Researchers at the Department of Animal and Veterinary Sciences have developed a new method to measure carbohydrates in feed ingredients. With near-infrared spectroscopy (NIRS), it is now possible to rapidly determine various carbohydrates and lignin in feed for monogastric animals such as pigs and poultry. The method is technical, but the benefits are clear: faster feed analysis can lead to more precise nutrition, better animal welfare, lower feed costs, and reduced environmental impact.

Why are carbohydrates and lignin important?

Carbohydrates make up most of the feed for monogastric animals. They represent a large group of compounds with different structures and nutritional values. Sugars and starches are digestible carbohydrates that provide energy. Other carbohydrates cannot be broken down by the animals’ own enzymes. These are dietary fibres, which are instead broken down by bacteria in the gut. How easily they break down depends on their structure. Fibres can vary in chain length, consist of different sugar units, and be linked in different ways. Lignin is also part of the fibre fraction. It is not a carbohydrate, but it is closely bound to plant fibres and affects how easily they are broken down. The composition of carbohydrates is therefore crucial for digestion, nutrient absorption, and animal health.

Familiar technique - new application

NIRS is a rapid method that requires minimal sample preparation. Near-infrared light is simply exposed to the sample. Some light is absorbed, while some is reflected. The reflected light is measured over the near infrared spectrum – creating a kind of fingerprint of the sample’s chemical content. By using statistical methods, researchers can then develop models that can predict the concentration of specific compounds.

NIRS is already used to measure water, protein, fat, ash, starch, and fibre in grains. What’s new is that researchers have now applied the method to measure many different types of carbohydrates simultaneously in various feed materials.

Limitations of traditional analyses

Traditional wet chemical methods for measuring carbohydrates are slow, expensive, and require specialized technical staff and equipment. Moreover, the most used methods only measure parts of the fibre content – such as crude fibre, NDF, and ADF. These values do not provide a complete picture of fibre’s composition and nutritional role.

Recognizing patterns in light

The researchers examined 304 feedstuff samples. These included grains (barley, wheat, triticale, rye, maize), by-products (bran, gluten, hulls), protein-rich feedstuffs (soybean, rapeseed, peas, lupin), and fibre-rich feedstuffs (lucerne, grass, beet pulp). The samples were first analyzed using classical methods and then scanned with NIRS. By comparing the results, the researchers developed models that can predict the chemical composition of the samples.

“We’ve scanned our fairly large collection of samples, which we’ve analyzed over decades,” explains Professor Knud Erik Bach Knudsen from Department of Animal and Veterinary Sciences at Aarhus University. He has dedicated most of his career to studying carbohydrates and their role in animal and human nutrition.

Precision and Potential

The models showed high precision – over 90% – for most carbohydrate types. Starch and cellulose were determined with the highest accuracy and are suitable for routine control. The fibre- fraction of polysaccharides (NSP) was also measured with good precision, though with slightly more uncertainty. The same applies to some of the components within the NSP fraction. Glucose and oligosaccharides, which are especially found in protein-rich feedstuffs like legumes, were measured with lower precision. This was partly due to the limited number of samples containing these compounds.

“Whether the precision is sufficient depends entirely on how the results will be used,” says Associate professor at Department of Animal and Veterinary Sciences Samantha Joan Noel, who led the NIRS analyses and model development. “In some cases, the estimates are good enough, in others not. The major advantage of the method is that you get values for many components at once – values that would otherwise be expensive and time-consuming to obtain,” she explains.

“We’re not the only ones who have used NIRS to measure carbohydrates,” adds Knud Erik Bach Knudsen. “But we’ve included more carbohydrate types and analyzed a wide range of samples. Importantly, we’ve also validated the method with an independent data set  of about 20% of the samples. That makes our study unique.”

A step toward more precise feeding

With NIRS, feed can be analyzed quickly and cost-effectively. This makes it easier to tailor feed to the animals’ needs, improve health and growth, reduce waste and environmental impact, and use additives – such as enzymes – more effectively. Precision feeding is about giving animals exactly the amount and type of nutrients they need. This requires detailed knowledge of feed composition – and NIRS can be a valuable tool.

“We’d like to continue developing the method with more samples, but that requires funding,” says Samantha Noel. “And if the method is to be used in practice, it will require an agreement with a company interested in commercializing it,” she concludes.

Additional information

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