Mechanochemical Synthesis of a Urea•Proline Cocrystal as Dairy Cattle Feed and Its Effect on Ruminal Degradation

Global nitrogen cycle management is critical due to its central role in food production. Engineering new, sustainable technologies and products that facilitate all facets of nitrogen activation, uptake, and transport is thus critical in reducing the amount of accumulation of activated nitrogen species that contribute to negative environmental impacts. In particular, developing next-generation cattle feed additives or using alternative protein sources can lead to reduced greenhouse gas emissions. In this work, sustainable and scalable mechanochemical methods were utilized for the synthesis of urea cocrystals with the amino acids dl- and l-proline resulting in the formation of the new cocrystals urea•l-proline•H2O, urea2•l-proline, and urea•dl-proline•H2O, which were fully characterized by X-ray diffraction and thermal analysis. The obtained highly soluble hydrated l-proline cocrystal was utilized as an N supplement to enhance the nutritional value of dairy cattle feed, contributing to minimizing environmental contamination by reducing microbial degradation during ruminant digestion. The results presented in this work show that crystal engineering using sustainable mechanochemical methods can be applied to develop new formulations used in cattle supplements to optimize nitrogen use efficiency.