Invloed van langdurige behandeling van koringstrooi met ureum of 'n ureum/bytsoda-kombinasie tydens die baalproses op die voedingswaarde daarvan vir skape (1989)

Effect of prolonged treatment of wheat straw with urea or a urea/caustic soda combination during baling on the nutritional value thereof for sheep . A study was undertaken to investigate the treatment of wheat straw with urea or urea plus caustic soda (combined treatment) during baling. Wheat straw treated as above, as well as wheat straw ammoniated with urea using a stack method, was evaluated in an intake and in vivo digestibility study with sheep following 2, 4, 8, 12 and 18 weeks of treatment. Untreated wheat straw was evaluated solely for reference purposes. Voluntary intake of all three treatments tended to be at its lowest level after two weeks of treatment. The voluntary intake of the combined treatment straw was higher (P ≤ 0,05) than that of the urea ammoniated straw, whether treated in the stack or in the baler (38,7 and 28,5% respectively). The organic matter (OM) digestibility of all three treatments increased by 22,7 to 28,9% after 2 weeks of treatment. The OM digestibility was significantly improved (P ≤ 0,05) by increasing the treatment period from 2 to 12 weeks. The combined treatment with urea/caustic soda did not show any additive effect with regard to OM digestibility. The neutral detergent fibre, acid detergent fibre and hemicellulose digestibilities tended to improve as the treatment period increased. The crude protein digestibility of the urea ammoniated straw was significantly (P ≤ 0,05) lower after 12 and 18 weeks treatment compared to a treatment period of 2 weeks. The nitrogen balance of sheep fed all three treated straw diets varied around zero, and no significant differences occurred. 'n Ondersoek na die behandeling van koringstrooi met ureum of 'n ureum/bytsoda-kombinasie tydens die baalproses is onderneem. Bogenoemde behandelings sowel as ureumbehandelde koringstrooi (miedmetode) is in 'n inname- en in vivo -verteringsstudie met skape 2,4,8, 12 en 18 weke na behandeling geevalueer. Onbehandelde koringstrooi is slegs vir verwysingsdoeleindes geevalueer. Vrywillige inname het by al drie behandelings geneig om die laagste te wees by die koringstrooi wat vir slegs 2 weke behandel is. Die vrywillige inname van die kombinasie-behandelde koringstrooi was hoer (P ≤ 0,05) as by ureum- geammoniseerde strooi, hetsy dit behandel is volgens die miedmetode of in die baler (38,7% en 28,5%, onderskeidelik). Die organiese materiaal(OM)-verteerbaarheid is 2 weke na behandeling van die strooi verhoog met 22,7 tot 28,9% vir die onderskeie behandelings. Die OM-verteerbaarheid van al drie behandelings is verder betekenisvol (P ≤ 0,05) verhoog met 'n verhoging in behandelingsperiode vanaf 2 tot 12 weke. Die kombinasiebehandeling met ureum/bytsoda het geen additiewe effek getoon met betrekking tot die OM-verteerbaarheid nie. Die selwand-, suurbestande vesel- en hemisellulose verteerbaarheid het geneig om toe te neem met toename van die behandelingsperiode. Die ruproteienverteerbaarheid van die ureum-geammoniseerde strooi was betekenisvol (P ≤ 0,05) laer na 12- en 18-weke behandeling in vergelyking met 2-weke behandeling. Die stikstofbalans van skape op al drie behandelde strooidiete het rondom nul gevarieer en nie betekenisvol verskil nie. Keywords : Ammoniation, causic soda, in vivo digestibility, treatment period, urea.