Factors influencing protein utilisation in legume silage and hay for ruminants

Authors: LEON-TINOCO, ANGELA - University Of Maine; GARCIA, MIRIAM - Alabama A & M University; Arther, Christina; BRITO, ANDRE - University Of New Hampshire; ROMERO, JUAN - University Of Maine

Submitted to: Grass and Forage Science
Publication Type: Review Article
Publication Acceptance Date: 6/3/2025
Publication Date: 6/18/2025
Citation: Leon-Tinoco, A.Y., Garcia, M., Arther, C.M., Brito, A.F., Romero, J.J. 2025. Factors influencing protein utilisation in legume silage and hay for ruminants. Grass and Forage Science. https://doi.org/10.1111/gfs.12729.
DOI: https://doi.org/10.1111/gfs.12729

Interpretive Summary: Forages are an important part of dairy rations that support nutrition and sustainability goals for the industry. Many forage legumes can be especially beneficial due to high protein content, but this protein degrades after harvesting which can lead to losses of both usable protein and overall nitrogen. Some forage legumes are more prone to this loss, such as alfalfa, while others have mechanisms that protect some protein from degradation, such as red clover. There are several management techniques that are used to preserve protein in legume forages, such as ensiling and hay production. These techniques need to be carried out carefully to optimize the amount of protein in the product. This review covers what is known about protein conservation in preserved legume forages and highlights work that still needs to be done in order to improve the quality of the end products.

Technical Abstract: Forage legumes are a vital source of sustainable, cost-effective protein for ruminants, but maintaining their protein quality after harvest is challenging. Preserved legumes with high protease activity and no anti-proteolytic mechanisms, like alfalfa, are prone to protein degradation, reducing nitrogen utilization efficiency. Proteolysis by plant proteases begins post-mowing and decreases as forage dry matter (DM) increases during wilting. Optimal ensiling at 35-55% DM minimizes secondary fermentation and protein degradation. In legume hay production, extensive crude protein losses occur due to leaf shattering if the forage is baled above 85% DM. At below 80-84% DM, aerobic spoilage decreases hay digestible crude protein. Effective legume hay preservatives include organic acids with or without buffering. For legume silage, homofermentative lactic acid bacteria and organic acids effectively decrease losses due to undesirable plant protease activity and secondary fermentation. High protein degradation during ensiling reduces nitrogen utilization efficiency, leading to nitrogen pollution and adverse effects on reproductive performance and health from excess rumen-degradable protein and biogenic amine production. Legume forages significantly impact animal production profitability, but the degree to which they do so is dependent on the quality of preserved protein. Proper harvesting and storage protocols are crucial for hay and silage production.