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Creeping Signalgrass Versus Bahiagrass for Cow and Calf Grazing

Ezenwa, Ike V., Kalmbacher, Robert S., Arthington, John D., Pate, Findlay M.
Agronomy journal 2006 v.98 no.6 pp. 1582-1588
vegetation cover, seasonal variation, digestibility, Urochloa humidicola, beef cows, pastures, phenology, dry matter accumulation, liveweight gain, crude protein, weaning weight, frost injury, forage grasses, calves, frost, Paspalum notatum, pasture plants, nutritive value, cold tolerance, Florida
Bahiagrass (Paspalum notatum Flügge) is the predominant pasture grass in Florida because it is well adapted to the extensive low-input cattle management typical of Florida's beef production. Creeping signalgrass [Urochloa humidicola (Rendle) Morrone & Zuloaga), syn. Brachiaria humidicola (Rendle) Schweick.] shares many of the desirable characteristics of bahiagrass, but no comparative grazing trials have been conducted. We measured calf body weight (BW) gains on signalgrass and bahiagrass from May to early August (weaning) and monitored cow BW changes from August through October over 4 yr. Calf BW at weaning averaged 250 kg on signalgrass and 235 kg on bahiagrass (P = 0.13), and calf average daily gain was 0.66 kg d⁻¹ for signalgrass and 0.48 kg d⁻¹ for bahiagrass (P = 0.07). Cows grazing signalgrass weighed more (P = 0.03) in October (564 kg) than cows on bahiagrass (513 kg) and had higher (P = 0.01) body condition scores (5.7 vs. 4.7, respectively)]. There was no difference between bahiagrass and signalgrass [8380 and 9580 kg dry matter (DM) ha⁻¹] for forage accumulation from May through October, but forage mass was greater for signalgrass than bahiagrass from July to October. A problem with signalgrass was that 33% of annual forage DM accumulation occurred in a 28-d period beginning with the start of summer rain. Signalgrass had greater organic matter digestibility (545 g kg⁻¹) than bahiagrass (476 g kg⁻¹), but it always contained less crude protein (87 vs. 107 g kg⁻¹). A freeze (−5°C) reduced signalgrass ground cover to ≈50% and delayed grazing in 1 of 4 yr. Forage production, nutritive value, and livestock gains on signalgrass equaled or exceeded those of bahiagrass, but poor cold tolerance, limited growth before May, and excessive growth in July are potential problems with signalgrass pasture production.