Coronavirus, calves and class

Coronavirus, calves and a home-school class

Herd Management
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Cows are calving, the media is awash with COVID-19 news and kids are schooling from home (or should that be from the farm?) - this article combines these three topics.

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EXPLOSION: Graph B shows how the actual numbers of bacteria in colostrum skyrocket as time goes on. Image by Dr Zoe Vogels.

EXPLOSION: Graph B shows how the actual numbers of bacteria in colostrum skyrocket as time goes on. Image by Dr Zoe Vogels.

Cows are calving, the media is awash with Covid-19 news and kids are schooling from home (or should that be from the farm?) - this article combines the three topics.

Two bacterial causes of calf scours (diarrhoea) are E. coli and Salmonella and can lead to significant disease and death in calves.

Both Salmonella and E. coli are spread through ingesting contaminated colostrum, milk, feed, water or bedding.

E. coli produces a toxin that drives water into the intestines resulting in calves having very watery scours within a day or two of birth and, without adequate oral electrolytes, these calves die from dehydration.

Salmonella can cause disease at any age from birth onwards, with watery to mucous diarrhoea that is often smelly and blood-tinged.

Salmonella can be severe, often with septicemia (blood poisoning), and calves need antibiotic treatment and supportive care to recover.

The way bacteria multiply is a great, real-life example of exponential maths: each grows larger and then splits into two new bacteria, doubling in number every generation (from 1 to 2 to 4 to 8 and so on).

In perfect conditions, a new generation can occur in 20 minutes: the colostrum we need to feed to calves is warm and full of fat and protein and these bugs love it.

Graph A shows how exponential growth is commonly displayed, where each horizontal line represents double the number of the line below.

Graph B shows the actual numbers of bacteria and you can see how bacterial numbers skyrocket as time goes on!

Let's use an analogy I use in school presentations.

Buy some packs of M&Ms and say that calves need only ingest something the size of an M&M to become infected (whether by sniffing/licking manure in the calving paddock or drinking contaminated colostrum).

Draw eight buckets of calf milk and label them "Generation 1" to "Generation 8".

Start with one M&M in the first bucket and then fill the other buckets, doubling the M&Ms as you go - how many M&M "bacteria" are there after eight generations?

Remember this number is how many calves that bucket of contaminated milk could infect - then let "students" eat the chocolate as a reward!

There are several key points about bacterial growth and reducing bacterial calf scours on-farm.

Bacteria grow exponentially and it doesn't take much to spread infection between calves so minimize contamination of milk and colostrum from the start by ensuring collection and storage equipment is clean.

Unless colostrum is fed straight away, bacterial growth must be slowed.

One way is by adding the preservative, potassium sorbate, or by cooling colostrum but it takes time for a fridge to do its work and potassium sorbate may still be needed.

Maximise antibody levels in newborn calves with an adequate volume of good-quality colostrum (at least 22 per cent on the Brix refractometer) as soon as possible after birth.

Vaccination of dry cows with colostral vaccines against E. coli and Salmonella is recommended but ask your vet to test faecal samples to confirm whether these pathogens are a problem on your farm before investing in a vaccination program.

Salmonella can infect us too; always wear gloves when working with calves and remember Covid-19 precautions also apply to diseases in the calf shed: wash hands well with warm soapy water after working and again before eating ... and don't touch your face!

About the author: Dr Zoe Vogels is a veterinarian at The Vet Group, Timboon.

The story Coronavirus, calves and class first appeared on Stock & Land.

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