Intake and Digestibility of Dry Matter and Fiber of Flaccidgrass and Switchgrass1

Abstract

AbstractSubtropical grasses are generally considered of lower nutritive value than temperate grasses. Flaccidgrass (Pennisetum flaccidumGriseb.) and switchgrass (Panicum virgatumL.) are subtropical species with high quality potentials. The objective of this study was to compare dry matter intake and the digestive coefficients for dry matter and several fiber constituents from hays of flaccidgrass (FG) and switchgrass (SG) with ‘Coastal’ bermudagrass [Cynodon dactylon(L.) Pers.] at similar neutral detergent fiber (NDF) concentrations. Initial growths were harvested as hay at appropriate development stages to obtain forages having similar NDF. Tall fescue (Festuca arundinaceaSchreb.) was included to provide comparisons with a temperate species. Hay intakes by eight Holstein heifers were measured in two squares of a 4 by 4 Latin square design. Digestion coefficients were calculated from data obtained during the fourth intake period of each square and were analyzed as a completely random design. The subtropical hays had similar NDF concentrations (0.710 to 0.753 g kg−1), but intakes differed. Coastal bermudagrass (CB) intakes of 2.70 kg 100 kg−1of body weight were followed by FG (2.29) and SG (2.09). Tall fescue (TF) intakes were similar to those for FG (2.25 vs. 2.29 kg 100 kg−1body weight). Dry matter digestibility of CB averaged only 0.496 compared with the greater but similar coefficients for the other three hays (0.624 g kg−1). The digestive coefficients for NDF and constituent acid detergent fiber (ADF) and cellulose were similar for FG, SG, and TF, averaging 0.649, 0.587, and 0.675, respectively, compared with lesser coefficients of 0.486, 0.435, and 0.517 from CB. Hemicellulose digestion was similar for FG and SG (avg 0.741) and appreciably greater than for CB (0.537); whereas, that for TF was intermediate (0.683). The greater digestibility of dry matter and fiber of FG and SG, compared with CB, partially explains the reported greater than expected animal daily performance from these two subtropical species and supports their use in ruminant feeding systems.