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Intake, Digestibility, and Nitrogen Balance of Steers Fed Gamagrass Baleage Topdressed at Two Rates of Nitrogen and Harvested at Sunset and Sunrise
Author(s) -
Sauvé A. K.,
Huntington G. B.,
Whisnant C. S.,
Burns J. C.
Publication year - 2010
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci2009.02.0105
Subject(s) - zoology , hay , morning , digestion (alchemy) , dry matter , nitrogen balance , nitrogen , biology , chemistry , botany , chromatography , organic chemistry
Maximum diurnal accumulation of soluble carbohydrates in warm‐season grasses is an economic way of increasing hay quality; however, in the humid East, haymaking is difficult. This study evaluated gamagrass ( Tripsacum dactyloides L.), topdressed with either 56 (LO) or 168 (HI) kg N ha −1 , direct baled after mowing in the afternoon (PM/LO and PM/HI) or morning (AM/LO and AM/HI), wrapped with plastic film, and conserved as baleage. The four baleage treatments were evaluated by steers for dry matter intake (DMI), digestibility, and N retention. Neither harvest time nor N rate altered DMI (mean = 1.87 kg 100 −1 kg body weight). Digestion was similar between PM and AM baleage but greater ( P = 0.05) for HI vs. LO N rate (536 vs. 506 g kg −1 ) as was cellulose digestion ( P = 0.02; 656 vs. 617 g kg −1 ). The digestion of crude protein was greater ( P = 0.01) in the AM vs. PM baleage (519 vs. 443 g kg −1 ) and greater ( P = 0.02) in HI vs. LO N rate (520 vs. 441 g kg −1 ). Fermentations differed ( P < 0.01) between PM and AM baleage, as pH averaged 5.4 and 4.5, respectively. Greatest ( P < 0.01) amounts of alcohols and least fatty acids occurred in PM baleage and N rate reduced ( P < 0.01) alcohols but increased fatty acids. Total nonstructural carbohydrates (TNC) prebaling was 120 g kg −1 in the PM and 97 g kg −1 in the AM, but baleage averaged <38 g kg −1 and explains the lack of steer response to the PM harvest. Gamagrass preserved well as baleage and was readily consumed, but the TNC fraction was not preserved.