits.co.uk/sceptical/1boobo91.html ]
"In chapter 30, he told of Jacob’s scheme to increase his wealth while he was still in the employ of his father-in-law Laban. The two had reached an agreement whereby Jacob would be given all striped, spotted, and speckled lambs and kids subsequently born in Laban’s flocks. Laban then removed all the striped, spotted, and speckled animals from his flocks and put them in his sons’ care at a three-day distance from the flock Jacob attended. Not to be outsmarted, Jacob devised a plan: Then Jacob took fresh rods of poplar and almond and plane, and peeled white streaks in them, exposing the white of the rods. He set the rods that he had peeled in front of the flocks in the troughs, that is, the watering places, where the flocks came to drink. And since they bred when they came to drink, the flocks bred in front of the rods, and so the flocks produced young that were striped, speckled, and spotted (30:37-39, NRSV). The editors of The New American Bible were reputable enough to affix a frankly honest footnote to this passage: Jacob’s stratagem was based on the widespread notion among simple people that visual stimuli can have prenatal effects on the offspring of breeding animals. Thus, the rods on which Jacob had whittled stripes or bands or chevron marks were thought to cause the female goats that looked at them to bear kids with lighter-colored marks on their dark hair, while the gray ewes were thought to bear lambs with dark marks on them simply by visual crossbreeding with the dark goats. We know today that the color characteristics of animals is purely a matter of genetics, so a modern, scientifically-educated person would never write anything as obviously superstitious as this tale of Jacob’s prosperity. The Genesis writer(s), however, knew nothing about the science of genetics, so to him the story undoubtedly made good sense."
B) A CLOSE ANALYSIS OF THE PASSAGE RESULTS IN SCIENTIFIC ACCURACY AS WELL AS AN INDICATION OF GOD’S SOVEREIGNTY IN ALL MATTERS
[Henry M. Morris states, (The Genesis Record, Baker Book House, Grand Rapids, Mich., 1994, pp. 470-471)]:
"By this time, Jacob had more than fulfilled his contract with Laban. He had agreed to serve with him seven more years, and more than that period of time must have elapsed by the time his four wives had borne him eleven or twelve children. He was with Laban a total of twenty years altogether (Genesis 31:38), including the fourteen years he had served for Leah and Rachel. Since the first seven years had been prior to his two marriages, all of his eleven sons and one daughter must have been born during a thirteen-year period at most…
Jacob now had a large family, and his work had been highly productive on Laban’s behalf, but he still had nothing of his own. He was also anxious to go home again…
1) [Gen 30:25-28]:
(v. 25) "After Rachel gave birth to Joseph, Jacob said to Laban, 'Send me on my way so I can go back to my own homeland.
(v. 26) Give me my wives and children, for whom I have served you, and I will be on my way. You know how much work I’ve done for you.'
(v. 27) But Laban said to him, 'If I have found favor in your eyes, please stay. I have learned by divination that the LORD has blessed me because of you.'
(v. 28) He added, ‘Name your wages, and I will pay them.’ "
[Morris, Ibid]:
"Finally, Jacob went to Laban and announced his decision to return to his home. He intended, further, to take his wives and all his children with him. He reminded Laban that he had more than lived up to his part of the bargain, so that he had no further moral of legal claim on him or his family.
Laban, however, was very reluctant to see him go. He had prospered greatly because of Jacob’s abilities and faithfulness, and he was willing to make almost any bargain that would keep him working for him. Laban even acknowledged that the Lord was with Jacob, and that it was of the Lord that he had profited so much through Jacob. Once before, he had gotten the better bargain by letting Jacob name his own wages; so now he made the same proposition again. Jacob had merely to name his price, and Laban assured him he would meet it, if Jacob would only keep working for him…
He had no other daughters to offer Jacob, of course; so this time the arrangement would have to be one of an actual payment of money or property. Laban’s offer seemed generous, but later developments showed he did not actually intend to let Jacob leave with anything.
The phrase “learned by experience” (verse 27) [“learned by divination” (NIV)] is interesting. It represents the Hebrew word nachash, and means literally ‘learned by enchantments.’ Laban had been somewhat perplexed by the fact that Jacob’s care of his flocks had resulted in such a great increase in his own wealth. Accordingly, he had in some way either carried out certain divination practices of his own, or else consulted some kind of soothsayer or oracle, seeing the secret. Laban, it becomes clear, though related to Abraham and knowing about Jehovah, had become to some degree a pagan mystic. At any rate, God so overruled his enchantments that, even through them, he had gotten the message that Jacob was under the special care of Jehovah and that it was because of this that God had blessed his service."
2) [Gen 30:29-34]:
(v. 29) Jacob said to him, 'You know how I have worked for you and how your livestock has fared under my care.
(v. 30) The little you had before I came has increased greatly, and the LORD has blessed you wherever I have been. But now, when may I do something for my own household?'
(v. 31) ‘What shall I give you?’ he asked. ‘Don’t give me anything,’ Jacob replied. 'But if you will do this one thing for me, I will go on tending your flocks and watching over them:
(v. 32) Let me go through all your flocks today and remove from them every speckled or spotted sheep, every dark-colored lamb and every spotted or speckled goat. They will be my wages.
(v. 33) And my honesty will testify for me in the future, whenever you check on the wages you have paid me. Any goat in my possession that is not speckled or spotted, or any lamb that is not dark-colored, will be considered stolen.'
(v. 34) ‘Agreed,’ said Laban. 'Let it be as you have said.'
[Morris, op. cit., pp. 472-473]:
"Jacob had apparently through the years said little about all this, simply keeping his agreement with Laban to the best of his ability. Laban on his part, had evidently never before admitted openly to Jacob that he knew it was because of Jacob and Jacob’s God that he had prospered so much in recent years. Jacob, therefore, took this opportunity to give his own testimony to this effect, indicating to Laban that he well knew all this, but had until now refrained from using it to his own advantage. He had been completely responsible for Laban’s flocks for over fourteen years, and a relatively small number of animals had become a great multitude under his care. This blessing had, indeed, come from Jehovah, though Jacob had done his part by faithful and industrious service.
Now, however, it was reasonable that he (Jacob), having fulfilled all his commitments to Laban, should begin to provide for his own family. Laban again, therefore, asked what he could give him to make him stay.
Jacob did not wish Laban to ‘give’ him anything. He had learned that God would supply what He wanted him to have, and he did not wish to be indebted in any way to a man whom he had come to know as a self-seeking, deceptive, ungodly schemer. He therefore made a proposition to Laban which would give God the opportunity to bless Jacob materially also, as He had Laban through Jacob. This plan would bring blessing to Jacob without taking anything belonging to Laban. Though Laban had doubtless expected Jacob to ask for a certain number of animals to begin his own flocks and herds, and would have been willing (at least outwardly) to give him whatever he would ask, Jacob would not take anything of Laban’s which then existed. Instead, he agreed to shepherd and supervise Laban’s flocks, exactly as he had been doing, and his pay would consist of those animals yet unborn that would be less desirable to Laban because of their markings. It would thus be entirely up to God as to how many animals would become Jacob’s.
Jacob agreed that none of the solid-color animals would be taken into his own flocks. If any should be found by Laban in Jacob’s flocks, Laban would have the right to take them out. Only those future animals that would be born speckled or striped or spotted, or abnormatively colored in some way, would become Jacob’s wages. The dominant color traits in Laban’s flocks and herds were evidently white among the sheep, black among the goats, and brown among the cattle. Most of the animals were of these colors, but there were a few that were spotted and speckled among the cattle and goats, and brown among the sheep. It was of such as these that Jacob’s pay would be.
However, Jacob further proposed that, not only would none of these living speckled animals be taken by him, but they would not even be used for breeding purposes. He would separate them into a separate flock, and keep them away from the normal-colored animals. Only such spotted and speckled animals as would be born in the future from the normal-colored animals would become his. Since the solid-colored animals were by far the more numerous, and since it was much less likely that they would bear striped and speckled offspring than those animals that were already striped and speckled - or brown among the sheep - this arrangement clearly was highly favorable to Laban and of very doubtful value to Jacob. Indeed, it was an act of pure faith on his part. He had put himself entirely at God’s mercy. It would be up to the Lord to indicate, by a very unlikely set of circumstances, whether Jacob should prosper personally or not.
Laban, who was willing to make a far more generous outlay than this to keep Jacob, immediately jumped at the chance to seal such a bargain. He would lose nothing that now belonged to him…
[and in all appearances, Laban stood not to be liable for losing much in the future - for Jacob would only possess the ‘abnormative’ animals which were far fewer in number and far less likely to breed many other ‘abnormative’ animals]
[Jacob] …had no breeding stock of his own, and none of the animals from which his pay was to come would be likely to produce spotted and speckled progeny of their own without a spotted and speckled population with which to interbreed…
3) [Gen 30:35-36]:
(v. 35) That same day he removed all the male goats that were streaked or spotted, and all the speckled or spotted female goats (all that had white on them) and all the dark-colored lambs, and he placed them in the care of his sons.
(v. 36) Then he put a three-day journey between himself and Jacob, while Jacob continued to tend the rest of Laban’s flocks.
[Morris, op. cit., p. 475]:
"Laban decided not to trust Jacob to keep the two sets of flocks separate. He himself… went through the flocks, culling out all the striped and spotted goats, the brown sheep, and other odd-colored animals, and put them into a separate flock, thus assuring himself that Jacob would not leave any of them in the main flock [for additional breeding and the possibility of further ‘abnormative’ offspring] Then, to make it quite impossible in the future for there to be any mixing, he gave the speckled flock into the hands of his sons, and told them always to keep them at least three days’ journey away from the main body of animals which would be tended by Jacob.
4) [Gen 30:37-43]:
(v. 37) Jacob, however, took fresh-cut branches from poplar, almond and plane trees and made white stripes on them by peeling the bark and exposing the white inner wood of the branches.
(v. 38) Then he placed the peeled branches in all the watering troughs, so that they would be directly in front of the flocks when they came to drink. When the flocks were in heat and came to drink,
(v. 39) they mated in front of the branches. And they bore young that were streaked or speckled or spotted.
(v. 40) Jacob set apart the young of the flock by themselves, but made the rest face the streaked and dark-colored animals that belonged to Laban. Thus he made separate flocks for himself and did not put them with Laban’s animals.
(v. 41) Whenever the stronger females were in heat, Jacob would place the branches in the troughs in front of the animals so they would mate near the branches,
(v. 42) but if the animals were weak, he would not place them there. So the weak animals went to Laban and the strong ones to Jacob.
(v. 43) In this way the man grew exceedingly prosperous and came to own large flocks, and maidservants and menservants, and camels and donkeys."
[Morris, op. cit., p. 474-477]:
"Jacob knew a great deal about sheep and goats and cattle, however - much more than Laban. He had kept his father’s flocks for decades, and now had been in charge of Laban’s for over fourteen years. As a very observant and intelligent man he had apparently learned something of what we now call Mendalian genetics, simply by long-continued observation of generation after generation of these animals. He knew that, even though a species of animal may have certain ‘dominant’ traits (such as the white color in this type of sheep). Furthermore, actual physical vigor and usefulness for man’s needs are quite independent of this matter of coloration… [Jacob selectively breeded the animals with the recessive trait of abnormative coloration with one another in such a manner as to increase their numbers even more than under normative conditions of herd life]
…A certain proportion of the solid-color animals… would be ‘homozygous’ [i.e., in this case with the same ‘abnormative’ color genes] and, if mated with other homozygous animals, would bear only solid-color offspring. The ‘heterozygous’ animals, which did contain in some proportion the genes for off-colored progeny, would be the ones which would have to supply his own future flocks; but by selective breeding he could eventually develop a flock of predominantly spotted and speckled animals…
Critics… [raise questions] …about [Jacob’s] …knowledge of science. His actions in peeling white stripes in rods from trees of poplar, hazel, and chestnut (or, perhaps more likely, storax, almond, and plane trees [as rendered in the NIV], and placing them in the cattle watering troughs, have been attacked as showing his belief in the outmoded ideas of prenatal influence. The idea is that Jacob supposed, by making the animals look at striped rods at the time of conception, he could induce them to bring forth striped offspring. The doctrine of prenatal influence is, of course, believed by modern zoologists to be nothing but an old wives’ tale.
It should not be overlooked, however, that Jacob was over ninety years old at this time, that he was a very intelligent and [a] careful observer, and that he had spent most of his long life raising and studying cattle, sheep, and goats. He would have been most unlikely to have been taken in by a groundless superstition…
There is a great deal, even today, that scientists have not been able to work out concerning the transmission of hereditary factors. In a certain population, there are multitudes of different characteristics which may appear in different individual animals of that species. The variational potential in the DNA molecular structure is tremendous. Exactly what it is that determines the actual characteristics a particular individual [or animal] may have, out of all the potential characteristics that are theoretically available in the gene pool, is not yet known in any significant degree. It may be that Jacob had learned certain things about these animals which modern biologists have not yet even approached.
There are, indeed, certain factors which can become prenatal influences, and which can determine to some degree the physical characteristics of the progeny. Though it is surely very unlikely that an external image can be transmitted through the visual apparatus to the brain and thence in some way as a signal to the DNA structure to specify certain characteristics to be triggered in the embryo, it is nevertheless true that certain chemicals can and do have a significant prenatal influence if they can reach the embryo or, prior to conception, the DNA in the germ cells. It is possible that certain chemicals in the wood of these trees - peeled rods of which were actually in the water which the flocks came to drink - were capable somehow of affecting the animals. If nothing else, water treated thus may have served as an aphrodisiac and fertility promoter among the cattle [and other animals]. At least one such chemical substance found in these trees has been used for such a purpose in both ancient and modern times.
Further, whether or not the sense of sight can actually ‘mark’ the embryo in some way, there is no doubt that what one sees may have a strong effect on certain physiologic mechanisms on his body. The phenomenon of blushing, the nauseous reactions produced by viewing gruesome sights, and the effect of pornographic pictures in stimulating the sexual apparatus are typical cases in point. The mere sight of the striped rods may have served simply as an aphrodisiac to the cattle when they came to drink. This in fact seems indicates by verse 38, in which the word translated ‘conceive’ in the King James Version [in heat, NIV] is actually the Hebrew yacham, meaning to be hot [i.e., to be in heat]. That is, the verse may be read:
’And he set the rods which he peeled before the flocks in the gutters in the watering troughs when the flocks came to drink, that they should become hot [or ‘’‘in heat’’’] when they came to drink.’ In some way not understood (but apparently confirmed by many practical animal raisers since), the sight of white-streaked rods seems to stimulate these animals to sexual activity…
…The bulk of the animals, which were Laban’s, were made by Jacob to face toward the separate flock of speckled and spotted lambs, but were kept separate from them. The reason for having them thus oriented is not clear; perhaps it was to make a subconscious impression on them that stripes and speckles were a mark of distinction in the flock, so as to make preparations for and augment the aphrodisiac influences of the striped rods. It is possible that, as a symbolic gesture, he had them face toward the three-days-distant flock of Laban’s ring-streaked cattle. Though they could not see them, this might have symbolized Jacob’s confidence that Laban’s pure-color flock would eventually produce a new ring-streaked flock for himself.
A further measure was taken by Jacob to ensure that the flocks so produced would be composed of strong animals. He divided the flocks into two shifts, composed of stronger and weaker animals, respectively. He used the rods in the troughs when the stronger animals drank, but not when the weaker ones came there. Thus the stronger animals were stimulated to mate, and the others were not… This measure, likewise, to the extent it would be effective, constituted a sound practice of animal husbandry, and should have been of as great benefit to Laban as to Jacob. It would ensure that, statistically at least, most of the newborn lambs and kids, whether solid color or spotted, would be sturdy and healthy. However, there continued to be produced an abnormally large proportion of spotted and speckled young. This meant that a greater and greater percentage of the animals in Jacob’s flock were strong animals, and an increasing percentage in Laban’s were weaker animals.
It was not until later that Jacob came to understand the providential intervention that caused the unusual percentage of streaked and spotted animals to be born…
5) [Gen 31:11-13]:
(v. 11) "The angel of the LORD said to me in the dream, ‘Jacob.’ I answered, 'Here I am.'
(v. 12) And He said, 'Look up and see that all the male goats mating with the flock are streaked, speckled or spotted, for I have seen all that Laban has been doing to you.
(v. 13) I am the God of Bethel, where you anointed a pillar and where you made a vow to Me. Now leave this land at once and go back to your native land.’ "
…In the meantime, within the space of only a few years - perhaps four or five - Jacob’s flock had grown so large, and he had prospered from it so greatly, that he had to employ many servants, both male and female, and had purchased many camels and asses. He had quickly become a very prosperous rancher. He had done so, not by any dishonest manipulation of his own, [or by some mystical methodology] but by means of sound practices of animal breeding which, by all normal standards, should have been of even greater benefit to Laban than to himself. The God of his fathers, however, had intervened in a marvelous and… [supernatural] way.
Jacob didn’t think the branches would influence the color, he only knew it would make them horny… 
oh… and about Mendalian genetics
No, I most certainly do not… and I do apologize if that is the way I came across.
…