Nutrients and antiquality factors in different morphological parts of the Moringa oleifera tree

Abstract

Moringa oleifera grows throughout most of the tropics and has several industrial and medicinal uses. The objective of this study was to evaluate the potential of different morphological parts of this tree as animal feed. The crude protein (CP) content of leaves, soft twigs and stems was 260, 70 and 60 g kg⁻¹ respectively. About 64, 79 and 67% of the total CP present in the leaves, twigs and stems respectively was found to be degradable after 24 h in the rumen. The protein insoluble in acid detergent fibre (ADIP), considered unavailable to animals, in these samples was 30, 150 and 170 g kg⁻¹ respectively. About 87% of the total CP was in the form of true protein in the leaves (60 and 53% in twigs and stems respectively). The leaves had negligible amounts of tannins (12 g kg⁻¹), and trypsin and amylase inhibitors, lectins, cyanogenic glucosides and glucosinolates were not detected. The saponin content of the leaves was 80 g kg⁻¹ as diosgenin equivalent, which did not show any haemolytic activity. The phytate content of the leaves was 21 g kg⁻¹. Tannins, saponins, cyanogenic glucosides and glucosinolates were detected in twigs and stems but the concentrations were negligible. Trypsin and amylase inhibitors were not detected in twigs and stems. Phytate contents of both twigs and stems were c. 30 g k⁻¹. In leaves, amounts of all the essential amino acids were higher than the amino acid pattern of the FAO reference protein and comparable to those in soyabeans. The CP and lipid contents of the kernel were 370 and 420 g kg⁻¹ respectively, and the CP of the meal (fat-free) was 610 g kg⁻¹. The kernels and meal are extracted with water and the extract is used for the purification of water in some developing countries. The residues left after water extraction of kernels and meal (designated as extracted-kernel and extracted-meal) had a CP content of 350 and 700 g kg⁻¹ respectively and all of this CP was in the form of true protein. After taking into account the ADIP contents in these samples, c. 38 and 69% of the total protein was calculated to be available in the post-rumen in extracted-kernel and extracted-meal respectively. The pepsin digestibility of these samples was 91 and 84% respectively. The sulphur-containing amino acids in kernel proteins were present at higher concentrations than those specified in the amino acid pattern of the FAO reference protein but other essential amino acids were deficient. Amongst the antinutritional factors mentioned above, glucosinolates and phytate were present in appreciable amounts (65·5 μmol/g and 41 g kg⁻¹ respectively) in meal. Haemagglutination activity was also detected in the meal. The extracted-meal was virtually free of all the antinutritional factors examined except for phytate (67 g kg⁻¹). The leaves of Moringa oleifera and the residue obtained after the recovery of oil and coagulants can be good sources of proteins for animal feeds.