Genetic mutation found in Simmental, Angus breeds
November 19, 2015
Simmental breeders noticed something odd about some of their calves.
After several American Simmental Association members reported calves born having eyes with pale blue irises around the pupil with a tan periphery and black coats that are slightly bleached to look grey or red, researchers identified the genetic condition called Oculocutaneous Hypopigmentation (OH).
Discovered by Dr. Jon Beever, University of Illinois geneticist, OH is inherited as a simple recessive. The source of the condition in the Simmental breed is likely a commercial Angus cow that was a founder animal to a line of black Simmental cattle.
"This defect goes back to the late 1970s," said Beever, whose lab has studied many genetic abnormalities in the last decade. "With this particular genetic condition, it's not really going to effect the performance of the calf. In fact, I had a breeder who sent me a photograph of a calf with this condition who ended up being the grand champion heifer at a county fair. She had nice crystal blue eyes, so I imagine she kind of stood out in the ring."
Although largely a cosmetic issue in the calves, it has yet to be determined whether the light eye color could cause photosensitivity.
"Because cattle have dark eyes, it's hard to see the pupil in cattle," explained Beever. "However, with the light irises, breeders can clearly see the pupil, which is actually an oblong slit. Folks may be interpreting the slit as squinted eyes and mistaking the shape of the pupil as a sensitivity to light. It's hard to determine whether this is an issue or not, but since this report has come out, we have received additional phone calls from breeders who have seen this genetic condition in some of their calves, as well."
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With additional reports coming in, Beever can get a more clear picture of what producers are dealing with.
"It is my hope that our research program at the University of Illinois is very accessible to our stakeholders — livestock producers and industry professionals," he said. "For the last 10-12 years, we've worked on genetic abnormalities that have been reported in different breeds and various countries. This is a continued effort in that area. We are hopefully some of the first guys people call when they observe some of these odd phenotypes."
The OH mutation has been seen in the Angus breed, as well, and the American Angus Association and American Simmental Association are working closely to identify the pedigrees who may be carriers.
Beever's lab recently screened 1,311 Angus bulls for the OH mutation. A complete list of Angus bulls tested can be found here: http://www.angus.org/Pub/OH/OHListing.pdf. Of the bulls tested, only one was identified as a carrier of the mutation, Sir Wms Warrant, (AAA 9196894) born in 1978. In 1982, Warrant as identified by the American Angus Association as a carrier of Heterochromia Irides (HI), commonly known as "White Eye."
Although OH and HI are two separate genetic conditions, the mutations exhibit many of the same characteristics. New research from Dr. David Steffan, University of Nebraska geneticist, concludes that Warrant is an OH carrier, not HI, and other animals previously reported as HI carriers are now under review.
"Commercial cattlemen probably won't see too high of a frequency of OH in their calves," said Beever. "The genetic mutation seems to be falling in the show lines instead."
A Simmental bull — Black Joker — has been confirmed as a carrier of OH, and a few others remain under investigation, including Hart's Black Casino (now deceased).
"We only have a handful of reported cases of OH so far," said Jackie Atkins, American Simmental Association Science and Education Operations director. "The calves reported have similar lineage if you dig far enough into their pedigrees. Hart's Black Casino is one of those bulls who has been implicated, but we won't be able to test the deceased bull to see if he was a carrier of OH."
While the genetic defect is simply a cosmetic mutation, breeders are already eager to identify which lines are carriers.
"Purebred breeders can test for this immediately if they go through Beever's lab," said Atkins. "OH will also be included in the next round of chips at GeneSeek, so any producer who does high density or low density DNA testing will be able to look for this."
Of course, when cattlemen hear about a genetic defect, it usually accompanies a little bit of hysteria. Images of dead calves suffering from curly calf — a genetic defect in the Angus breed — spring up, and Atkins wants to reiterate that this defect should not impact producers economically.
"This is a low frequency within the Simmental population, and it really is a simple cosmetic abnormality, so we would hate to place too much emphasis on eliminating certain lines," said Atkins. "There is no need for hysteria about OH. Test results are posted online, and folks can weigh the pros and cons of using an animal that is a carrier."
"If we as the academic community did a better job of education, there wouldn't be so much drama about genetic defects," added Beever. "The Hereford breed has different classifications for defects, which is the distinction between economic loss such as the death of the calf or a cosmetic defect. Because there isn't that designation in the Angus or Hereford breeds, when you say the word 'defect' or 'abnormal appearance,' it probably gets over emphasized. I would still avoid breeding these cattle with these defects, but it's certainly not a huge deal to worry about."
As the Simmental and Angus associations work closely with Beever's lab, more information will be unveiled about OH and HI — the similarities, the carriers, and how to avoid these genetic mutations.
"This is one of those instances where we try to keep an eye on things for producers, so if it is genetic mutation, it doesn't get out of hand," said Beever. "In the Simmental population, there was an early, popular bull in the mid-'90s that was a carrier, and now there are some show-oriented lines that have extended the mutation a little further. This situation just shows how there can be an interaction between breeders and the scientific community to catch these things early. I would encourage anyone who has seen this mutation in their calves to report them to our lab for further study."
Producers with information can contact Dr. Beever's at firstname.lastname@example.org or (217) 333-4194.