Comparison of different indicators for the evaluation of feed mixing efficiency

• The time required to achieve homogenous dry and wet feed mixes was between 65 and 80 s.
• Most of the tested indicators had mixing CV below 5%, except vitamin B2 (21%) and CuCl2 (15%).
• l-Threonine showed the best mixing CV (3%).
• Powder and liquid sources of industrial amino acids had similar mixing efficiency.

The mixing process is essential for manufacturing animal feed, and due to the increased use of low-inclusion ingredients, its efficiency becomes even more important, as well as the methods to evaluate this efficiency. This study aimed to compare different internal and external indicators of feed mixing efficiency. Using an experimental horizontal paddle mixer, we evaluated dry mix cycle with dl-methionine 99%, L-lysine HCl 99%, l-threonine 98%, inorganic minerals (NaCl, CuCl2, MnSO4 and ZnSO4), vitamin B2 80%, and MicroTracer® (external indicator), and the wet mix cycle with dl-HMTBA (liquid analogue of methionine) 88% and liquid l-lysine 50%. The time required to achieve a homogeneous mix was also evaluated based on the coefficient of variation (CV) of such indicators every 15 s between 20 and 155 s of mixing. The mixing CV was below 5% for most of the tested indicators, except for vitamin B2 (21%) and CuCl2 (15%), whereas l-threonine showed the best mixing CV (3%). Powder and liquid sources of methionine and lysine had similar mixing efficiency at the end of the mixing cycles. The study indicated that the usage of powder and/or liquid industrial amino acids as internal indicators is suitable for evaluating the mixing efficiency as well as time required for achieving homogeneous mixes of feed mixers.