Growth-suppressingand related effects on rats of unextracted and ethanol-extracted grains of certain sorghum cultivars

Abstract

Samples of the grains of 6 different sorghum cultivars, whole as well as ethanol-extracted to reduce tannin content, were fed in balanced diets to young male rats (12 per sample) in an experiment aimed at assessment of the effect of sorghum grain feeding on growth rate and liver lipid content, as well as determination of the digestibility of the sorghum protein. The possible involvement of tannins in the biological utilisation of the sorghum grains was also considered. The results revealed statistically significant differences among cultivars, mainly in respect of effect on growth rate and protein digestibility. With regard to the possible cause(s) of such differences it was found that there were significant correlations between (i) growth rate and protein digestibility; (ii) protein digestibility and dietary tannin content; and (iii) growth rate and dietary tannin content. The degree of correlation observed varied in descending order from (i) to (iii). It was concluded that differences among cultivars in respect of effect on growth were essentially due to differences in protein digestibility, and that the digestibility figure provides the most convenient basis for selection of cultivars for bre~ding purposes. Observed sample-to-sample variations in protein digestibility and effects on growth were only partially explicable in terms of variations in dietary tannin content. The data obtained on liver lipid content could not be explained on the basis of the reaction involving detoxification of gallic acid through O-methylation and the consequent reduction of available supplies of the methyl donors, methionine and choline.

S. Afr. Med. J., 48, 1691 (1974).