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Microfloral and compositional changes in alfalfa hay treated with sodium diacetate and stored at different moisture contents
Animal Feed Science and Technology, 17 (1987) 45-56
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Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands
Microfloral and Compositional Changes in Alfalfa Hay Treated with Sodium Diacetate and Stored at Different Moisture Contents* J.H. CHERNEY', K.D. JOHNSON', J. TUITE 2 and J.J. VOLENEC'
'Department of Agronomy and 2Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN (U.S.A.) (Received 22 May 1986; accepted for publication 2 September 1986)
ABSTRACT Cherney, J.H., Johnson, K.D., Tuite, J. and Volenec, J.J., 1987. Microfloral and compositional changes in alfalfa hay treated with sodium diacetate and stored at different moisture contents. Anita. Feed Sci. Technol., 17: 45-56. Third-cut alfalfa (Medicago sativa L.) hay at high (26.1 and 25.4% ) and low (13.1 and 15.7% ) moisture content was treated with sodium diacetate and made into small bales ( 0.46 × 0.56 × 0.91 m). Hay was sampled initially and stored in stacks of 30-44 bales each in two separate experiments. The temperature of the stacks was monitored and samples were taken during and after the storage period. Hay samples were analyzed for actinomycetes, bacteria and fungi. Fibre composition, digestibility and total non-structural carbohydrates were determined for all samples. Sodium diacetate treatment (3.25 or 1.30 g k g - ' ) was ineffective in preventing microbial growth or heating of wet alfalfa hay. Wet hay temperatures in both experiments increased to 44-46 °C after I week of storage and maintained a high level for I week. Fungi and bacteria were abundant in the hay at the start of storage, but the bacterial population declined as the hay dried in the stacks. Actinomycetes were not detected at the end of the storage period. Aspergillus glaucus developed in the wet hay and was the major microorganism present. Neutral detergent fibre concentration increased in the wet hay and was associated with a relatively large increase in the apparent hemicellulose concentration. The increase in hemicellulose did not have a major effect on the digestibility of the wet hay.
INTRODUCTION
Hay baled at >20% moisture content (m.c.) favors the development of microorganisms, is generally reduced in quality and may have severe losses of dry matter ( Lechtenberg and Holt, 1982 ). Dry weight loss in stored hay averages approximately 1% for each percentage point above 10% at time of storage *Contribution from the Purdue University Agricultural Experiment Station, Journal Paper No. 10723, West Lafayette, IN, U.S.A.
0377-8401/87/$03.50
© 1987 Elsevier Science Publishers B.V.
46 (Kjelgaard et al., 1983). Dry matter losses of 8.5% were found for fourth-cut alfalfa (Medicago sativa L. ) baled at 26.2% m.c., and of 9.8% for hay baled at 35.2% m.c. ( Clanton et al., 1965 ). Greenhill et al. (1961) noted that dry matter losses did not relate well to nutritional losses determined by chemical changes in constituents. There has been little research dealing with the microbial changes in moulding alfalfa hay. Grass hay baled at 16% m.c. contained a relatively small microbial population after storage ( Gregory et al., 1963). However, hay at 25% m.c., heated to 45 ° C and moulded with AspergiUus glaucus, and hay with an initial m.c. of 40% heated to 60 ° C and contained a large population of thermophilic fungi. The density at which alfalfa and grass hay bales were formed did not affect their storage characteristics or quality ( Nelson, 1966, 1972 ). The maturity of alfalfa at harvest was of secondary importance and the primary factor affecting storage and quality was m.c. Mohanty et al. (1967) found that thirdcut alfalfa, when stored wet, heated to 50 ° C and reduced weight gains of steers to 75% of those obtained with well-cured hay. Steers receiving hay baled at low m.c. gained weight faster than those receiving hay baled at high m.c., but no differences were found in forage intake (Miller et al., 1967). A variety of chemicals have been used as preservatives on grass and legume hays baled at high moisture contents. Organic acids inhibited mould growth and reduced heating and storage losses ( Sheaffer and Clark, 1975 ), but organic acids are corrosive to equipment. Anhydrous ammonia successfully preserved wet hay and improved overall nutritive value, especially of low-quality hay (Weiss et al., 1982; Moore et al., 1985). Urea also has been used as a yeastand mould-inhibitor in tall fescue (Festuca arundinacea Schreb. ) hay baled at 33% moisture ( Henning and Dougherty, 1985). Lacey et al. (1983) concluded that current application techniques for hay preservatives may not be adequate for uniform application of the product. Our objectives were to: (1) determine the influence of moisture on microbial populations in stored alfalfa hay and the subsequent effects on forage quality; ( 2 ) evaluate the effectiveness of sodium diacetate as a hay preservative. MATERIALSAND METHODS
Experiment I Harvest and treatment application Third-cut alfalfa hay was made into small bales (0.46 × 0.56 X 0.91 m ) at the Animal Sciences Farm, Purdue University, West Lafayette, IN, U.S.A., on 2 August 1983. Drying conditions were excellent with clear skies, a high temperature of 32 ° C, low humidity and a 16 km h 1 wind. Hay m.c. was monitored in the field by microwave drying of samples. Hay was cut with a conventional mower-conditioner on 1 August 1983 and baled on 2 and 3 August when hay
47 m.c. had fallen below 30 and 20%, respectively. Hay moisture contents of ovendried field samples taken at baling were 26.4% m.c. on 2 August and 13.1% m.c. on 3 August. Sodium diacetate ( "Crop Cure" ) was applied as a granular powder at baling. The commercially available "Crop Cure" contained 50% sodium diacetate by weight, along with fillers, dust suppressors and trace minerals (dried whey, sodium bentonite, salt, sodium silico aluminate, vegetable fat, soy lecithin, calcium stearate, ferrous sulphate, manganous oxide, cobalt carbonate, copper oxide and iron oxide). A spreader was mounted on a New Holland 310 Hayliner baler and two plastic tubes were used to distribute the preservative over the hay as it entered the bale chamber. The spreader was powered by an electric motor operated from the tractor. The rate of preservative application was 3.25 g "Crop Cure" kg -1 wet hay for hay at 26.1 m.c., and 0.95 g "Crop Cure" kg -1 wet hay for hay at 13.1% m.c. The actual rate applied for wet hay was higher than recommended by the manufacturer, and this rate was lowered for the second experiment.
Storage Six bales were weighed and placed in the centre of a four-tiered stack of 44 bales and all bale stacks were stored indoors. All bales in a stack were from the same treatment. Two thermocouples were placed in the centre bales of the dry stacks and three thermocouples were placed in the centre bales of the wet stacks. Temperatures were monitored daily for 30 days and three times per week for an additional 27 days until the temperature of all treatments equilibrated. Ambient air temperature reached a maximum at 32.2 °C early in the storage period and declined gradually throughout storage, with a low temperature of 12.8°C.
Sampling and quality analysis Six bales in each of the four treatments were sampled initially by taking six cores with a Pennsylvania State forage sampler. After 7 days of storage, two bales in the interior of each stack were sampled by taking six cores. After 57 days of storage the temperature in all stacks had equilibrated. The stacks were taken apart and six of the centre bales were weighed and sampled by taking six cores. Forage samples for chemical analysis were dried at 60 ° C and ground to pass through a l-ram screen. Neutral detergent fibre (NDF), cellulose, hemicellulose and permanganate lignin were determined, as described by Goering and Van Soest (1970), at 0, 7 and 57 days of storage. Dry matter digestibility in vitro (IVDMD) was determined by the modified procedure of Marten and Barnes (1980) and total non-structural carbohydrates (TNC) were analyzed according to Smith (1981).
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Experiment 2 Harvest and treatment application Third-cut alfalfa hay was made into small bales at a farm near Lafayette, IN, U.S.A. The crop was cut with a conventional mower-conditioner on the afternoon of 29 August 1983. Drying conditions were again excellent with clear skies, a high temperature of 29.4 ° C, low humidity and a 16-24 km h-~ wind. Hay was baled on 31 August when hay m.c. had fallen below 30%, and on 1 September when hay m.c. dropped below 20%. Actual hay m.c. based on ovendried field samples was 25.9 and 15.7%, respectively. Sodium diacetate was applied as in Experiment 1, except for a reduced application rate on wet hay. Hay at 25.9% m.c. was treated with 1.3 g "Crop Cure" kg -~ wet hay, and hay at 15.7% m.c. was treated with 0.8 g "Crop Cure" kg -1 wet hay.
Storage Storage was in four-tiered stacks of 30 bales, with two stacks per treatment. Six bales were weighed per treatment and three were placed in the centre of each stack. Stacks were stored indoors and two thermocouples were placed in the centre of each stack. Stack temperatures were monitored for 55 days, after which all treatment temperatures had equilibrated. Ambient air temperature reached a maximum of 25.5 ° C early in the storage period and declined gradually to 9.4 ° C.
Sampling and quality analysis Three bales in each of the eight stacks were sampled initially by taking six cores. After 7 and 14 days a centre bale in each of the stacks was sampled by taking six cores. After 55 days of storage, three of the centre bales in each stack were sampled. Chemical analyses were similar to those in Experiment 1.
Microbiological analysis Sample cores taken from both experiments for microbial assays were refrigerated immediately after sampling. Samples (10 g) were blended in 500 ml sterile 0.1% agar and 1:10 dilutions were made. Dilutions were added to 3 separate petri dishes and cooled molten media were added for each of 3 media. Malt salt (6% NaC1) was used to detect xerophytic fungi; potato dextrose agar containing 100 mg kg-1 Tergitol NPX and 30 mg kg-1 chlorotetracycline was used to isolate other fungi. Beef peptone plus 100 mg kg-~ Actidione (cycloheximide) and 0.2% casein (BP) were used to isolate bacteria and actinomycetes.
Statistical analysis Experiments 1 and 2 were analyzed separately for forage quality using the general linear models option of the Statistical Analysis System ( S.A.S. ) pack-
49 TABLE I Hay moisture,bale weightand dry-matterloss of alfalfa hay baledat two moisturelevels Moisture content ( %) At baling1
Afterstorage2
Bale weight Dry matter loss at baling~ duringstorage2 (kg) (g kg- 1 )
Experiment 1 Wet Dry
26.4 13.1
12.3 10.3
30.8 24.9
65.5 51.7
Experiment2 Wet Dry
25.9 15.7
11.9 11.9
34.6 27.7
66.9 32.6
1Meansof 15 fieldsamplesfor wet hay and 10 fieldsamplesfor dry hay. 2Meansof 12 bales. age (1982). The experimental design was a randomized complete block with a factorial arrangement of sampling date, moisture and chemical treatment factors. Since Experiment 2 included multiple stacks of each hay treatment, this was also included in the factorial arrangement. Differences between sampling dates were determined using the Bayes least significance difference (BLSD) test (Smith, 1978). RESULTS
Experiment I Owing to dry conditions, yield of third-cut alfalfa was low and three swaths were raked together prior to baling. Hay was of very high quality and dried rapidly in the field without rain damage. Moisture content at baling and initial bale weights are given in Table I. Bale temperature initially exceeded 33°C, but declined to approximately ambient air temperature within 24 h. The temperature of the dry hay followed that of ambient air temperature, except that stacks were well buffered and responded slowly to abrupt changes in air temperature. The temperature of wet hay rose after 3 days of storage and reached 44 ° C after 5 days. This was 17°C higher than the temperature of dry bales. This temperature was maintained for 8 days and then gradually declined. There was no difference in temperature between the sodium diacetate-treated and untreated bales. Bale m.c. at the end of the storage period declined to similar levels for wet and dry hays (Table I). Approximately 66 and 52 g kg -1 of the initial dry matter were lost in storage for the wet and dry hays, respectively. Fungi and bacteria were abundant in the hay at the start of storage (Table
5O TABLE II Microbial populations cultured from alfalfa hay at three sampling dates during Experiment 1 (propagules×10 4g ~) Actinomycetes Sampling date 0 Days 2 7 Days 3 57 Days 2
Bacteria
AspergiUus sp.
Yeast and other fungi ~
1.96 0.66 < 0.01
10 676 10 210 2 299
0.1 150.5 212.3
72.7 9.6 12.0
Moisture Wet 4 Dry 4
1.28 0.56
5 587 8 452
159.1 68.5
23.3 52.1
Sodium diacetate Treated 4 Untreated 4
0.96 0.87
7 425 6 613
99.3 128.3
37.2 38.1
1Includes yeast, Alternaria sp., Cladosporium sp., Penicillium spp., Phoma sp. and unknown spp. 2Means of 24 bales. ~Means of 8 bales. 4Means of 28 bales from 3 sampling dates.
II). Most of the fungi isolated grow only in high-moisture environments and are normal pre-harvest flora. There were no interactions between sodium diacetate treatment and m.c. or sampling date. After 7 days, AspergiUusglaucus, a xerophytic fungus, grew and sporulated only in the wet hay, with no appreciable sporulation of any fungi in the dry hay. Bacterial populations declined in the wet hay and were isolated in greater numbers in the dry hay during the first week of storage (Fig. 1 ). Bacterial populations then declined in the dry hay and bacterial numbers were relatively low after 57 days in both wet and dry hays. Actinomycetes were present in significant numbers initially, but declined during storage, and were not detected at the end of the storage 120 ~D
100 80
50 "~
40
4~
20
ca
o
0
i Sampling Date (weeks)
e
Fig. 1. Bacterial counts in wet and dry hay during storage. Means of treated and untreated hay for Experiments 1 and 2.
51 TABLE III Fibre components, dry matter digestibility in vitro (IVDMD) and total non-structural carbohydrates ( T N C ) of alfalfa hay at three sampling dates for Experiment 1 (g kg - 1 dry weight) NDF
Cellulose
Hemicellulose
Lignin
IVDMD
TNC
280 292 368 29
135 134 166 9
94 106 137 21
38.6 38.8 55.5 5.1
750 746 710 11
85.1 63.1 75.4 NS
Moisture Wet 4 Dry 4 Significance ~
333 306 **
148 149 NS
127 101 **
44.7 47.1 NS
727 737 **
74.0 81.5 **
Sodium diacetate Treated 4 Untreated 4 Significance
317 322 NS
148 149 NS
114 114 NS
44.8 46.9 NS
734 730 NS
74.8 80.8 NS
Samplingdate 0Days 1 7Days 2 57Days 1 BLSD 3
1Means of 24 bales. 2Mans of 8 bales. 3Bayes least significant difference (k = 100; approximately P = 0.05) ; NS = not significant (P=0.05). 4Means of 28 bales from 3 sampling dates. ~**Significant at the 0.05 probabilitylevel.
period. Aspergillus sp., primarily members of the A. glaucus group, were identified in the dry and wet hays at the end of the storage period. There were significant interactions ( P < 0.05) between sampling date and m.c. for forage quality characteristics (Table III). These were due to the wet and dry hays being similar in quality at the beginning of the storage period, but differing significantly at the final sampling. Neutral detergent fibre, cellulose, hemicellulose and lignin concentrations increased in all hays during storage. Dry matter digestibility in vitro was significantly lower at the end of the storage period, with no significant changes in TNC concentrations during storage. Wet hay was higher in NDF and cellulose and lower in TNC than dry hay. Digestibility was slightly higher in the dry hay. Sodium diacetate treatment had no effect on forage quality of the alfalfa hay.
Experiment 2 Two swaths were raked together prior to baling of the third-cut alfalfa in this experiment. Hay was again of high quality with no rain damage and dried quickly in the field. Actual moisture contents of wet and dry hays at baling
52 TABLE IV Microbial populations cultured from alfalfa hay taken at three sampling dates during Experiment 2 (propagules× 10-4 g- 1) Bacteria
AspergiUus sp.
Yeast and other fungi I
Sampling date 0 Days2 7 Days3 55 Days2
4640 2872 2042
0.0 21.0 289.4
25.0 5.2 12.0
Moisture Wet4 Dry4
2569 3979
254.1 0.0
13.0 20.2
Sodium diacetate Treated 4 Untreated 4
3248 3300
125.3 128.8
15.0 18.1
1Includesyeast, Alternaria sp., Cladosporiumsp., Penicilliumspp., Phoma sp. and unknown spp. 2Means of 24 bales. 3Means of 8 bales. 4Means of 28 bales from 3 sampling dates. were similar to those in Experiment I (Table I). A lower rate of sodium diacetate (1.3 g kg -1 ) was applied to the wet hay than in Experiment 1. H a y from each t r e a t m e n t was divided into two separate stacks to determine if variability could be reduced. Temperature changes, microbial development and forage quality were similar between stacks of the same treatment. Temperature of dry-harvested hay was 31 ° C, while that of wet hay exceeded 38 ° C. Temperature of dry hay dropped close to ambient air temperature and remained there throughout storage. Temperature of wet hay declined for 2 days before increasing to 46°C after 7 days of storage. This was 21°C greater than the temperature of dry bales. Wet hay remained at this temperature for 10 days and gradually declined to ambient air temperature. After 55 days all wet and dry hays reached the same temperature. Again there were no temperature differences between sodium diacetate-treated and untreated bales. Initial bale m.c. declined to similar levels for wet and dry hays by the end of storage (Table I ). Wet hay lost approximately twice as much dry matter during storage as dry hay. No detectable actinomycetes ( < 50 000 g - 1) were found in any treatments prior to, or during, the storage period (Table IV). Bacterial numbers were not as high as in Experiment 1, but trends were generally similar (Fig. 1). No Aspergillus sp., including A. glaucus, were found in freshly harvested hays. No AspergiUus sp. developed in the dry hay during the entire storage period, but
53 TABLE V Fibre components, dry matter digestibility in vitro (IVDMD) and total non-structural carbohydrates (TNC) of alfalfa hay at three sampling dates for Experiment 2 (g kg - ~dry weight) NDF
Cellulose Hemicellulose
Lignin
IVDMD
TNC
Sampling date 0 Days 1 7 Days 2 14 Days 2 55 Days ~ BLSDa
303 310 343 376 30
151 148 158 177 17
100 108 126 131 20
44.1 45.9 52.2 61.6 6.9
754 745 744 705 16
49.6 57.1 53.1 48.5 NS
Moisture Wet4 Dry4 Significance 5
356 317 **
165 157 **
130 102 **
52.8 50.9 NS
729 737 NS
49.3 51.8 NS
Sodium diacetate Treated4 Untreated4 Significance
333 339 NS
161 162 NS
113 119 NS
52.0 51.8 NS
735 731 NS
49.8 51.3 NS
1Means of 24 bales. 2Means of 8 bales. 3Bayes least significant difference (k = 100; approximately P = 0.05) ; NS = not significant (P=0.05). 4Means of 28 bales from 3 sampling dates. 5**Significant at the 0.05 probability level. A. g/aucus n u m b e r s in t h e wet h a y i n c r e a s e d to a level similar to t h a t o b s e r v e d at t h e last s a m p l i n g of E x p e r i m e n t 1. Yeast a n d o t h e r fungi r e m a i n e d at relatively low p o p u l a t i o n s t h r o u g h o u t storage, w i t h slightly h i g h e r n u m b e r s in the dry hay. As in E x p e r i m e n t 1, forage quality c h a r a c t e r i s t i c s did n o t differ initially b e t w e e n wet a n d d r y hays, r e s u l t i n g in significant i n t e r a c t i o n s ( P < 0.05) b e t w e e n s a m p l i n g date a n d m.c. for all quality factors. N e u t r a l d e t e r g e n t fibre, cellulose, hemicellulose a n d lignin c o n c e n t r a t i o n s i n c r e a s e d in all hays d u r i n g storage a n d I V D M D d e c r e a s e d ( T a b l e V ) . C o n c e n t r a t i o n s o f N D F , cellulose a n d hemicellulose were g r e a t e r ( P < 0.05) in wet h a y t h a n in d r y hay. N o differences were f o u n d in T N C c o n c e n t r a t i o n s a n d s o d i u m d i a c e t a t e t r e a t m e n t h a d no effect o n t h e s e forage quality characteristics. DISCUSSION H a y m.c. at baling as m e a s u r e d b y o v e n - d r i e d field samples was s o m e w h a t lower t h a n p r e d i c t e d by m i c r o w a v e d r y i n g in t h e field. T h i s was p r o b a b l y due
54 to the very rapid drying of the hay caused by excellent drying conditions. Field m.c. samples were taken during baling and microwave samples had been taken prior to baling. The ability to select a representative sample from the swath for m.c. determination appeared to be more important than the differences between microwave and oven drying. Sodium diacetate applied as a powder appeared to give less uniform coverage than liquid preservatives. A significant proportion of the chemical dropped to the ground and was very unpleasant if inhaled. Sodium diacetate is also corrosive to metal components of equipment. Bale to bale variation was much more important than variation between stacks of bales of the same treatment. No differences between stacks of the same treatment were found in Experiment 2, but there was considerable bale to bale variation. Dry-matter losses found in both experiments were similar to those found in alfalfa hay baled at 26.2% m.c. by Clanton et al. (1965). During the first week of storage bacterial populations increased in the dry hay, but declined substantially in the wet hay, possibly because of the growth ofA. glaucus (Fig. 1 ). Bacteria then declined in the dry hay, owing to the low m.c. Wet hay was visibly moulded at the end of the storage period. Although sodium diacetate has been found to inhibit the growth of pure cultures of microorganisms normally found in high-moisture hay (Woolford, 1984), sodium diacetate had no effect on fungal and bacterial populations in this study. This agrees with the results of Walgenbach and Massingill (1986), who found that applications of liquid sodium diacetate in excess of 7.0 g kg- 1 wet hay did not reduce visual mould ratings compared to untreated bales. The heating of wet hay was similar to that recorded by other researchers. Gregory et al. (1963) stored grass hay at 25% m.c. and found that a maximum temperature of 45 ° C was reached 7 days after baling. Their hay moulded, mainly with A. glaucus. Lacey et al. (1983) stored alfalfa hay baled at 25-30% m.c., treated it with ammonium bis-propionate and measured a maximum bale temperature of 46 oC 4 days after treatment. The A. glaucus group were also the predominant fungi which sporulated in their hay. Forage quality characteristics did not differ initially between wet and dry hays, even though the dry hay should have lost more leaves during raking and baling. The similar quality of wet and dry hays at baling may have been due in part to the excellent drying conditions of both experiments. Wet hay was significantly higher in NDF than dry hay, and this difference was associated with a large increase in apparent hemicellulose concentration in the wet hay in both experiments. Although sodium diacetate had no effect on forage quality of alfalfa hay in this study, Russell and Buxton (1985) did find a small increase in the recovery of digestible dry matter from large round bales treated with sodium diacetate at the rate of 1.25 g kg- 1 of wet hay. In Experiment 1, hemicellulose concentration in the wet hay increased from 91 to 165 g kg-1. In Experiment 2, hemicellulose concentration in the wet hay
55
increased from 95 to 158 g kg- 1 during storage. This increase in hemicellulose was not reflected by a large decrease in digestibility. Soluble sugars may have been converted to an insoluble form by microbial activity and bale heating and were then removed in the hemicellulosic fraction during fibre analysis. If this occurred they were still apparently digestible, since digestibility was not greatly affected by the changes in composition of the wet hay. Sodium diacetate treatment of alfalfa hay baled at 26% m.c. was not effective in preventing mould development or heating. Application of a preservative in a dry form appears to have limited value, since uniform coverage of the hay by the chemical is not likely.
REFERENCES Clanton, D.C., Nelson, L.F. and Hochne, O.E., 1965. Nutritive value of hay baled at various moisture contents. Beef Cattle Prog. Rep. University of Nebraska, pp. 6-8. Goering, H.K. and Van Soest, P.J., 1970. Forage Fibre Analysis; Apparatus, Reagents, Procedures, and some Applications. USDA Agricultural Handbook No. 379, U.S. Government Printing Office, Washington, DC., 20 pp. Greenhill, W.L., Couchman, J.F. and De Freitas, J., 1961. Storage of hay. III. Effect of temperature and moisture on loss of dry matter and changes in composition. J. Sci. Food Agric., 12: 293-297. Gregory, P.H., Lacey, M.E., Festenstein, G.N. and Skinner, F.A., 1963. Microbial and biochemical changes during the moulding of hay. J. Gen. Microbiol., 33: 147-174. Henning, J.C. and Dougherty, C.T., 1985. Urea as a yeast and mould inhibitor of grass hay. Agron. Abstr., p. 125. Kjelgaard, W.L., Anderson, P.M., Hoffman, L.D., Wilson, L.L. and Harpster, H.W., 1983. Round baling from field practices through storage and feeding. In: J.A. Smith and V.W. Hayes (Editom), Proc. 14th Int. Grassl. Congr., Lexington, KY. West View Press, Boulder, CO, pp. 657-660. Lacey, J., Lord, K.A. and Cayley, G.R., 1983. Problems of testing novel chemicals for the preservation of damp hay. Anim. Feed Sci. Technol., 8: 283-301. Lechtenberg, V.L. and Holt, D.A., 1982. Innovations in hay harvesting and storing. In: Proc. 1982 Alfalfa Symp., 6 April 1982, University of Kentucky, Lexington, pp. 38-47. Marten, G.C. and Barnes, R.F., 1980. Prediction of energy digestibility of forages with in vitro rumen fermentation and fungal enzyme systems. In: W.J.Pigden, C.C. Balch and M. Graham (Editors), Standardization of Analytical Methodology for Feeds. Proceedings of a Workshop held in Ottawa, Canada, 12-14 March 1979, International Development and Research Centre, Ottawa, pp. 61-71. Miller, L.G., Clanton, D.C., Nelson, L.F. and Hoehne, O.E., 1967. Nutritive value of hay baled at various moisture contents. J. Anim. Sci., 26: 1369-1373. Mohanty, G.P., Jorgensen, N.A., Owens, M.J. and Voelker, H.H., 1967. Effect of moulding on the feeding value and digestibility of alfalfa hay. J. Dairy Sci., 50:990 (abstract). Moore, K.J., Lechtenberg, V.L. and Hendrix, K.S., 1985. Quality of orchardgrass hay ammoniated at different rates, moisture concentrations, and treatment durations. Agron. J., 77: 67-71. Nelson, L.F., 1966. Spontaneous heating and nutrient retention of baled alfalfa hay during storage. Trans. ASAE, 8."509-512. Nelson, L.F., 1972. Storage characteristics and nutritive value of high-density native hay bales. Trans. ASAE, 15: 201-210. Russell, J.R. and Buxton, D.R., 1985. Storage of large round bales of hay harvested at different
56 moisture concentrations and treated with sodium diacetate and/or covered with plastic. Anita. Feed Sci. Technol., 13: 69-81. S.A.S. Institute, 1982. S.A.S. User's Guide: Statistics. S.A.S. Institute, Cary, NC, 583 pp. Sheaffer, C.C. and Clark, N.A., 1975. Effects of organic preservatives on the quality of aerobically stored high moisture baled hay. Agron. J., 67: 660-662. Smith, C.W., 1978. Bayes least significant differences: A review and comparison. Agron. J., 70: 123-127. Smith, D., 1981. Removing and analyzing total nonstructural carbohydrates from plant tissue. Wis. Agric. Exp. Stn. Res. Rep. R2107, 13 pp. Walgenbach, R.P. and Massingill, L.J., 1986. Research techniques and performance evaluations of hay preserving agents. In: Proc. Forage Grassl. Conf., 15-17 April 1986, Athens, GA, American forage and Grassland Council, Lexington, KY, pp. 172-176. Weiss, W.P., Colenbrander, V.F. and Lechtenberg, V.L., 1982. Feeding dairy cows high moisture alfalfa hay preserved with anhydrous ammonia. J. Dairy Sci., 65:1212-1218. Woolford, M.K., 1984. The antimicrobial spectra of organic compounds with respect to their potential as hay preservatives. Grass Forage Sci., 39: 75-79.
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Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands
Microfloral and Compositional Changes in Alfalfa Hay Treated with Sodium Diacetate and Stored at Different Moisture Contents* J.H. CHERNEY', K.D. JOHNSON', J. TUITE 2 and J.J. VOLENEC'
'Department of Agronomy and 2Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN (U.S.A.) (Received 22 May 1986; accepted for publication 2 September 1986)
ABSTRACT Cherney, J.H., Johnson, K.D., Tuite, J. and Volenec, J.J., 1987. Microfloral and compositional changes in alfalfa hay treated with sodium diacetate and stored at different moisture contents. Anita. Feed Sci. Technol., 17: 45-56. Third-cut alfalfa (Medicago sativa L.) hay at high (26.1 and 25.4% ) and low (13.1 and 15.7% ) moisture content was treated with sodium diacetate and made into small bales ( 0.46 × 0.56 × 0.91 m). Hay was sampled initially and stored in stacks of 30-44 bales each in two separate experiments. The temperature of the stacks was monitored and samples were taken during and after the storage period. Hay samples were analyzed for actinomycetes, bacteria and fungi. Fibre composition, digestibility and total non-structural carbohydrates were determined for all samples. Sodium diacetate treatment (3.25 or 1.30 g k g - ' ) was ineffective in preventing microbial growth or heating of wet alfalfa hay. Wet hay temperatures in both experiments increased to 44-46 °C after I week of storage and maintained a high level for I week. Fungi and bacteria were abundant in the hay at the start of storage, but the bacterial population declined as the hay dried in the stacks. Actinomycetes were not detected at the end of the storage period. Aspergillus glaucus developed in the wet hay and was the major microorganism present. Neutral detergent fibre concentration increased in the wet hay and was associated with a relatively large increase in the apparent hemicellulose concentration. The increase in hemicellulose did not have a major effect on the digestibility of the wet hay.
INTRODUCTION
Hay baled at >20% moisture content (m.c.) favors the development of microorganisms, is generally reduced in quality and may have severe losses of dry matter ( Lechtenberg and Holt, 1982 ). Dry weight loss in stored hay averages approximately 1% for each percentage point above 10% at time of storage *Contribution from the Purdue University Agricultural Experiment Station, Journal Paper No. 10723, West Lafayette, IN, U.S.A.
0377-8401/87/$03.50
© 1987 Elsevier Science Publishers B.V.
46 (Kjelgaard et al., 1983). Dry matter losses of 8.5% were found for fourth-cut alfalfa (Medicago sativa L. ) baled at 26.2% m.c., and of 9.8% for hay baled at 35.2% m.c. ( Clanton et al., 1965 ). Greenhill et al. (1961) noted that dry matter losses did not relate well to nutritional losses determined by chemical changes in constituents. There has been little research dealing with the microbial changes in moulding alfalfa hay. Grass hay baled at 16% m.c. contained a relatively small microbial population after storage ( Gregory et al., 1963). However, hay at 25% m.c., heated to 45 ° C and moulded with AspergiUus glaucus, and hay with an initial m.c. of 40% heated to 60 ° C and contained a large population of thermophilic fungi. The density at which alfalfa and grass hay bales were formed did not affect their storage characteristics or quality ( Nelson, 1966, 1972 ). The maturity of alfalfa at harvest was of secondary importance and the primary factor affecting storage and quality was m.c. Mohanty et al. (1967) found that thirdcut alfalfa, when stored wet, heated to 50 ° C and reduced weight gains of steers to 75% of those obtained with well-cured hay. Steers receiving hay baled at low m.c. gained weight faster than those receiving hay baled at high m.c., but no differences were found in forage intake (Miller et al., 1967). A variety of chemicals have been used as preservatives on grass and legume hays baled at high moisture contents. Organic acids inhibited mould growth and reduced heating and storage losses ( Sheaffer and Clark, 1975 ), but organic acids are corrosive to equipment. Anhydrous ammonia successfully preserved wet hay and improved overall nutritive value, especially of low-quality hay (Weiss et al., 1982; Moore et al., 1985). Urea also has been used as a yeastand mould-inhibitor in tall fescue (Festuca arundinacea Schreb. ) hay baled at 33% moisture ( Henning and Dougherty, 1985). Lacey et al. (1983) concluded that current application techniques for hay preservatives may not be adequate for uniform application of the product. Our objectives were to: (1) determine the influence of moisture on microbial populations in stored alfalfa hay and the subsequent effects on forage quality; ( 2 ) evaluate the effectiveness of sodium diacetate as a hay preservative. MATERIALSAND METHODS
Experiment I Harvest and treatment application Third-cut alfalfa hay was made into small bales (0.46 × 0.56 X 0.91 m ) at the Animal Sciences Farm, Purdue University, West Lafayette, IN, U.S.A., on 2 August 1983. Drying conditions were excellent with clear skies, a high temperature of 32 ° C, low humidity and a 16 km h 1 wind. Hay m.c. was monitored in the field by microwave drying of samples. Hay was cut with a conventional mower-conditioner on 1 August 1983 and baled on 2 and 3 August when hay
47 m.c. had fallen below 30 and 20%, respectively. Hay moisture contents of ovendried field samples taken at baling were 26.4% m.c. on 2 August and 13.1% m.c. on 3 August. Sodium diacetate ( "Crop Cure" ) was applied as a granular powder at baling. The commercially available "Crop Cure" contained 50% sodium diacetate by weight, along with fillers, dust suppressors and trace minerals (dried whey, sodium bentonite, salt, sodium silico aluminate, vegetable fat, soy lecithin, calcium stearate, ferrous sulphate, manganous oxide, cobalt carbonate, copper oxide and iron oxide). A spreader was mounted on a New Holland 310 Hayliner baler and two plastic tubes were used to distribute the preservative over the hay as it entered the bale chamber. The spreader was powered by an electric motor operated from the tractor. The rate of preservative application was 3.25 g "Crop Cure" kg -1 wet hay for hay at 26.1 m.c., and 0.95 g "Crop Cure" kg -1 wet hay for hay at 13.1% m.c. The actual rate applied for wet hay was higher than recommended by the manufacturer, and this rate was lowered for the second experiment.
Storage Six bales were weighed and placed in the centre of a four-tiered stack of 44 bales and all bale stacks were stored indoors. All bales in a stack were from the same treatment. Two thermocouples were placed in the centre bales of the dry stacks and three thermocouples were placed in the centre bales of the wet stacks. Temperatures were monitored daily for 30 days and three times per week for an additional 27 days until the temperature of all treatments equilibrated. Ambient air temperature reached a maximum at 32.2 °C early in the storage period and declined gradually throughout storage, with a low temperature of 12.8°C.
Sampling and quality analysis Six bales in each of the four treatments were sampled initially by taking six cores with a Pennsylvania State forage sampler. After 7 days of storage, two bales in the interior of each stack were sampled by taking six cores. After 57 days of storage the temperature in all stacks had equilibrated. The stacks were taken apart and six of the centre bales were weighed and sampled by taking six cores. Forage samples for chemical analysis were dried at 60 ° C and ground to pass through a l-ram screen. Neutral detergent fibre (NDF), cellulose, hemicellulose and permanganate lignin were determined, as described by Goering and Van Soest (1970), at 0, 7 and 57 days of storage. Dry matter digestibility in vitro (IVDMD) was determined by the modified procedure of Marten and Barnes (1980) and total non-structural carbohydrates (TNC) were analyzed according to Smith (1981).
48
Experiment 2 Harvest and treatment application Third-cut alfalfa hay was made into small bales at a farm near Lafayette, IN, U.S.A. The crop was cut with a conventional mower-conditioner on the afternoon of 29 August 1983. Drying conditions were again excellent with clear skies, a high temperature of 29.4 ° C, low humidity and a 16-24 km h-~ wind. Hay was baled on 31 August when hay m.c. had fallen below 30%, and on 1 September when hay m.c. dropped below 20%. Actual hay m.c. based on ovendried field samples was 25.9 and 15.7%, respectively. Sodium diacetate was applied as in Experiment 1, except for a reduced application rate on wet hay. Hay at 25.9% m.c. was treated with 1.3 g "Crop Cure" kg -~ wet hay, and hay at 15.7% m.c. was treated with 0.8 g "Crop Cure" kg -1 wet hay.
Storage Storage was in four-tiered stacks of 30 bales, with two stacks per treatment. Six bales were weighed per treatment and three were placed in the centre of each stack. Stacks were stored indoors and two thermocouples were placed in the centre of each stack. Stack temperatures were monitored for 55 days, after which all treatment temperatures had equilibrated. Ambient air temperature reached a maximum of 25.5 ° C early in the storage period and declined gradually to 9.4 ° C.
Sampling and quality analysis Three bales in each of the eight stacks were sampled initially by taking six cores. After 7 and 14 days a centre bale in each of the stacks was sampled by taking six cores. After 55 days of storage, three of the centre bales in each stack were sampled. Chemical analyses were similar to those in Experiment 1.
Microbiological analysis Sample cores taken from both experiments for microbial assays were refrigerated immediately after sampling. Samples (10 g) were blended in 500 ml sterile 0.1% agar and 1:10 dilutions were made. Dilutions were added to 3 separate petri dishes and cooled molten media were added for each of 3 media. Malt salt (6% NaC1) was used to detect xerophytic fungi; potato dextrose agar containing 100 mg kg-1 Tergitol NPX and 30 mg kg-1 chlorotetracycline was used to isolate other fungi. Beef peptone plus 100 mg kg-~ Actidione (cycloheximide) and 0.2% casein (BP) were used to isolate bacteria and actinomycetes.
Statistical analysis Experiments 1 and 2 were analyzed separately for forage quality using the general linear models option of the Statistical Analysis System ( S.A.S. ) pack-
49 TABLE I Hay moisture,bale weightand dry-matterloss of alfalfa hay baledat two moisturelevels Moisture content ( %) At baling1
Afterstorage2
Bale weight Dry matter loss at baling~ duringstorage2 (kg) (g kg- 1 )
Experiment 1 Wet Dry
26.4 13.1
12.3 10.3
30.8 24.9
65.5 51.7
Experiment2 Wet Dry
25.9 15.7
11.9 11.9
34.6 27.7
66.9 32.6
1Meansof 15 fieldsamplesfor wet hay and 10 fieldsamplesfor dry hay. 2Meansof 12 bales. age (1982). The experimental design was a randomized complete block with a factorial arrangement of sampling date, moisture and chemical treatment factors. Since Experiment 2 included multiple stacks of each hay treatment, this was also included in the factorial arrangement. Differences between sampling dates were determined using the Bayes least significance difference (BLSD) test (Smith, 1978). RESULTS
Experiment I Owing to dry conditions, yield of third-cut alfalfa was low and three swaths were raked together prior to baling. Hay was of very high quality and dried rapidly in the field without rain damage. Moisture content at baling and initial bale weights are given in Table I. Bale temperature initially exceeded 33°C, but declined to approximately ambient air temperature within 24 h. The temperature of the dry hay followed that of ambient air temperature, except that stacks were well buffered and responded slowly to abrupt changes in air temperature. The temperature of wet hay rose after 3 days of storage and reached 44 ° C after 5 days. This was 17°C higher than the temperature of dry bales. This temperature was maintained for 8 days and then gradually declined. There was no difference in temperature between the sodium diacetate-treated and untreated bales. Bale m.c. at the end of the storage period declined to similar levels for wet and dry hays (Table I). Approximately 66 and 52 g kg -1 of the initial dry matter were lost in storage for the wet and dry hays, respectively. Fungi and bacteria were abundant in the hay at the start of storage (Table
5O TABLE II Microbial populations cultured from alfalfa hay at three sampling dates during Experiment 1 (propagules×10 4g ~) Actinomycetes Sampling date 0 Days 2 7 Days 3 57 Days 2
Bacteria
AspergiUus sp.
Yeast and other fungi ~
1.96 0.66 < 0.01
10 676 10 210 2 299
0.1 150.5 212.3
72.7 9.6 12.0
Moisture Wet 4 Dry 4
1.28 0.56
5 587 8 452
159.1 68.5
23.3 52.1
Sodium diacetate Treated 4 Untreated 4
0.96 0.87
7 425 6 613
99.3 128.3
37.2 38.1
1Includes yeast, Alternaria sp., Cladosporium sp., Penicillium spp., Phoma sp. and unknown spp. 2Means of 24 bales. ~Means of 8 bales. 4Means of 28 bales from 3 sampling dates.
II). Most of the fungi isolated grow only in high-moisture environments and are normal pre-harvest flora. There were no interactions between sodium diacetate treatment and m.c. or sampling date. After 7 days, AspergiUusglaucus, a xerophytic fungus, grew and sporulated only in the wet hay, with no appreciable sporulation of any fungi in the dry hay. Bacterial populations declined in the wet hay and were isolated in greater numbers in the dry hay during the first week of storage (Fig. 1 ). Bacterial populations then declined in the dry hay and bacterial numbers were relatively low after 57 days in both wet and dry hays. Actinomycetes were present in significant numbers initially, but declined during storage, and were not detected at the end of the storage 120 ~D
100 80
50 "~
40
4~
20
ca
o
0
i Sampling Date (weeks)
e
Fig. 1. Bacterial counts in wet and dry hay during storage. Means of treated and untreated hay for Experiments 1 and 2.
51 TABLE III Fibre components, dry matter digestibility in vitro (IVDMD) and total non-structural carbohydrates ( T N C ) of alfalfa hay at three sampling dates for Experiment 1 (g kg - 1 dry weight) NDF
Cellulose
Hemicellulose
Lignin
IVDMD
TNC
280 292 368 29
135 134 166 9
94 106 137 21
38.6 38.8 55.5 5.1
750 746 710 11
85.1 63.1 75.4 NS
Moisture Wet 4 Dry 4 Significance ~
333 306 **
148 149 NS
127 101 **
44.7 47.1 NS
727 737 **
74.0 81.5 **
Sodium diacetate Treated 4 Untreated 4 Significance
317 322 NS
148 149 NS
114 114 NS
44.8 46.9 NS
734 730 NS
74.8 80.8 NS
Samplingdate 0Days 1 7Days 2 57Days 1 BLSD 3
1Means of 24 bales. 2Mans of 8 bales. 3Bayes least significant difference (k = 100; approximately P = 0.05) ; NS = not significant (P=0.05). 4Means of 28 bales from 3 sampling dates. ~**Significant at the 0.05 probabilitylevel.
period. Aspergillus sp., primarily members of the A. glaucus group, were identified in the dry and wet hays at the end of the storage period. There were significant interactions ( P < 0.05) between sampling date and m.c. for forage quality characteristics (Table III). These were due to the wet and dry hays being similar in quality at the beginning of the storage period, but differing significantly at the final sampling. Neutral detergent fibre, cellulose, hemicellulose and lignin concentrations increased in all hays during storage. Dry matter digestibility in vitro was significantly lower at the end of the storage period, with no significant changes in TNC concentrations during storage. Wet hay was higher in NDF and cellulose and lower in TNC than dry hay. Digestibility was slightly higher in the dry hay. Sodium diacetate treatment had no effect on forage quality of the alfalfa hay.
Experiment 2 Two swaths were raked together prior to baling of the third-cut alfalfa in this experiment. Hay was again of high quality with no rain damage and dried quickly in the field. Actual moisture contents of wet and dry hays at baling
52 TABLE IV Microbial populations cultured from alfalfa hay taken at three sampling dates during Experiment 2 (propagules× 10-4 g- 1) Bacteria
AspergiUus sp.
Yeast and other fungi I
Sampling date 0 Days2 7 Days3 55 Days2
4640 2872 2042
0.0 21.0 289.4
25.0 5.2 12.0
Moisture Wet4 Dry4
2569 3979
254.1 0.0
13.0 20.2
Sodium diacetate Treated 4 Untreated 4
3248 3300
125.3 128.8
15.0 18.1
1Includesyeast, Alternaria sp., Cladosporiumsp., Penicilliumspp., Phoma sp. and unknown spp. 2Means of 24 bales. 3Means of 8 bales. 4Means of 28 bales from 3 sampling dates. were similar to those in Experiment I (Table I). A lower rate of sodium diacetate (1.3 g kg -1 ) was applied to the wet hay than in Experiment 1. H a y from each t r e a t m e n t was divided into two separate stacks to determine if variability could be reduced. Temperature changes, microbial development and forage quality were similar between stacks of the same treatment. Temperature of dry-harvested hay was 31 ° C, while that of wet hay exceeded 38 ° C. Temperature of dry hay dropped close to ambient air temperature and remained there throughout storage. Temperature of wet hay declined for 2 days before increasing to 46°C after 7 days of storage. This was 21°C greater than the temperature of dry bales. Wet hay remained at this temperature for 10 days and gradually declined to ambient air temperature. After 55 days all wet and dry hays reached the same temperature. Again there were no temperature differences between sodium diacetate-treated and untreated bales. Initial bale m.c. declined to similar levels for wet and dry hays by the end of storage (Table I ). Wet hay lost approximately twice as much dry matter during storage as dry hay. No detectable actinomycetes ( < 50 000 g - 1) were found in any treatments prior to, or during, the storage period (Table IV). Bacterial numbers were not as high as in Experiment 1, but trends were generally similar (Fig. 1). No Aspergillus sp., including A. glaucus, were found in freshly harvested hays. No AspergiUus sp. developed in the dry hay during the entire storage period, but
53 TABLE V Fibre components, dry matter digestibility in vitro (IVDMD) and total non-structural carbohydrates (TNC) of alfalfa hay at three sampling dates for Experiment 2 (g kg - ~dry weight) NDF
Cellulose Hemicellulose
Lignin
IVDMD
TNC
Sampling date 0 Days 1 7 Days 2 14 Days 2 55 Days ~ BLSDa
303 310 343 376 30
151 148 158 177 17
100 108 126 131 20
44.1 45.9 52.2 61.6 6.9
754 745 744 705 16
49.6 57.1 53.1 48.5 NS
Moisture Wet4 Dry4 Significance 5
356 317 **
165 157 **
130 102 **
52.8 50.9 NS
729 737 NS
49.3 51.8 NS
Sodium diacetate Treated4 Untreated4 Significance
333 339 NS
161 162 NS
113 119 NS
52.0 51.8 NS
735 731 NS
49.8 51.3 NS
1Means of 24 bales. 2Means of 8 bales. 3Bayes least significant difference (k = 100; approximately P = 0.05) ; NS = not significant (P=0.05). 4Means of 28 bales from 3 sampling dates. 5**Significant at the 0.05 probability level. A. g/aucus n u m b e r s in t h e wet h a y i n c r e a s e d to a level similar to t h a t o b s e r v e d at t h e last s a m p l i n g of E x p e r i m e n t 1. Yeast a n d o t h e r fungi r e m a i n e d at relatively low p o p u l a t i o n s t h r o u g h o u t storage, w i t h slightly h i g h e r n u m b e r s in the dry hay. As in E x p e r i m e n t 1, forage quality c h a r a c t e r i s t i c s did n o t differ initially b e t w e e n wet a n d d r y hays, r e s u l t i n g in significant i n t e r a c t i o n s ( P < 0.05) b e t w e e n s a m p l i n g date a n d m.c. for all quality factors. N e u t r a l d e t e r g e n t fibre, cellulose, hemicellulose a n d lignin c o n c e n t r a t i o n s i n c r e a s e d in all hays d u r i n g storage a n d I V D M D d e c r e a s e d ( T a b l e V ) . C o n c e n t r a t i o n s o f N D F , cellulose a n d hemicellulose were g r e a t e r ( P < 0.05) in wet h a y t h a n in d r y hay. N o differences were f o u n d in T N C c o n c e n t r a t i o n s a n d s o d i u m d i a c e t a t e t r e a t m e n t h a d no effect o n t h e s e forage quality characteristics. DISCUSSION H a y m.c. at baling as m e a s u r e d b y o v e n - d r i e d field samples was s o m e w h a t lower t h a n p r e d i c t e d by m i c r o w a v e d r y i n g in t h e field. T h i s was p r o b a b l y due
54 to the very rapid drying of the hay caused by excellent drying conditions. Field m.c. samples were taken during baling and microwave samples had been taken prior to baling. The ability to select a representative sample from the swath for m.c. determination appeared to be more important than the differences between microwave and oven drying. Sodium diacetate applied as a powder appeared to give less uniform coverage than liquid preservatives. A significant proportion of the chemical dropped to the ground and was very unpleasant if inhaled. Sodium diacetate is also corrosive to metal components of equipment. Bale to bale variation was much more important than variation between stacks of bales of the same treatment. No differences between stacks of the same treatment were found in Experiment 2, but there was considerable bale to bale variation. Dry-matter losses found in both experiments were similar to those found in alfalfa hay baled at 26.2% m.c. by Clanton et al. (1965). During the first week of storage bacterial populations increased in the dry hay, but declined substantially in the wet hay, possibly because of the growth ofA. glaucus (Fig. 1 ). Bacteria then declined in the dry hay, owing to the low m.c. Wet hay was visibly moulded at the end of the storage period. Although sodium diacetate has been found to inhibit the growth of pure cultures of microorganisms normally found in high-moisture hay (Woolford, 1984), sodium diacetate had no effect on fungal and bacterial populations in this study. This agrees with the results of Walgenbach and Massingill (1986), who found that applications of liquid sodium diacetate in excess of 7.0 g kg- 1 wet hay did not reduce visual mould ratings compared to untreated bales. The heating of wet hay was similar to that recorded by other researchers. Gregory et al. (1963) stored grass hay at 25% m.c. and found that a maximum temperature of 45 ° C was reached 7 days after baling. Their hay moulded, mainly with A. glaucus. Lacey et al. (1983) stored alfalfa hay baled at 25-30% m.c., treated it with ammonium bis-propionate and measured a maximum bale temperature of 46 oC 4 days after treatment. The A. glaucus group were also the predominant fungi which sporulated in their hay. Forage quality characteristics did not differ initially between wet and dry hays, even though the dry hay should have lost more leaves during raking and baling. The similar quality of wet and dry hays at baling may have been due in part to the excellent drying conditions of both experiments. Wet hay was significantly higher in NDF than dry hay, and this difference was associated with a large increase in apparent hemicellulose concentration in the wet hay in both experiments. Although sodium diacetate had no effect on forage quality of alfalfa hay in this study, Russell and Buxton (1985) did find a small increase in the recovery of digestible dry matter from large round bales treated with sodium diacetate at the rate of 1.25 g kg- 1 of wet hay. In Experiment 1, hemicellulose concentration in the wet hay increased from 91 to 165 g kg-1. In Experiment 2, hemicellulose concentration in the wet hay
55
increased from 95 to 158 g kg- 1 during storage. This increase in hemicellulose was not reflected by a large decrease in digestibility. Soluble sugars may have been converted to an insoluble form by microbial activity and bale heating and were then removed in the hemicellulosic fraction during fibre analysis. If this occurred they were still apparently digestible, since digestibility was not greatly affected by the changes in composition of the wet hay. Sodium diacetate treatment of alfalfa hay baled at 26% m.c. was not effective in preventing mould development or heating. Application of a preservative in a dry form appears to have limited value, since uniform coverage of the hay by the chemical is not likely.
REFERENCES Clanton, D.C., Nelson, L.F. and Hochne, O.E., 1965. Nutritive value of hay baled at various moisture contents. Beef Cattle Prog. Rep. University of Nebraska, pp. 6-8. Goering, H.K. and Van Soest, P.J., 1970. Forage Fibre Analysis; Apparatus, Reagents, Procedures, and some Applications. USDA Agricultural Handbook No. 379, U.S. Government Printing Office, Washington, DC., 20 pp. Greenhill, W.L., Couchman, J.F. and De Freitas, J., 1961. Storage of hay. III. Effect of temperature and moisture on loss of dry matter and changes in composition. J. Sci. Food Agric., 12: 293-297. Gregory, P.H., Lacey, M.E., Festenstein, G.N. and Skinner, F.A., 1963. Microbial and biochemical changes during the moulding of hay. J. Gen. Microbiol., 33: 147-174. Henning, J.C. and Dougherty, C.T., 1985. Urea as a yeast and mould inhibitor of grass hay. Agron. Abstr., p. 125. Kjelgaard, W.L., Anderson, P.M., Hoffman, L.D., Wilson, L.L. and Harpster, H.W., 1983. Round baling from field practices through storage and feeding. In: J.A. Smith and V.W. Hayes (Editom), Proc. 14th Int. Grassl. Congr., Lexington, KY. West View Press, Boulder, CO, pp. 657-660. Lacey, J., Lord, K.A. and Cayley, G.R., 1983. Problems of testing novel chemicals for the preservation of damp hay. Anim. Feed Sci. Technol., 8: 283-301. Lechtenberg, V.L. and Holt, D.A., 1982. Innovations in hay harvesting and storing. In: Proc. 1982 Alfalfa Symp., 6 April 1982, University of Kentucky, Lexington, pp. 38-47. Marten, G.C. and Barnes, R.F., 1980. Prediction of energy digestibility of forages with in vitro rumen fermentation and fungal enzyme systems. In: W.J.Pigden, C.C. Balch and M. Graham (Editors), Standardization of Analytical Methodology for Feeds. Proceedings of a Workshop held in Ottawa, Canada, 12-14 March 1979, International Development and Research Centre, Ottawa, pp. 61-71. Miller, L.G., Clanton, D.C., Nelson, L.F. and Hoehne, O.E., 1967. Nutritive value of hay baled at various moisture contents. J. Anim. Sci., 26: 1369-1373. Mohanty, G.P., Jorgensen, N.A., Owens, M.J. and Voelker, H.H., 1967. Effect of moulding on the feeding value and digestibility of alfalfa hay. J. Dairy Sci., 50:990 (abstract). Moore, K.J., Lechtenberg, V.L. and Hendrix, K.S., 1985. Quality of orchardgrass hay ammoniated at different rates, moisture concentrations, and treatment durations. Agron. J., 77: 67-71. Nelson, L.F., 1966. Spontaneous heating and nutrient retention of baled alfalfa hay during storage. Trans. ASAE, 8."509-512. Nelson, L.F., 1972. Storage characteristics and nutritive value of high-density native hay bales. Trans. ASAE, 15: 201-210. Russell, J.R. and Buxton, D.R., 1985. Storage of large round bales of hay harvested at different
56 moisture concentrations and treated with sodium diacetate and/or covered with plastic. Anita. Feed Sci. Technol., 13: 69-81. S.A.S. Institute, 1982. S.A.S. User's Guide: Statistics. S.A.S. Institute, Cary, NC, 583 pp. Sheaffer, C.C. and Clark, N.A., 1975. Effects of organic preservatives on the quality of aerobically stored high moisture baled hay. Agron. J., 67: 660-662. Smith, C.W., 1978. Bayes least significant differences: A review and comparison. Agron. J., 70: 123-127. Smith, D., 1981. Removing and analyzing total nonstructural carbohydrates from plant tissue. Wis. Agric. Exp. Stn. Res. Rep. R2107, 13 pp. Walgenbach, R.P. and Massingill, L.J., 1986. Research techniques and performance evaluations of hay preserving agents. In: Proc. Forage Grassl. Conf., 15-17 April 1986, Athens, GA, American forage and Grassland Council, Lexington, KY, pp. 172-176. Weiss, W.P., Colenbrander, V.F. and Lechtenberg, V.L., 1982. Feeding dairy cows high moisture alfalfa hay preserved with anhydrous ammonia. J. Dairy Sci., 65:1212-1218. Woolford, M.K., 1984. The antimicrobial spectra of organic compounds with respect to their potential as hay preservatives. Grass Forage Sci., 39: 75-79.