Effects of Cultivar and Plant Fraction on Oxalate Content and Nutritional Composition of Napier Grass and Selected Non-Napier Forages

Napier grass (Pennisetum purpureum) is an important tropical forage valued for its high biomass yield and carbohydrate content, which supports efficient rumen fermentation. However, its utilisation is limited by antinutritional factors, particularly oxalic acid, which is generally higher in Napier grass than in other tropical forages. Excessive oxalate intake impairs calcium and magnesium metabolism, which can lead to metabolic disorders and renal dysfunction in animals. In this study, the effects of cultivar and botanical fraction on the oxalate content and proximate composition of Napier grass and selected non-Napier forages were investigated. Seven Napier cultivars (Dwarf, Taiwan, Zanzibar, King, Purple, Pakchong, and Indian), as well as Indigofera tinctoria and Trichanthera gigantea, were collected from farms in Kedah and Kelantan, Malaysia. The leaves and stems were analysed separately for soluble oxalate, total oxalate, and composition of constituents. The results showed that Dwarf Napier had the highest crude protein content, but also an increased content of soluble oxalate, especially in the leaves. For all forage varieties, the oxalate content was consistently higher in the leaves than in the stems, highlighting the importance of variety selection and the ratio of leaves to stems in feed formulation to optimise nutritional value while minimising the risks associated with oxalate in ruminant diets.