Introduction to NIR moisture testers (Dr. Michelle Windle)
Click here to download Windle’s PowerPoint presentation.
By Dr. Michelle Windle, Vita Plus forage products and dairy technical service specialist
Near infrared spectroscopy (NIRS) was first discovered in the 19th century, with the first industrial applications in the 1950s. This technology is used today in agriculture, physics, physiology and medicine. The potential it holds for modern applications is virtually limitless.
NIRS is used in agriculture to measure moisture and nutrients, for quality control, to estimate digestibility, and to estimate energy potential of different feeds.
The basic science behind NIRS is that light, made of many different rays of energy with varying wavelengths, is shone at a sample of feed. Different nutrients in the sample (starch, protein, moisture, etc.) absorb different wavelengths of light. Laboratories correlate the amount of each wavelength of light that is absorbed with wet chemistry results of the same feed. They use this information to develop NIRS equations. In this way, light can be used to measure the amount of particular nutrients in a feed. Note that each laboratory has its own set of equations, which it may use and sell to other laboratories.
The benefit of NIRS is that it is fast, easy and cheap. However, the technology does have some pitfalls. NIRS technology cannot be more accurate than the wet chemistry methods used as a basis for the correlation equations. Furthermore, it takes a large library of samples, such as those that pass through a commercial forage laboratory, to create these equations.
In wet, unground samples, NIRS measures moisture accurately and may show large differences in other nutrients, such as starch, protein or fat. However, the background absorbance from moisture readings makes it difficult to detect small changes in nutrients other than moisture. For this reason, on-farm NIRS focuses on moisture.
On-farm moisture testing is important both at harvest and at feeding. For example, harvesting based on moisture produces the best quality feed with the lowest dry matter losses.