Chemical and in Vitro Digestible Dry Matter Composition of Maize Stalks after Selection for Stalk Strength and Stalk‐Rot Resistance1

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Abstract
Although maize (Zea mays L.) is a major forage crop, little attention has been given to possible alteration of forage quality associated with breeding for increased resistance to stalk lodging. This study was designed to evaluate changes in stalk composition and digestibility resulting from three cycles of recurrent selection each for improved stalk strength (BSlMS) and stalk‐rot [Diplodia maydis (Berk.) Sacc.] resistance (BSlSR). The second elongated internmode plus half of each adjacent internode from plants of the original population (BSlCO) and from C1 to C3 for the BSlMS and BSlSR populations were sampled approximately 35 days after midsilking for chemical and in vitro digestible dry matter (IVDDM) evaluation. Major composition changes from the BSlCO to BSlMSC3 and BSlSRC3 populations, respectively, were: concentration of cell wall constituents, 616 to 520 and 542 g kg−1; concentration of acid detergent fiber, 422 to 353 and 373 g kg−1; concentration of lignin, 57 to 42 and 47 g kg−1; concentration of total nonstructural carbohydrates (TNC), 184 to 258 and 244 g kg−1; and concentration of IVDDM, 514 to 621 and 594 g kg−1. Both selection regimes increased TNC concentration, which diluted stalk fiber concentration and resulted in a net increase in IVDDM. Recurrent selection for traits associated with improved stalk lodging resistance did not have negative effects on the forage quality of maize stalks in late reproductive stages.