By-products of some novel oil seeds for feeding: laboratory evaluation

Abstract

Thirty-six samples of intact seeds or by-products from expelling or solvent extraction of the novel oil seeds Crambe abyssinica, Dimorphotheca pluvialis, Euphorbia lagascae, Limnanthes alba and Calendula officinalis were collected and tested for proximate analysis and composition of the mineral, protein and cell wall fractions. Apparent digestibility of organic components in ruminants and pigs was determined in vitro with rumen fluid and enzyme cocktails. Crambe and limnanthes were also tested for contents of glucosinolates and their derivatives. Decortication of crambe seeds prior to defatting improved nutritive value as expressed by decreased fibre content (from 402 to 108 g cell walls, determined as neutral detergent fibre (NDF) per kg fat-free dry matter (ffDM)), increased crude protein (CP) fraction (277 vs. 490 g CP kg −1 ffDM) and increased in-vitro digestibility (% of organic matter digested by rumen fluid (dOt): 57.3% vs. 85.0%). As glucosinolate content increases, adequate detoxification is essential to safeguard the animals consuming the feed. Decortication of euphorbia seeds resulted in improvement of feeding characteristics of its by-products (NDF 381 vs. 202 g kg −1 ffDM; CP 417 vs. 608 g kg −1 ffDM; dOt 55.3 vs. 74.9%). Detoxification of such by-products requires further study. By-products of dimorphotheca showed considerable variation in composition (84–263 g ash, 203–266 g CP and 419–538 g NDF kg −1 ffDM) and unsatisfactorily low digestibility (dOt 51.4 ± 5.8%). Limnanthes meal showed a favourable amino acid profile but was less well digested (dOt 67.4%) than expected from the level and composition of the fibre fraction. Calendula meal was poorly digested (dOt 34.9%) due to its extremely high fibre content (731 g NDF kg −1 ffDM). Adequate processing is essential for the profitable inclusion of some of the byproducts of novel oil seeds in livestock diets.