**4.1. Definition of degree of processing**

Maintaining an optimum degree of processing that maximizes the utilization of wheat grain, and while ensuring animal health is challenging and critical to the livestock industry. The quality of the processed wheat and its particle size can be affected by kernel uniformity, test weight, kernel plumpness, and wheat variety. Kernel uniformity is a major concern for the efficiency of rolling as grain kernels vary in size and shape, making it impossible to achieve optimal processing for all kernels with a single roller setting.

There is no standardized measurement that has been established to assess the degree of grain processing [4]. Coarse, medium and fine are descriptors commonly used in research reports, but these terms are relative, and specific only to the treatments within a given study [26]. As a consequence, medium-processed grain referred to in one study may actually be equivalent to coarsely processed grain in another study. The need for a quantitative measurement of grain processing is evident. In the feed industry, the degree of grain processing has been described using a processing index, which refers to the volume weight (g/L) of grain after processing expressed as the percentage of its volume weight before processing [26]. This index reflects the fact that the more extensively wheat is processed, the finer the particle will be, hence, the lower the volume weight will be, and consequently, the lower the processing index. However, this processing index is influenced by the processing method used. The values generated with dry-rolling can differ substantially, depending on the hardness of wheat kernels, whereas, temper- or steam-rolling make fractured particles that are more likely to adhere together contributing to reduced fines.
