There is a lot farmers can do to prevent exposure to and transfer of diseases, along with good feeding management to improve calves’ immunity.
MSD Animal Health-sponsored Dr Gemma Chuck spoke at the Dairy Women’s Network conference in May on growing great calves and the biology of calf diseases.
The Australian-based veterinarian is completing a PhD in how practical changes to colostrum management can affect morbidity, mortality and liveweight gain on dairy farms in south-west Victoria.
The key to successful calf rearing is decreasing a calf’s exposure to disease and increasing its resistance through colostrum, Chuck says.
The four major problems that impact calves are scours, pneumonia, navel-ill and joint-ill.
There is no blanket treatment for calf diseases. There are preventative vaccines available, but they’re not silver bullets. They can be an incredibly useful tool, however, if farmers are treating more than 10% of their calves each season, or more than 3% are dying, she says.
The vaccines increase antibodies in colostrum, but if colostrum is not managed as it should be, calves won’t get the full value of those antibodies.
The most common sign of calf disease is scours, which can be caused by bacteria, viruses or protozoa, often in combination with each other. Scours will often lead to pneumonia.
“We don’t often know which came first. They all affect different areas of the gut and these calves can get very sick, very quickly.”
Scours are more often caused by E coli, salmonella, rotavirus, coronavirus, cryptosporidia and coccidia.
Nutritional scours are typically overdiagnosed by farmers, Chuck says.
“If you’re feeding two litres two-three times a day that’s not nutritional scours. With nutritional scours the calves are still bright.”
Onfarm prevention
The pathogens responsible for calf scours are primarily present in the faeces of infected calves and carrier cows.
The first step, therefore, is to take calves out of the paddock straight away because as soon as calves are born they are exposed to faeces, Chuck says.
Twice-daily picking up of calves is best practice.
“They haven’t had any colostrum yet, their navels are open, they are sitting ducks.”
With navel-ill and joint-ill the bacteria gets up through the navel and can lodge in joints and later spread to the lungs and heart.
Spray calves’ navels with iodine in the paddock and then again in the calf pen. When transporting a calf to the calf shed farmers should ensure the trailer is cleaned daily. Every single calf on the farm goes on to that trailer so the potential for it to get contaminated is huge, she says. Rubber matting is easily hosed down and can be disinfected. Straw is good, but should be changed daily. A cover at the front of the trailer could help to stop faeces flicking up into the trailer. It’s also important to minimise regular traffic driving past the calf sheds as they could be flicking mud and faeces towards the calf pens.
Once the calf is safely in the calf pen the next step is to ensure it has had a feed of colostrum. Colostrum is the calf’s first defence against bacteria, viruses and protozoa. It contains antibodies that a calf needs to fight disease and infection in early life. The absorption of antibodies from the gut declines in the first 12 hours after birth. If a calf is fed two hours after birth its gut will absorb 35% of colostral antibodies compared with only 5% at 12 hours after birth.
Colostrum is absorbed from the gut faster if calves are teat-fed, however, tube feeding is an alternative if necessary, she says.
A key point to remember is that colostrum and transition milk are not the same thing.
Colostrum is the milk produced in the udder in the first milking after calving. The milk from the second to the eighth milking is transition milk, Chuck says.
A consistent feeding regime is also important because any change in nutrition or feeding schedule can cause stress.
Appropriate colostrum storage is important to reduce exposure because bacteria spreads in milk at a rapid rate. Heat treatment of colostrum kills pathogens including salmonella and E coli. Feeding calves with heated colostrum also increases antibody absorption.
Calf housing has to be clean, with adequate space and ventilation. Pens should have appropriate bedding. If calves are dirty and wet the bedding is not working, she says. Solid partitions between pens is key to preventing calves transferring scours and pathogens.
“If you have communication between pens, then you may as well have them all running around together.”
Farmers should use a calf-in, calf-out policy, without moving calves between pens. It’s important not to mix different age groups because calves are exposed to different diseases at different ages, Chuck says.
Having a nursing pen is a bad idea because having all calves go through that means huge potential for infection.
The water source is crucial and it should be at the front of the pen. The back of the pen is the dry area where calves like to sleep.
“Drums provide a temptation to keep filling them up. If a calf poos or urinates in it, it becomes contaminated.”
It’s better to only third-fill troughs full every day and empty them out because it’s easier to pick them up and empty away from the pen.
Treatment
When farmers do find sick calves it’s important to isolate them immediately and remember there is no blanket treatments when calves get sick.
If calves show signs of scours it is important to take multiple samples to the vet to confirm what is causing them so the calf can get the correct treatment option.
“It’s about prompt and appropriate treatment.”
Sick calves will often be dehydrated and should be kept warm and dry.
* References from the CalfWise Right from the Start Field Guide.
Calf morbidity (sickness) rates less than 10% and less than a 3% mortality (death) rate are deemed acceptable. Rates of 10-15% morbidity and 3-8% mortality mean room for improvement, but greater than 15% morbidity and 8% mortality means farmers should seek immediate veterinary advice.
