Forage Legumes for Grazing and Conserving in Ruminant Production Systems

As a plant group, forage legumes present some unique advantages and disadvantages for ruminant production. When compared to grasses or cereals their main advantages are generally (i) low reliance on fertilizer nitrogen (N) inputs, (ii) high voluntary intake and animal production when feed supply is non-limiting and (iii) high protein content. The main disadvantages of forage legumes are generally (i) lower persistence than grass under grazing, (ii) high risk of livestock bloat and (iii) difficulty to conserve as silage or hay. In comparison to grass or legume monocultures, grass + legume mixtures have particular advantages such as more balanced feeding values, increased resource use efficiency and increased herbage production. However, maintaining the optimum legume contents (40-60% of herbage dry matter) to achieve these benefits remains a major challenge on farms. When compared to ruminant systems based on grass or cereals supplemented with fertilizer N, forage legume based ruminant systems tend to have less negative environmental impact on biodiversity, N losses to water and greenhouse gas emissions. Economically, the primary advantage of forage legumes over other forages is their ability to reduce fertilizer N costs and their main disadvantage is usually lower intensity of animal production per ha of land. Despite the numerous benefits of forage legumes for ruminant farming (to the farmer and wider society), their use is reported as being low or declining relative to other forages in many regions. This is most likely a result of their disadvantages being perceived to outweigh their advantages at farm level. This may change if the price ratio of fertilizer N to product (meat/milk) continues to increase as it has done in some regions in recent years.