The effect of substituting Kenyan Serena sorghum for maize in broiler starter diets with different dietary crude protein and methionine levels

Currently there is interest in many parts of Africa in developing crops which can be grown in the semi-arid regions to help alleviate a feed and food shortage. Sorghum is well suited to cultivation in areas that are too dry or too hot for the production of other cereals. Although sorghum is similar in composition to maize, brown sorghum contains the anti-nutritive factor tannin. The possibility of overcoming any detrimental effects of sorghum tannin on the growth rate and feed efficiency of broiler chicks by supplementing the diet with intact crude protein (CP) or D,L-methionine (Met) was studied in two 4-week feeding trials of 280 chicks each. In each trial the effects of feeding maize or brown sorghum were compared under three dietary specifications (control, increased CP, increased Met). In both trials, the tannin content of the control brown sorghum diet was 1.3% catechin equivalents (dry matter basis). A seventh diet, with dietary specifications similar to the control diets, was included in each trial for comparison with the six main diets. In Trial 1 the seventh diet contained a combination of white and brown (w/b) sorghum (50/50, w/w) as the main energy source while in Trial 2 the main energy source of the seventh diet was white sorghum alone. In both trials there were no significant differences in final body weight among the three control diets (770.2, 759.0, and 753.0 g for the broilers on the maize, brown sorghum, and w/b sorghum diets in Trial 1; and 822.7, 764.8, and 827.2 g for the broilers on the maize, brown sorghum, and white sorghum diets in Trial 2). In addition, there were no significant differences in feed conversion ratio (FCR) between the maize and brown sorghum fed broilers (2.01 vs. 2.03 in Trial 1; and 1.82 vs. 1.94 in Trial 2). In Trial 2, however, the FCR for the broilers receiving the white sorghum diet (1.73) was significantly lower than for those receiving the brown sorghum control diet (1.94), but not significantly different from those receiving the maize control diet (1.82). There was no effect of Met supplementation on final body weight or FCR in either trial. In Trial 1, increasing dietary CP content had no effect on final body weight or FCR for both the maize and brown sorghum fed broilers. In Trial 2, however, increasing the dietary CP content resulted in significantly lower final body weights (708.2 vs. 822.7 g) and higher FCR (2.06 vs. 1.82) for the maize fed broilers. The results of this study suggest that high tannin sorghum can be substituted for white maize in broiler starter diets with no significant adverse effects on growth or feed efficiency. The dietary treatments of increased CP or Met levels, which have been reported to be successful at overcoming the detrimental effects of sorghum tannins, were not required. A leg abnormality previously reported by other sorghum researchers was observed in both trials but the incidence and severity were low. Broilers receiving maize based diets with increased Met were most affected suggesting that the abnormality is related to increased Met and not to tannins.