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.
Two bacterial causes of calf scours (diarrhoea) are E. coli and Salmonella and, given the opportunity, these can cause 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 in which 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 as little as 20 minutes and here's the thing: 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 in the media, you'll have seen such graphs displaying Covid-19 data, 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!
I wanted to share an analogy I use in school presentations to help demonstrate this concept of exponential growth.
Buy some packs of M&Ms and pose the idea 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).
On a piece of paper, draw eight buckets of calf milk and label them "Generation 1" to "Generation 8".
Start off 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?
Remind your "students" that this number is how many calves that bucket of contaminated milk could infect - then let them 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 are clean.
Unless colostrum is fed straight away, bacterial growth needs to be slowed and one way is by adding the preservative potassium sorbate.
Bacterial growth can also be slowed by cooling colostrum in a refrigerator; remember it takes time for a fridge to do its work and potassium sorbate may still be needed (another science task: give kids a thermometer and get them to graph the temperature every 30 minutes as 10 litres of 37C colostrum cools down to 4C).
Maximise antibody levels in newborn calves by feeding an adequate volume of good quality colostrum (22 per cent or more on the Brix refractometer) as soon as possible after birth.
Vaccination of dry cows with colostral vaccines against E. coli and Salmonella is also recommended; talk to your vet about how to collect and test faecal samples to confirm whether these pathogens are a problem on your farm before investing in a vaccination program.
It is important to know that Salmonella can infect us; always wear gloves when helping out with calves.
The recommendations that help prevent catching COVID-19 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.
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