Amino acid digestibility of chemically treated and extruder cooked defatted rice polishing.

Rice polishing is a by-product of rice milling. It is a good source of energy and an assortment of amino acids. The anti-nutritive factors associated with rice polishing reduce the availability of amino acids and other nutrients to poultry. Defatted rice polishing (DRP) was chemically treated with 0.4N HCl and 6% H2O2 solutions by soaking in ratio of 1:1.5. After the chemical treatments, one portion of each was further cooked with an extruder cooker maintained at 130oC for 10 seconds. The amino acid digestibility trial of untreated and treated DRP was done using precision fed cockerel assay. Thirty White Leghorn cockerels of 24 weeks of age, having uniform weight, were selected for the experiment and divided into five groups of six cockerels each. Three birds in each group were force-fed treated DRPs @ 25g per bird through crop intubation with the help of a funnel and plunger passed via the oesophagus. The other three were kept without feed throughout the experimental period to measure the endogenous amino acids excreted in the faeces. The excreta voided during 24 hours following force-feeding was collected at 12-hour intervals. The excreta of different groups were weighed, oven-dried and used for amino acid analysis. The results indicated that chemical or chemical plus extrusion cooking decreased the total amino acids present in DRP. The content of several amino acids were reduced as a result of chemical treatment. Further reduction of the amino acid content was observed when the chemically treated DRP were subjected to extrusion cooking. However, the acid (0.4N HCl), acid plus extrusion cooking and 6% H2O2 treatments improved the amino acid digestibility. On the other hand, treating DRP with 6% H2O2 plus extrusion cooking reduced the amino acids digestibility.