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Arkansas Animal Science Department Report 2001
the entire 65-d storage period. All bales were weighed at the
end of the 65-d storage period. Dry matter recovery was
determined by dividing the post-storage DM weight by the
pre-storage DM weight of the bales.
Dry matter recovery, visual mold score, indices of
spontaneous heating and initial bale characteristics were analyzed
by PROC ANOVA of SAS (SAS Institute, Inc., Cary,
NC) as a randomized complete block design with three replications.
The mean square for the bale moisture x block interaction
was used as the error term. Fisher’s protected least
significant difference test was used to compare the actual
treatment means of bale characteristics.
Results and Discussion
Bale characteristics of hay packaged at three concentrations
of moisture are presented in Table 1. Bale densities
were generally comparable to those reported for alfalfa and
bermudagrass hays made with comparable equipment at similar
concentrations of moisture (Buckmaster and Rotz, 1986,
Coblentz et al., 2000). Bale weight and bale density (as-is
basis) decreased (P < 0.05) as the forage became drier at baling.
Bale weight (dry matter basis) was greatest (P < 0.05) for
HM bales prior to storage.
Internal bale temperature vs. time curves for the three
moisture treatments (Fig. 1) were similar to those reported
previously for both alfalfa and bermudagrass packaged under
similar conditions (Coblentz et al., 1996; 2000). The respiratory
processes of plant enzymes and microorganisms associated
with the plants in the field have been associated with the
initial heating phase (Wood and Parker, 1971). For all treatments,
a distinctly elevated bale temperature that was
observed initially was partially subsided by d 2 of storage.
Immediately following this depression, internal bale temperatures
increased for all treatments, and remained elevated in
all cases for about 21 d. This secondary heating phase has
been attributed to the respiratory processes of storage
microorganisms. The intensity and duration of this heating
phase was consistent with that reported previously for
bermudagrass hay packaged under similar conditions
(Coblentz et al., 2000). In the present study, changes in internal
bale temperatures observed after 18 d in storage were
caused primarily by fluctuations in ambient temperature.
The HDD accumulated during the storage period for
these treatments decreased (P < 0.05) with moisture concentration
at baling (Table 2). The maximum internal bale temperature
was greater (P < 0.05) in HM than in LM bales; the
maximum temperature in MM bales was intermediate
between HM and LM bales, but did not differ (P > 0.05) from
either. Temperature maxima for all treatments exceeded
122°F, indicating that measurable heating occurred in all
cases. Average temperatures over the initial 30 d of storage
and over the entire 65-d storage period decreased (P < 0.05)
with moisture concentration at baling. During the course of
this project, the ambient air temperature exceeded 95°F on 30
d out of the 65-d storage period; this may have positively
influenced the total HDD accumulated during storage relative
to studies conducted earlier in the summer or later in the fall.
Dry matter recovery after the 65-d storage period decreased
(P < 0.05) from 96.4% in the LM treatment to 90.2% in the
HM treatment. This result was expected; moisture content at
baling is considered to be the major factor affecting dry matter
recovery (Rotz and Muck, 1994; Collins et al., 1995) and
the recoveries of dry matter reported here were generally consistent
with those reported previously (Coblentz et al., 2000)
for bermudagrass hay packaged and stored similarly.
Elevated concentrations of moisture in hay bales provide
a favorable environment for microbial growth (Roberts,
1995). Visual appraisals of mold increased (P < 0.05) with
moisture content at baling. The LM bales exhibited some
presence of spores between the flakes, while the HM bales
had spores throughout the bale and evidence of a mycelial
mat between the flakes.
Implications
Visual mold, temperature observations and bale
weights increased with concentration of moisture in these
bales while dry matter recovery increased with decreasing
concentrations of moisture. These results are similar to those
reported previously for alfalfa and bermudagrass hay.
Literature Cited
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