ASI provides recommendations for maintaining sheep hoof health
Lameness is a worldwide problem for sheep farmers and flocks. The American Sheep Industry (ASI) SheepCast podcast welcomed University of Birmingham, United Kingdom (U.K.), Life and Environmental Sciences Professor Laura Green to discuss sheep foot health and evolving recommendations for foot disease.
Causes of lameness
Most of the causes of lameness in sheep occur in the feet, but there are two key differences – they can be either infectious or non-infectious, Green notes.
“Infectious causes dominate because they spread from sheep to sheep, whereas non-infectious causes will be seen in individual sheep,” she says. “In the U.K., foot rot is the most common cause of lameness, contributing to roughly 70 percent of lameness issues.”
Contagious ovine digital dermatitis (CODD) is another cause of lameness in the U.K. and European countries, which causes severe and common infectious foot disease.
“CODD is another increasing, infectious bacterial disease and is responsible for approximately 30 percent of lameness,” says Green. “But, then we get these other non-infectious causes or granulomas.”
One of the most common types of toe granuloma, or foot damage, is caused by excessive foot-trimming and foot-bathing. They can appear in a fleshy, “strawberry” appearance and happen as a response to cutting into sensitive tissue beneath the hoof horn.
White line disease (WLD), also known as shelly hoof, is another example of a non-infectious disease. WLD is an extensive degeneration of the white line.
Disease lameness, injury lameness, foot rot
If an instance of lameness occurs in the foot, it will be difficult to determine if it is caused by an injury or disease.
Green says until one does a further examination at the foot, producers won’t know what the cause of lameness is.
“Sometimes people can see sheep that are not weight bearing at all. For example, they might have a swollen joint or fracture up the leg, and they won’t bear any weight. But, producers need to look at the sheep to actually decide,” she says.
Dichelobacter nodosu, formerly known as Bacteroides nodosus, is the pathogen or bacteria causing foot rot.
“This pathogen is specific – the only thing it does is cause foot rot in sheep, and it’s very specialized to the feet of sheep,” she says. “It’s not found anywhere else, and it can only live in a diseased foot.”
She notes this pathogen can be spread through soil, pasture or bedding, but it’s only alive in and able to reproduce on the foot of a diseased sheep. In some instances, some producers might not see any signs or symptoms of the disease besides the sheep being lame, but in a few days typical signs and symptoms include extreme pain, elevated body temperature, bilateral swelling of the interdigital space and a loss of hair, foul odor and decreased feed intake.
“We know Dichelobacter nodosu won’t cause disease unless the skin is damaged in some way,” says Green.
She continues explaining wet skin for more than 24 hours for a few days is enough for the skin integrity to get weaker and cause Dichelobacter nodosu to invade. In dry conditions, Dichelobacter nodosu will die within minutes, and with some moisture, it can survive for one to two days.
“The thing to think about is these feet diseases have millions of Dichelobacter nodosu organisms on them. Every time they walk, they are planting millions of these organisms in the soil,” explains Green. “Although, each one might only survive 48 hours, it only takes one sheep to come along and step in an infectious footprint to be infected.”
She adds there can be contamination over a 24/7 period, although organisms are dying off rather quickly.
Different strains of this bacteria can affect sheep differently, she notes.
“The strains themselves don’t determine how severe the disease is,” says Green. “What determines the severity of the disease is the number of fimbriae – otherwise known as molecular and filamentous polymetric protein structures located on the surface of bacterial cells – seen on the bacteria or Dichelobacter nodosu.”
The more fimbriae on any one organism, the more it’s able to invade, she mentions.
Foot rot diagnosis
Green notes clinical signs for foot rot is necessary in making a foot rot diagnosis. In many cases, veterinarians will conduct a polymerase chain reaction test, which are highly accurate diagnosis of certain infectious diseases and genetic changes. The test works by finding DNR or ribonucleic acid of a pathogen or abnormal cells in a sample.
“If we know we’ve got foot rot in a country or a flock with odor or clinical signs, we don’t need to go through the clinical diagnosis,” she says.
If animals have a poor or inadequate diet, livestock can be more susceptible to disease, but by in large, as long as the basis of health and nutrition are being met, foot rot is not a disease caused by a deficiency.
“The way we control foot rot is by thinking of it as an infectious disease and doing treatments and biosecurity measures,” she says.
For a long time, the best recommended treatment for foot rot was to trim the hoof of the infected sheep, even to the point of exposing bacteria to oxygen to kill it. Green has found by doing so, it delays healing.
“This disease has been around for several hundreds of years, and the industry hasn’t had antibiotics for very long. Maybe at some point in the past, this was the best we could do,” says Green. “But what we know is, if we trim feet and trim them severely, they don’t grow back in the same way.”
For treatment she recommends giving a long-lasting antibiotic, giving the right dosage to meet the body weight of the sheep, applying a topical treatment for all four feet of the sheep, treating infected sheep within three days of becoming lame and not trimming at all.
She says for some diseases it is necessary to trim the foot, but not to the point of sensitivity. Green recommends producers keep records of what sheep are being treated for lameness, and if sheep are being treated two to three times a year, she encourages producers to cull them.
In closing she mentions, “My big take home message is to stop trimming, start treating promptly and effectively and get lameness levels down under two percent in six to 12 weeks.”
Brittany Gunn is the editor of the Wyoming Livestock Roundup. Send comments on this article to firstname.lastname@example.org.