The Effects of Sorghum Type and Inclusion Level, Protein Level, and Pelleting, on the Feeding Vaue of Sorghum-Based Broiler Chicken Rations

Abstract

SUMMARY : A study was carried out to investigate the effects of sorghum type, sorghum inclusion level, protein level and pelleting, on the feeding value of broiler chicken rations. The study consisted of three experiments. In experiment l, 1200 commercial broilers were used in a 2x3x3 Factorial arrangement, in a Randomized Complete Block Design. Two commercial blends of red and white sorghum, of tannin levels 1.24% and 0.05% respectively, were used to substitute for white maize in broiler rations at three inclusion levels of 0, 29 and 58%. The diets were formulated with three crude protein levels of 19% (low), 20% (standard), and 22% (high). The levels of lysine and methionine + cystine were adjusted to vary with the levels of crude protein. In the second experiment 1280 commercial broilers were used in a similar factorial arrangement and experimental design. This comprised two feed forms; mash and pellet, three sorghum blends; white, red and light red, and three sorghum inclusion levels; 0, 29 and 58%. All the diets in both experiments were isocaloric at 3000 kcal ME/kg. Feed and water were provided ad libitum, and weekly data on body weight gain, feed intake and feed:gain ratio (fcr) was collected. The third experiment was a variable cost evaluation of experiment l. Red sorghum diets significantly depressed both the growth rates and the fcr, compared to white sorghum or maize diets. There was no significant difference between the standard and high protein levels in both body weight gain and fer. Low protein diets resulted in significantly (p<0.05) lower body weight gain and poorer fer. Diets containing red sorghum resulted in significantly (p<0.05) better performance at the 29% than the 58% V inclusion level. There was no difference in performance at 29 and 58% sorghum inclusion levels for chickens on white sorghum diets. Lncreasing protein levels above the standard, did not significantly improve on the feeding value of red sorghum for broiler chicken, and this indicates that the depression of protein utilisation might be only one of the effects of sorghum tannin. Commercial blends of white sorghum containing 0.05% tannin, can completely replace maize at up to 58% i.nclusion levels in broiler rations. There was no beneficial effect of pelleting on the weight gains, feed intake or feedzgain ratio. Difficulties in feed intake were associated with inadequate crumbling of the pellets. The pelleting of diets containing high tannin sorghum appeared to be of benefit in improving the fcr. This however, needs to be confirmed by more work using broiler rations of standard nutritive value and pellets of smaller size. The cost of the feeds was the largest contributing factor to the cost of production at 59.7%. The purchase price of the day old chicks was the next highest cost at 31.2%. Electricity, veterinary and labour costs accounted for 5.7, 1.2 and 0.8% of the production costs respectively. Protein supplementation raised the cost of the feeds but did not improve on the feeding value of the sorghum diets. Lowering the inclusion level significantly lowered the cost of production with white sorghum diets, but had no significant effect with red sorghum diets. All sorghums irrespective of tannin content cost the same in the markets. A price mechanism is therefore necessary to ensure that the red sorghums (high tannin) which have a lower feeding value for monogastric animals are sold cheaper than the white ones (low tannin) which are preferred by humans. This would free the high tannin sorghums for animal feeds at a lower price than that of maize.