In situ ruminal degradation of dry matter and fiber from bermudagrass fertilized with different nitrogen rates and harvested on two dates

Ruminal in situ disappearance kinetics of dry matter and fiber in growing steers for common crabgrass forages sampled on seven dates in northern Arkansas1

“…Although the potential extent of ruminal DM disappearance for crabgrass forages decreased with quartic (P = 0.009), quadratic (P < 0.001), and linear (P < 0.001) effects of time (Table 6), the potential extent remained exceptionally high (≥83.2%) on all dates, and the total decrease with maturity was very small (range = 4.8 percentage units). The potential ruminal DM disappearance for the bermudagrass hay was very high relative to other work, exceeding estimates made by Galdá mez-Cabrera et al (2003) for common bermudagrass harvested in late May and August in northwest Arkansas by 3.5 to 10.8 percentage units, and far exceeding estimates made by Mandebvu et al (1999) for Tifton 85 and Coastal bermudagrass grown in southern Georgia. Despite the exceptional ruminal availability of the bermudagrass hay evaluated in the present study, the bermudagrass did not differ (P = 0.64) from crabgrass forages.…”

“…These factors are assumed frequently to work together to limit DMI with forage-based diets. In this study, the overall mean disappearance rate for crabgrass exceeded (P < 0.001) that of our high-quality bermudagrass hay control by 44%; however, based on other estimates of ruminal DM disappearance reported for bermudagrass (Mandebvu et al, 1999;Galdá mez-Cabrera et al, 2003), it is possible that crabgrass could disappear from the rumen at rates approaching twice those of more typical bermudagrass forages.…”

“…For the bermudagrass hay, Fraction A was similar to an estimate by Galdá mez-Cabrera et al (2003) for common bermudagrass harvested in late May in northwestern Arkansas, but was substantially greater than estimates by Mandebvu et al (1999) for Tifton 85 and Coastal bermudagrasses produced in southern Georgia. Fraction A was smaller by 4.7 to 7.3 and 10.2 to 12.8 percentage units in the bermudagrass (P < 0.001) and orchardgrass (P < 0.001) hays, respectively, than in crabgrass forages.…”

“…To the best of our knowledge, ruminal disappearance rates of DM for crabgrass have not been determined previously. Our estimates of disappearance rate for crabgrass (overall mean = 0.078 h −1 ; Table 6) were more rapid than reported for other warm-season perennial grasses, including eastern gamagrass (0.035 to 0.048 h −1 ; Coblentz et al, 1998), common bermudagrass fertilized with 0 to 168 kg of N/ha and harvested in late May or mid August (mean values = 0.033 and 0.036 h −1 , respectively; Galdá mez- Cabrera et al, 2003), and Tifton 85 and Coastal bermudagrass (0.028 h −1 ; Mandebvu et al, 1999). It is assumed commonly that the suitability of warm-season perennial grasses for use within diets of livestock with high nutrient demands, such as dairy cows, is limited by high concentrations of fiber components and slow ruminal disappearance rates.…”

“…Dry matter and NDF were partitioned into three fractions based on relative susceptibility to ruminal disappearance. The A fraction was defined as the immediately soluble portion, although it also may have included some minute insoluble particles that could have washed out of the Dacron bags (Coblentz et al, 1998;Galdá mez-Cabrera et al, 2003). Fraction B represented that portion of DM and NDF that disappeared at a measurable rate, and fraction C was defined as the portion of DM and NDF that was undegraded in the rumen.…”