When Traits Seem to Skip Generations
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My late husband always said that he’d never forget the look on my face as we watched one of our early Fell Pony foals being born. The foal had a huge white star, the biggest I’d ever seen on any equine, let alone on a jet black Fell Pony. I suspect I was holding my breath. I eventually let out a big sigh. “He’s a purebred,” I said. “I wonder where that came from.” From that day on, the further I got into Fell Pony breeding, the more I heard, and even said myself, “Traits can skip generations.”
I’m grateful to Sue Millard, who wears many hats in our international Fell Pony community, for making the connection between epigenetics and the oft-uttered phrase “traits can skip generations.” Epigenetics is the study of genes that express themselves differently than through heredity. Dr. Carey Satterfield says, “I would define epigenetics as alterations in the pattern of gene expression, such as ‘off/on’ or ‘a little/a lot,’ that are based on changes in the structural configuration of the DNA rather than its sequence. These changes can be permanent and have been shown to be heritable, but not always.” (1) Satterfield says that every day there are new findings, so the definition will continue to evolve.
What causes alterations in gene expression? There’s more unknown than known, but the environment in which a fetus develops in-utero and neonatally is known to influence gene expression. Click here to read about how room in the womb influences size at and after birth, for instance. Some epigenetic modifications occur only on genes passed by the father and some passed only by the mother. Some affect only the current generation and some can be passed to the next generation.
Some traits that are thought to be influenced by epigenetics include coat color patterns and markings, cannon bone circumference, and glucose metabolism. How mares are fed before and during gestation has received some study. Ardennes foals whose mothers were fed concentrates in addition to forage were eight times as likely to develop the joint condition osteochondritis versus those whose dams were fed a forage-only diet. Saddlebreds fed forage-only diets had foals with thinner cannon bones, less efficient glucose metabolism and delayed testicular development compared to foals from mares who’d received concentrates in addition to forage. (2) There is concern that mares who are overweight when bred could produce foals more likely to have the easy-keeper’s disease equine metabolic syndrome. Another area of concern and potential research is whether human handling of foals neonatally could cause epigenetic changes in the foal. (3)
Many Fell Pony breeders have experienced similar surprise to mine when they have a foal born with white markings to two solid-colored parents. I often think of the late Tom Capstick’s comment (paraphrased here) that the best way to breed white markings is to breed non-marked parents together. A review of Fell Pony foal markings from 1993 to 2018 indicates that, of the foals born to solid-colored parents, an average of 25% have white markings. Overall, we have an average of 33% of each foal crop with some sort of white markings. (4) Mr. Capstick’s comment, then, isn’t far off with one in four foals carrying markings despite solid-colored parents!
Oke, Stacey, DVM. “Understanding Epigenetics and Early Equine Fetal Development,” thehorse.com article #120762, 1/1/2012.
Chavatte-Palmer, Pascale, et al. “Developmental programming in equine species: relevance for the horse industry,” Animal Frontiers, July 2017, Vol. 7, No. 3.
Satterfield, M. Carey, et al. “Review of Fetal Programming: Implications to Horse Health,” AAEP Proceedings, Vol. 56, 2010, p. 207.
Color/markings reports from the author’s Fell Pony Pedigree Information Service software for 17 years between 1993 and 2018.
© Jenifer Morrissey, 2020
More articles like this one can be found in my book Fell Ponies: Observations on the Breed, the Breed Standard, and Breeding, available internationally by clicking here or on the book cover.
