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Influence of Moisture Concentration at Baling on the Nutritive Value
of Bermudagrass Hay as Affected by Time in Storage
J. E. Turner, W .K. Coblentz, D. A. Scarbrough, D. W. Kellogg, K. P. Coffey, L. J. McBeth, and R. T. Rhein 1
Story in Brief
Concentrations of moisture > 20% are known to cause spontaneous heating and associated deleterious effects on
forage nutritive value in hay. ‘Greenfield’ bermudagrass [Cynodon dactylon (L.) Pers.] was packaged in conventional
rectangular bales at 21.9, 26.5, and 30.2 % moisture (LM, MM, and HM, respectively). Bales made at each concentration
of moisture were core sampled before storage (d 0) and after 4, 8, 12, 24 and 65 d of storage. Concentrations of
most fibrous and fiber-associated N components increased (P < 0.05) with time in storage. Concentrations of N
increased (P < 0.05) with time in storage for HM and MM bales, but the concentration of N in the driest bales did not
change (P > 0.05) with time in storage. The results of this study demonstrate that negative changes occur in bermudagrass
hay packaged at concentrations of moisture > 20.0%. Nitrogen in these bales was clearly susceptible to the effects
of heating; N became more associated with fiber constituents as a result of nonenzymatic browning, suggesting a concurrent
reduction in bioavailability.
Introduction
Concentrations of moisture >20% in alfalfa (Medicago
sativa L.) and bermudagrass hays produce spontaneous heating,
mold growth, and deleterious changes in forage nutritive
value (Collins et al., 1987; Coblentz et al., 1996; 2000).
Negative changes in nutritive value are a result of microbial
activity and the subsequent production of heat. Rotz and
Muck (1994) have indicated that increased microbial activity
and the associated heating can result in greater concentrations
of fiber components and heat damaged N. The nutritional
value of the hay and the subsequent productivity of livestock
consuming these forages can be reduced as a result of these
factors.
It is especially important to develop a clear understanding
of these relationships for bermudagrass, which is the most
important forage grown throughout the southeastern U.S.
(Burton and Hanna, 1995). The objectives of this study were
to describe the relationship between changes in nutritive
value and time in storage for bermudagrass hay made at three
concentrations of moisture.
Experimental Procedures
A second cutting of a well-established stand of
“Greenfield” bermudagrass was selected for this trial. On
July 13, 1999, the bermudagrass forage was mowed in three
blocks of 12 swaths each. Swaths in each block were randomly
assigned to one of three moisture concentrations
30.2% (high moisture, HM) 26.5% (medium moisture, MM),
and 21.9% (low moisture, LM), which were chosen to produce
intense, moderate and minimal spontaneous heating and
similar associated changes in forage nutritive value. Twelve
conventional rectangular bales were made from each block
for each concentration of moisture.
Bales were stacked on wooden pallets placed on the
concrete floor of an open-air pole barn. Six bales from each
group of 12 were placed side by side (strings up) on top of the
wooden pallets. The remaining six bales from each treatment
were positioned in the same orientation on top of the first six
bales, thereby creating stacks two bales high and six bales
wide for each field replication of each treatment. Individual
stacks containing 12 bales were surrounded on the sides and
top by dry bales of wheat straw to limit the effects of diurnal
variations in ambient temperature.
Core samples were taken from two bales selected at
random from each stack prior to stacking and at 4, 8, 12, 24,
and 65 d postbaling using a Multi-Forage Sampler (Star
Quality Samplers, Edmonton, AB, Canada). Based on previous
temperature versus time in storage curves for bermudagrass
hay (Coblentz et al., 2000), these sampling dates were
selected to approximately coincide with the end of the initial
heating period (d 4); the onset, peak, and end of the secondary
heating phase (d 8, 12, and 24, respectively); and the end
of the study (d 65). The d 0 sampling date served as a prestorage
estimate of forage nutritive value. Bales were removed
from each stack for coring and then returned to their previous
location in the stack for the remainder of the trial to maintain
the integrity of the stack. All forage samples were dried under
forced air at 131°F for 72 h; for bales sampled on d 0, this
technique was used to estimate the initial concentration of
moisture for each baling treatment.
Dry forage samples were ground through a Wiley mill
1 All authors are associated with the Department of Animal Science, Fayetteville.
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