Effects of enzyme supplementation and irradiation of rice bran on the performance of growing Leghorn and broiler chickens

Abstract

Three experiments investigated the effects of different concentrations of a crude enzyme preparation (RM-1) and rice bran from two sources (China and Malaysia) on the performance of growing Leghorn and broiler chicks when added to a wheat or a corn soya-bean meal basal diet. In the first experiment rice bran from Malaysia was also irradiated. In this experiment enzyme supplementation of the wheat-basal diet containing 400 g kg −1 Malaysian rice bran improved ( P < 0.05) weight gains up to 9.6% and feed to gain ratio up to 5.4% while irradiation of rice bran at moderate (10 kGy) and high 50 (kGy) doses had no effect ( P > 0.05) on these parameters. Chinese rice bran in contrast to Malaysian rice bran did not respond to enzyme treatment ( P > 0.05). Similar improvements were obtained in the second experiment with RM-1 addition to the corn basal diet containing 250 and 500 g kg −1 Malaysian rice bran, but not when added to the corn diet without rice bran. In addition, rice bran did not have any deleterious effects ( P < 0.05) on growth and feed conversion efficiency of Leghorn chicks when incorporated into diets without enzyme supplementation. In contrast to the results with Leghorn chicks, the performance of broiler chicks was depressed ( P > 0.05) when 250 and 500 g kg −1 Malaysian rice bran was added to the diet. Chicks fed the diet containing 500 g kg −1 rice bran compared to those fed the control diet had decreased body weight gains (17%) and increased feed to gain ratios (11%), relative weights of the gastrointestinal tract (40%), and incidence of vent pasting (from 0 to 67%). Enzyme addition (10 mg kg −1) to the 500 g kg −1 rice bran diet improved ( P < 0.05) the feed to gain ratio (4%), and reduced the size of the gastrointestinal tract (7%) and the incidence of vent pasting (from 67 to 33%). These studies indicate that high concentrations (400–500 g kg −1) of rice bran can be added to the diet of Leghorn chicks, at least over a relatively short period of time, without a deleterious effect on performance while as low as 250 g kg −1 rice bran in the diet can depress broiler chick performance. The crude enzyme when added to diets containing rice bran produced equivocal results in chicks as it improved performance with one rice bran but not the other.