New method to assess digestibility of aquafeeds
Imagine having a magic wand that you could wave over food and determine how nutritious it is. Or having the same wand that could be used to measure the loss of undigested nutrients in faeces?
CSIRO has been developing models that use near-infrared spectroscopy (NIRS) to determine the digestibility of diets and ingredients for aquaculture species. When a beam of near-infrared light is shone on a material, different amounts of each wavelength are absorbed or reflected depending on the composition of the material.
We can use this technology to infer the nutrient profile of diets, ingredients, and faeces to determine how well foods are being digested. Feed is often the highest cost for producers in the industry after labour. In addition, diets that are poorly digested lead to reduced growth in fish and subsequently longer periods to grow fish to market size. Digestibility has traditionally been measured by collecting samples of ingredients, diets and faeces and measuring the chemical composition in the laboratory. However, such analyses are laborious, expensive and time consuming.
This concept has been recently successfully trialed in Yellowtail Kingfish (YTK), an important aquaculture species in Australia. The researchers discovered that NIRS could be used to accurately predict the apparent digestibility of diets with an accuracy close to that obtained by using traditional laboratory analysis (± 1–3% error for most nutrients). Scanning new diets without having to feed them to fish again provided a relatively good degree of error for protein digestibility (5%), but this method was still relatively inaccurate, particularly for other nutrients. While collecting animal faeces and analysing a digestibility marker was still required for accuracy, NIRS can enable much lower volumes of faeces to be collected and shorten digestibility trials, improving welfare and cost of assessing the nutritional quality of diets. This finding and future work in this area is important to continually improve the nutrition of aquaculture species including kingfish, reducing waste and leading to a more efficient and productive aquaculture industry.
More details of the research can be found here https://doi.org/10.1016/j.aquaculture.2021.737624
CSIRO Aquaculture contact
Dr Cedric Simon – Principal Research Scientist