Abnormal Hair Whorl Patterns Pre-and Postnatal Effects on Hair Whorl Patterns and Behavior Part III

There are countless examples in the scientific literature of animals with genetic defects through inbreeding, exposure to environmental toxins, or many other factors causing brain abnormalities that affect behavior. In livestock animals, inbreeding, or what most people call purebred animals, have some of the worst defects. This effect is well-known in cattle, dogs, horses, pigs, and chickens.

Signs or symptoms include aggressive behavior, confusion, disorientation, forgetfulness, memory loss, personality and behavior changes, poor judgment, and poor problem-solving abilities. The deficiencies might cause sound sensitivities, vision problems, biomechanical imbalances, immunodeficiencies, gastrointestinal problems, and many more abnormalities too extensive to summarize here.

???????? ??????? ?? ????? ???????

A substantial body of evidence in animals suggests that the gestational environment can impact fetal brain structure and function and increase long-term susceptibility to stress. These effects can occur independently or in connection with genetic or postnatal factors. Environmental influence during fetal development is powerful in the brain. Significant brain structure differentiation occurs during early gestation, creating more susceptibility to environmental conditions and upbringing. Brain development involves several interactions with the environment, so even small changes from the typical developmental path during fetal life can become progressively exaggerated, producing long-lasting or permanent changes to the brain and, ultimately, the hair whorl(s) that form simultaneously. As outlined in an earlier post, the hair and brain form simultaneously from the same fetal cell layer between 10 and 16 weeks of early fetal development. The body at this stage of fetal development is so primitive that it doesn’t resemble the horse (see picture). All mammals look very similar the same at this stage of development.

At this development period, stress levels in the mother during pregnancy can affect brain function and behavior in her offspring as stress hormones transfer through the placenta. Although I am unaware of any direct studies examining the effects of prenatal stress in foals, I speculate that the effects of stress in the mare during gestation are similar to those shown in other animals. Find the scientific studies on this topic in “Genetics and the Behavior of Domestic Animals” Second Edition (2014), Chapter 7 by Mark Deesing and Temple Grandin, page 240.

In summary, under stress, a mare can affect the early development of the fetus’s brain and, ultimately, the position, number, and type of hair whorl(s). Mare’s that show strong defensive behavior toward their foals are stressed, and this stress may be present before birth and manifest itself after giving birth. I believe most of my success with foals that did not exhibit exaggerated stress during postnatal development started with the mare. When the mare trusts me, she will likely allow me to handle her foal.

????????? ??????? ??? ??????? ??????? ?? ????? ??????

Work done by the National Institutes of Health on the genetic control of postnatal (after birth) brain growth shows that within the first postnatal year, the brain grows to approximately 70% of its adult size.

In simple terms, the early brain after birth has not fully developed. The first half of gestation determines the formation and migration of neurons. By the second half of pregnancy, neuronal connectivity develops into immature circuits that set the stage for how the brain will continue to undergo extraordinary developmental changes in connectivity and connective tissue development over the first two years of life. Simply put, the baby horse is highly vulnerable to stress, inadequate nutritional needs, infection, toxins, and the mare’s behavior after birth. If the mare avoids people, so does the foal.

??? ???? ?????? ?????????? ?? ????????? ?????

In the twenty-two years I bred and raised colts and fillies on my ranch in Colorado, I only had one born with abnormal whorls (Jim). His mother had given me one foal from the same stallion and one more after from a different stallion, and both had typical high-hair whorls. Jim was different because within two months after the breeding, I had to travel to work on a cattle project for two weeks and relied on one of my boarders to feed the horses while I was gone. When I returned, I noticed a lot of wasted and leftover hay on the ground in the corrals that the horses didn’t eat because it was moldy. I always bought good quality hay by the truckload, but sometimes, some bales were moldy. I always threw out moldy bales, but my boarder, who fed the horses while I was away, didn’t know the danger of feeding horses moldy hay. I’m guessing here, but it was the only reason I could conclude. I suspected Jim’s mother was exposed to toxins during the early stage of gestation at his critical stage of brain development. The spring pastures were growing, and the horses were still eating grass/alfalfa hay before the summer turnout. They were hungry because the pastures were closed, and they ate what my helper fed them.

????? ??????

Exposure to toxins can be one cause; genetic compatibility is another. Genetic incompatibility describes the process by which mating yields nonviable offspring, prone to disease or genetically defective in some way. Scientists have concluded that rather than the genes of the female alone or the male alone being the reason for this, it is a result of the relationship and compatibility of their genes.

Another cause is what’s called incomplete dominance. Incomplete dominance results from a cross in which each parental contribution is genetically unique, giving rise to progeny with intermediate characteristics. Semi-dominance or partial dominance are other terms used to describe this. Early in my observations, while training and shoeing horses, I noticed that when one parent had a high whorl, and the other had a low whorl, most times, the high whorl was dominant. I noticed the offspring most times had a whorl in-between but closer to the high side, but if incomplete dominance occurs, the offspring have two stacked whorls, one high and one low. When this happens, and the brain is still developing, environmental conditions and upbringing determine how the brain responds during the first year and may cause behaviors expressed by the mare and other behaviors from the stallion, like a dual personality similar to what the USU behaviorist explained in his horse. He said the horse was mainly calm but unpredictable, which caused him to buck at unexpected times.

???????

At conception, hereditary potential unfolds in concert with the environment. Early intervention, especially when tailored to a horse’s characteristics, can help shift the odds toward more optimal pathways of later growth. Still, there are no guarantees because the nature-nurture interaction is dynamic over time. This complex interaction means that giving young horses an excellent early start increases but does not guarantee later success and that horses who begin life at a disadvantage are not doomed to enduring difficulty. It’s important to remember the importance of creating conditions that respect inherited characteristics, recognizing that nature-nurture is a source of continuing potential change across the life course.