Forage quality of selected warm-season weed species.

Forage quality was determined at vegetative, flowering, and fruiting stages for nine cool-season weed species and four cultivated forages. When compared at the vegetative stage of maturity, Carolina geranium (Geranium carolinianum L. #3 GERCA), Virginia pepperweed (Lepidium virginicum L. # LEPVI), Virginia wildrye (Elymus virginicus L. # ELYVI), wild oats (Avena fatua L. # AVEFA), cheat (Bromus secalinus L. # BROSE), and little barley (Hordeum pusillum Nutt. # HORPU) had high nutritive quality as in- dicated by in vitro dry-matter digestibility (IVDMD) values equal or superior to rye (Secale cereale L.), tall fescue (Festuca arundinacea Schreb.), and ladino clover (Trifolium repens L.). Cutleaf evening primrose (Oenotbera laciniata Hill # OEOLA) and curly dock (Rumex crispus L. # RUMCR) had lower IVDMD values than the cultivated forages and all weed species except wild oats. However, the rate of decline in IVDMD as plants matured was generally greater for the weed species compared to cultivated forage plants. All weed and culti- vated forage species had adequate levels of Ca and K for livestock. Nearly all weed and cultivated forage species had suboptimum levels of P for high-producing ruminant animals; Carolina geranium and cutleaf evening primrose had high Ca:P ratios, which can cause metabolic disorders. Carolina geranium, Virginia wildrye, wild oats, cheat, little barley, and all the cultivated forage species had inadequate levels of Mg and could be considered "tetany prone". Most of the forbs had high Mg concentrations. Additional index words. Digestibility, crude protein, calcium, phosphorus, magnesium.