EFFECT OF REPLACING MAIZE WITH RAW OR ROASTED BARLEY (Hordeum vulgare) ON FEED INTAKE, WEIGHT GAIN AND CARCASS CHARACTERISTICS OF COBB 500 BROILER CHICKENS

Abstract

A study was conducted to assess the effect of replacing maize with raw or roasted barley, as an energy source in concentrate based diets, on feed intake, weight gain and carcass characteristics of broiler chickens for a period of 56 days. Based on the ingredients chemical analysis results, seven treatment rations were formulated in mash form. In the control diet (T1), maize was served as the main energy source without barley grain inclusion and six treatment rations in which maize component was substituted with raw barley (T2, T3 and T4) and roasted barley (T5, T6 and T7) weight for weight (w/w) at 33.3%, 66.7% and 100%. Two hundred and ninety four (294) as hatched unsexed Cobb 500 broiler chickens were randomly assigned to the seven treatment diets in a Completely Randomized Design (CRD) with three replicates of 14 chicks per pen. A twophase feeding system was employed, the starter phase up to three weeks and the finisher phase for the remainder up to eight weeks. At the end of the feeding trial, two male and two female broilers (close to mean in weight) per pen were selected and slaughtered for the evaluation of carcass characteristics. The results of the first three weeks revealed that, feed intake of broilers (ranged 37.57 to 37.94 g/chick/day) was significantly (p<0.05) decreased linearly with increasing levels of barley; but no significant (p>0.05) difference in weight gains, growth rate and feed conversion ratio (FCR) were observed up to 66.7% of maize replacement with raw or roasted barley. The high barley diets resulted in a significant increase in FCR. From week 4 onwards, there was no significant (p>0.05) difference on feed intake (ranged 141.85 to 134.78 g/chick/day) and daily weight gains (ranged 40.37 to 51.74 g) of broilers fed maize-based control diet (T1) and broilers fed barley-based diets of 33.3% of maize replaced with raw barley (T2) and up to 66.7% with roasted barley (T5 & T6). In the overall experimental period, the total feed intakes were 102.89, 102.66, 101.65, 98.33, 102.69, 102.48 and 99.94 g/chick/day (SEM=0.36) and daily body weight gains were 38.8, 37.9, 35.9, 31.2, 38.6, 37.1 and 35.3g (SEM=0.60) for T1, T2, T3, T4, T5, T6 and T7, respectively. No significance (p>0.05) difference observed for replacement of maize up to 66.7% with roasted barley (T5 & T6) and 33.3% with raw barley (T2). After the starter phase, no improvement in growth performance of broilers was observed because of raw barley above 33.3% replacement for maize, but FCR was not affected up to 66.7%. The results of carcass evaluation revealed no significant (p>0.05) difference in carcass yield of broilers fed maize-based diet (T1) and broilers fed maize/barley diets (T2, T3, T5 & T6). In general, sole barley diets resulted in poor performance of broilers and roasting had no effect on weight gain and carcass yield, but growth and FCR were improved by roasting when chicks fed high barley diets. It was therefore concluded that replacement of maize up to 66.7% with roasted or raw barley would not adversely affect broilers performance and economic return.