THE EFFECT OF SUBSTITUTING KENYAN SERENA-SORGHUM FOR MAIZE IN BROILERSTARTER DIETS WITH DIFFERENT DIETARY CRUDE PROTEIN AND METHIONINE LEVELS

Currently there is interest in many parts of Africa in developing crop s 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 tha t are too dry or too hot for the production of other cereals. Although sorghum is similar in composition to maize, brown sorghum contains th e anti-nutritive factor tannin. The possibility of overcoming any detr imental effects of sorghum tannin on the growth rate and feed efficien cy of broiler chicks by supplementing the diet with intact crude prote in (CP) or D,L-methionine (Met) was studied in two 4-week feeding tria ls of 280 chicks each. In each trial the effects of feeding maize or b rown 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 matt er 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 whi te and brown (w/b) sorghum (50/50, w/w) as the main energy source whil e in Trial 2 the main energy source of the seventh diet was white sorg hum alone. In both trials there were no significant differences in fin al 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 maiz e, brown sorghum, and white sorghum diets in Trial 2). In addition, th ere were no significant differences in feed conversion ratio (FCR) bet ween 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 lo wer than for those receiving the brown sorghum control diet (1.94), bu t not significantly different from those receiving the maize control d iet (1.82). There was no effect of Met supplementation on final body w eight or FCR in either trial. In Trial 1, increasing dietary CP conten t had no effect on final body weight or FCR for both the maize and bro wn sorghum fed broilers. In Trial 2, however, increasing the dietary C P 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 subs tituted for white maize in broiler starter diets with no significant a dverse 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 re quired. A leg abnormality previously reported by other sorghum researc hers was observed in both trials but the incidence and severity were l ow. Broilers receiving maize based diets with increased Met were most affected suggesting that the abnormality is related to increased Met a nd not to tannins.