32
Chemical Hay Preservation
R.L. Dovel and J. Rainey'
INTRODUCTION
Producer interest is increasing in hay preservatives that would
allow baling forage at moisture contents higher than normally possible.
This enables producers to avoid inclement weather and increase yields by
reducing the time that hay lies on the field impeding regrowth. Many
hay producers are currently using or experimenting with different hay
preservatives.
Ammoniation of hay using anhydrous ammonia as a post-baling treatment has reduced yeast and mold growth in wet hay (20 to 30 percent
moisture) and improved forage quality by increasing both N content and
digestibility; however, hay ammoniation using anhydrous ammonia is both
inconvenient and hazardous. Recent research has shown that the application of a urea or an ammonia/urea solution to wet hay can reduce yeast
and mold growth without the inconvenience of a post-baling treatment or
the hazard of handling anhydrous ammonia. The inclusion of urease in
the solution would eliminate the dependence on naturally occurring
urease on the plant surface. The slow release of ammonia, as urease
converts urea to ammonia, also produces similar affects on forage quality as ammoniation.
PROCEDURES
Experiment I: Alfalfa Hay Conservation with AUBUS
The first experiment was a factorial experiment examining application rates of an ammonia/urea/biuret/urease solution (AUBUS) across
different alfalfa hay moisture contents. Rates of approximately 10,
20 and 30 gallons/ton of wet hay were applied at hay moisture contents
ranging from 17 percent to 27 percent moisture. (The intent was to
examine preservation of hay in three distinct moisture conditions.)
After stacking treated bales separately, bale temperature was monitored
using a thermocouple thermometer. After bale temperature had stabilized
or begun to decline, bales were visually examined for mold growth.
Visual estimates of mold growth were taken 45 days after baling using
a scale from 1 to 5, with 1 representing green hay with no mold growth.
Hay with no objectionable mold growth but some discoloration was rated
2. Hay which was more extensively discolored with a slightly moldy or
1/ Assistant Professor and Biological Sciences Research Technician,
respectively, Klamath Experiment Station.
Acknowledgments: Appreciation is expressed to Unocal Research
for financial support and donation of materials.
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dusty smell was rated 3. Hay with mycelial growth present and objectionable odor was rated 4. The presence of extensive mycelial growth and
an abundance of spores resulted in a rating of 5. Hay rated above 3 was
considered to be unmarketable. Core samples were also collected for
quality and moisture analysis. Quality analysis included both acid
detergent fiber (ADF), to predict digestibility, and crude protein content (CP). The experiment was conducted twice with four replications
in each trial.
Experiment II: Time of Application of AUBUS and UBUS
The time of application of AUBUS and a urea/biuret/urease solution
(UBUS) was also examined. In this experiment AUBUS and UBUS were
applied to hay at a rate of 20-25 gallons/ton of wet hay. AUBUS was
applied at swathing, the afternoon prior to baling, or at baling. UBUS
was only applied at swathing. Hay from all treatments, including an
untreated control, was baled at approximately 20-25 percent moisture.
Treated bales were stacked separately and bale temperature monitored
using a thermocouple thermometer. Bales were examined for mold growth
and rated approximately one month after baling. Quality analysis of
treated bales was performed as described in Experiment I. The experiment was conducted twice with four replications in each test.
Experiment III: Chemical Drying Agents
This experiment examined the effect of various chemical treatments
on alfalfa hay drying rates. Chemicals used included AUBUS, Potassium
Carbonate, EnQuik and SURpHTAC. The experiment was conducted on both
July and August alfalfa harvest dates. When the trial was repeated in
August UBUS was also included. Materials were applied by a boom
attached in front of the cutting bar on a swather. Following swathing,
samples were collected at 3:00 pm daily to monitor drying rate.
Samples were also collected in the morning to estimate moisture
readsorption during the night. The morning sample was retained for
quality analysis as described in Experiment I. The experiment was
arranged in a randomized complete block design with four replications.
RESULTS AND DISCUSSION
Experiment I: Alfalfa Hay Conservation with AUBUS
Different application rates of AUBUS were needed to conserve hay
at different moisture contents. Also the type of moisture in the hay
affected application rates needed for hay conservation. Hay with large
amounts of stem moisture, moisture locked within the stem tissue, required more AUBUS to conserve hay than hay which had mostly dew moisture, moisture adsorbed onto the surface of the hay as humidity increases at night. The highest rate of AUBUS used in this study was
required to keep mold growth at acceptable levels in moist hay with
substantial stem moisture. In contrast, the lowest rate was sufficient
to virtually eliminate mold growth on moist hay (19.9 percent moisture)
which had mostly dew moisture. Even large amounts of dew moisture (27.3
percent moisture) overcame the ability of AUBUS to inhibit mold growth
under the conditions of this study.
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Application of AUBUS increased estimates of crude protein in treated
samples by 2.5 to 13.0 percent depending on application rate. However,
it should be noted that increasing crude protein levels above 23 percent has not resulted in improved animal performance in some studies.
The benefits of AUBUS application on forage protein content would be
greater in grass hay than in alfalfa. Urea is a component of many dairy
rations. If urea is to be added to the ration it might be more
profitable to add it to hay as a preservative and to enhance forage
digestibility.
Response of alfalfa ADF content to AUBUS application was variable
with significant decreases in ADF content resulting from AUBUS application in three of the five application dates recorded.
Experiment II: Time of Application of AUBUS and MIS
In the first harvest, application of AUBUS at swathing and at baling
resulted in significantly less mold growth than the control. In the
second harvest, all three times of application of AUBUS and the application of UBUS at swathing resulted in substantially less mold growth than
the control. All bales receiving no preservative were very moldy and
totally unusable. The bales receiving AUBUS at swathing and on the
afternoon prior to baling, and the UBUS treatment all resulted in very
marketable hay. There was no mold growth or heat damage on hay treated
with AUBUS at swathing; however, it was rated discolored by bleaching
or yellowing caused by the free ammonia.
Bales receiving AUBUS at baling were of noticeably lower quality
than those receiving chemical treatment earlier. Roughly one-quarter of
the AUBUS bales treated at baling were unmarketable. When results of
both harvests are combined, hay from all treatments is significantly
less moldy than the control and there is no difference in mold control
due to the time of application of AUBUS.
Experiment III: Chemical Drying Agents
The only treatment in the trial to significantly increase drying
rates of alfalfa hay was potassium carbonate. Application of AUBUS and
SURpHTAC retarded drying rates. This may be due to the hygroscopic
nature of urea in the case of AUBUS. Although EnQuik produced rapid
desiccation of leaves, they tended to shatter and stems did not dry more
rapidly than the control. Although urea solutions provide good control
of mold growth in hay when applied at swathing, application of these
solutions do not aid in hay desiccation.
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Table 1. Effect of Moisture content at baling and AUBUS application
rate on mold growth. Alfalfa hay was baled at various moisture
contents using four rates of AUBUS. Percent stem moisture in
hay was estimated by determining hay moisture content at 6:00
p.m. on the evening prior to baling. Visual ratings of mold
growth range from 1 (no mold growth) to 5 (very moldy).
Moisture at baling, 'I 17.3
27.3
19.9
19.9
18.3
Moisture at 6:00 p.m.,
12.2
15.8
11.8
11.3
0
10
20
30
4.5
4.2
3.7
3.0
Mold growth rating 1.0
2.5
4.7
1.0
5.0
1.7
1.0
4.2
2.0
1.0
3.4
1.2
2.7
1.0
1.0
1.0
LSD(0.05)
1.0
0.8
0.4
23.3
Application rate
gal/ton
NS
0.7
Table 2. Effect of moisture content at baling and AUBUS application rate
on ADF content of alfalfa hay. Alfalfa hay was baled at various
moisture contents using four rates of AUBUS. Percent stem moisture in hay was estimated by determining hay moisture content at
6:00 p.m. on the evening prior to baling.
23.3
Moisture at baling,
19.9
17.3
27.3
19.9
Application Rate
(gal/ton)
18.3
Moisture at 6:00 p.m.,
12.2
15.8
11.8
11.3
0
1
2
3
36.3
34.2
32.7
32.1
32.7
32.0
33.3
31.3
ADF, X
34.2
33.8
32.4
39.4
32.4
34.8
35.3
31.2
34.1
30.5
34.7
33.3
LSD(0.05)
2.1
NS
NS
1.6
2.7
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Table 3. Effect of time of application of AUBUS/UBUS solutions on mold
control. AUBUS was applied at swathing, the afternoon prior to
baling or at baling. UBUS was applied at swathing only. Visual
mold scores are compared to controls. Hay was baled at 21.8%
moisture at both cuttings.
Control
UBUS at Swathing
AUBUS at Swathing AUBUS Afternoon prior
to Baling
old growth rating M
Cutting II
Cutting I
5.0
2.5
1.0
2.0 (yellowed)
1.7
3.2
2.0
AVG.
3.7
1.9
2.1
AUBUS at Baling
1.0
3.2
2.1
LSD(0.05)
0.8
1.0
1.0
Table 4. Effect of chemical treatment on drying rate of alfalfa hay.
1
Control
AUBUS
EnQuik
Potassium Carbonate
SURpHTAC
LSD(0.05)
Days after swathing
2
3
Moisture, % 4
46.2
51.4
49.6
38.9
47.1
22.9
29.1
23.7
15.0
28.4
13.9
17.5
13.9
11.8
15.3
12.0
13.5
11.9
10.9
12.9
6.4
4.7
1.5
1.2