Ureumammonisering van koring-, hawer- en garsstrooi en hawerhooi. 1. Laboratoriumondersoek na die invloed van vogpeil, ureumpeil en behandelingsperiode op die chemiese samestelling en in vitro-verteerbaarheid

Abstract

Urea ammoniation of wheat-, oat- and barley straw and oat hay. 1. A laboratory investigation into the effect of urea- and moisture level and treatment period on chemical composition and in vitro digestibility. The effect of treatment on the chemical composition and in vitro organic matter digestibility (IVOMD) of wheat, oat and barley straw and oat hay at 25°C was investigated in a 4x3x2x5 factorial experiment. Apart from the four roughages, urea levels of 30, 50 and 75 g kg^-1 roughage, moisture levels of 250 and 400 g kg^-1 roughage and treatment periods of 4, 6, 8, 12 and 18 weeks were included as independent variables. The dependent variables included crude protein (CP) content, urea content, cell-wall constituents (CWC) and IVOMD. Hydrolysis of urea to ammonia was significantly (P ≤ 0,05) improved at the higher moisture level and longer treatment periods. IVOMD values of all treated roughages were increased at all treatment periods investigated. The interaction between treatment period and moisture level as well as urea level indicated that the level of urea ammoniation at low moisture and urea levels may be improved by increasing the treatment period. It is, however, evident that 30 g kg^-1 urea was not sufficient for effective treatment, and that extending the treatment period provided no further advantage. CWC values of the cereal straws and oat hay decreased during each of the treatment periods investigated. In the case of the 3% urea treatment, CWC remained constant from 12 to 18 weeks of treatment.

Die invloed van behandelingskondisies op die chemiese samestelling en in vitro organiese materiaal verteerbaarheid (IVOMV) van koring- hawer-, en garsstrooi en hawerhooi teen 25°C is in 'n 4x3x2x5- faktoriaaleksperiment ondersoek. Benewens die vier ruvoere is ook ureumpeile van 30-,55- en 75 g kg^-1 ruvoer, vogpeile van 250- en 400 g kg^-1 ruvoer en behandelingsperiodes van 4-, 6-, 8-, 12- en 18 weke, ingesluit. Die afhanklike veranderlikes het totale stikstof-, ureum- en selwand(SW)-inhoud sowel as IVOMV ingesluit. Die omsetting van ureum na ammoniak is betekenisvol (P ≤ 0,05) verhoog by die hoër vogpeil en langer behandelingsperiode. Die IVOMV van al die behandelde ruvoere is verhoog by al vyf behandelingsperiodes. Die interaksies van behandelingsperiode met vogpeil en ureumpeil toon dat die vlak van ureumammonisering by 'n lae vog- en ureumpeil verhoog kan word deur 'n langer periode van behandeling. Dit blyk egter dat 30 g kg^-1 ureum onvoldoende was vir effektiewe behandeling, en dat die verlenging van die behandelingsperiode dus geen voordeel sal inhou nie. Die SW-inhoud van al die tipes strooi en hooi is verlaag by al vyf behandelingsperiodes. By die 3%-ureumbehandeling het die SW-inhoud egter onveranderd gebly vanaf die 12- tot 18-wekebehandelings.

Keywords: Barley straw, oat hay, oat straw, treatment conditions, urea ammoniation, wheat straw