Mineral forage value in the INRAE feeding system for ruminants

International audience

English. Mineral supplementation is necessary for ensuring optimal growth, health and productivity of productive ruminants for almost all diets. However, it also represents an economic cost and can induce supplementary losses of mineral elements in the environment. Thus, mineral supplementation must be adjusted as accurately as possible to insure that the total mineral supplies for animals are equivalent to their requirements. For ruminants, a significant part of the nutrient, and more specifically mineral, supplies are provided by the forages. The mineral contents of forages is highly variable, even within a farm, if we considered the evolution of plant mineral content according to the species present in the field, the meteorological conditions and the plant physiological stage. Thus, the provision of tables of forage mineral composition seems to be an interesting tool to allow a first assessment of mineral supplies allowed by the basal diet before choosing adequate supplementation. The aim of the presentation is be to make a synthesis on the table of forage mineral contents backed in the INRAE feeding system and to share some perspective of evolution. The INRAE feed tables for forage is based on 740 mineral analyses in fresh forages (mainly herbages). Correlations with forage crude protein contents were used to adjust the effect of the plant physiological stage of mineral contents. For macro-element (Ca, P, Mg, Na, K, Cl and S), the effect of conservation was assessed from comparisons between fresh forages and hays and fresh forages and silages. Given that P, Ca and Mg requirements are predicted thanks to a factorial approach in absorbable amounts, true absorption coefficient are determined according to the forage family and the conservation methods according to syntheses from published data. New analytic methods could now allow cheaper and quicker mineral analyses of forage. Thus, emerging questions about these tables are to evaluate their representativeness considering the diversity of pedoclimatic context and species grown in France and to determine if their use can allow a reasonable assessment of mineral supplies allowed by the basal diets, especially for trace elements.