Chemical Drying Agents for Alfalfa Hay: Effect on Nutrient Digestibility and Lactational Performance

Chemical Drying Agents for Alfalfa Hay: Effect on Nutrient Digestibility and Lactational Performance C. J. ZIEMER, A. J. HEINRICHS,1 C. J. CANALE,2 and G. A. VARGA Department of Dairy and Animal Science The Pennsylvania State University University Park 16802 ABSTRACT

Effects of chemical drying agents for hay on plasma profile, lactational performance, and nutrient digestibility by cows were studied. First-cutting alfalfa (late bud) was harvested as hay and treated when cut by applying untreated control, a commercial drying agent (7.64 kglha) , or a mixture of active ingredients, potassium carbonate and sodium carbonate (7.47 kglha). Six multiparous Holstein cows (120 to 150 d postpartum) were fed diets (two cows per treatment) containing 55% hay and 45% concentrate (DM basis) in a balanced two period changeover design. Plasma profiles were similar for all cows, regardless of hay treatment. There were no differences in milk yield, milk fat, or milk protein percentages for control, drying agent, or mixture. Intake of DM was not different among treatments. Apparent digestibilities of DM, OM, CP, NDF, and ADF were not different among treatments. Treatment of alfalfa hay with chemical drying agents did not alter plasma profile, milk production, or nutrient digestibility in midlactation cows. (Key words: hay drying agent, digestibility, milk production) Abbreviation key: eM = commercial drying agent mixture, M = active ingredient mixture, U = untreated control. INTRODUCTION

Received November 30, 1990. Accepted March 21, 1991. 1Reprint requests. 2Current address: Cooperative Feed Dealers, Inc., Cherumgo Bridge, NY 13745. 1991 ] Dairy Sci 74:2674-2680

In many parts of the US, weather conditions can delay the harvest of high quality hay. Rain causes direct losses of DM (16, 19); practices that reduce field drying time could 1) improve hay quality, 2) allow harvest at an optimum maturity, and 3) facilitate crop removal from the field before the occurrence of inclement weather conditions. Solutions containing potassium carbonate have been used to increase the drying rate of alfalfa cut for hay (8, 13, 17). Drying agents appear to have little effect on the nutrient composition of hay. Valentine et al. (17) found no differences in digestible DM in vitro or CP content between alfalfa treated with potassium carbonate and untreated control. Similarly, there were no effects on amounts of CP, NDF, or ADF for chemically conditioned alfalfa hay (8, 12, 13). Although treated hay had a slightly higher CP content than untreated hay, in vitro DM, NDF, and cellulose digestibilities were not affected by treatment (4). Dry matter intake and digestibilities of NDF and CP by sheep were higher for hay treated with drying agent than for control hay (4). Hong et al, (8) found no differences in DMI or total tract digestibilities of DM, CP, NDF, and ADF when sheep were fed untreated control or hays treated with potassium carbonate. However, such treatment increased DM, CP, NDF, and ADF digestibilities in late lactation, dairy cattle fed for ad libitum intake (8). Cows fed hay treated with a commercial potassium carbonate-sodium carbonate-based drying agent had greater DMI and milk yield than those fed control hay (12). The effect of drying agent on digestibility of hay and subsequent performance of dairy cows fed this hay is not well established. Furthermore, potassium carbonate may be able to act as a buffer (8) and alter acid-base balance. Our objectives were to determine the effects of feeding lactating dairy cows diets containing hay treated with a chemical drying agent on

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DRYING AGENT-TREATED HAY FOR DAIRY COWS TABLE 1. Chemical composition of experimental drying agents.

Compound

CM

M

---(%)---

Potassium carbonate Sodium carbonate Citric acid Dye

50.00 50.00 5.00.00 .02.00

47.49 47.49

lCM = Commercial drying agent (Church and Dwight Co., Inc.); M active ingredient mixture.

=

plasma metabolite prof1le, lactational perfonnance, and nutrient digestibility and to determine if there were differences between a commercial fonnulation and one containing only the active ingredients, potassium carbonate and sodium caIbonate. MATERIALS AND METHODS

Forages

First-<:utting alfalfa was harvested in the late bud stage of maturity in June 1988. Mowing and harvest days were warm (27"q and sunny. Treatment consisted of spraying (273 L/ ha) either a commercial drying agent (Church and Dwight Co. Inc., Princeton, NJ; 2.17 glkg OM, 7.64 kglha) or a mixture of the active ingredients (2.12 g/kg OM, 7.47 kglha) at mowing via a spray boom mounted on the mower conditioner. Due to a difference in slope, the field was divided into two sections, each with three blocks (approximately .37 hal block), and treatments were assigned randomly to one block in each section. Composition of the drying agents is presented in Table 1. Forages were cut in the following order to prevent treatment carryover: untreated control (U), active ingredient mixture (M), and commercial drying agent mixture (eM). Cutting time was 1.75 h for all treatments or approximately .6 h/treatment. Spray equipment was rinsed between treatments. Hay was raked 20 to 22 h after cutting. All hays were baled in the late afternoon 28 to 30 h after cutting in ~ verse order of cutting. At the time of baling, hays were about 85% OM; the U hay was at slightly lower (2 to 4%) OM than M and CM hays. Prior to feeding, hays were chopped with

2675

a forage harvester to an average particle length of 1.5 to 3.0 em. Animals and Diets

Six multiparous, midlactation Holstein cows (120 to 150 d postpartum) were fed complete mixed diets consisting of 55% chopped alfalfa hay (U, eM, or M) and 45% concentrate (OM basis) in a balanced two period changeover design (6). Periods were 25 d with the first 10 d for adaptation. Diets were formulated based on NRC (11) recommendations for 600-kg cows producing 30 kg of milk daily. All animals received the same concentrate mix regardless of forage. Chemical composition of the hays and complete diets is presented in Table 2. Diets were hand mixed and fed to animals in stanchion stalls equipped for measurement of individual intakes and refusals. Animals were fed for ad libitum intake twice daily at 0600 and 1600 h to achieve 10% arts. Body weights were recorded on the first 2 d of each experimental period. Plasma Profile

Blood samples were collected on the first 2 d of each experimental period (d 11 and 12) via jugular venipuncture into evacuated heparinized and serum separation tubes. Heparinized blood was placed on ice and analyzed within 30 min for hematocrit and blood pH, HC03, and partial pressure of C02 (Corning 170 pH/Blood Gas Analyzer, Ciba Coming Diagnostics Corp., Medfield, MA). Plasma and serum were harvested after centrifugation (3000 x g) and frozen (-20°C) for later analyses. Plasma samples were analyzed for urea N by direct colorimetric method (Technicon Autoanalyzer D; Industrial Method No. 339..01, Technicon Inc., Tarrytown, NY) and for glucose by glucose oxidase enzymatic determination (Sigma Diagnostics, Catalog Number 510; Sigma Chemical Co., St Louis, MO). Serum samples were analyzed for Na, K, and CI using ion selective electrodes (Nova 5 Electrolyte Analyzer, NOVA Biomedical, Waltham MA). Feed Intake and Milk Production

Individual feed intake and ons were measured daily. Hays, concentrate, and orts were Journal of Dairy Science Vol. 74, No.8, 1991

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2'JEMER ET AL.

TABLE 2. Chemical composition of treated hays and complete diets fed to lactating cows. Oiet 1,2

Hayl

Component OM CP NDF

ADF Ash K

Ca P Mg NEL,4 Mcallkg DM

U

CM

M

SE3

U

CM

M

SE

- - - - - - - - - - - - (% OM) - - - - - - - - - - - 87.60 .38 88.16 88.20 88.30 .42 87.51 87.54 16.15 .20 17.53 17.33 17.44.36 16.20 16.09 .39 30.01 45.08 44.69 44.76 .69 30.19 29.97 .53 21.76 36.61 36.46 36.28 .97 21.94 21.85 .06 8.94 9.01 9.01.11 6.88 6.92 6.92 .04 1.82 2.62 2.76 2.67.09 1.80 1.88 .61 .03 1.03 .95 .97.05 .65 .61 .41 .01 .30 .29 .29 .01 .41 .41 .20 .01 .20 .19 .20 .01 .21 .20 1.57 .01 1.34 1.34 L35 .01 1.56 1.56

=

=

=

lU Untreated control; CM commercial drying agent; M active ingredient mixture. 2Composition of concentrate for all diets (air-dried basis): cracked shelled com, 87.50%; 48% CP soybean meal, 5.00%; liquid molasses, 4.50%; urea, 1.00%; monosodinm phosphate, .75%; magnesinm oxide, .15%; seleninm premix (.06%)•.10%; limestone, .05%; salt. 1.00%; traee-mineral premix, .15%; vitamin A, 8800 IUIkg; vitamin 0.4400 IU/kg; and vitamin E, 44 IU/kg. 31be SE of least squares means, n = 2.

4rhe

NEL predicted from hay ADF (1) and NRC (10) values for concentrate ingredients.

sampled daily for 7 d beginning on d 9. composited, and subsampled. Samples were dried at 55·C in a forced-air oven and then ground to pass through a 1-mm screen prior to analysis. Feed and orts samples were analyzed for OM, ash, CP (2), NDF, and ADF (7). Mineral content of hays and concentrate was determined by The Pennsylvania State University Plant Analysis Laboratory. Acid and base buffering capacities and pH of the hays were determined according to Jasaitis et al. (9). Values for NEL were predicted from hay and complete diet ADF content (1, 10). Milk weights were recorded daily at each milking during each experimental period. Milk was sampled daily (a.m. and p.m. milkings) for 9 d beginning after the adaptation period and analyzed for fat and protein (Foss 203B MilkoScan; Foss Electric, Hillerod, OK) at the Pennsylvania OIDA Milk Testing Laboratory. Apparent Digestibility

Apparent total tract digestibilities of OM, OM, CP, NDF, and ADF were determined using chromic oxide as a marker. Cows were dosed orally at 0800 h with 10 g of chromic oxide in a gelatin capsule each day for 10 d beginning on d 5. Fecal grab samples were Journal of Dairy Science Vol. 74, No.8, 1991

taken every 8 h for the last 5 d of marker dosing; the sampling schedule was advanced 1.5 bid in order to minimize the error associated with the diurnal pattern of chromic oxide excretion. Fecal samples were composited for each cow within a period. Dry matter and CP were determined on wet fecal samples (2). Fecal samples were dried at 55·C, ground to pass through a 1-mm screen. and analyzed for ash (2), NDF. and ADF (7). Ashed fecal samples were prepared for Cr analysis according to Williams et al. (21). Chromium concentration was determined by atomic absorption spectrophotometry using a hollow cathode lamp at 357.7 nm under a nitrous oxide-acetylene flame (red cone of 20 mm). Statistical Analysis

Oata were analyzed as a balanced, two period changeover design with three treatments (6). The general linear models procedure of SAS (14) was used to analyze all data. Linear contrasts of U versus CM + M and CM versus M were tested. Effects and contrasts were considered to be significant if the F statistic probability was less than .05. All data are presented as least squares means. The statistical model used was

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DRYING AGENT-TREATED HAY FOR DAIRY COWS

where is the overall mean, is the effect of animal, is the effect of period, is the effect of drying agent treatment, and is the experimental error. RESULTS AND DISCUSSION

Ideal weather conditions at the time of harvest were probably the reason that the DM of the hays was such that all could be baled at the same time. Although U hay had a slightly lower DM content than that of either treatment, there was no evidence of molding or spoilage. Because all hays were baled at the same time and the same moisture content, our study examined the effect of treatment application without environmental factors. Field effects were not included in the model because hays from field blocks were mixed within treatments when chopped The forage to concentrate ratio (55:45) was chosen to simulate feeding conditions on farms for cows in midlactation. Composition of CM and M hays and complete diets was not different, and all hays were good quality (Table 2). Other work also has shown no differences in the chemical composition of treated versus control hays (8, 12, 13, 17). As expected, the K content of CM and M hays tended to be higher than that of U hay, as noted also by Hong et al. (8).

There was no effect of treatment on pH of hay (Table 3). Likewise, acid and base buffering capacities were similar among treatments. However, the titratable acidity of treatment CM was less than that of treatment M (P < .05). Titratable acidity is defined as the miI1iequivalents of acid required to lower the sample pH to 4; acid buffering capacity is the miI1iequivalents of titrated acid divided by the change in pH. Titratable acidity does not take into account the change in pH that occurs and, therefore, is not as useful in describing the hays as the buffering capacity. There were no differences in titratable alkalinity. Buffering capacities were in the range of those reported for alfalfa hays (9). The DM yield per hectare of alfalfa hay was less than predicted. Additionally, due to drought conditions in 1988, we were unable to harvest a second cutting. Due to the low DM yield, the balanced two period changeover design (6) was selected. This is a completely balanced design in which periods are orthogonal to treatments. The minimum efficiency for three treatments relative to standard changeover designs is .75; however, it may be much higher (6). The CM and M treatments did not affect plasma metabolite proftle. All measures were within normal clinical ranges for lactating dairy cows (5). Mean values for blood measurements were as follows: blood pH, 7.40; hematocrit, 31.5%; HC03, 26.6 mmol/L; partial pressure of CO2 , 44.1 mmol/L; Na, 145.2 mmol/L; K, 5.47 mmol/L; CI, 105.3 mmol/L; plasma urea N, 17.9 mg/dl; and

TABLE 3. The pH and acid and base buffering capacities of alfalfa bays treated with chemical drying agents. Treatment! Measurement

u

Hay pH

5.96 6.00 6.05 .03 _ _ _ _ _ _ _ _ _ (meq x 103) - - - - - - - - -

Titratable acidity Acid buffering capacity Titratable alkalinity Base buffering capacity

240.0 124.2 142.5 46.5

CM

237.5 119.0 140.0 46.1

M

245.0" 117.8 145.0 48.5

1.4 2.7 3.2 1.8

aSignificant linear contrast of CM versus M (P < .05). IV = Untreated control; CM = commercial drying agent; M = active ingredient mixture. 2nle SE of least squares means, n

= 4. Journal of Dairy Science Vol. 74. No.8. 1991

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ZIEMER ET AL.

TABLE 4. Effect of feeding lactating cows drying agent-treated alfalfa hay on milk yield and composition. Treatment 1 Measurement

U

CM

M

SE2

Milk yield. kgld Milk fat, % Milk protein, % Milk fat yield, kg/d Milk protein yield, kg/d 4% FCM yield. kgld

27.2 3.42 3.34 .94 .92 25.1

27.2 3.48 3.24 .94 .88 25.0

27.7 3.37 3.28 .94 .92 25.3

.7 .15 .03 .OS .02 .9

lU

= Untreated

control; CM

= commercial drying

agent; M

= active

ingredient mixture.

2-rhe SE of least squares means, n = 4.

plasma glucose, 73.2 mg/dl. Application of a drying agent has the potential to alter the acidbase balance because of the chemical ingredients; potassium carbonate may be an effective dietary buffer (20). Feed intake and in vitro rumen pH were increased when potassium carbonate was fed as a dietary buffer to lactating dairy cows. However, drying agent treatment was not expected to alter plasma metabolic prof1les because the amount of chemical (.2% of herbage OM) that was applied to the plant was very low. Composition and yield of milk were not different among treatments (Table 4). There was a trend (P < .10) for decreased percentage milk protein for both CM and M. Yield of 4% FCM was similar among treatments. Dry matter intake, BW, and OM! as a percentage of BW did not differ among treatments (Table 5). The OM! were exceptionally high for the milk

production and stage of lactation of cows in our trial. High OM! levels with high quality alfalfa have been found in other work (10, 15). Also, there were no differences in apparent digestibilities of OM, OM, CP, NDF, or ADF. Low digestibilities of OM may have occurred as a result of high OM! and an increased passage rate. In this study, drying agent treatment did not affect OM! or milk production of midlactation cows. When late lactation and nonlactating cows were fed potassium carbonate treated or untreated hays, OM! was similar (8). Oellermann et al. (12) found increased OMI and milk yield when hay treated with a potassium carbonate-sodium carbonate-based drying agent was fed to cows in early lactation. They concluded that the production response was due to improved nutrient availability; in vitro OM disappearance tended to be higher for treated

TABLE 5. Effect of feeding lactating cows drying agent-treated alfalfa hay on DM! and nutrient apparent digestibility. Treatment l Measurement

U

CM

M

DMI, kg/d BW. kg DM!. % BW

25.2 621 4.06

24.7 610 4.06

25.2 617 4.09

1.3

9 .18

(%)

Apparent digestibility DM OM CP NDP

59.4 59.5 60.2 42.6 40.2

ADP

=

=

61.3 61.5 62.7 40.7 41.0

lU Untreated control; CM commercial drying agent; M 2-rhe SE of least squares means, n = 4. Journal of Dairy Science Vol. 74, No.8, 1991

57.8 57.8 57.5 40.8 39.9

= active

ingredient mixture.

3.5 3.7 3.8 42 4.2

DRYING AGENT-TREATED HAY FOR DAIRY COWS

hay (12). In contrast, others have shown no difference in in vitro OM disappearance between treated and untreated hay (4, 13, 17). The lack of effect of drying agent treatment on nutrient digestibility of alfalfa hay found in our study supports these in vitro data and also the results detennined in situ and in vivo by Van Hom et al. (18). However, total tract apparent digestibilities of OM, CP, NDF, and ADF were increased for potassium carbonate-treated versus untreated hays when fed to dairy cattle (8). These conflicting results are difficult to reconcile but may be related to cutting number, stage of maturity, or concentration of drying agent solution. Differences between our study and previous work (8, 12) may be due to differences in cutting number. Both of the previous studies used third-cutting alfalfa hay (8, 12), whereas in our study first-cutting alfalfa hay was used because later cuttings were affected by drought conditions. Drying agents may be more effective when used on second or third cuttings (13, 19). This may be due in part to different stem to leaf ratios and different physical structure of the stems. Additionally, the animals used in each of these studies were in different stages of lactation. In our study, cows were in midlactation. Oellennann et al. (12), however, used cows in early lactation; Hong et al. (8) used cows that were in late lactation as well as nonlactating cows. The application rate of potassium carbonate was much higher in the study by Hong et al. (8), 18 kg/ha compared with an average of 7.55 kglha, based on manufacturer recommendations, for the potassium carbonate-sodium carbonate-based drying agents in our study. Potassium carbonate alters the hydrophobic properties of plant surface waxes, resulting in increased hydration of the capillary spaces between wax platelets (3). With higher application rates than those used in our study, there may be enough potassium carbonate residue on the hay to facilitate hydration of plant material in the rumen. When application rates similar to those in our study were used, there were no differences in in situ OM or in vivo DM, CP, or ADF digestibilities (18). CONCLUSION

Drying agent treatment did not affect chemical composition, pH, or buffering capacity of

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early first-cutting alfalfa hay. When CM and M hays were fed to midlactation dairy cows, OMI, nutrient digestibilities, milk yield and composition, and plasma profiles did not differ among treatments. Furthennore, there were no differences between U hay or hays treated with either CM or M. Drying agent treatment of alfalfa hay does not appear to affect nutritive value or perfonnance of midlactation dairy cows. ACKNOWLEDGMENTS

The authors wish to thank Church and Dwight Co., Inc. and Agway, Inc. for partial support of this research and Penn State Farm Services for harvest and spraying of hays. REFERENCES 1 Adams. R. S. 1980. Forage testing service revised regression equations. Pennsylvania State Univ. Dairy Sci. Ext. Bull. 80-56, University Park. 2 Association of Official Analytical Chemists. 1975. Official methods of analysis. 12th ed. AOAC. Washington, DC. 3 Chambers. T. C.• and J. V. Possingbam. 1963. Studies of the fme structure of the wax layer of sultana grapes. Aust. J. BioI. Sci. 16:818. 4 Ehle, F. R.• A. EI Housni, M. Yazid, and J. Danker. 1985. Influence of chemical drying agents on drying time. composition and digestibility of alfalfa hay measured by several techniques. J. Dairy Sci. 68(Suppl. 1):126.(Abstr.) 5 Fraser. C. M. ed. 1986. The Merck veterinary manual: a handbook of diagnosis. therapy. and disease prevention and control for the veterinarian. 6th ed. Merck and Co.• Inc., Rahway, NJ. 6 Gill, J. L.. and W. T. Magee. 1976. Balanced twoperiod changeover designs for several treatments. J. Anim. Sci. 42:775. 7 Goering, H. K., and P. J. Van Soest. 1970. Forage fiber analyses (apparatus, reagents, procedures. and some applications). Agric. Handbook No. 379. ARSUSDA, Washington, DC. 8 Hong, B. J., G. A. Broderick, and R. P. Walgenbach. 1988. Effect of chemical conditioning of alfalfa on drying rate and nutrient digestion in ruminants. J. Dairy Sci. 71:1851. 9 Jasaitis, D. R.• J. E. Wohlt, and J. L. Evans. 1987. Influence of feed ion content on buffering capacity of ruminant feedstuffs in vitro. J. Dairy Sci. 70:1391. 10 Kawas. J. R. 1983. Significance of fiber level on nutritive value of alfalfa hay-based diets for ruminants. Ph.D. Diss., Univ. Wisconsin, Madison. 11 National Research Council. 1989. Nutrient requirements of dairy cattle. 6th rev. ed. Natl. Acad. Sci.• Washington, DC. 12 Oellermann, S. 0., M. J. Arambel. and J. L. Walters. 1989. Effect of chemical drying agents on alfalfa hay and milk: production response when fed to dairy cows Journal of Dairy Science Vol. 74, No.8. 1991

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in early lactation. I. Dairy Sci. 72:501. 13 Rotz, C. A., S. M. Abrams, and R. J. Davis. 1987. Alfalfa drying, loss and quality as influenced by mechanical and chemical conditioning. Trans. Am. Soc. Agric. Eng. 30:630. 14 SAS~ Users Guide: Statistics, Version 5 Edition. 1985. SAS Inst., Inc., Cary, NC. 15 Shaver, R. D., A. I. Nytes, L. D. Satter, and N. A. Iorgensen. 1986. Influence of amount of feed intake and forage physical form on digestion and passage of prebloom alfalfa hay in dairy cows. I. Dairy Sci. 69: 1545. 16 Shepherd, I. R, H. G. Wiseman, R. E. Ely, C. G. Melin, W. I. Sweetman, C. H. Gordon, L. G. Schoenleber, R. E. Wagner, L. E. Campbell, R. D. Roane, and W. H. Hosterman. 1954. Experiments in harvesting and preserving alfalfa for dairy cattle feed. USDA Tech. Bull. 1079, Washington, DC. 17 Valentine, S. C., M. I. Cochrane, and R. B. Wickes.

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1983. Effects of potassium carbonate solution on the rate of drying and nutritive value of lucerne, grassl clover and oat crops cut for hay. J. Ausl. IDsl. Agric. Sci. 49:224. 18 Van Hom, H. H., O. C. Ruelke, R P. Cromwell, M. Ryninks, and K. Oskam. 1988. Effects of chemical drying agents and preservatives on composition and digestibility of alfalfa hay. J. Dairy Sci. 71:2256. 19 Vough, L. R., and T. H. Miller. 1985. Advances in preserving hay quality. 1985. Page 45 in Proc. Am. Forage Grassl. Conf., Hershey, PA. 20 West, J. W., C. E. Coppock, D. H. Nave, and G. T. Schelling. 1986. Effects of potassium buffers on feed intake in lactating dairy cows and in rumen fermentation in vivo and in vitro. J. Dairy Sci. 69:124. 21 Williams, C. H., D. I. David, and O. Iismaa. 1962. The determination of chromic oxide in faeces samples by atomic absorption spectrophotomelIy. I. Agric. Sci. (Camb.) 59:381.