Sub-Clinical Laminitis
click on images for detail
Introduction
The information available on sub-clinical laminitis tends to be unreliable. Therefore, you are offered the "best-guess" scenario. This section contains an overview of the factors which may be involved in contributing to sub-clinical laminitis. You will note that there are many "links" to other topics. Careful study of each of these topics will be helpful in understanding how this disease works.
Description
This
is a disease affecting the small blood vessels between the claw capsule
and the bone beneath. (See
anatomy)
Bleeding starts in the layer of cells where the horn is created. The layer of blood takes up to three months to reach the surface. (click image)
Discoloration of the sole with blood is a finding many clinicians associate with this disease.
Discoloration of the sole can also be caused by bruising. Bruises tend to be purple in color, the sole is usually thin and flexible and is more likely to be painful when pressed.
The
disease causes the animal discomfort as a result of which it walks and
stands slightly abnormally. (see
posture and gait) If the annual incidence of the following diseases
exceeds 10%, the diagnosis of sub-clinical laminitis is likely. (click
image)
The reason these diseases are so common is that sub-clinical laminitis generates horn that is of softer texture than normal. (click image)
In
herds in which this disease has become established for many years, changes
will be be seen in the wall of the claw. (See
horizontal grooves)
"Puffy feet" is a term applied by producers to a slightly
pink and swollen band of skin above the coronary band and around dew claws.
Puffy
feet may only appear for a few hours, mostly in recently calved cows.
It is accepted as an indication of an animal's failure to adjust to the
consumption of concentrates. If the prevalence is high and/or puffy feet
persist for more than 12 hours, the daily rate at which carbohydrate is
being increased should be reviewed. (click
image)
Cause
Rapidly Fermenting Carbohydrates
The use of grains that ferment rapidly should be avoided. Some grains are more rapidly fermented than others, e.g., barley. The digestibility of grain may be increased by the manner in which it is processed. Ground and moist grains are more digestible than dry rolled grain.
When carbohydrates break down in the rumen, acids are produced.
When the intake of carbohydrates is particularly high, acidity increases faster than it can be neutralized by saliva (acidosis).
Useful bacteria in the rumen are destroyed and poisons (toxins) are released.
Toxins Work on the Blood Vessels in the Claws
The tiny blood vessels that supply the horn-producing
tissues are very vulnerable to attack by toxin. Under the influence of
toxins, the vessels may expand to increase the pressure inside the claw
and cause discomfort.
The damage to the vessels causes clots to form, which in turn reduces the blood supply to the horn-producing tissues. In young animals, if the sub-clinical laminitis 'episode' is short, recovery can occur but the animal becomes very sensitive to further insults. (click image)
When the pressure is confined to the toe, the toe bone will 'rotate' and eventually penetrate the sole. (see toe ulcer)
Clots turn into scar tissue and this causes irreversible damage.
What about Fibre?
Depending on its quality, fibre acts indirectly as a buffer to neutralize rumen acids. Fibre stimulatrumination and the flow of saliva. A cow can produce up to 50 gallons of saliva each day. Saliva is rich in sodium bicarbonate.
The trick in managing acidosis involves maintaining a balance between carbohydrate and the fibre in forage. Different batches of forage have differences in the quality of fibre. Managing the balance is particularly difficult around calving time. (See troubleshooting dairy nutrition)
The Multifactorial Concept
In recent years most specialists believe that stress is also a very important factor.
It is found that in one herd, fed in a particular way, there is a problem, but in another "apparently" fed the same way, there is no problem. The answer is believed to be found in the manner in which management modified the behavior of the animals. This factor also involves cow comfort.
Nutritional factors of which there are several are of first importants. Other factors such as exercise, lying time, social confrontation and cleanliness all may play a part.
Treatment
Sub-clinical laminitis cannot be treated as it is impossible to anticipate the onset of this condition. Attempting to prevent this disease is the only rational alternative.
Control
In principle you must first look for either "a sudden change in nutrition" or "a critical imbalance" in the forage:concentrate ratio or perhaps an unexpected change in the quality of the forage.
How you feed, how often you feed, and how the feed is processed all have an important bearing on the end result. These changes can occur without the producer being aware that anything different has taken place.
Please familiarize yourself with: Troubleshooting dairy nutrition
After and only after you have thoroughly investigated every possible nutritional problem turn your attention to review the factors below:
If you are not already doing so initiate a program of claw trimming.
The implications of stress in a herd will become clearer if you consult the section dealing with herd investigation.
In many dairy herds the problems commence when the animals are heifers.
If this is the case review rearing replacement stock.
The Final Word
When a cow is lying down she is making money for you. More blood is passing through the udder each second and she is more likely to ruminate and produce saliva which netralizes the acid in the rumen.
A cow that can exercise will pump more nutrient and oxygen rich blood through the feet she will have more healthy feed than an animal that stands around with blood "pooling" in her feet.
Dairy producers need to understand this disease and should consult their veterinarian to develop a control protocol. Sub-clinical laminitis is a very complicated disease.
