Laminitis is also known as founder. It is defined as the inflammation of the sensitive structures of the hoof which may be of infectious or nutritional in origin. Non-infectious causes of lameness affecting the bovine digit are ulcers, white line disease and traumatic lesion of the sole. Some conditions of laminitis are predisposed by metabolic disorders such as ruminal acidosis. Deficiency of trace minerals and vitamins also lead to laminitis in the dairy farm.
Lameness is a major disease with heavy economic loss in dairy farms. In large dairy herds where mechanized systems are often more readily available, lame cows are treated by supervisors or farm employee itself. As a consequence, foot care and claw trimming is performed by either commercial trimmers or farm employees. Methods and technical expertise amongst trimmers varies significantly. This occurs both because of a lack of formal training programs and that apprenticeship is not often required for a person to become established inthe foot care business. As a result, the quality of foot care available to dairy farms in some areas is inconsistent and sometimes even contributes to a greater amount of lameness. So understanding of laminitis is of utmost importance to the dairy farmers for the prevention of laminitis.
Anatomical and histological perspectives of laminitis
Hoof in physiological perspective is defined as the modified skin (epidermis) covering the tip of the digit enclosing all the structures. Hoof is formed by keratinization of epithelial layer and modification of underlying dermis to thicken and cornified to be called as Hoof. Hoof provides protection to distal limb which is resistant to mechanical and chemical damage. So hoof is modification of epidermis, dermis and subcutaneous layer. Structure of hoof varies among species.
The epidermal region of the hoof is associated with dermal region called as corium. Corium has four distinct regions i.e. Solar corium, Perioplic corium, Laminar corium and Coronary corium which produces different portions of the hoof.
Adjacent to the corium, there lies basement membrane and epithelial cell layers. They are called germinal layer of epithelial cells. Germinal epithelium contains two types of cells such as Keratinocytes and Basal cells. Keratinocytes have ability to produce and accumulate Keratin inside them. Keratin is a fibrous scleroprotein imparting strength to the hoof and resistance to physical and chemical injuries. These cells are cemented by lipoprotein that binds the keratinocytes together. The keratinocytes move outward and away from their nutrient source. Therefore these cells are in the continuous process of slow death as they reach upper layer.
Pathogenesis of Laminitis
Pathogenesisof laminitis is associated with disruption of microcirculation of blood within corium, leading to breakdown of dermal- epidermal junction claw wall and bone. In commercial dairying, ruminal acidosis is a major predisposing cause of laminitis. Ruminal acidosis produces its destructive effects through lactate, endotoxins and histamines reaching the blood. They cause dilatation of arterioles and constriction of venules resulting in reduction the blood flow to hoof area. So endothelial cells get damaged and fluid from blood escape into extracellular space. The end result is inflammation accompanied by edema, hemorrhage and necrosis of corium. Collagen fibres supporting P3 also degrade.These vascular effects also
interrupt the differentiation and proliferation of keratinocytes in the germinal layer of epithelium. It leads to reduced keratinization in the horn cells. So structural rigidity and strength of horn reduces. Poor keratinized hoof is weaker and less resistant to infection and chemical injuries.
Different forms of laminitis
Depending on the severity of the condition laminitis can be acute, chronic and subclinical form. Acute laminitis is most commonly seen in first lactation cows within 30 days of lactation. Inflammation is severe and sudden.Inflammation of the corium is evident. It is diagnosed by redness, stiffness, pain, unwilling to walk. Dairy cows will stand with arched back with camped under posture. Animals spend most of the time lying down.
Chronic cases of laminitis are mild and undetectable. Sometimes changes can be seen in hoof wall. In chronic cases claw widens, flatten and develop horizontal ridges. Inflammation develops more gradually.
Subclinical laminitis is more common.This can be a long and slow process depending upon persistency of low-grade insults. The inflammation ultimately results in internal hemorrhaging. It is syndrome associated with a variety of lesions. It may be associated with third phalanx or production of poor quality horn or less resistant to injuries. Poor quality horn causes structural abnormality of the capsule of claw. There are some foot problems which are associated with subclinical laminitis. They are Sole ulcers, White line Disease, Heel erosions, Bruised soles, Sole abscesses, Toe ulcers, Wall cracks.
Sole ulcers are also known as pododermatitis. It is a circumscribed loss of horny sole that exposes the corium. The typical location of the lesion is near the axial border of the heel-sole junction of the lateral claws of the hind feet. Sole ulcers on the front feet are rare but when they occur they usually involve the medial claws. Bilateral lesions of the hindfeet are common. Lameness usually isn’t severe until granulation tissue develops from the exposed corium and protrudes from the defect in the sole.
White line disease is a non-infectious condition that occurs when the sole separates from the side wall of the hoof, allowing foreign material to penetrate and infect the white line region.White line disease is a major cause of lameness with the incidence in older cows being as high as 35%.
Heel horn erosion or ‘slurry heel’ is recognized by the damage to the surface of the bulb of the heel. Actual evidence of mobility problems becomes evident after severity of laminitis. It is often linked to interdigital dermatitis. It is more commonly associated with poor hygienic conditions in housed dairy herds and towards the end of the winter.
Sole bruising is recognized by the presence of red and sometimes yellow marks or areas on the sole and often occurs where the sole is particularly thin.Any disturbance in blood flow to the corium can result in the necrosis of the corium tissues, bleeding and swelling – often referred to as ‘laminitis’ – which eventually manifests itself in areas of sole bruising. It can also lead to separation of the soft tissues of the foot and the pedal bone can become misplaced, compressing the soft tissues within the foot, causing sole ulcers.
Sole abscess is located between sensitive laminae and horny sole of the hoof. Purulent exudate is found in the abscess. Abscess is caused due to damage in the integrity of the sole. Damage to the sole leads to bacterial growth under the sole.
Economic considerations of laminitis in a dairy farm
The consequences of foot related diseases are much greater than the treatment costs. Reduced milk yields, lower reproductive performance, increased involuntary cull rates, discarded milk and the additional labor costs to manage cows with laminitis accounts for the largest monetary loses.
In a study by M. Vatandoost et. al it has been found that milk production loss was more severe in high milk producing cows than medium and low producing cows. He found milk production loss for high yielding cows to be 0.98 kg per day per cow. Loss for medium and low producing cows found as 0.68 and 0.26 kg milk per day per cow respectively.
Laminitis and Nutrition of dairy cows
Rapidly fermenting carbohydrates such as starch and sugar may lead toruminal acidosis. The concentration of propionic and lactic acid increases. So a shift in fermentation occurs away from crude fiber digestion. Feed particle size (finely ground), processing (steam flaking) and starch source (wheat v corn) influence the rate of fermentation. Sugars have faster rates of rumen fermentation (found in high quality pasture). Starch and sugar feeding has been recommended as 25 to 28 % and 2-4 % respectively.
Excess level feeding of protein to dairy cows may impart to laminitis. NRC, 2001 has recommended feeding of total mixed ration having CP 17.5 % and 36 % rumen undegradable protein. Higher level of fermentable protein may produce such fermentation products which adversely affects hoof health.
Effective fiber is very important for rumen health. Fiber maintains normal rumen pH (6) and normal cud chewing. Normally a dairy cow spends 550 to 600 minutes for cud chewing daily. A dairy cow should be fed 2.5 kg of forage having particles size over one inch length. As per NRC 19 to 21 percent effective NDF on dry matter basis can meet requirements of a dairy cow.
Feeding unprotected fats at higher levelcan depress the growth of crude fiber digesting bacteria so digestibility of crude fiber reduces in the rumen.Vegetable oil as oilseeds can be included in the feed up to 2.5 %. By pass fat can be added to increase total fat level from 6 to 7 percent. Unsaturated fatty acids are hydrogenated in acidic pH of rumen to trans fatty acids which is toxic to fiber digesting bacteria of rumen. So milk fat level drops.
Zinc is essential mineral for synthesis of keratin, therefore improves the strength of hoof. Zinc has a role in wound healing, maintenance of epithelium and keratin synthesis and maturation. Organic zinc can reduce somatic cell counts and increase milk production. Recommended levels in the total ration dry matter is 40 to 60 ppm (1/3 organic zinc sources and 2/3 inorganic zinc sources).
Sulfur is needed for synthesis of sulfur containing amino acids made by rumen bacteria (ratio of 10 to 12 parts nitrogen to one part sulfur). Harder hooves have been reported with added sulfur in the ration. Recommended level of Sulphur in total ration is 0.25 to 0.28 percent. Sulphur is the component of disulphide bond in the protein molecule.
Copper impact the claw health by increasing the production of thiol oxidate which increases the hoof strength. Cattle fed on copper deficient feed are more susceptible to heel cracks, foot rot and sole abscesses. Suggested level of total copper in the ration on dry matter basis is 10 to 15 ppm (1/3 from organic copper sources and 2/3 from inorganic copper sources).
Biotin is needed for keratin formation and claw horn development in cattle and horses. Hoof improvement by feeding biotin requires 6 to 8 months to observe a response. The recommended level of biotin is 20 milligrams per cow per day. Green fodder is rich source of vitamin A, E and B complex. Feeding green or good quality hay is very good for hoof health.
Prevention and control of laminitis
Ruminal acidosis and trace mineral deficiency play big role in prevalence of laminitis. Zinc is important for synthesis of keratin in the hoof. There are several technologies for mineral supplementation in the dairy farms. Zinc propionate provides zinc with higher bioavailability. It provides zinc with higher retention in body. As per NRC 2001, 45 ppm of zinc to be fed on dry matter basis of total mixed ration.
Lameness is usually a multifactorial problemhaving origin from infection, management and feeding. Prevention of the herd from laminitis can be done by farm audit for management and feeding program, history of illness and proper diagnosis of the lesion. Antibiotic therapy is practiced for infectious causes of laminitis.Floor has big impact on occurrence of laminitis in dairy cows. Concrete floor with rough surface physically damages hoof to develop cracks. So laminitis develops in dairy cows.
Ruminal acidosis and mineral nutrition have a big role in pathogenesis of laminitis. Ruminal acidosis is managed by feeding a ration with enough physically effective fibre and sodium bi carbonate. Zinc and copper have important role in prevention of laminitis. There are several technologies for mineral nutrition in animals. Propionate technology provides essential minerals at very high bio-availability. The retention of minerals is also high enough to prevent laminitis effectively in dairy cows. Some of the following managemental tools will benefit the farm from laminitis.
1. Provide soft, smooth and dry floor in the farm.
2. Provide adequate effective fiber.
3. Feed the cows with balanced feed.
4. Provide foot bath with disinfectant and copper sulphate 5 %.
5. Regular monitoring of cows for BCS and locomotion scoring. Treat cows at earliest for best effective result.
6. Check hoof very regularly by a trained personnel.
7. Regular hoof trimming at 6 month interval.
8. Avoid overcrowding and provide adequate exercise and comfort.
References available on request
by Dr. Kumar Prashant, Kemin Industries South Asia