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Plant maturity effects on intake, digestibility, and rumen kinetics of leaf and stem fractions of Sandhills grasses in beef steers
Abstract
Plant maturity and leaf:stem ratios affect performance and production of livestock. Limited research is available on the effects leaves and stems on organic matter intake (OMI), organic matter digestibility (OMD), and rumen kinetics. Two trials evaluated (1) effects of immature and mature leaves and stems of Sandhills subirrigated meadow hay on OMI, OMD, dry matter (DM) fill, and digestive kinetics in beef steers, and (2) the effects of different sources (urea or corn steep liquor) of rumen degradable protein on OMI, OMD, DM fill, and particulate passage of senescent mature grass leaves from Sandhills range hay in wether lambs. Leaves and stems were separated with a dual air flow, Clipper Cleaner Model Super 69D. In Trial 1, 4 steers (avg body weight = 418 kg) were assigned in a 4 x 4 Latin square. Treatments diets were: (1) immature leaves; (2) immature stems; (3) mature leaves; and (4) mature stems. Steers had greater (P $<$ 0.05) OMI, OMD and particulate passage rates were faster for immature hay fractions than mature fractions. No differences (P $>$ 0.05) were observed in OMI, or OMD for leaves and stems within maturity. Regardless of stage of maturity, particle size of stems was greater (P $<$ 0.05) than leaves. Differences in OMI and OMD between immature and mature hay fractions were not due to changes in leaf to stem ratios, but was attributed to slower rates of passage. In Trial 2, 14 lambs (avg body weight = 36 kg) were used in a replicated 7 x 3 balanced incomplete Latin square. Treatments were: (1) forage only, (2) forage plus 3.0% corn steep liquor, (3) forage plus 9.0% corn steep liquor, (4) forage plus 15.2% corn steep liquor, (5) forage plus 0.5% urea, (6) forage plus 1.5% urea, and (7) forage leaves plus 2.5% urea. Supplements were formulated to provide 15.6, 50.0, or 89.3 g N kg$\sp{-1}$ DM. Urea and corn steep liquor diets had similar OMI and OMD (P $>$ 0.10). Organic matter intake increased linearly (P $<$ 0.10) with increasing levels of rumen degradable protein. Particulate passage rates were similar (P $>$ 0.10) for all treatments. Senescent mature leaves were deficient in rumen degradable protein, and corn steep liquor was similar to urea as a source of rumen degradable protein. With forage senescence, forage quality declines which reduces forage intake and digestibility. Leaves and stems at the same maturity are of equal forage quality when consumed by ruminants.
Subject Area
Livestock|Range management
Recommended Citation
Lamb, James Bernard, "Plant maturity effects on intake, digestibility, and rumen kinetics of leaf and stem fractions of Sandhills grasses in beef steers" (1996). ETD collection for University of Nebraska-Lincoln. AAI9620342.
https://digitalcommons.unl.edu/dissertations/AAI9620342