Wheat Straw as animal feed poor quality dry roughage given to the cattle (ruminants) as fillers because straw hardly has any feeding value highly deficient in minerals, vitamins, proteins DCP=0.0; TDN=48.3
Digestive utilisation of straw Straw has Parietal carbohydrates in their cell wall The microbes in the rumen colonise the ingested feed particles The cellulolytic strains partially degrade (or hydrolyse) the cellulose and the hemicelluloses through using the enzyme, cellulase
The degradation of the cell walls requires the microbes to attach themselves to the feed particles so that the enzymes can penetrate inside the fibrous structures, hence the need for the microflora which secretes these enzymes. But wheat straw shows a high proportion of lignified walls, incrusted with lignin in a very complex manner
the lignified walls resist for a long time the microbial degradation and the peristatic mastication (of rumination) and they are thus only digested slowly.
Conditions for good digestiveutilisation In order for the cellulolytic fermentation process to be correctly carried out, the microorganisms in the rumen must be able to find • the nutritive elements which they need for self development and to enable them to degrade (through cellulolysis) the polysaccharides of the cell walls of the wheat straw
the physical and chemical conditions for maintenance of good cellulolysis.
Importance of wheat straw fibrous in nature Generally low in digestibility produce laxative effect after absorbing more water from intestine. cheap and readily available source of energy to the animal body
Need for urea treatment of straw To increase nutritive value (protein source as in rumen microorganism convert nitrogen into protein) of wheat straw To increase digestibility of wheat straw
Urea treatment: principle CO (NH2)2 + H2O -------> 2 NH3 + CO2 urease urea +water ammonia+carbonic gas Once hydrolysis is completed one molecule of urea(i.e. 60 g) generates two molecules of ammonia (i.e. 34 g). 5 kg of urea thus allows production of 2.83 kg of ammonia.
Urea treatment : process Three ways of urea treatment – Treating small quantities within walled enclosures – Treatment of large amounts of forage in stacks or heaps – the use of urine
Convential method of ureatreatment Weigh the urea about 4% of straw. Prepare the urea solution (30-50%) Sprinkle the urea solution on wheat straw Press the straw and seal in the plastic bag or silo or pit or trench
Procedure(new method) Weigh the required amount of urea (4% of straw) Mix it with double the amount of farm manure (as urease source) 30% moisture by adding water Putting this mixture in a bag, piling the straw on the bag, again moistening the straw with water (50% of straw)
Incubating this material for a month under the cover of plastic sheet or mud plaster.
Difference from conventionalmethodThree steps are eliminated preparation of urea solution sprinkling of solution on straw pressing the straw during treatment processResult in labour saving upto 55%However, efficiency is 30% less than the conventional urea treatment method
Urea treatment : Advantages It acts in just the same way on the vegetal matter as if anhydrous ammonia is used: – dissolving the parietal carbohydrates (mainly the hemicelluloses) – swelling the vegetal matter in an aqueous environment, so easing access by the rumens cellulolytic microorganisms
– reducing the physical strength of the cells, so easing mastication by the animal and digestion by the microbes,– enriching the forage in nitrogen, as is also the case if anhydrous ammonia is used.
Key success factors for ureatreatment Practical conditions affecting successful treatment include the: – presence of urease – application rate of urea – moisture content – ambient temperature – the length of the treatment period – the degree of hermetic sealing achieved during the treatment – the quality of the wheat straw to be treated