Screening Grain Sorghums For Bird Tolerance And Nutritional Quality

A sorghum breeding program is described in which the major objective was to develop tannin-containing group II sorghums that resist bird damage in the early stages of grain development, and then ripen into palatable grain of high nutritional quality. In the bird-resistance screening nursery, group II, standard group I, and standard group III sorghum entries exposed to high levels of bird-feeding pressure, were assessed for bird damage and content of protein binding (i.e. active) tannins at 21 days after half-anthesis (DAHA), and at physiological maturity. Although several group II entries were equivalent to group III (brown sorghums) standards in bird resistance and active tannin content at 21 DAHA, none had measurable active tannins in the mature grain. These observations were corroborated by nutritional studies. Sixteen group II entries with bird tolerance and agronomic desirability were tested for nutritional quality in rat feeding studies. Four group II entries were nutritionally equivalent to the group I (non-tannin) standard line. Seven entries equalled the group III (nutritionally deleterious) standards in feeding value. Although classic tannin effects were observed in some sorghum varieties, it appeared that non-tannin chemical effects were affecting feeding by birds in others. A group I (non-tannin) sorghum was almost avoided.