Beware bale contamination

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Following a very dry start to 2022, baled silage can be prone to soil contamination due to dust and slurry being incorporated into bales, suggests Daniel Robinson from agricultural testing specialist Eurofins Agro UK. “If slurry is not incorporated into the soil the crop will not see the full benefit and any residues risk contaminating bales with harmful bacteria such as enterobacteriaceae. High applications followed by dry weather can also cause the fibre from the applied slurry to lift up into the crop, but this can be detected by accurate ash analysis,” says managing director Daniel Robinson. 

Normal ash levels in the plant should be around 6% to 8%, depending on the crop. Higher numbers indicate additional mineral content which will have occurred due to soil being incorporated into the bale. Soil can contain clostridia, spores and enterobacteria, which can be become a challenge to overcome. “A test will show contamination by providing data on Volatile Fatty Acids (VFAs). Contaminated bales will be high in butyric acid and low in lactic acid, causing dry matter losses. A slower fermentation in the bale will been shown in a higher than optimal pH level which will lead to the bale not storing well and losing protein,” he adds.

Harmful bacteria

Pre-cut dry NIR tests should be carried out to establish sugar levels and nitrate content. During the cutting and baling process, soil can be incorporated into the bale which can lead to potentially harmful bacteria being present in the forage. “A higher pH combined with spoilage and harmful organisms can result in moulds and yeasts growing, resulting in further dry matter loss, and potentially producing mycotoxins which can cause health problems in livestock and impact on productivity.”

Mr Robinson suggests that a dry NIRS test provides true ash content data by burning the sample at 550°c which can help to remove any doubt: 

“Some tests only estimate ash content by using NIR, but we provide a separate ash test to be more accurate. This will prevent contaminated forage from bales being fed out to milkers and means it can be either discarded or fed to other animals.”

The dry NIRS process also provides data for dry matter content, pH levels, ME and 23 other parameters. “By removing the moisture in the sample, we are essentially removing the ‘fog’ that other tests cannot see through. Drying the sample leaves only the solid content which, once ground to a consistent 1mm thickness, is exposed to the infrared light to provide greater detail than any other test on the market,” explains Mr Robinson. 

Uniquely, Eurofins can test samples using only data generated about that forage type. “We can test against all forage types, having calibrations for 27 separate forages. This provides accurate analysis regardless of forage type, whether that be grass or maize, or a mixed whole crop like beans and barley. We benchmark each sample against datasets that only include other like for like samples. The accuracy is unparalleled,” he concludes.

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About Author

Editor of Agronomist and Arable Farmer as well as responsibility for the Agronomist and Arable Farmer and Farm Business websites. After 17 years milking cows on the family farm John started writing about agriculture in 1998 and has since written for a variety of publications and has developed a wide circle of contacts within the industry. When not working John is an avid follower of Stoke City.