Improving the nutritive value of Nigerian rubber kernel (Hevea braziliensis) products through processing. II. Apparent nutrient and metabolizable energy values

Abstract

A metabolism trial was designed to investigate the effect of method of processing (raw sundrying, oven-drying, soaking, autoclaving, and roasting), rate of inclusion (ROI), and method of estimation (regression or single-level assay) on apparent nutrient and metabolizable energy value of full-fat and fat-extracted rubber kernel meals and oil using 264 seven-day-old Ross broiler chicks. The oil and full-fat meals were incorporated at levels to provide 40, 80, and 120 g kg-1 of added oil in the basal diet. Fat-extracted meals were also included at the equivalent levels in the full-fat meals. Apparent metabolizable energy (AME) values were not significantly influenced by ROI with the values determined by regression being more precise than those estimated by single-level assay. Heat treatment generally improved AME, and for the full-fat meals, moist heating heat-processing (autoclaving or soaking prior to oven-drying) was more effective than dry-heating (oven-drying and roasting). The AME of the roasted full-fat was 16.1 MJ kg-1 dry matter (DM) while the mean value of soaked and autoclaved full-fat (21.3 MJ kg-1 DM), was significantly greater than the mena of oven-dried and roasted full-fat meals (18.7 MJ kg-1 DM). Rubber kernel oil had an AME value of 35.3 MJ kg-1 DM. An improvement in energy and nutritive value brought about by processing suggests inhibition of inherent deleterious factors, the specific nature and definite levels of which would require