Genetic differences determine how fast a horse turns gray and if they end up as a gray or white horse.

Scientists from the Texas A&M College of Veterinary Medicine and Biomedical Sciences (VMBS) and Uppsala University in Sweden now understand why some gray horses turn completely white as they age, while others remain an eye-catching “dappled” gray color.

As published in the journal Nature Communications, the deciding factor is the number of copies of a small DNA sequence within the gray coat gene carried by each horse; while “slow-graying” horses have a gene variant with two copies of the duplication, “fast-graying” horses — those that will eventually become white — have a gene variant with three copies.

There are horses that are born white because they carry a gene variant that is causing white coat color, but the great majority of white horses don’t have this gene variant. Instead, gray horses are born with normal coat pigment — like black or brown — that gradually lightens as they age and eventually becomes gray or white.

Whether a horse has two or three copies of the duplicated sequence in the gray gene determines how fast a horse turns gray and if they end up as a gray or white horse.

Some horses, the ones that will eventually become white, begin to grow gray eyelashes and hairs at the base of the tail within the first week after birth. A horse that is ‘slow graying’ will typically not show signs of gray until it is 5 to 7 years old.

While having a gray or white coat color doesn’t appear to influence a horse’s athletic performance or overall health, it does make a horse more prone to developing melanomas — a type of skin cancer that has a well-established connection with the gray gene in horses.

“Horses that are ‘fast graying’ are more likely to develop melanomas, whereas we don’t see an elevated risk in horses that are ‘slow graying’,” Andersson said.

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JOHNSON GRASS – FRIEND OR FOE

For better or worse. It is tough. The rhizomes are like the proverbial ‘nine lives’ of a cat.

Most often we think of Johnsongrass as a weed. It germinates from seed in the spring, but also aggressively emerges from spreading rhizomes. So, control methods are foremost on our mind. There are several chemical options for Johnsongrass control, according to a comprehensive University of Georgia Extension document “Johnsongrass Control in Pastures, Roadsides, and Noncropland Areas,” https://extension.uga.edu/publications/detail.html?number=B1513. The document—confirm suggestions with current herbicide labels—summarizes the different situations where control is desired. These include:

•Use of pre-emerge dinitroaniline herbicides will suppress germination from seed, but do not affect rhizome growth, emergence, and spread.

•Selective herbicides for control in existing hay patches and pastures. These include sulfosulfuron (acetolactate synthase ALS-inhibiting herbicide) which can be used cautiously in existing bermudagrass and bahiagrass. Also, combinations of nicosulfuron + metsulfuron and imazapic may also control Johnsongrass in bermudagrass pastures though Univ. of Georgia suggests this latter combination may be more injurious to existing bermudagrass. A positive for these active ingredients is there are no grazing restrictions.

•For Johnsongrass that infests non-grass crops like forage legumes, herbicide with active ingredients like clethodim and quizalofop-P-ethyl may be used.

•Other Johnsongrass control options for include other herbicides and glyphosate to translocate and kill the root (most common formulation is Roundup) if it is acceptable to kill all vegetation. (It would seem rhizomes might be somewhat impervious to this mechanism.)

University of Georgia notes long-term control of Johnsongrass if best with fall applications.

What is Johnsongrass?

Johnsongrass (Sorghum halpense) is a cousin of grain sorghum (Sorghum bicolor), but it is a distinctly different species. There are genetic differences in the genes (haploid vs. tetraploid). Grain sorghum and closely related crops like sorghum/sudan do not produce rhizomes.

When will farmers might have Roundup-Ready grain sorghum. The answer has always been ‘never.’ This would lead potentially to the crossing of grain sorghum and Johnsongrass resulting in glyphosate-resistant populations of Johnsongrass. Not good!