“Colostrum must be clean and not contaminated with bacteria,” he said.
“Calves are born with a functioning immune system, but few immune resources – like a gun without ammunition. Feeding plenty of clean, antibody-rich colostrum as soon as possible after birth gives a calf a chance to absorb antibodies directly into her blood. They provide temporary immunity until the calf develops her own antibodies.”
This passive transfer could fail, however, if high levels of bacteria were present in colostrum as they have been shown to reduce the uptake of antibodies. When the calf has too little immunity acquired from colostrum to protect her from pathogens, she gets ill.
Current data suggested that total bacteria levels up to about 250,000 cfu/ml* may not have a major impact on absorption efficiency, but as many as 33% of farm samples may well be double that figure – “something I call ‘bacteria soup,” he said.
Colostrum could easily become contaminated with bacteria, particularly coliforms, right from the start with poor hygiene at milking, followed by a dirty dump bucket. But it’s the less-than-ideal storage conditions that really allowed bacteria to take hold.
“Stored in a typical dairy temperature, the shelf-life of colostrum is just 24 hours. At 21C, the number of coliforms doubles every hour; by 12 hours there can be over one million cfu/ml in the calf’s first feed, hence the term bacteria soup.”
The implications for gut health were serious (see box) and obvious, but long-term, chronic scours could also lead to pneumonia. This was because the calf’s immune system was compromised by fighting off infection in the gut, leaving her with a weakened defence against respiratory infections, especially bacterial infections in the upper lung.
Because the calf wasn’t growing and gaining weight, she wasn’t making the antibodies needed to replace those originally from colostrum.
“The antibody ‘fuel tank’ is starting to run dry at about three weeks of age. The heifer is very vulnerable to respiratory infections at this point. This isn’t good, even if we treat her and she recovers, because we know the kind of permanent damage that pneumonia does to lungs.”
That is why Leadley was keen to promote culturing colostrum for bacteria. The aim was to identify high risk situations – coliform counts of more than 10,000 cfu/ml, or total bacteria counts of more than 100,000cfu/ml (see shaded box). For onfarm decision-making about hygiene and colostrum handling, he said only approximate bacteria numbers were needed.
“It’s reasonable to expect coliforms to be less than 5,000 cfu/ml and total bacteria count to be under 50,000 cfu/ml. On many UK farms, I see the total plate counts well over 100,000cfu/ml and that is all we need to know.”
He suggested a testing schedule based on calving pattern and problem level. For block calving herds, sampling as-fed colostrum as soon as calving begins, allowed any improvements to be made before the bulk of the herd calved. Resampling every fortnight would pick up any significant drift from the correct colostrum harvest and handling protocol.
“For year-round calving herds, the sampling and culturing schedule depends on the lab results: where 80% of the samples are below the farm thresholds, then I recommend a quarterly culturing schedule. The sampling protocol involves collecting about 10ml of colostrum from the nipple on the nursing bottle, or the tip of the drenching tube, just before feeding a newborn calf.”
Coliform bacteria can double in numbers every 20 minutes at cow body temperature, as demonstrated by Sam Leadley’s coffee grinds.
Leadley liked to see at least five samples, whatever the calving pattern, from each stage to get a reliable picture. For problem herds with high bacteria counts, the next step was to sample the colostrum at different stages: in the collection bucket, other storage containers, and sampling after refrigeration if colostrum was stored.
“Of course, the results from 10 samples will be more reliable than that from five, but we have to consider the cost of culturing,” he said.
Colostrum testing was now available in Britain for as little as £20/sample, DairyCo scientist Dr Jenny Gibbons said.
“Lab testing for the bacterial load in colostrum is a great way to identify high-risk farms. While it was easy to see gross contamination and dirty equipment, it wasn’t always possible to see bacteria levels, so it was important to assess colostrum hygiene,” she said.
“We know that the common causes of a high bacteria count are dirty milking equipment, poor cooling and poor udder preparation. Coliform counts above 10,000 cfu/ml indicate poor udder preparation: put simply, muck left on teats ends up in the colostrum.
“If your samples come back with high coliform levels, you’ll need to look at your hygiene and cleanliness routines for possible sources of contamination. Containers, for instance, are ideal breeding grounds for bacteria. To minimise the risk to your calves, all equipment should be cleaned thoroughly after each feeding, with scratched or pitted equipment replaced as it provides a perfect location for bacteria. When washing feeding equipment, first rinse with lukewarm water to remove milk residue, manure and dirt. Don’t use hot water as this simply makes the milk proteins stick to surfaces and, again, become a breeding ground for bacteria.”
As part of DairyCo’s research partnership, led by the University of Nottingham, researchers at the Royal Vet College have been working to create best-practice guidance on calf colostrum management.
Producing and harvesting top quality colostrum with high levels of immunoglobulins, yet low bacterial contamination, would be repaid in healthier, more productive heifers. Leadley said US studies showed that, after proper colostrum feeding, calves had fewer cases of scours in their first 21 days, compared with those that had insufficient colostrum.
The death rate in well-fed calves was up to 12% less, while vet and med costs averaged US$4/head less.
“Weight gains, as well as feed conversion rates are also better,” he said.
“Testing colostrum, therefore, isn’t a cost – it’s an investment in your herd’s future.
Setting the standard
Dr Sam Leadley’s colostrum coliform bacteria standards for calf health from onfarm observations.
- < 5000 cfu/ml – low impact, minor scours problems in fewer than one-third of the calves.
- 5000-20,000 cfu/ml – moderate scours problems in up to three-quarters of the calves, tends to last seven to 10 days rather than only two to four days.
- 21,000-50,000 cfu/ml – occasional deaths at three to five days, usually severe scours between seven and 21 days in nearly all the calves.
- 51,000-250,000 cfu/ml – very severe scours problems, enterotoxaemia starting to be a problem causing rapid onset of death, bloated calves in two to six day range, scours problems that won’t stop up to three weeks of age affecting nearly all calves, respiratory illness frequently a secondary infection.
- More than 250,000 cfu/ml – frequent mortality associated with enterotoxaemia, nearly all the calves have severe scours, most of the calves require antibiotic treatment, many require IV or subcutaneous fluids.
Cleanliness checklist
Dr Sam Leadley’s checklist for reducing coliform counts in colostrum
- Clean teats in the dairy
- Clean milk dump buckets including lids, valves and gaskets
- Clean buckets and/or bottles into which to pour colostrum
- Covers for all milk dump buckets and buckets, especially in the dairy
- Prompt feeding of fresh colostrum. The goal is to feed in less than 30 minutes after collecting colostrums – sooner is better
- Cool colostrum promptly before for storage. The goal is to get colostrum under 16C in less than 30 minutes after collection – sooner is better
- Clean containers for stored colostrum
- Clean feeding bottles and teats
- Clean tube feeder including the oesophageal tube
- Feed warmed-up colostrum promptly. The goal is to feed in less than one hour after it comes out of the refrigerator.
For further information visit www.calffacts.com
