"The amount of muscle function loss and the location of the dysfunctional muscles determine the ability to stand or become recumbent by default."
From the large animal clinic
Muscle tears most often occur in cows around calving time, or while being ridden (e.g. estrus, bull breeding) but can occur at any time. The muscle tear most commonly causing down cows is the gastrocnemius muscle, located just behind the stifle joint. This occurs most often due to slipping or falling while being ridden by another cow, or sometimes due to hypocalcemia or calving paralysis (obturator nerve damage). There will be a lot of heat and swelling in the area, and if the cow can stand at all, she cannot bear weight on the leg. The most severe swelling is located above and behind the stifle. In severe cases, the cow's hock will be very close to, or parallel with, the ground. Prognosis is very poor for recovery in these cases, unless the damage is minimal. Your veterinarian can assess the degree of damage.
Tendon ruptures can occur due to excessive tension on the tendon, infection, or trauma. Commonly, these ruptures occur at calving, due to falls or slipping, due to trauma (such as farm machinery, tin siding, etc.), or due to infections which weaken the bone or tendon. Most commonly, ruptures occur in the flexor tendons on the back of the legs below the knee (carpus) or hock, and the hind leg is most commonly affected. These cows are alert, but have obvious injuries or abnormal position of the lower limb. There is often swelling and heat at the site. The cow either cannot bear weight, or her toes will be turned up off the ground when she does bear weight on the limb. Your veterinarian can assess the damage, and prognosis is often fair to go od with treatment and rest.
Ligament tears usually result in severe swelling and lameness, and can lead to recumbency. Most often, the stifle is affected, especially in breeding bulls. The stifle joint becomes unstable, and the animal will develop arthritis. Treatment includes surgery, rest, confinement, and anti-inflammatory drugs. Surgery is only successful when treatment is attempted early in the progression of the disease. Once arthritis develops, the prognosis is poor. Immediate veterinary attention is required for these cases.
Rupture of a Ligament, Joint Luxation Description:
Rupture of a ligament can occur following trauma to any joint. In all cases the most useful sign for diagnosis is the opening of the joint space when lateral or medial pressure is put on the limb. The medial and lateral collateral ligaments of the stifle are especially at risk. Muscle Injury, soreness, bruide, trauma, Compartmental Syndrome Description: In any species trauma to a muscle may cause soreness and lameness. In horses a syndrome resembling compartment syndrome in man has been seen. There is firmness and pressure sensitive swelling of muscle following injury, and there can be associated decreases in sensation and pulse distal to the injury. Dx by signs, history, and ruling out injuries to other anatomical structures.
Your veterinarian should examine this cow. The prognosis ie. likelihood of recovery, can be predicted from a blood test. When cows have been down, their muscles break down and release enzymes into the bloodstream. These enzymes can be measured to give an indication of the severity of muscle damage and therefore the likelihood of recovery. Muscle breakdown products are toxic to the kidneys and therefore renal failure can be a complication of downer cows that makes the prognosis grave. Again the degree of renal damage can be determined from a blood test. Often the reason many downers never get up is other complications such as dislocated hips, damaged back or fractured bones. Your veterinarian is the best person to determine whether any of these possible complications are present. I know everyone has their favourite cocktail treatment for the "downer cow" but as a rule of thumb the best results come from getting an accurate diagnosis as soon as possible. We routinely take a blood sample from each downer that we see before we commence treatment. Obviously if the cow gets up we throw the blood away but if she doesn't, at least we have the option of sending it to the lab.This is invaluable for giving a prognosis and ruling out any underlying problem that may be present.
Regional damage to muscles causes release of breakdown products into the systemic circulation which leads to elevated levels of enzymes such as creatinine kinase (CK) and myoglobinuria which is seen as brown urine during the first few days of recumbency. In the most severe cases renal damage may result from massive amounts of muscle breakdown products overwhelming the kidney. Renal damage then leads to uremia and other systemic signs of renal failure. Therefore, the interplay of systemic and regional factors can go in both directions. Source: The many causes of down cows.
From the large animal clinic
Fractures are common in cattle. They occur due to trauma, falls, or in calves they may occur during calving. The most common sites are the cannon bones, but fractures of the tibia, radius and ulna, or femur are not uncommon. A fracture will cause severe pain and swelling. The limb may be at a strange angle. Sometimes the bone will be sticking through the skin. These animals are alert and unable to bear weight on the limb. Most closed fractures can be treated with casts, splints, bone pins, plates, or stall rest, depending on the size of the animal and the location of the fracture. Open fractures with bone exposed have a lesser prognosis due to infection and require surgical treatment.
Immediate veterinary treatment is required for these cases. Luxations are dislocations of a joint. Most often, we see the hip joint dislocated in adult cows following calving or a fall, often while being ridden by another cow. These cows usually can't stand, but if they do, they will appear lopsided from behind, with the dislocated hip higher or lower. One leg may appear shorter than the other. Your veterinarian can diagnose this with a rectal exam, physical exam, and sometimes x-rays. Adult cows usually do not recover well unless treated immediately. The first 12 hours after injury are the most critical to initiate treatment. The prognosis for an adult cow with a luxation is guarded. Calves may have a better prognosis. Immediate veterinary attention is required.
Fracure of a Long Bone
Description: Fracture of any long bone, such as the femur or tibia, can occur in any species. Onset is usually acute, and follows trauma. Dx by clinical signs and radiography. The presence of crepitation and mobility in a non-joint area are useful signs in diagnosis. Lameness due to a fracture is usually severe. Calcium-phosphorus problems can predispose to fracture in severe cases. Primary or metastatic neoplasia can weaken bones, leading to fractures.
Pelvic, Pelvis Fracture Description:
May remain ambulatory or go down. Crepitus on palpation of the pelvis while doing a rectal may be diagnostic, but can get false negatives. Fracture of the tuber coxae will give a flattened appearance, which may not cause lameness. Neurologic deficits in the pelvic, perineal and hind limb areas can occur due to associated nerve damage. Dx by radiography. Ultrasonography can be used for diagnosis in some cases (Shepherd and Pilsworth).
Coxofemoral Discoloration, Hip Luxation in Large Animals
Description: Rupture of the ligament of the head of the femur in cattle usually follows dystocia, or early post partum, but could occur at other times following trauma. There is pain in the acetabular region and auscultation may sugest that the femoral head is loose in the acetabulum. In complete dislocation the head of the femur may be palpable in the obturator foramen. Also occurs in other species, but is less common. Treatment (in cattle) was described by Hull and by Reynolds. Treatment in horses was discussed by Malark et al and by Field et al.
Longitudinal section of the vertebral column with a bandsaw may reveal a vertebral fracture in the lumbar region or an abscess. An abscess of a vertebral body may be the result of infectious material finding its way into the region and "settling down" via the mechanism mentioned above for vertebral lymphoma. Such an abscess can result in a so-called pathologic fracture and subsequent injury to the roots of the lumbosacral plexus and the cauda equina (the bovine cord ends at the level of the cranial part of the sacrum).
From the large animal clinic
Post mortem examination of experimental and clinical downer cows reveal similar lesions which are for the most part localized in the upper hind limb. This is because the upper parts of the hind limb are compressed against the pelvis while the more distal parts are positioned under the belly which is soft. While the abdomen is soft, it is also heavy and this weight on the common peroneal nerve can cause compression damage where the nerve crosses the stifle joint, especially the lateral surface of the head of the fibula1. For this reason, knuckling over on the fetlock, a sign of peroneal damage is often seen in recovered downer cows. This deficit is usually temporary, but it can be permanent.
Spinal trauma occurs usually as a result of riding other cows, being ridden by other cows, or by inadvertent trauma from farm implements. Other problems of the spine, such as lymphosarcoma tumors, or abscesses of the vertebrae will resemble spinal trauma. These cows may be able to stand weakly on their hind limbs. If they can, the hind limbs will usually knuckle over, especially at the fetlock. More often, they will be recumbent. Reflexes on the hind limbs are reduced. These cows can rarely be treated, and the prognosis is poor.
Calving paralysis is a commonly-used term to describe the paralysis of the hind legs which is seen in cows just after calving. It is caused by damage to the obturator nerve as the calf passes through the pelvic canal. This condition is most often seen after difficult calvings, the birth of large calves, or prolonged calvings. The cows are down, but alert and bright, usually eating. Most of these cows will recover with time and medical therapy.
If dystocia has occurred then calving paralysis may be a contributing factor as well. Calving paralysis is the preferred term for what is often referred to as obturator paralysis. Bilateral experimental transection of only the obturator nerves will not put a cow down unless the cow is on slippery concrete7. These cows will appear normal at a walk on dry concrete, but will spread the hocks wide when running. When they fall on dry concrete they can regain standing, but on a wet surface they have a hard time standing. The larger lumbar root of the sciatic nerve, as well as the obturator nerves, is vulnerable to compression damage between a fetus and the bony pelvic inlet portion of the birth canal. When both the lumbar root of the sciatic and the obturtator nerve are cut bilaterally, the experimental cow will be ataxic and not able to rise to a standing position in most cases.
Calving, Postfoaling, Paralysis
Description: Neurologic problems in downer cows following a calving are probably due to a combination of sciatic and obturator damage. Dx by signs of involvement of both nerves.
Fibular, Peroneal, Nerve Parasis, Paralysis
Description: Usually due to pressure on peroneal nerve while down, or trauma. If tibial nerve uninvolved can support at the hock. Could occur in any species, but most common in cattle following dystocia or being down for other reasons, and in small animals as a sequel to trauma, such as being hit by an automobile. Full weight can be taken on the limb, but there is knuckling of the fetlock. Skin sensation is lost on the dorsal tarsus and metatarsus.
Radial Nerve, Paresis, Paralysis
Description: Radial nerve innervates the extensors of the forelimb. Lesion of the lower motor neuron of the radial nerve leads to weakness or paralysis of the extensors, with flexion of the elbow, carpus and phalangeal joints. The leg is advanced with difficulty, and weight bearing is affected. Skin sensation is reduced on the dorsal metacarpus and phalanges.
Sciatic, Ischiatic, Nerve Paresis, Paralysis
Description: Could occur in any species but most common in cattle following calving and small animals following trauma. Occurs occasionally in all species following injection into the sciatic nerve, especially in small or young animals. In addition to knuckling the animal may show a dropped hock due to tibial nerve involvement. Skin sensation is affected in the entire limb with the exception of the area supplied by the saphenous nerve.
A controlled laboratory trial
Experimental induction of the downer cow condition has been used to study the effect of muscle and nerve compression in a controlled laboratory trial free of the numerous variables present in clinical cases3. Healthy non-pregnant cows were anesthetized with halothane anesthesia for 6, 9 and 12 hours to mimic the effects of recumbency in parturient paresis. All experimental cows were positioned on a hard rubber cow mat with the right hind limb under the body . Blood gases were monitored throughout the anesthetic period, and positive pressure ventilation with a mechanical respirator was used to maintain normal blood gases.
Within 30 minutes after the end point of anesthesia the cows were attempting to rise. Half (8 of 16) of the experimental subjects were able to rise within 3 hours after the end of anesthesia, but some of these showed temporary peroneal nerve paralysis on the previously down hind limb. Several cows which were not able to stand were able to rise on their forelimbs into an unusual bovine "dog sitting" position. All the others were able to stand on their forelimbs when lifted with clamps on the tuber coxae.