Silage alcohol and cows – a question of balance

The effect of alcohol in the silage fed to cows is being studied in a new project at the University of Aarhus.

Many of us have faced the challenge of trying to walk a straight line after having consumed a wee dram or two! It now appears that cows may also have a problem with balance if they consume alcohol. And this they will do most days – at least if they eat maize or grass silage, which is a major constituent of the daily ration fed to dairy cows in Denmark.

Scientists at the Faculty of Agricultural Sciences at the University of Aarhus will now be examining how different types of alcohol affect cows.

The fact that cows have a balance problem after consuming alcohol does not mean, however, that they lose their ability to walk straight. First of all, the amounts involved are hardly enough to make them fail a breathalyzer test! Secondly, the imbalance that may result is a metabolic one: it would appear that certain types of silage cause an imbalance in their ability to convert feed.

Silage is made from plant materials such as grass or maize that undergo a microbial fermentation. There may be large variations in the quantities of alcohol, lactic acid and short-chain fatty acids produced by the bacteria and also in the types of alcohol produced.

Ethanol is the most common form of alcohol, but some bacteria also produce propanol, which gives silage a bad smell.

Some silage lots may have an alcohol content of several percent. Although this has no obvious effect on lactating cows, they will nevertheless have an increased level of alcohol in their blood for several hours. The question is whether cows in the early lactation stage are able to convert this alcohol as readily as non-lactating cows, as their livers at this time are also having to cope with the increased burden of a high milk production.

The research studies are carried out using a special technique using a ruminal cannula. The technique enables the fate of nutrients, fungal toxins, alcohol and other substances to be closely followed from the ingestion stage and through the rumen, the bloodstream and liver to the final output stage in milk, urine and faeces.
In addition, the cows have a sort of door into their side – a so-called fistula – which enables samples of the rumen content to be extracted.

The desire to examine the effect of alcohol on cows arose as a result of practical experience. Dairy farmers noticed that if the silage had a strange odour, the cows tended also to have production problems. After calving, the cows failed to thrive, they were more likely to be ill and their milk production fell. On the background of around 200 silage samples from around the country, it turns out that the silage with the bad odour was characterised by having a high propanol content.

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Silage alcohol and cows – a question of balance