Effect of Conservation Method on Digestibility, Nitrogen Balance, and Intake of Alfalfa1

Effect of Conservation

Method

on Digestibility,

Nitrogen

Balance, and Intake of Alfalfa I M A R T I N CLANCY 2 , P. J. WANGSNESS, and B. R. 8 A U M G A R D T Department of Oairy and Animal Science The Pennsytvania State University University Park 16802 ABSTRACT

maturity, voluntary intakes of silage dry matter (DM) by ruminants is usually less than of hay (5, 12, 18, 22, 23). A linear relationship often has been reported between intake and DM content (8, 15). However, a causal relationship is by no means established, and data of Thomas et al. (22) showed no significant difference between intakes of dried wilted silage and wilted silage, though data for their rewetted hay and hay contrasts were inconclusive. Many workers share Campling's view (5) that length of time in the gut may be responsible in part for the low intake of silage, and that rate of disappearance of feed from the reticulo-rumen is dependent on its rate of digestion. Although Peterson et al. (19) did not report any significant differences in feeding behavior in eating alfalfa haylage or hay, eating rates are responsive to physical characteristics of the feed (2). Experiments which included a metabolism phase, studies of rate of digestion, and studies of feeding behavior were designed to examine factors causing the lower intake of alfalfa silages and to test formaldehyde treatment as a possible solution. Possible relationships of these and other dietary parameters with digestible energy intake (DEI) are discussed.

Alfalfa diets were fed to growing wethers to examine factors lowering intakes of alfalfa silage and to identify dietary characteristics related to voluntary intake. Direct-cut silage (Silage), direct-cut silage dried to the same dry matter as hay (Drysil), heat-dried hay (Hay), hay with water added to give the same dry matter as silage (Wethay), direct-cut silage treated with .5% of 2:1 formaldehyde (37%):formic acid (90%) mix at ensiling (Formal), and 24-h wilted silage (Wilted) were made from forage cut and chopped similarly. Digestible dry matter of Silage (50.5%) was lower than Formal (54.5%)and Wethay (57.4%)with other diets intermediate. Number of meals per day tended to be greatest for the Silage diets. Eating rates were highest for Formal and Wilted diets. More than 1.81% of nitrogen was in the acid detergent fiber insoluble fraction, resulting in low nitrogen digestibilities and negative nitrogen balances for Silage, Drysil, and Formal diets. Voluntary digestible energy intakes (Silage, 190; Drysil, 177; Hay, 202; Wethay, 228; Formal, 225; Wilted, 200 kcal/weight kg.7 s) were not related to moisture content of the forages. Digestibility, density, rate of digestion of cell wall constituents, and behavioral patterns were discussed as possible factors related to intake.

EXPERIMENTAL PROCEDURE

Six diets were prepared from an essentially pure alfalfa sward and fed to 24 growing wethers in a metabolism study. Digestibilities, nitrogen balance, and intakes were measured; feeding behavior data was collected concurrently.

INTRODUCTION

In comparisons of conserved forages harvested from the same source and at the same

Metabolism Study

August 16, 1976. Authorized for publication on July 26, 1976, as paper no. 5134 in the journal series of the Pennsyb vania Agricultural Experiment Station. 2 Qeleq Ltd., Dundalk, Ireland.

Alfalfa, second cutting, early bloom stage, was conserved in various ways to give six dietary treatments: direct-cut high moisture silage (Silage); direct-cut silage, dried before feeding to the same DM as hay (Drysil); artificially dried hay (Hay); hay with water

Received

572

INTAKE AND UTI LI ZAT1ON OF CONSERVED ALFALFA added to give the same DM as silage (W.ethay); direct-cut silage treated with .5% of a 2/1 formaldehyde (37%) formic acid (90% concn) mix added at ensiling (Formal); and silage wilted for 24 h during hot, sunny weather before ensiling (Wilted). All alfalfa was cut at the same time from the same field. The Silage, Formal, and Wilted treatments were ensiled in experimental metal tower silos, 1.2 m diameter and 2.4 m high, weighted with a concrete disk. The interior was lined with 4-mm thick polyethylene, and silos were covered with a metal cap. After 7 wk, silages were taken out and stored at - 2 0 C in strong plastic bags. The hay treatment was baled and dried on forced-air drying wagons (50 C, 24 h) and stored in a barn loft. The hay later was chopped finely and stored in burlap bags. The Wethay treatment was prepared by mixing the hay with an appropriate amount of water in a small feed mixer (paddle t y p e ) for 15 min to give a product with approximately 25% DM. The Wethay was stored in a refrigerator for 12 h before feeding; a fresh batch was mixed every 12 h. Drysil treatment was prepared from silage after 7-wk fermentation by putting into burlap bags and stacking in a drier which had forced air at 60 C entering through floor grids. Bags were taken out after 4 days and placed in the barn loft with the hay. The four treatments that went through the ensiling process were chopped finely at pickup. Four growing wethers (.75 Suffolk crosses) were allotted to each diet to equalize average weights per treatment (mean of 33.2 kg), and housed in individual metabolism crates (3) in a temperature-controlled environment (18 -+ 1 C). They had trace mineralized salt and water available ad libitum and were fed throughout the 23-day precoUection and 10-day sample collection periods to give about 10% feed refusals. Samples of feed, feed refusals, feces, and urine were collected over 10 days to allow calculation o f ad libitum intakes, digestibilities, and nitrogen (N) balances. Details o f collection, storage, and preparation of samples for the various moisture and chemical determinations are described (6). Moisture contents as measured by the chemical saponification m e t h o d of Hood et al. (16) and N as determined on the wet samples were used for estimations of digestibility and intake. Solid and bulk densities were measured on the feeds both as fed and after drying and

573

grinding through a Wiley mill (1 mm screen)as described (7). Water displacement density of the as-fed diets was measured by immersing about 400 g DM of feed in a 30-liter capacity cylinder fitted with an overflow spout to allow collection and weighing of the overflow. Rate of digestion of cell wall constituents (CWC) was measured as outlined by Smith et al. ( 2 1 ) w i t h modifications (7). Incubation of 400 mg of air dry samples was stopped at 0, 6, 12, 20, 28, 36, 44, 52, and 72 h, and CWC remaining were measured by the procedure of Van Soest and Wine (24). Variances for measures were analyzed as one-way classifications, and differences between means were compared by Duncan's New Multiple Range Test (10). Simple correlation and regression programs and a step-up multiple regression program were used for relating dietary and feeding behavioral parameters with intake. Behavior Study

Feeding behavior of the 24 lambs was studied during 5 days of the metabolism phase. The methods of data collection have been described by Peterson et al. (19). Counter-balanced feeder doors equipped with a cam and microswitch were added to the feeder entrance of the metabolism crates. To eat, the animal deflected the door which closed the microswitch in the 28-V DC circuit causing a deflection of an event pen on a recording chart running at 6.46 cm/h. In this way, a record of eating activity was permanent, and meal eating behavior was determined from the chart record. A meal was represented by a deflection of at least 1.5-rain duration and separated from the previous mea| by at least 20 rain. Deflections within a meal were summed to give actual meal duration as distinct from the total meal time which was termed overall meal duration. Number of meals per day, actual and overall meal duration per day, as well as actual and overall duration per meal, were the criteria studied. These data were combined with 24-h intake data to calculate eating rates. RESULTS AND DISCUSSION Metabolism Study

Table 1 shows the chemical analysis of the Journal of Dairy Science Vol. 60, No. 4

574

CLANCY ET AL. -r

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diets as fed. The silages were preserved well, and the hay was excellent quality. The lactic acid content of Silage and Formal was high and together with the pH <4.2, indicated a desirable fermentation process. The DM manipulations were with close precision; the rewetted hay (Wethay) had a DM of 25.29% identical to the direct-cut silage (Silage) while the dried silage (Drysil) DM, 88.47% was close to the 87.41% for the hay (Hay). All ensiled materials had less cell solubles than the Hay and Wethay, which probably represent effluent runoff from the silos which totaled 26.9 and 17.3 liters from approximately 2,000 kg of Silage and Formal during the 40 days after ensiling. The lower crude protein content probably represented larger N losses in the high moisture silages (25). The digestibilities of these silage-hay diets (Table 2) show significant differences among diets for all digestibilities. Silage dry-matter digestibility (DDM) of 50.5% was significantly less than Formal (54.5%) and Wethay (57.4%) which had the highest DDM. The trend was similar for the digestibility of the organic matter (DOM) and digestible energy (DE). The higher digestibility of the formaldehyde-formic acid treated silage (Formal) compared to the untreated (Silage) also was reported by Waldo et al. (26), though not by Waldo and Keys (27). The acid detergent fiber (ADF) protein values in Table 1 are high and according to criteria of Goering and Waldo (14) are classified as overheated or overprotected protein; i.e., >1.81% ADF protein. These authors showed high negative correlations between acid detergent insoluble N and N digestibility. Data in Table 2 confirm low and decreasing (P<.05) digestible crude protein (DCP) contents-Wethay through Formal. The digestibility of Formal CP (46.6%) was lower than all others and much lower than the 63.1% reported for a similarly treated orchard grassqadino-red clover forage eaten by Holstein heifers (26). This would be expected because the feeds of Waldo et al. (26) had higher protein. However, these workers observed a depression (P<.10) from the control. Nitrogen balances (g of N retained/head/day) were unusually large (+ or - ) ; Silage (-42.14), Drysil (--9.0), Hay (25.5), Wethay (40.8), Formal (-13.7), and Wilted (39.0). Values for Silage were significantly lower than all others except Formal. Corn-

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parably low N balance data had been reported by Roffler et al. (20) for similar hay crop silages with 17.3% CP when DM was determined by toluene distillation and Kjeldahl N determined on the wet sample. The tendency for the Formal N to be retained more than that of Silage despite the significantly lower DCP content in the Formal probably reflects some protective action of the formic acid-formaldehyde treatment on the alfalfa protein resulting in a more useful form of N being absorbed. Although digestible energy contents (DE, ¢~xj kcal/g) (Table 3) had the same trend as the digestibility of the energy (%), Formal and Wethay again having the highest values; DE contents were not significantly different. The greater as-fed densities of the high •moisture diets (Table 3) reflect the greater density of water than dry forage• Measured on the dried sample, the density which was .347 for the parent forage decreased after ensiling, particularly for the untreated, while the 12-h water soaking (Wethay) increased the density• Caloric density values, products of density, and DE content were used in subsequent correlation o and regression analyses. Average DEI of Silage and Drysil (Table 4) = o were less (P<.05) than Wethay and Formal with Wilted and Hay intermediate• Similarly significantly greater DEI was reported for formaldehyde treated silage versus untreated by Waldo .~ et al. (26) and Waldo and Keys (27) though Barker et al. (1) found no differences in DMI .=. (kg/day) for wilted, formic acid treated, or formic-formaldehyde treated alfalfa-brome grass silages• The DMI for the Wilted treatment =0 was equal to the Hay. This response is typical E of many experiments in which intakes of high o dry matter silages (haylage or wilted) are equal to or even greater than untreated silages (17, •~ 20). Both curvilinear (11, 17, 20) and linear (8, 15) relationships between DMI and DM content of forages have been reported. Because our data contained only one data point (Wilted silage) between the extremes in moisture content, it was not possible to evaluate whether the ~= relationship between DM1 and DM was curvilinear. From the data in Table 4, however, the relationship is not due directly to the moisture content of the consumed feed since intake was t~ not responsive to DM content per se. Voluntary ~" intakes of DMI/weight kg-TS/day for Hay and Wethay (89.4 versus 99.6 g), and for Drysil and Journal of Dairy Science Vol. 60, No. 4

Ox ga

T A B L E 3. Digestible energy a n d densities of silage and h a y diets. Diets

o ¢

Z O

Item

Silage

Drysil

Hay

Wethay

Formal

Wilted

Digestible energy c o n t e n t (kcal/g) of dry m a t t e r

2.17 ± .10a

2.24 ± .10 a

2,26 -+ .09 a

2,29 ± .06 a

2.28 ± ,06 a

2.18 ± .04 a

Density (g/ml) Box m e t h o d (as fed) Water displacement (as fed) Graduate d cylinder m e t h o d b

.3155 .9417 .2944

.0907 .4291 .3178

,1160 .3952 .3580

.3560 .9361 .3718

.2976 .9834 .3387

.1773 .6507 .3375

.g,

a v a l u e s do n o t differ significantly, bDiets were dried at 90 C, air equilibrated, a n d g r o u n d t h r o u g h 1 m m screen Wiley mill (%92% dry matter).

z

T A B L E 4. Average voluntary intakes b y wethers fed silage and hay diets. Diets Item Dry m a t t e r intake/weight kg -75/ day (g) Digestible energy intake/weight kg-75/day (kcal) Undigested neutral d e t e ~ e n t fiber intake/weight kg-75/day (g)

Silage

Drysil

Hay

Wethay

Formal

Wilted

86.8 -+ 2.9 ab

76.8 -+ 3,1 a

89.4 ± 4,4 ab

99.6 ± 6.4 b

98,8 ± 6,7 b

92.0 -+ 3,5 b

190.5 ± 6.9 a

177.1 ± 7.8 a

201.5 ± 11.6 ab

228.0 ± 13.1 b

224.7 ± 10.8 b

199.7 ± 4.oab

27.0-+ 2.3 a

22.8+- 1,9 a

27,6 ± 1.9 a

27.8±

2.6 a

a'b'eMeans a n d s t a n d a r d errors with a c o m m o n letter io their superscript on the same row do n o t differ significantly (P<.05).

27.8-+

2.8 a

2 6 , 8 ± 1.6 a

T A B L E 5. Daily intake, n u m b e r o f meals, meal size, eating duration, a n d eating rate b y wethers fed silage a n d hay diets. Diets Silage Item V o l u n t a r y intake g/row (DM)a ml/mw b ml/mw c

~

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80.9 256 275

4.1 de 13 de 14 d

~

Hay SE

71.2 785 224

~

Wethay SE

~

Formal SE

3.O d 33 f 10 e

88.4 762 247

5.8 e 50 f 16 de

84.0 236 226

5.5 de 16 d 15 e

2.9 de 16 8 de

1.2

10.3

1.3

10.1

2.2

14.0

.5

12.7

.4

Meal size g / m w (DM)

6.6

.6

7.9

1.5

9.0

1.3

9.6

1.9

6.7

.4

6.5

.3

Overall eating duration, rain/day

364

25

336

49

333

7

353

4

383

17

366

18

Actual eating duration, rain/day

291

18

273

35

255

23

293

20

211

42

203

20

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.283 .96

.03 d .10 ef

.275 .87

.04 d .13 ef

aWeight kg.75. bBulk density, b o x m e t h o d , uncorrected: v o l u m e intake as fed.

.351 .98

.02 de .06 ef

.287 .77

.01 de .03 f

CBulk density, graduated cylinder m e t h o d o n air dry (%92% DM) g r o u n d samples.

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.494 1.46

.08 f .23 d

.427 1.27

.06 ef .17 de

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578

CLANCYET AL.

Silage (76.8 versus 86.8 g) were not different, but the trend was toward higher intake for Wethay and Silage. These observations confirm observations by Thomas et al. (23) when they fed similarly treated silages and hays to dairy heifers. Data of Thomas et al. (23) is equivocal for some increases of intake of their rewetted hay. However, their evidence for no difference between intakes of dried silage and silage was highly significant in two trials and agrees with the Drysil/Silage contrast reported here. Bull and Tamplin (4) also observed no differences in DMI when they fed unfermented corn plant either undried (31.2% DM) or oven dried to 50.7%, 68.5%, and 93.2% DM. Rate of in vitro digestion, as % digestible CWC digested/h for Silage, Drysil, Hay, Wethay, Formal, and Wilted diets, respectively, were 1.5, 2.0, 1.4, 2.7, 2.6, and 4.4. The rates represented slopes of the 6 through 36-h portion of the 72-h incubation curve (7). There were substantial differences in rate of digestion among the six diets. We were interested in possible relationships between rate of digestion and intake of these forages because rate of digestion has been related to intake (7, 13). Behavior Study

Number of meals, meal sizes, and eating durations by these wethers were not significantly different (Table 5). The DMI were similar though not identical to those of the whole 10-day metabolism phase (only 5 days' behavior data were compiled). Formal DMI was, in this phase, the highest, Drysil lowest, with the other diets intermediate. When intake was expressed on a volume as-fed basis, there were changes in the order of magnitude of the intake differences. Intake of as-fed volume of wet material was lower because the as-fed density reflected the differences caused by the greater density of water in the wet forages. The volume of dry matter intake, however, may reflect more clearly the fill limiting potential of the diets. If so, it might be argued that volume intake of Silage had reached its plateau at 275 ml DM/weight kg.75/day. Such a hypothesis would leave unexplained the lower intakes of DM volume of Wethay and Drysil. Contrasts in eating rates (Table 5) show that actual eating rates of Formal were greatest, Journal of Dairy Science Vol. 60, No. 4

.494 g/weight kg-TS/min compared to .275 g and .283 g/weight kg-7S/min for Drysil and Silage with other diets intermediate. Volume consumption of DM of the Formal diet per rain of actual eating duration was greater than all diets except Wilted. The Silage versus Formal contrast suggests that the rate of eating silages is not limited by their moisture content but by some other factor or factors. If durations of overall and actual eating (Table 5) are contrasted, sheep fed the Formal diet ate only 55% of the time spent at the feeder while on Silage diets they ate approximately 80% of the time. Though the differences were not significant, the number of meals per day tended to be greater for silages than hays. This agrees with data by Dulphy (9), who fed sheep hay and silage during successive periods and always found an increase in number and a decrease in length of meals upon switching from tall fescue hay to silage. SUMMARY

This study has reemphasized the problem of reduced intake and impaired nitrogen metabolism of some silage diets. Formaldehyde-formic acid treatment of silage reduced both problems. There were also marked differences in feeding behavior and rate of digestion among the six forages. Considering all measurements on the six forages, the Silage and Drysil treatments did not appear to be "normal" forages. For the remaining four forages, correlations of DEI with a number of measures of dietary and feeding behavior were determined. In general, digestible dry matter and bulk caloric density (DE × bulk density of the dried, ground sample) gave highest correlations with intake. Moisture content per se of the six forages was not related to intake. Thus, it seemed possible that additional, unknown component(s) of the silage diets depressed intake. A subsequent report will consider this possibility. Combination of the data from the present experiment with additional data on a wide range of forage diets may provide a sufficiently large data base to enable subsequent use of multiple regression to identify dietary factors related to intake. ACKNOWLEDGMENT

Appreciation is expressed to Agway, Inc., for financial support of this research.

INTAKE AND UTILIZATION OF CONSERVED ALFALFA REFERENCES 1 Barker, R. A., D. N. Mowat, J. B. Stone, K. R. Stevenson, and M. G. Freeman. 1973. Formic acid or formic acid-formalin as a silage additive. Can. J. Anita. Set. 53:465. 2 Baumgardt, B. R., A. D. Peterson, and M. Clancy. 1973. Feeding behavior by sheep fed complete diets. Fed. proc. 32:899. (Abstr.) 3 Bratzler, J. W. 1951, A metabolism crate for use with sheep. J. Anita. Sci. 10:592. 4 Bull, L. S., and C. B. Tamplin. 1974. Effect of moisture on intake in sheep. J. Anita. Sci. 39:234. (Abstr.) 5 Campling, R. C. 1966. The intake of hay and silage by cows. J. Brit. Grassl. Soc. 21:41. 6 Clancy, M., P. J. Wangsness, and B. R. Baumgardt. 1977. Effects of moisture determination method on estimates of digestibilities and intakes of conserved alfalfa. J. Dairy Sci. 60:216. 7 Clancy, M., L. S. Bull, P. J. Wangsness, and B. R. Baumgardt. 1976. Digestible energy intake of complete diets by wethers and lactating ewes. J. Anita. Sci. 42:960. 8 Dodsworth, T. C. 1954, Further studies on the fattening value of grass silage and on the effect of dry matter percentage of the diet on dry matter intake in ruminants. J. Agr. Sci. Camb. 44." 383. 9 Dulphy, J. P. 1972. Etude de quelques relations • t" / entre la mode de conservation du fourrage mgere et le comportement alimentaire et meryeique des moutons. Ann. Zootech, Paris. 21:429. 10 Duncan, D. B. 1965. A Bayesian approach to multiple comparisons. Technometrics 7:171. 11 Forbes, T. J., and N. Jackson. 1971. A study of the utilization of silages of different dry matter content by young beef cattle with or without supplemental barley. J. Brit. Grassl. Soc. 26:257. I2 Forbes, T. J., and J. H. D. Irwin. 1968. The use of barn dried hay and silage in fattening young beef cattle. J. Brit. Grassl. SOc. 25:96. 13 Gill, S. S., H. R. Conrad, and J. W. Hibbs. 1969. Relative rate of in vitro cellulose disappearance as a possible estimation of digestible dry matter intake. J. Dairy Sci. 52:1687. 14 Goering, H. K., and D. R. Waldo. 1974. Protein value of heat and formaldehyde-treated ruminant feeds, proc. Maryland Nutr. Conf., College Park,

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MD. 15 Gordon, C. H., J. C. Derbyshire, H. G. Wiseman, E. A. Kane, and C• G. Melin• 1961. preservation and feeding value of alfalfa stored as hay, hayiage, and direct-cut silage. J. Dairy Sci. 44:1299. 16 Hood, R. L., C. E. Allen, R. D. Goodrich, and J. C. Meiske. 1971. A rapid method for the direct chemical determination of water in fermented feeds. J. Anita. Set. 33:1310. 17 Larsen, J. J., E. L. Jensen, and R. F. Johannes. 1971. A comparison of haylage and wilted grass silage plus hay in the dairy cow diet. Res. Report No. 78. College of Agriculture and Life Sciences, Univ. of Wisconsin, Wl. 18 Murdoek, J. C. 1964. Some factors affecting the intake of roughage by sheep. J. Brit. Grassl. Soc. 19:316. 19 Peterson, A. D., B. R. Baumgardt, and T. A. Long. 1974. Relationship between intake of some forage and feeding behavior of sheep. J. Anita. Sci. 38:172. 20 Roffler, R. E., R. P. Niedermeier, and B. R. Baumgardt. 1967. Evaluation of alfalfa-brome forage stored as wilted silage, low moisture silage, and hay. J. Dairy Sci. 50:1805. 21 Smith, L. W., H• K. Goering, D. R. Waldo, and C. H. Gordon. 1971. In vitro digestion rate of forage cell wall components. J. Dairy Set• 54:71. 22 Thomas, J. W., L. A. Moore, M. Okamoto, and J. F. Sykes. 1961. A study of factors affecting rate of intake of heifers fed silage. J. Dairy Sci. 44:1471. 23 Thomas, J. W., L. D. Brown, R. S. Emery, E. J. Benne, and ]. T. Huber. 1969. Comparisons between alfalfa silage and hay. J. Dairy Set. 52:195. 24 Van Soest, P. J., and R. H. Wine. 1967. Use of detergents in the analysis of fibrous feeds. IV. Determination of plant cell wall constituents. ]. Ass. Official Anal. Chem. 50:50. 25 Watson, S. J., and M. J. Nash. 1960, The Conservation of Grass and Forage Crops. Oliver and Boyd, Edinburgh. 26 Waldo, D. R., J. E. Keys, Jr., and C. H. Gordon. 1973. Formaldehyde and formic acid as a silage additive. J. Dairy Sci. 56:229. 27 Waldo, D. R., and J. E. Keys, Jr. 1974. Paraformaldehyde compared to formic acid as a silage preservative. J. Dairy Sci. 57:618. (Abstr.)

Journal of Dairy Science Vol. 60, No. 4