Diagnosing and treating downer cattle (Proceedings)

Down cattle represent a major welfare issue for the dairy industry.  Modern housing facilities containing more concrete do not provide sufficient footing for struggling cattle and result in more injuries as a result.  Estimation of the incidence of downer cattle on dairy farms varies widely.  Older studies have estimated down cow incidence, which was defined as being non-ambulatory for 24 hours or more, between 0.4-2.4% (Erb, 1988; Cox, 1986). 

A survey completed by the United States Animal Health Association determined that 78.2%of surveyed operations had a least one downer cow per year with an annual incidence estimated at 0.4% for 2003 and 0.38% for 2004 (USAHA, 2006).  Based on these estimates, the USDA (2005) determined there to be approximately 500,000 non-ambulatory cows in the US every year. 

Cox (1986) estimated that 58% of downer cows became non-ambulatory within one day of calving and an additional 37% of the downer cows in their survey occurred by one hundred days in milk.  Risk factors commonly associated with down cows included dystocia, milk fever, stillbirth and retained placenta.  According to a study by Correa (1993), cattle that developed milk fever were 5.6 times more likely to be non-ambulatory, cows that had a stillbirth were 4.9 times more likely to be non- ambulatory, and cows that experienced a dystocia were 5.7 times more likely to become non-ambulatory. 

Studies looking at the outcome of down cows indicated that 33% of down cows recovered, 23% were slaughtered, while 44% of the cows died (Cox, 1986).  Obviously this study was completed before the implementation of a ban on non-ambulatory cattle in the United States in 2003. Analyses done by the author in 2004, on well managed Arizona dairies, indicated that death loss increased by 15-25% in 2004 compared to the average annual death loss for those dairies from 2000-2003.  This increase was attributable to down cows that were no longer able to be processed for meat and were subsequently euthanized.

Differential diagnosis

Differentiating the cause for non-ambulatory cattle can difficult to determine due to the animal's size and often times multi-factorial in nature.  Down cattle need immediate attention to determine and correct the cause for being recumbent but, also to prevent secondary damage to muscle and nerves.  When confronted with a down animal, a good history should be taken and a complete physical exam should be completed to determine the underlying cause and prognosis. 

After completing the physical exam, concentration can then be placed on the affected limb(s) to aid in the determination of the exact cause and prognosis.  To aid in the exam, strategies such as lifting the cow using a hip lift to assess her ability to bear weight on affected limbs, placing pressure in the interdigital space with a hemostat, rolling the cow over to more completely evaluate the limb on the down side, or judicious use of a battery operated prod to see if the cow will attempt to rise using the affected leg.  During the exam of the affected limb, pay particular attention for signs of pain, swelling, deformation, crepitus, or wounds. 

Limb fractures are best detected by deep palpation of the limbs looking for swelling, deformation and appearances of pain upon palpation.  Each affected joint should be individually evaluated by flexing, extending, abducting and adducting the joint.  The coxofemoral joint should be evaluated by noting the location of the greater trochanter of the femur in relation to the tuber coxae and the tuber ischii.  Also, note if crepitus over the location of the coxofemoral head is present.  If rupture of the cranial cruciate ligament of the stifle is suspected, palpation of joint for swelling and crepitus should be completed followed by evaluation of the joint for the presence of a positive drawer. 

The differential diagnosis can established using a mechanisms approach to place the cause into one of several categories including injury, neuropathy, metabolic, inflammatory, infectious, or nutritional.  Examples of problems that can be associated with the above categories include:

                Injury-Fracture-long bone or hip, joint luxation–coxofemoral joint, ligament–cranial cruciate ligament, muscle tears–gastrocnemius muscle, spinal cord compression

                Neuropathy-Obturator or sciatic nerve damage

                Metabolic-Hypocalcemia, hypophosphatemia, hypokalemia, hypomagnesemia, fatty liver syndrome

                Inflammatory-Toxic mastitis, toxic metritis, peritonitis

                Infectious-Clostridial myositis, lymphosarcoma

                Nutritional-Vitamin E/Selenium deficiency

In addition to the above list of primary causes, it is not unusual for cows to develop secondary neuropathy or myopathy of the down rear limb due to a “compartment-like syndrome” resulting in pressure necrosis from the animal's weight.  Pressure necrosis of nerve and muscle tissues in the down cow can occur within 6 hours of being recumbent, so it is imperative that therapy be administered as soon as possible.  It is also common for cattle to tear muscle or ligaments when struggling.

Prognosis and treatment

Establishing a prognosis and a treatment strategy is dependent upon the primary cause of recumbency, length of time the animal has been recumbent, and availability of nursing care to attend to the animal.  There are very few reliable indicators of prognosis currently available.  One of the best indicators in the authors experience is length of time the animal has been recumbent prior to initiation of therapy.  Anderson (2011) indicates that creatine kinase (CK) values >20,000 have a guarded prognosis and less than a 50% of chance recovery while cows with a CK value in excess of 50,000 have less than a 10% chance of recovery but, this data is not uniformly supported (Stull, 2007; Burton, 2009).  A study completed in the United Kingdom indicated that the quality of the nursing care available to look after the cow was the single best prognostic indicator (Chamberlain). 

Treatment should be focused on correcting the underlying cause of recumbency and providing proper supportive care to minimize secondary problems.  Animals that are recumbent due to primary causes with poor prognosis, such as long bone fracture or severe hypokalemia, should be euthanized immediately in order to minimize un-necessary suffering.  Because farm workers are internal optimist and do not like to make decisions regarding euthanasia, it is imperative the farm personnel be trained to objectively evaluate down cows and establish a prognosis as to whether the animal can become non-recumbent before permanent muscle and nerve damage occurs. 

In order to minimize further injury, the recumbent animal should be placed on a bedded area that protects the animal from the environment and predators, and provides solid footing and keeps the area around the cow dry in order to minimize decubital ulcers and urine scald.  One of the best bedding materials that will accomplish many of these goals is a deep bed of sand.  Moving animals to the bed or pack should never be accomplished by dragging the animal as this will result in further injury and pain.  Movement of down cattle should completed by placing the animal on a skid or rolling them into a loader bucket. 

Pain and inflammation can be mitigated through the administration of an anti-inflammatory product.  Non-steroidal anti-inflammatory products like flunixin meglumine require IV administration and carry short milk and slaughter withdrawals.  The corticosteroids dexamethasone and isoflupredone acetate are labeled for pain for cattle.  Dexamethasone contains no milk or slaughter withdrawal while isoflupredone acetate has a seven day slaughter withdrawal.  Isoflupredone acetate has been shown to initiate severe hypokalemia with a single dose and should be used with caution in dairy cows (Coffer, 2006).  Oral or IV fluids should be provided as needed to prevent dehydration.  In addition, make sure feed is always readily available within reach of the cow.   

In order to minimize secondary muscle and nerve damage, cows must be moved from side to side at least every six hours.  Use of hip lifts for short periods (10-15 minutes maximum) can be used effectively to improve circulation and reduce swelling in affected pelvic limbs.  Use of hip lifts for longer periods of time will result in pressure necrosis to the musculature around the tuber coxae.  Hip lifts will not properly support the animal to provide relief for thoracic limb injuries. 

The use of slings will help support thoracic limbs and will minimize the negative effects to the musculature around the tuber coxae.  However, slings are much more difficult to maintain on the cow because of interference with the udder.  When in use, they put pressure on abdominal organs, which in turn compresses the diaphragm and may lead to respiratory distress. 

Float tanks can be an effective way to provide supportive care for recumbent animals.  Placement of cattle into a float tank evenly supports the body weight and improves blood flow to the peripheral tissues as the tissues are no longer compressed.  Studies that have looked at the effectiveness of float tanks have shown 37% and 46% success rates (Burton, 2009; Smith, 1997).  The latter study also showed a 78% success rate when only looking at dystocia induced paralysis. 

Animals can be successfully floated for long periods of time (>24 hrs.) provided there is an adequate source of warm water or a device to re-heat the water is available. Prognosis is guarded if the animal becomes distressed upon placing it in the float tank.  Cows that were floated were 4.8 times more likely to survive if they were able to back out of the tank and support their weight on all four legs after the water was removed, were 2.9 more likely to survive if they stood normally in the tank once it was filled with water, and were 1.9 times more likely to survive if they ate while in the float tank (Burton, 2009).

Fractures of bones are best repaired with casts, pins, splints, plating techniques, or stall rest.  Younger animals typically respond better to these procedures.  Open fractures require surgical treatment and long term antimicrobial therapy and have a grave prognosis.

Spinal compression due to trauma or lymphosarcoma present with knuckling at the fetlock or paresis and paralysis in the hind limbs.  The prognosis for these cows is very poor.

Knuckling at the fetlock is also seen with calving paralysis.  Damage to the obturator nerve occurs as a result of dystocia or prolonged calvings.  Many of these cows can be successfully treated with anti-inflammatory therapy and good nursing care. 

Luxations of the coxofemoral joint have a poor prognosis in adult cattle unless they are diagnosed and repaired within twelve hours after the injury.  Likewise, fractures of the coxofemoral head have a poor prognosis.    

Treatment of metabolic disorders will be discussed in companion papers in these proceedings.

Summary

Down cows are common problems on dairy farms and are often associated with the periparturient period.  The differential diagnosis for down cows is multifactorial and requires a complete physical exam and a thorough exam of the long bones and joints of the affected limbs.  Secondary muscle, joint, and nerve damage is common and attempts to assess this should be made initially and daily during treatment.  Delaying the initial therapy beyond six hours results in a guarded to poor prognosis due to irreversible muscle and nerve damage to the rear leg.  If cattle are recumbent for longer than twenty-four hours, recovery rates have been shown to be only 33%.

Availability of good nursing care has been shown to be the single best predictor of a successful treatment.  Recumbent cattle should be rolled from side to side at least every six hours.  Judicious uses of float tanks, hip lifts, or slings have been shown to improve the prognosis of recumbent cattle.  Additional support for these can be provided with the administration of oral or IV fluids and appropriate anti-inflammatory products.  In some cases, euthanasia is necessary due to a guarded to poor prognosis.  Veterinarians and farm personnel need to be trained to objectively evaluate the prognosis of a down animal in order to minimize un-necessary animal suffering.