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Feeding calves acidified milk has health benefits - here's why...

Using formic acid to acidify calf milk will allow longer storage, enable the feeding of colostrum for a longer period, and help reduce harmful pathogens which can easily cause upsets to young digestive tracts. Vet Chris Watson gives us a few pointers.


Acid treatment for calf milk feeding is not new. Many years ago as a student, I remember going to a meeting at a National Agricultural Advisory Service (NAAS) experimental husbandry farm to see acid systems for preserving and feeding colostrum.


The dairy unit used several plastic dustbins of colostrum with ordinary tropical fish tank heaters in them to promote natural lactic acid fermentation to stabilise the product.


The colostrum became acidic, which prevented any further bacterial growth, but still allowed protective benefits of colostrum feeding for longer periods without throwing it away. It also separated the milk curd, mimicking the natural process in the calf’s stomach. A few years later, cold acid feeding for calves became commonplace.


Here, acid was included in the milk powder formulation to prevent bacterial spoilage in milk so it could be available cold ad-lib in front of the calf at all times. Again, there were health benefits and the constant access to cold acid milk resulted in higher growth rates.

Calf feeding

Recently there has again been interest in using added acids to lower the pH of waste milk and colostrum for calf feeding. The problem now is we are more aware of the risks of Johne’s disease being spread through milk and colostrum, so we need to carefully assess risks for calf feeding, especially when milk is bulked together from several cows.


So what is the science and what are the risks? Well, the calf’s stomach will naturally produce acid which clots and separates milk curd. This helps retain milk feed in the abomasum for longer, so it can start to be digested and prevents too much fermentable ingesta getting into the intestines which could promote scouring.


It also helps with killing bacteria and other pathogens which are either ingested with the milk feed or are trying to invade ‘upwards’ from lower in the intestinal tract. This is the main reason potentially harmful bacteria, such as E.Coli, do not normally grow in the stomach or higher reaches of the intestines, and is thus a natural protective process.


It is perfectly logical that acidifying milk before feeding could have some health benefits, as it will enhance this system, more easily regulate it and help prevent scours. The risk of Johne’s being transmitted through communal milk feeding needs to be assessed.


This bacterium will get into milk either directly through the udder from an infected cow or far more likely due to faecal contamination on teats allowing the organism into milk at milking. The risks though are not high if care is taken with clean milking and if high risk cows are excluded as part of your Johne’s health plan.


The acid system commonly used is to add formic acid to milk on farm to produce predictable artificial acidification, not wait for more variable natural fermentation to produce lactic acid. Artificial acidification will kill bacteria straight away.


Producing an acid level of about pH 4.4 will kill most coliform bacteria and it is possible lower pH values (more acidic) could significantly reduce the level of Johne’s bacteria in milk, preventing disease from contaminated milk being passed on. It is thought a pH of 4.1 left for eight hours may achieve this.


We need to be careful though. That is because when testing samples being fed by this system in the practice I often found this lower pH was not being achieved on farm, and it needed a lot of care to get near this level.


It could present a risk if it was not done without proper pH measurement using a meter and enough formic acid being used.


From a practical point of view, most farms found the product difficult to use as the milk quickly separated with the acid treatment and needed more than just a little effort to get it liquid enough to feed.


In practice, a mechanical mixer is usually needed to re-suspend the clot before it can be fed. Additionally, there is no evidence about the effect on viruses such as coronavirus or rotavirus, so it cannot be assumed it will safeguard against these diseases.


However, the acidified route has some benefits. Firstly, it allows you to safely store and use waste milk. Secondly, it is possible to reduce Johne’s disease risk if pooled waste milk is being used to feed calves.


Thirdly, it can improve calf health by reducing gut pathogens and allowing the benefits of continued colostrum feeding. Lastly, it can improve calf growth rates by allowing higher feeding levels.


It is not an answer to Johne’s control though, and should never be assumed as such, but it could be a useful tool for farms which want to use waste milk as part of a healthy calf feeding plan.

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