Nonstructural carbohydrate and digestibility patterns in orchardgrass swards during daily defoliation sequences initiated in evening and morning

Griggs, T.C. and McAdam, J.W. and Mayland, H.F. and Burns, J.C. (2005) Nonstructural carbohydrate and digestibility patterns in orchardgrass swards during daily defoliation sequences initiated in evening and morning. Crop Science. 45:1295-1304.

PDF 1163.pdf Download (359kB)

Abstract

Herbage soluble carbohydrate (SC) levels vary diurnally and livestock
intake can be higher for herbage harvested or allocated to
animals in the evening than in the morning. Few assessments of SC
and digestibility patterns have been made during sward depletion in
rotationally stocked orchardgrass (Dactylis glomerata L.). We tested
the hypothesis that simulated evening daily pasture allocation increases
24-h mean herbage SC and digestibility levels relative to morning
allocation. Total nonstructural carbohydrate (TNC) and in vitro
true dry matter digestibility (IVTDMD) levels were compared during
24-h clipping sequences initiated at 1900 h (PM) and 0700 h (AM).
Sward height was progressively reduced from 40 to 8 cm at 6-h intervals
in October, June, and August. Successively lower horizons from defoliation
sequences and also from control areas that were not under
progressive defoliation were analyzed. Digestibility and TNC levels
varied diurnally and seasonally, and were often higher for PM sequences,
but differences among 24-h means were small. Daily mean
TNC levels for defoliation sequences initiated in PM and AM were
138 vs. 132, 93 vs. 88, and 72 vs. 60 g kg' in October, June, and August,
respectively. In all periods, digestibility decreased from approximately
920 to 800 to 890 g kg' during sward depletion and displayed similar
patterns between defoliation sequences. Patterns of TNC and digestibility
during sward depletion may not be represented by those in
intact swards, and PM allocation of daily herbage may not increase
24-h mean dietary TNC density relative to AM allocation. Daily quantities
of ingested TNC could be higher for PM herbage allocation if
livestock consume proportionately more herbage in the PM than
we simulated.

Item Type:	Article
NWISRL Publication Number:	1163
Subjects:	Irrigated crops > Grass forage > Chemistry Mass Import - autoclassified (may be erroneous)
Depositing User:	Dan Stieneke
Date Deposited:	20 Nov 2010 21:49
Last Modified:	02 Nov 2016 18:47
Item ID:	16
URI:	https://eprints.nwisrl.ars.usda.gov/id/eprint/16