THE NUTRITIVE-VALUE OF STACKBURNED YELLOW MAIZE FOR LIVESTOCK - TESTSIN-VITRO AND IN BROILER CHICKS

Differences in the nutritive value of four grades of stackburned yello w maize, obtained from a single storage unit in Mozambique, were exami ned. Samples were analysed for chemical composition, and subjected to the following in vitro assays for estimating digestibility: total diet ary fibre and pancreatin for non-ruminants, and gas production using s heep rumen fluid for ruminant livestock. Samples were also fed to broi ler chicks at 600 g/kg diet in a growth trial. There were no significa nt differences in crude protein contents of the maize samples, but the re was evidence for the development of Maillard reaction products. Det ectable amino acids were lower in discoloured maize, with decreases of 52% in lysine, 35% in arginine, and 15% in glycine concentration in t he most severely discoloured sample compared with control. Total starc h, reducing sugar, acid-detergent fit,re and amylase-neutral-detergent fibre values increased, while total non-reducing sugar content decrea sed with increased discolouration. Total dietary fibre and pancreatin assays indicated a lowering in digestibility of maize with increasing discolouration. Weight gain of chicks (P = 0.0228), efficiency of feed utilization (P = 0.0009) and the metabolizable energy value of diets decreased (P < 0.0001) with increasing stackburn discolouration. There were no significant effects on N retention of diets. In vitro ferment ation using sheep rumen fluid showed a linear decrease in gas producti on with increasing maize discolouration, indicating a reduction in rum en degradability with stackburn.