The relation between sorghum tannins and nutritive value of the grain

Abstract

Cultivars of Sorghum bicolor (L.) Moench grain were evaluated by rat feeding trials and chemical analyses. The samples consisted of grain which varied in: pericarp color, plan color, glume color, and presence or absence of a pigmented testa. Where possible, samples were selected from segregating populations to provide grain with similar genetic background that varied only for the character being studied. Tannin content of the diets ranged from 0.05 to 4.42 mg./100 mg catechin equivalents and was negatively correlated with weight gain (r=-0.53**), protein efficiency ratio (PER) (r= -.50**), and dry matter disappearance (DMD) (r= -0.78**) when weight gain and PER were calculated on an equal lysine basis. Lysine content of the grain (% protein) ranged from 1.56 to 2.93% and, as expected, was positively correlated with weight gain (r=0.55**), feed intake (r=0.24), and PER (r=0.48**). Reduction in DMD, for the entire study and within segregating populations, was related to two grain characteristics: brown pericarp and presence of a pigmented testa. Reduction in DMD resulted with grain that had red or white pericarp when a pigmented testa was present. This illustrates that reduced performance is related to these grain characters, rather than to undefined varietal differences. Red pericarp did not reduce nutritional value of the grain when compared to white pericarp. Plant color and glume color did not influence the nutritional value of the grain as measured by rat performance..