Influence of Moisture Content of Mixed Rations on Feed Intake and Milk Production of Dairy Cows P. H. ROBINSON, P. L. BURGESS,1 and R. E. McQUEEN, AgriculbJre Canada Research Station, PO Box 20280, Fredericton, New Brunswick E3B 4Zl ABSTRACT

Rations with target DM proportions of 35, 45, and 65%, attained by soaking the grain mix in water for 24 h, were fed to 46 mid to late lactation, multiparturient dairy cows in two experiments (Experiment 1,35 and 45% DM; Experiment 2, 45 and 60% DM) to examine the effect of DM percentage of the totally mixed ration on intake and production of cows. Water-soaked concentrate and alfalfa silage were mixed daily and fed ad libitum. Dry matter intake and milk yield and composition were not influenced by the moisture content of the mixed ration in either experiment. Ruminal pH, ammonia N concentration, total VFA, and molar proportions of individual VFA also were not influenced by ration DM in either experiment. Results suggest that rumen water efflux, as influenced by addition of water to the concentrate portion of the mixed ration, is not a factor limiting intake in dairy cows fed high moisture mixed rations. (Key words: romen water efflux, dairy cow, high moisture feeds) INTRODUCTION

Dairy cows consume more DM from wellpreserved hay than from well-preserved silage (2, 9). Production systems employed in the last 20 yr for free stall housing operations have emphasized use of total mixed rations (TMR) incorporating ensiled forages and high moisture by-product ingredients. Dry matter intake of dairy cows declines as the moisture content of

Received February 14, 1990. Accepted May 9. 1990. IPresent address: Agriculture Canada Experimental Farm, Nappan, Nova Scotia, BOL 1CO. 1990 J Dairy Sci 73:2916-2921

the TMR increases, regardless of whether that moisture is from high moisture silage or from high moisture by-product ingredients (1). Practical experience suggests that the decline in DM intake becomes significant as the DM proportion of the TMR falls below 45% (3). Early attempts to determine the reason for reduced OM intake from silage rather than hay concentrated on the water content of the ration. For example, Thomas et al. (12) added water to low moisture silages and hays fed dairy heifers and observed no change in OM intake. Later work emphasized the potentially negative effects of silage fermentation endproducts on DM intake. Results have been mixed, but addition of silage extracts to hay, or the romen directly, clearly depresses OM intake (6, 7). However, the extent of the depression caused by addition of silage extracts does not seem of the magnitude observed with ensiled rather than dry feedbased diets, suggesting that moisture content of the ration also may contribute to reduced DM intake of cows fed high moisture TMR. No studies have been reported on the influence of diet moisture content on OM intake and productivity of dairy cows fed a TMR in which the source of additional water is from soaking the grain mixture with water. The objective of this study was to examine the influence of water added to the concentrate mixture, thus changing the DM content of the TMR in the range of 35 to 60% DM, which is the normal range for practical TMR. MATERIALS AND METHODS Cows, Diets, and Design

Forty-six mid to late lactation, multiparturient Holstein cows were used in two experiments of 24 and 22 cows. Cows were in tie stalls and had free access to water. They were offered a TMR of alfalfa silage (fable 1) and a concentrate (fable 2) soaked with different amounts of water for 24 h to vary the OM

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RATION MOISTURE PROPORTION TABLE 1. Composition of the alfalfa silage utilized (Experiments 1 and 2).

pH

DM,l %

Experiment 1

Experiment 2

Composition

4.43 33.8

4.78 48.0

Ingredient, kg/t as mixed Barley grain, roned Com grain, coarse ground Soybean meal, 48% CP Liquid molasses Dicalcium phosphate Trace-mineralized salt1 Vitamin mixture2

- - - - % of DM - - - Organic matter

NDF

ADF Nitrogen Total Ammonia

ADI2

TABLE 2. Ingredient and chemical composition of the concentrate mixture (Experiments 1 and 2).

91.9 54 38

90.6 47 37

.27

2.80 .31

.46

.46

2.32

Chemical, % DM Organic matter

2Acid-detergent insoluble.

CP

proportion of the final mixed ration (fable 3). This mixture was offered in two meals per day at 1500 h (80% of total offered) and 0600 h (20%). Orts were removed and weighed between 1100 and 1200 h. The amount of feed offered was varied daily to provide approximately 5% weighback. Cows were blocked into pairs for each experiment based upon pre-experiment milk yield and then assigned randomly to treatment. All cows were fed the assigned diet for 84 d in each experiment. sampling

Mixed ration offered and refused was recorded daily. Feedstuffs (alfalfa silage and concentrate) were sampled weekly and composited by d 1 to 42 and 43 to 84 of each experiment. Daily milk production was recorded by individual milking for each cow. Milk. samples were collected from a.m. and p.m. milkings on d 41, 42, 83, and 84 of each experiment and composited for analyses by period. Cows were weighed on three consecutive days at the beginning and end of each experimental period. Samples of blood were taken to vacutainers containing heparin by jugular venipuncture on d 28 and 56 of each experiment between 0830 and 1030 h. Blood was centrifuged at 2000 x g for 10 min and plasma preserved at -15°C until assay. Samples of rumen fluid were collected from each cowan d 28 and 56 of each experiment between 0830 and 1030 h by vacuum stomach tube. Samples (100 ml) were preserved with .1 ml of saturated mercuric chloride.

183 50 23 10 .67

92.7

NDF

ADF

334

887.2

DM, l05'C

ITo1uene distillation procedure.

400

12

5 18.2

lOuaranteed analysis: NaCl (minimum), 86%; I, 87 mg/ kg; Co, 35 mg/kg; Fe, 3600 mg/kg; en, 290 mg/kg; Mn, 1050 mg/kg; Zn, 3500 mg/kg; and Se, 10 mg/kg. Zouaranteed analysis: 10,000,000 IU/kg vitamin A, 1,000,000 IU/kg vitamin D, and 75,000 IU/kg vitamin E.

AnalytIcal Procedures

All analytical procedures were as described by Robinson and Burgess (8). Statistical Analysis

Each experiment was analyzed individually as two periods of 42 d each. All parameters were analyzed as a split plot design (11); each period was considered a repeated measure as described with SAS (10). Probability at .05 was used in all cases to determine statistical significance. RESULTS

All cows assigned to the experiments successfully completed the assigned periods. The design of the two experiments was identical except that in Experiment 1 the difference in DM content between 35 and 45% DM was examined, whereas in Experiment 2 the difference between 45 and 60% was examined. Differences between the studies, particularly the 45% DM treatment common to both, reflect the different alfalfa silages used, the different times of the year that the two experiments were completed (Experiment 1, December to May; Experiment 2; September to November), and the different cows. Evaluating the last two differJournal of Dairy Science Vol. 73,

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TABLE 3. Ingredient and chemical composition of the mixed diets (Bxperiments I and 2). Experiment 2

Experiment I

Composition Ingredient, kg/t as mixed Alfalfa silage Concenttate

Water

DM, toluene2 Chemical, % DM

350 DM l

450 DM

450 DM

600 DM

530

645 245 110 437.5

460 250 290 446.0

615

200 270 363.0

55 591.3

330

Organic matter

92.8

92.8

92.6

92.4

~F

~

35

AJ>F CP NE.. 3 mcal/kg

23 15.4 1.56

26

30 22 16.7 1.59

32 23 17.3 1.59

15.3 1.56

lTarget DM proponion (g/kg) in the mixed ration. ~oluene distillation procedure. 3Calculated from NRC (5).

ences is difficult, but the alfalfa silage clearly differed among experiments, with that used in experiment 2 having the highest nitrogen proportion (Table 1). This is reflected in the higher CP content of the mixed rations in Experiment 2 compared with Experiment 1 (Table 3). The chemical composition of the concentrate was the same for both experiments (Table 2).

Plasma urea N, plasma glucose, and BW changes also were not influenced by diet (Table 6) in either experiment. Plasma urea N in Experiment 2 cows was over twice that of cows in Experiment 1, reflecting the higher CP of diets in Experiment 2. Cows in Experiment 2 gained weight at almost three times the rate of cows in Experiment 1, reflecting the higher energy content of the silage used in Experiment 2.

Feed Intake and Milk Production

Dry matter intake and milk yield and composition were not influenced by the OM percentage of the mixed ration in either experiment (Table 4). Cows in Experiment 2 ate 17.8% more OM, reflecting the higher forage quality in Experiment 2, but other differences between experiments were small. Cows were observed not to selectively refuse any portion of the mixed diet offered. Rumen Fermentation and Plasma Parameters

Characteristics of rumen fennentation did not differ among cows fed diets of differing OM proportion in either experiment (Table 5). Concentrations of rumen anunonia N in Experiment 2 were over 100% higher than those in Experiment 1, and total VFA concentrations were 11.4% higher. These differences reflect the higher CP and lower fiber contents of the silage, and the TMR, used in Experiment 2. Molar proportions of major VFA were not influenced by diet. Joumal of Dairy Science Vol. 73,

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DISCUSSION

Practical observations indicate that OM intake of dairy cows declines as the moisture content of the TMR increases (1, 3). At least three potential factors are associated with increasing moisture content of rations that could result in depressed OM intake. The first factor is not related to the moisture content but rather to increasing concentrations of fermentation end products in feeds with increasing moisture content. These soluble components can restrict OM intake (6, 7). The second factor is the increased bulk of feedstuffs caused by intracellular, or nonexpressible water. This could limit intake due to rumen fill until cellular structures are destroyed, through mastication or fermentation, to release contained water. This factor becomes more important as the diet forage proportion increases. 1be third factor related to increasing moisture content that could restrict intake is the increased intake of water. This could limit intake by exceeding the capacity to

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RATION MOISlURE PROPORTION

TABLE 4. Influence of moisture content of the mixed ration on OM intake as well as milk: production and composition (Experiments I and 2). Treatment1 Item

Experiment

350 OM

OM, kg/d

I 2

19.6

1

29.0

Milk Pat Protein Lactose

Pat Protein Lactose

2 I 2 1 2 1 2

450 OM 19.7 23.9 Yield (kg/d) 29.2 30.6 1.05 1.19 .93 1.02 1.42 1.50 Composition (%)

1.11 .93 1.44

I 2 I 2 I 2

3.64

3.85 3.98 3.19 3.42 4.86 4.91

3.16 4.96

600 OM

SEM

22.5

.3 .3

30.0 1.17 1.01 1.48

3.96 3.39 4.92

.5 .5 .02 .02 .02 .02 .03 .02 .39 .30 .22 .13 .22 .12

ITarget OM proportion (gIkg) in the mixed ration.

TABLE 5. Influence of moisture content of the mixed ration on rumen ammonia and VFA levels (Experiments 1 and 2). Treatment 1 Item

Experiment

pH

I 2 1 2 1 2

Ammonia N, mg/L Total VFA, meqIL

350 OM 6.66 130.7 87.82

450 OM 6.80 6.56 142.8 280.8 90.85 97.69

600 OM 6.51 298.8 101.29

SEM .06 .04 9.1 8.0 4.09 2.03

mo1% Acetate Propionate Butyrate lsovalerate Valerate Acetate:propionate ratio

1 2 1 2 1 2 1 2 1 2 1 2

67.0 17.6 12.2 1.7 1.3 3.86

66.7 64.3 18.5 19.8 11.8 12.3 1.7 2.0 1.2 1.8 3.70 3.34

64.7 19.5 12.1 2.1 1.7 3.35

.4 .2 .4 .3 .2 .2 .1 .1 .03 .02 .09

.05

ITarget OM proportion (gIkg) in the mixed ration. Journal of Oairy Science Vol. 73,

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ROBINSON ET AL.

TABLE 6. Influence of moisture content of the mixed ration on plasma urea N and plasma glucose as well as BW change (Experiments 1 and 2). Treatment l Experiment Plasma urea N, mg/L Plasma glucose, mg/L Initial BW, kg BW change, kg/d

1 2 1 2 1 2 1 2

350 DM 12.31 610.1

634 .21

450 DM 13.30 25.09 637.1 728.5 616 602 .15 .47

600 DM

SEM

.90 26.05 725.6

607 .59

.30 17.4 10.0 7 6 .09 .13

lTarget DM proportion (g/kg) in the mixed ration.

transport water from the rumen, thereby restricting intake due to rumen fill. Results of the present study clearly demonstrate that reduced intake of higher moisture rations is not related to the water content of the ration per se. This is in broad agreement with von Englehardt (13), who demonstrated a net postprandial influx of water to the rumen in response to release of osmotically active feed components to ruminal fluid. In our study, water intake from the diet was about 35 kg/d for the diet with the highest moisture content. This compares to an estimated water requirement of 70 to 110 kg/d (5), suggesting that the most likely adaptation of cows fed high moisture diets was to reduce free water intake, especially postprandially. Results of the present study seem at odds with data reported by Lahr et al. (4). In that study, DM intake and milk production in dairy cattle declined linearly as the moisture content of the mixed ration was increased by addition of water. However, in their study, water was added directly to the mixer with other feed ingredients immediately prior to feeding. With this method. water has little time to be absorbed by feed ingredients prior to feeding, and high moisture diets tend to separate in the feed bunk, making differentiation of the influence of palatability and water intake difficult. In the present study, water absorption by the grain mix was complete prior to its mixing with silage, making reduced palatability unlikely. The present study is partially confounded by the higher DM and overall nutritional quality of the alfalfa silage used in Experiment 2. Nevertheless, dietary water addition in the concentrate portion of the TMR did not result in a reduction in intake or production. These results Journal of Dairy Science Vol. 73,

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suggest that rumen water efflux is not a factor limiting intake in dairy cows similar to those examined in this study. This finding indicates that future research on intake reduction with high moisture diets focus on other characteristics of high moisture feeds. ACKNOWLEDGMENTS

The authors thank H. Moore and D. Adamson for feed preparation; R. Mundle, S. Rynax, L. Dalton, and A. Nason of the FRS Dairy Research Unit for care of the cows; T. Veerkamp and C. Grady for sample analyses; and M. van Groenewoud for sample collection and most analyses. REFERENCES

1 Chase, L. E. 1977. Effect of high moisture feeds on feed intake and milk production in dairy cattle. Page 52 in Proc. Cornell Nutr. Coni. Feed Manuf., Cornell Univ., Ithaca, NY. 2 Gordon, C. H., J. C. Derbyshire, W. C. Jacobsen, and J. L. Humphrey. 1965. Effects of dry matter in lowmoisture silage on preservation, acceptability and feeding value for dairy cows. J. Dairy Sci. 48:1062. 3 Hutjens, M. F. 1988. The role of dietary buffers for lactating cows. Page 13 in Proc. Ninth Westem Nutr. Coni., Univ. Manitoba, Winnipeg, MD, Canada. 4Lahr, D. A., D. E. Otterby, D. G. Johnson, J. G. Linn, and R G. LundquisL 1983. Effects of moisture content of complete diets on feed intake and milk production in dairy cows. J. Dairy Sci. 66:1891. 5 National Research Council. 1988. Nutrient requirements of dairy cattle. 6th rev. ed. Nat!. Acad. Press, Washington, DC. 6Pbillip, L. E., J. G. Buchanan-Smith, and W. L. Orovum. 1981. Effects of infusing the rumen with acetic acid and nitrogenous constituents in maize silage extracts on food intake, ruminal osmolality and blood acid-base balance in sheep. J. Agric. Sci. (Camb.) 96: 429.

RATION MOISTURE PROPORTION 7 Phillip, L. E., J. G. Buchanan-Smith, and W. L. Orovum. 1981. Food intake and rumen osmolality in sheep: Differentiation of the effect of osmolality from that of the products of maize silage fermentation. J. Agric. Sci. (Camb.) 96:439. 8 Robinson, P. H., and P. L. Burgess. 1990. Energy supplementation of high forage diets for mid lactation dairy cows. Can. J. Anim. Sci. 70:867. 9 Roffler, R. E., R. P. Niedenneier, and B. R. Baumgardt 1967. Evaluation of aIfaIfa-brome forage stored as wilted silage, low moisture silage, and hay. J. Dairy Sci. 50:1805.

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IO SAS~ User's Guide: Statistics, 1985. Version 5 Edition. SAS Inst, Cary, NC. 11 Steel, R.OD., and J. H. Torrie. 1980. Principles and procedures of statistics. 2nd ed. McGraw-Hill Book Co., Inc., Toronto, ON, Canada. 12 Thomas, J. W., L. A. Moore, M Okamoto, and J. F. Sykes. 1961. A study offactors affecting rate of intake of heifers fed silage. J. Dairy Sci. 44:1471. 13 von EDglehaIdt, W. 1969. Movement of water across the rumen epithelium. Physiology of digestion and metabolism in the ruminant. A. T. Phillipson, ed. Oriel Press, Newcastle-upon-Tyne, Engl.

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