The growth habits of tropical legumes affect the nutritive herbage value more than harvesting frequency

Abstract

Context Harvest regimes may change the nutritive herbage value of tropical legumes depending on growth habit and regrowth capability. Aim This study aimed to compare the nutritive values of butterfly pea herb (Clitoria ternatea L.) to the sub-shrub stylo cv. Campo Grande (Stylosanthes capitata Vog. × Stylosanthes macrocephala M. B. Ferr. & N. S. Costa) and shrub hedge lucerne (Desmanthus pernambucanus (L.) Thellung) harvested at 60 and 90-day regrowth. Methods The trial used a randomised complete block design with a split-plot arrangement and four replicates. Leaves and stems were collected in the rainy seasons of 2019 and 2020 and analysed for chemical-bromatological composition and digestibility. Key results Higher crude protein contents were observed in butterfly pea (233 g/kg) than in stylo leaves (179 g/kg). Elevated proportions of insoluble fractions of carbohydrates (259 g/kg) and proteins (137 g/kg) were found in hedge lucerne leaves, also extremely high levels of condensed tannins (303 g/kg). High levels of dry matter digestibility were found in stylo (788 g/kg) and butterfly pea leaves (774 g/kg). The harvest frequencies changed the nutritive values inconsistently. Conclusions The butterfly pea herb and the sub-shrub stylo cv. Campo Grande can be managed under varied harvest frequencies without changing the nutritional value significantly. Prolonged harvest intervals must be avoided in hedge lucerne management for animal feeding because of its high contents of secondary metabolites. Implications This study restated the already-known nutritional variations among tropical legumes due to different growth habits and revealed a significant presence of condensed tannins in hedge lucerne’s leaves.