Correctly Identifying the Lame Claw

Over the years I have witnessed multiple occasions where farm staff have attacked hooves with knives, grinders and hoof trimmers before correctly determining the site of lameness. This will have frequently resulted in an exacerbation of the overall lameness in the cow.

Before putting any lame cows into the crush, it is important to determine which leg is affected. Our vets tend to record these on a recording sheet. Look for:

• obvious swelling (and hoof shape)

• weight bearing while standing still (the lame foot will be positioned so not to carry as much load)

• a head nod while walking in the case of front leg lameness

• the stride length and speed (the lame leg will have a short stride before taking weight, then the sound leg swings through with a longer stride and is weight loaded for longer.

Once you have determined the lame leg, have tied it up, washed it down and checked for footrot, use hoof testers to confirm where the lameness is located. This simple tool works by squeezing and putting pressure on the claw. Watch for a repeatable pain response which is easy to recognise in the hind legs by a tensing of the ‘hamstring’ muscles and the front legs by a tensing of the shoulders. Cows with sole bruising will often have very soft hooves and you will see that the testers easily depress the sole. If there is no response to either claw to hoof testers, then chances are you either have the wrong foot or the cause of lameness is located further up the leg.

Yersinia in Calves

In December we start to see outbreaks of Yersinia in weaned calves, typically from post-weaning through to about May. Yersinia bacteria are found in the intestines of most calves – 85% of herds (calves) have Yersinia as a normal gut resident. Stress/immunosuppression associated with parasites, nutrition, trace element deficiencies and BVD may result in an overgrowth of this bug in the intestines. Overgrowth results in a severe scour. Because of a constantly irritated bowel, faeces are often seen dribbling down on to the back legs.

As infection spreads, so does infection pressure and faecal-oral transmission then occurs. Large percentages of a mob are often affected severely checking growth rates. Mortality rates of 5-10% are not uncommon. Faecal culture confirms the diagnosis; however, a presumptive diagnosis can often be made on history and clinical signs. Isolation of affected animals to reduce the spread and treatment with oxytetracycline antibiotic for 3-5 days is an effective treatment/control.

Rare Presentation of an Acute Severe Aspiration Pneumonia

Earlier this month the after-hours team received a rather unusual call to examine a bloated cow struggling to breathe. Although this initially did not sound too out of the ordinary, across the district we had been seeing a few cases of bloat with the lush spring grass. However this case was different with the farmer was reporting the cow to have a face like a bull and be looking like a hippo.

Upon arrival it was quickly apparent this was no regular bloated cow. This cow had a large amount of air trapped under her skin extending across her whole body, including under her eyelids, over the hocks and udder. She had quite literally been turned into a walking drum, where tapping her skin would make a sound.

With there not being any possible treatment course to remedy this cows situation she was euthanized. A post mortem examination performed to allow for diagnosis and an explanation of how such a situation had occurred. The entire subcutaneous tissue (under the skin) has been filled with air creating a bubble wrap like appearance. A large majority of the lung tissue had been destroyed creating large air pockets between normal lung tissues. With the help of histology testing through the laboratory it was determined that the process had been started by aspiration of feed material causing a degree of airway blockage. This would have then allows the secondary complication of air leaking into/around the lungs. With each breath in, air would have traveled down into the lungs, then the air would have been escaping out of the lungs in to the chest. Then every breath out would have acted like a foot pump pushing air out the neck and under the skin, essentially blowing up the cow like a balloon from the inside.

It is not unheard of for this process to occur, in which damage to lungs allows air to escape under the skin. However this particular case was rather severe example of this due to the degree of damage resulting in such a severe presentation. Typically aspiration pneumonia presents as a sick cow, off milk/losing condition, she may have a fever and abnormal lung sounds and on post mortem examination often abscess formation within the lungs. This particular case did not have any abscess within the lungs, this is likely due to the rapid time line not having time for abscess to have formed.

The proper diagnosis would be an acute severe aspiration pneumonia with obstruction of bronchioles/broncholi leading to severe interlobular and pulmonary emphysema and secondary severe generalized subcutaneous emphysema. All in all, a very unlucky cow and a very interesting case. If you or someone on your farm finds an interesting case you would like to discuss, or investigate further, please do not hesitate to get in contact with one of our experienced team.

IBR - Infectious Bovine Rhinotracheitis

IBR is caused by infection with bovine herpes virus type 1 and is highly prevalent in New Zealand cattle. Approximately 90% of local dairy herds will have been exposed to IBR and it is the most common reason for China export heifers being rejected.

IBR causes herpes virus lesions in the respiratory tract and/or the reproductive tract. Typical of herpes virus, once an animal is infected it is infected for life. Infected animals can shed the virus on multiple occasions, especially when the animal is under stress and the immune system is overwhelmed.

Clinical signs of IBR are usually associated with an upper respiratory tract viral infection:

• High fever.

• Runny eyes

• Nasal discharge. This is highly irritating, and animals will often rub their nose on sticks which can become stuck up the nose.

• Coughing.

• Difficulty breathing.

• Anorexia occurs, as a result the animals are lethargic and appear ill thrifty with reduced milk production.

IBR can also cause vesicles on the vulva and penis, neither of which is desirable during mating. IBR tends to be a problem in herds when naive heifers enter the herd and are exposed to the herpes virus for the first time.

Treatment

While there is no direct treatment to eliminate the viral infection. Infected animals should be isolated from the rest of the herd and treated with anti-inflammatories and antibiotics.

Prevention

Vaccine is available to prevent herpes virus infection in cattle and can be used in herds where IBR is problematic. It is especially useful to vaccinate naive heifers prior to entering the herd.

First Two Months of Lactation - Minimising Weight Loss

A good start to a cow’s season requires careful management through the springer and colostrum period to ensure that she maintains a high dry matter intake. Initial focus should be placed on prevention of metabolic disease, optimising immune function, adequate feed allocation and manipulating cow behaviour.

However, the first month of lactation beyond the colostrum mob is still very critical. Most cows will spend this period in negative energy balance – i.e. more energy is leaving their system than coming in and therefore they will lose body condition. This is why providing consistently high feed quality is imperative. We are already seeing many farms that are struggling to manage very high pre-graze covers due to good growth rates through the winter. These are impacting voluntary intakes and may have lower ME.

Cows in significant negative energy balance may develop clinical or sub-clinical ketosis. Ketones are a by-product of inefficient fat break down and have a side effect of further appetite suppression.

Cows which are well fed/have a good appetite in the first month of lactation will lose less weight and have better mating performance. Try some of the following:

• Optimal pre-graze covers of 3,000 to 3,400 kgDM/ha in the first round will ensure good quality and easy harvest for the cow. You still need to maintain a residual at 1,550-1,600kgDM/ha to ensure quality in subsequent rounds.

• Aim to get your milking cows eating 4% of body weight in dry matter ASAP.

• Know what your daily cow requirement is and calculate your allocation every day - where feed deficits exist on any given day fill it with appropriate supplement.

• Use monensin (Rumenox), to increase feed conversion efficiency, by driving proprionate production. Clinical trials show boost in milk protein production and far less BCS loss. Use strategically from calving up until end of mating.

• Internal parasites – the biggest impact these have is on appetite suppression. Almost all farms will have high levels of over wintered larvae this year. Aim to drench your herd by early/mid September.

• Vitamin B12 – is a requirement for energy extraction. Deficient cows will lose appetite. We see B12 levels drop at the same time as spring grass goes lush. This is partly due to rapid transit times through the gut impeding B12 absorption. A good rule of thumb is when faeces starts becoming loose look to give Vit B12.