Effects of Moisture Content of Complete Diets on Feed Intake and Milk Production by Cows1

Effects of Moisture Content of Complete Diets on Feed Intake and Milk Production by Cows 1 D. A. LAHR, D. E. OTTERBY, D. G. JOHNSON, J. G. LINN, and R. G. LUNDQUIST Department of Animal Science University of Minnesota St. Paul 55108 and West Central Experiment Station Morris 56267 ABSTRACT

In two trials, 47 and 54 Holstein cows were fed diets containing ensiled forages, ensiled and dry forages, or diets of different moisture contents. In trial 1, diets were fed during a preliminary dry period, early lactation, late lactation, a second dry period, and a second early lactation. In trial 2, four diets identical except for moisture content (78, 64, 52, and 40% dry matter) were fed for the first 200 days of lactation. Substitution of dry hay for alfalfa silage increased dry matter intake during the first early lactation, whereas partial substitution of corn silage with straw did not affect intake during dry periods. Dry matter intake increased linearly as dry matter content of diet increased in trial 2. Neither milk production nor body weight were affected by treatment in either trial. Percentage total solids increased linearly as dry matter content of diet decreased in trial 2. Volatile fatty acids differed slightly, but no trends were consistent. No differences of daily chewing time were observed. From these trials, diets of less than 60 to 65% dry matter may reduce intake by lactating dairy cows. INTRODUCTION

High milk production from dairy cows is partially dependent on the amount of dry matter (DM) consumed. Measures to achieve

Received November 5, 1982. IScientific Journal Series Paper No. 13,137, Minnesota Agricultural Experiment Station, St. Paul 55108. 1983 J Dairy Sci 66:1891-1900

maximum feed intake must be a primary concern in dairy feeding. Factors influencing dietary intake include feed digestibility (5), energy o u t p u t of the cow (2), rumen fill (4), particle size and rate of passage of feed residues (4), silage pH (14), products of silage fermentation (22), and moisture content of feeds (7, 11, 15). High moisture in diets may be advantageous for a variety of reasons. Adequate moisture in complete diets may prevent or reduce separation of ingredients. High moisture diets would allow liberal use of wet by-products and liquid ingredients. Silages or high moisture grains may be favored over drier feeds because of ease of preservation, reduced harvest losses, and increased quality. Increased moisture contents may increase palatability by improving texture or may dilute undesirable flavors. In contrast, high moisture in dairy cattle diets has several disadvantages; it possibly can prevent cattle from achieving maximum intake and production. Several researchers (10, 18, 22) reported that cattle consume more DM from hay than from haylage. Also, ensiled legumes or grasses harvested at high moisture (45 to 75% DM) contents were consumed less than if harvested at lower moisture (20 to 40% DM) (3, 9, 10, 12, 16, 18, 21, 22). Researchers (10, 13, 16, 18) showed significant decreases of DM consumed when wetter feeds replaced drier feeds in some trials but not in others (7, 22). The effects of moisture content of ensiled feeds on feed intake are not separated easily from other factors such as silage pH, fermentation products, or particle size. A trial in which water was added to dry hay to reduce DM content did not reduce intake by heifers (22). The literature does not indicate effects of moisture content alone on intake and milk production of lactating cows. Therefore, objectives two trials were: 1) to

1891

1892

LAHR ET AL.

determine effects of substituting dry forages for ensiled forages in complete diets on DM intake and milk production in early lactation and dry period, and 2) to determine effects of water added to complete diets on dry matter intake, milk production and components, body weight, pH and volatile fatty acids of rumen contents, and eating and rumination time.

EXPERIMENTAL PROCEDURE Trial 1

Forty-seven Holstein cows (16 first-parity, 31 multiparous) were assigned to one of two dietary sequences according to parity and calving date. The experiment consisted of five periods: 1) a preliminary dry period; 2) the first 150 days of lactation; 3) late lactation; 4) a second dry period; and 5) the first 60 days of a second lactation. Cows in first parity were assigned to diets as parturition and were not included in the preliminary dry period. The first six multiparous cows to calve also were assigned at parturition and were not included in

the preliminary dry period. Subsequently, all multiparous cows began the trial with the dry period. Numbers of cows included in each period were 25, 47, 46, 36, and 36. Ingredient content of the diets is in Table 1. Diets of sequence A consisted of ensiled forages, high moisture shelled corn, soybean meal, and supplement (Table 1). During both dry periods (1 and 4) only corn silage and supplement were fed. Diets of sequence B (Table 1) were similar to those of A except alfalfa silage was replaced during the lactation phases with an equivalent amount of DM from alfalfa hay. In dry periods, one-third of the corn silage DM of A was replaced with chopped oat straw. Dietary DM fed during early lactation (periods 2 and 5) was approximately 55% concentrate and 17% crude protein (CP) whereas in period 3 it was 30% concentrate and 14% CP. Dietary DM fed in the dry periods was formulated to be 11% CP. Cows were fed once daily in the morning in stalls equipped with partitioned mangers allowing for measurement of individual feed intakes. Feeds were offered at 105 to 110% of ad libitum intake. An appropriate amount of

TABLE 1. Ingredient content of diets, trial 1. Period

Sequence A

Sequence B

1, First dry period

Corn silage Supplement b

97.5

Supplement b

65.0 32.5 2.5

2, Early lactation (first 150 days)

Corn silage Alfalfa silage HMSCc Soybean meal Supplement b

15.0 30.0 48.5 4.0 2.5

Corn silage Alfalfa hay HMSCc Soybean meal Supplement b

15.0 30.0 48.5 4.0 2.5

3, Late lactation (after 150 days)

Corn silage Alfalfa silage HMSCc Supplementb

50.0 20.0 27.5 2.5

Corn silage Alfalfa hay HMSCc Supplementh

50.0 20.0 27.5 2.5

4, Second dry period 5, Second lactation (first 60 days)

Repeat of period 1 Repeat of period 2

(%)a 2.5

(%)a Corn silage Oat straw

Repeat of period 1 Repeat of period 2

apercent of dietary dry matter. bsupplement was 40% urea, 24% trace mineralized salt, 12% dicalcium phosphate, 12% monosodium phosphate, 3.6% magnesium oxide, 3.6% elemental sulfur, and 4.8% vitamin A and D premix, providing about 5290 IU vitamin A and 2120 IU vitamin D/kg ration dry mattter. CHigh moisture shelled corn. Journal of Dairy Science Vol. 66, No. 9, 1983

MOISTURE CONTENT OF COMPLETE DIETS TABLE 2. Ingredient composition of dietary dry matter, trial 2. Ingredient (%) Alfalfa hay Corn silage Beet pulp Shelled corn Oats Soybean meal Dry molasses

27.00 10.00 10.00 24.05 13.20 7.90 2.30 3.00 .80 .60 .60 .25 .18 .12

Bentonite

Dicalcium phosphate Urea Trace mineralized salt

Vitamin premix a Methionine hydroxy analog Mineral premixb

1893

recorded from a.m. and p.m. milkings twice weekly (Monday and Thursday). Individual samples from each cow were taken at both milkings, composited every second Monday, and analyzed for fat by Babcock (1) and solids-not-fat (SNF) by the method of Golding (8). Body weights were taken every Tuesday following the morning milking. Data were summarized by 15-day intervals within the five periods and analyzed by least squares (19). Diet, parities one, two, three, and more, and interaction diet x parity were independent variables of the model. In periods 1, 3, and 4, in which records of different lengths were possible, a covariant for period length was included in the model. Trial 2

apremix supplied approximately 4220 IU vitamin A and 1300 IU vitamin D/kg ration dry matter. bpremix contained approximately 22% sulfur, 18% potassium, and 11% magnesium.

corn silage, grain, and supplement, previously blended in a mixer wagon, was added to tubground hay, alfalfa silage, or tub-ground straw, and mixed by fork in the manger. Weights of refused feed were recorded daily. Feeds were sampled weekly and composited monthly. Refusals were sampled weekly from a mixture of weighbacks within treatment. Samples were analyzed for DM, CP, and crude fiber (CF) by AOAC (1) procedures. Cows were housed in a tie stall barn equipped with a pipeline milker. Milk weights were

Fifty-four Holstein cows (23 first-parity and 31 multiparous) were assigned randomly to one of four experimental diets according to parity and calving date. Treatment groups were balanced for mature equivalent production. Cows were fed one of four complete mixed diets containing 78, 64, 52, or 40% DM. All diets were identical in feed ingredients and composition (Table 2) except for moisture content, which was adjusted by addition of tap water during mixing in a horizontal mixer equipped with load cells. All diets contained 53% concentrate and 17% CP (DM). Ten to 14 days prior to parturition, multiparous cows were fed corn silage and a grain mix low in sodium and calcium and composed of ground corn, ground oats, wheat bran, molasses, urea, m o n o a m m o n i u m phosphate,

TABLE 3. Analyses of diets containing ensiled forages (sequence A) or ensiled forages and dry hay or straw (sequence B), trial 1.a Period

1

Dry matter, % Crude protein, b % Crude fiber, b %

2

3

4

5

A

B

A

B

A

B

A

B

A

B

42.3 11.9 19.5

46.3 12.0 23.2

55.7 18.0 16.1

67.0 17.7 17.4

47.9 15.1 19.6

51.2 13.8 20.9

42.3 11.5 20.3

49.2 11.2 24.9

59.1 18.2 18.9

64.1 15.7 22.2

aMeans weighted by number of cows on treatment at time of sampling.

bDry matter basis. Journal of Dairy Science Vol. 66, No. 9, 1983

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LAHR ET AL.

and vitamin and mineral premixes. Experimental diets were offered beginning the 1st day after parturition, and data were collected from day 4 to day 200 of lactation. The trial was between September, 1980, and August, 1981. Cows were fed twice daily at 0800 and 1300 h in stalls equipped with partitioned mangers for individual feeding. Feeds were offered at 105% of ad tibitum intake. Feed weighbacks were obtained every Monday, Wednesday, and Friday mornings• Feed and refusuals were sampled weekly and analyzed for DM and CP according to AOAC (1) procedures. Monthly composites of these samples were analyzed for acid detergent fiber (ADF) by the Van Soest procedure (23). Cows were milked twice daily in their stalls at 0400 and 1500 h. Milk was weighed at each milking and sampled from each cow (evening and morning) every second Thursday for fat analysis by Babcock (1), CP by macro-Kjeldahl (1), and total solids by oven drying at 100°C for 6 h. Four percent fat-corrected milk (FCM) was calculated by the formula of Overman and Gaines (17). Cows were released into an open lot for about i h daily before the morning feeding for exercise and heat detection. They were weighed every Thursday prior to the morning feeding. Changes of b o d y weight were calculated as the difference between means of the first 2 wk of the lactation and the last 2 wk of the trial. Between the 12th and 15th wk of lactation, one rumen fluid sample per cow was collected by esophageal tube approximately 3 h after morning feeding. The fluid was strained through cheesecloth, immediately analyzed for pH, and treated with 1 ml saturated HgCl~/50 ml to stop bacterial action. Samples were stored frozen until prepared and analyzed for volatile fatty acids (VFA) by gas chromatography (6). Six cows from each treatment were observed for chewing time during three separate 24-h periods• Cows were observed individually once every 5 min and recorded eating, ruminating, or not chewing. Observations were summarized as each cow's activity for that 5 min. Data were summarized by 14-day intervals and analyzed by least squares (19). Treatment, parities one or two and more, and interaction of treatment × parity were independent variJournal of Dairy Science Vol. 66, No, 9, 1983

~ t< eq ~ 0o~o •e~q ~ ,6 e,i e,i .~.~

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MOISTURE C O N T E N T OF COMPLETE DIETS

ables in the model. Orthogonal contrasts for linear and quadratic effects were performed. RESULTS AND DISCUSSION

Trial 1

Chemical analyses of diets are in Table 3. In all periods, diets containing hay or straw (sequence B) were higher in DM than those containing only ensiled forages (sequence A). Diets were formulated to be isonitrogenous between treatments within a period and were similar except for periods 3 and 5, in which the CP content of A was higher than B, a consequence of higher CP in alfalfa silage than in hay. Crude fiber content of diets of B (hay or straw) was higher than that of A (all ensiled forages) in all periods because of replacement of corn silage with straw during periods 1 and 4 (dry periods) and possibly because of slight differences of fiber content of hay and hay silage in periods 2, 3, and 5. Estimated net energies (NE) for diets of sequence A were 1.55 Mcal/kg (periods 1 and 4), 1.60 Mcal/kg (periods 2 and 5), and 1.56 Mcal/kg (period 3). Estimated NE for diets of sequence B were similar except for periods 1 and 4 for which 1.37 Mcal/kg was calculated. Multiparous cows consumed more DM, produced more milk, and weighed more than cows in first parity in all periods of lactation. Interactions of treatment x parity were not common, and data have been grouped to include all parities, with one exception, which is noted. Daily intakes of DM, CP, and CF (Table 4) were not affected by treatment in period 1. In early lactation (period 2), cows fed diets containing alfalfa hay (B) consumed more DM (P<.05) and more CP (P<.O05) than cows fed diets with alfalfa silage (A). The difference of CF intake was attributable to greater DM intake and higher CF content of the diet containing hay (B). During period 3, cows fed A consumed more CP (P<.O05) than cows fed B because of higher CP in alfalfa silage than in hay. Intakes of dry matter and CF did not differ between treatments in this period. Crude fiber intake was higher (P<.05) during period 4 for cows fed diets containing corn silage, straw, and supplement than for cows fed diets of corn silage and supplement only because of the

1895

higher CF content of the straw. Dry matter and CP intakes were similar. Crude fiber intake also was higher (P<.05) during period 5 for cows fed alfalfa than for cows fed alfalfa silage, a consequence of the higher CF content of the hay diet and also because of the slightly greater (nonsignificant) DM intake of the hay ration. Crude protein intake did not differ between treatments. Although differences of DM intake were significant (P<.05) only in period 2, cows fed diets of sequence B showed a trend to consume more DM during the periods of lactation and less during the dry periods as compared with cows fed diets of A (Figure 1). Figure 2 shows trends of milk production

22 7--F 2C~

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LACTATION

~_ _2 ~ _

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~ _ ~

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150

i

i

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DRY,, 330

ACT

0

60

DAYS Figure 1. Dry m a t t e r intake of cows fed diets containing ensiled forages (sequence A - - ) or ensiled forages and dry hay or straw (sequence B .... ), trial 1.

35

20

15

1O

EARL Y LACTATION

LA TE LACTATION

DRY

LACT

5 O

150

330

60

DAYS

Figure 2. Milk production of cows fed diets containing ensiled forages (sequence A - - ) or ensiled forages and dry hay (sequence B . . . . ), trial 1.

Journal of Dairy Science Vol. 66, No. 9, 1983

1896

LAHR ET AL.

TABLE 5. Milk production of cows fed diets containing ensiled forages (sequence A) or ensiled forages and dry hay (sequence B), trial 1. Period 2

3

5 m

No. cows Milk, kg/day Milk fat, % Milk fat, kg/day Solids-not fat, % Solids-not-fat kg/day

A

B

SDb

A

B

SDb

A

B

SDb

24 25.0 3.56 .88 8.88

23 25.5 3.63 .91 8.67

2Z9" .37 .11 .99

24 15.5 3.96 .61 8.70

22 15.2 4.02 .60 8.69

214' .36 .11 .24

21 26.5 3.78 .99 8.50 c

15 29.2 3.92 1.12 8.72 d

412" .45 .19 .30

2.20

2.21

.29

1.34

1.32

.21

2.24 c

2.54 d

.35

aLeast square means. bx/Error mean square. C'dMeans with different superscripts within a column heading differ (P<.05).

during periods of lactation. Daily p r o d u c t i o n of milk, fat, and SNF (Table 5) did n o t differ b e t w e e n t r e a t m e n t s in periods 2 and 3. During the first 60 days of the second lactation (period 5), cows fed B tended to p r o d u c e m o r e milk (P = .075) than cows fed A. Cows fed hay (B) also p r o d u c e d more S N F (P<.05) than cows fed ensiled forages (A) in this period. Body weights were similar b e t w e e n treatments in a11 periods. Trends of b o d y weight are in Figure 3. An interaction of t r e a t m e n t × parity (P<.005) for b o d y weight occurred in period 1. Cows fed A averaged 594, 621, and

750

700

650

f

,'-

724 kg of b o d y weight after their first, second, and third and later lactations. B o d y weights for cows fed Diet B were 5 5 1 , 7 1 8 , and 684 kg for the respective lactation parity. Trial 2

Dry m a t t e r c o n t e n t s of feeds differed as planned (Table 6). There were small differences of CP and A D F analyses among diets. This m a y be attributable to presampling separation of ingredients, especially in the 78% DM diet. The estimated NE of the diets was 1.59 Mcal/kg. Multiparous cows c o n s u m e d m o r e DM, p r o d u c e d m o r e milk, and had greater b o d y weights than cows in first lactation. There were no interactions of t r e a t m e n t × parity for any of the measures in trial 2; therefore, all data have been grouped to include first parity and multiparous cows. Dry m a t t e r intake of cows increased linearly

b-

600

0m

TABLE 6. Average analyses of diets (dry basis), trial 2.

550

EARL Y

5OO

--45

~Y

LACTATION

i

i

i

l

Dry matter content

LA TE LACTATION i

i

l

J

150

ORY J

i

i

78%

64%

77.7 16.0 27.7

65.0 16.6 26.5

52%

40%

52.7 16.8 26.6

39.7 17.0 24.9

r

330

0

60

(%)

OAYS

Figure 3. Body weights of cows fed diets containing ensiled forages (sequence A - - ) or ensiled forages and dry hay or straw (sequence B . . . . ), trial 1. Journal of Dairy Science Vol. 66, No. 9, 1983

Dry matter Crude protein Acid detergent fiber

MOISTURE CONTENT OF COMPLETE DIETS

18 97

TABLE 7. Influence of dietary dry matter content on intakes, milk production and components, and body weigh't, trial 2. a Dry matter content (%) Item No. cows Intake Dry matter, kg/day Crude protein, kg/day Acid detergent fiber, kg/day Production Milk, kg/day Milk fat, kg/day Crude protein, kg/day Total solids, kg/day 4% FCM,g kg/day Milk fat, % Crude protein, % Total solids, % Body weight Initial, kg Final, kg Change, kg

78

64

52

40

SD b

14

13

13

14

22.3 c 3.7 c 6.2 e

20.5 d 3.4 cd 5.5 f

19.4 d 3.3 d 5.2 f

19.4 d 3.4 cd 5.0 f

2.2 .4 .6

29.1 .93 .91 3.39 25.6 3.20 3.14

27.6 .90 .87 3.24 24.4 3.24 3.17 11.78 cd

27.6 .94 .89 3.34 25.1 3.38 3.22 12.08 d

27.6 .92 .89 3.30 24.9 3.36 3.26 12.00 cd

4.5 .14 .13 .51 3.8 .28 .18 .50

11.68 c

538 569 + 31

528 552 + 25

536 546 + 10

527 548 + 22

...

49 53 34

aLeast square means. bx/Error mean square. C'dMeans in the same row without a common superscript differ (P<.05). e'fMeans in the same row without a common superscript differ (P<.O05). g4% fat-corrected milk.

( P < . 0 1 ) as r a t i o n DM c o n t e n t increased. Cows fed the 78% DM diet c o n s u m e d 1.8 k g / d a y m o r e DM ( P < . 0 5 ) t h a n cows fed t h e 64% DM diet (Table 7) a n d 2.9 k g / d a y m o r e DM ( P < . 0 0 5 ) t h a n cows fed t h e 52 a n d 4 0 % diets d u r i n g t h e 28 wk trial. H o w e v e r , m o s t o f t h e d i f f e r e n c e of DM i n t a k e o c c u r r e d a f t e r t h e 8 t h wk of l a c t a t i o n (Figure 4). Cows fed t h e 78% DM diet c o n s u m e d m o r e CP ( P < . 0 5 ) t h a n cows fed t h e 52% DM diet b e c a u s e o f t h e g r e a t e r DM i n t a k e o f cows fed t h e 78% DM diet. Also, because o f greater DM i n t a k e a n d higher A D F analysis, cows fed t h e 78% DM diet c o n s u m e d m o r e A D F ( P < . 0 1 ) t h a n cows fed a n y of t h e o t h e r diets. W h e n o r t h o g o n a l c o n t r a s t s were used t o c o m p a r e t r e a t m e n t s , i n t a k e o f b o t h CP a n d A D F increased linearly ( P < . 0 1 ) as r a t i o n DM c o n t e n t increased. T h e s h a r p decrease o f i n t a k e d u r i n g t h e last p a r t o f trial r e p r e s e n t s many data collected during the summer months a n d r e d u c e d i n t a k e p r o b a b l y was a c o n s e q u e n c e of hot weather. P r o d u c t i o n did n o t differ a m o n g t r e a t m e n t s

(Table 7; Figure 5) b u t t e n d e d t o b e slightly h i g h e r for cows fed t h e driest diet, especially a f t e r peak l a c t a t i o n . F a t p e r c e n t a n d c r u d e p r o t e i n p e r c e n t of m i l k increased linearly (P =

2a 26 24

22

~ --

a

2o 1~

16 14 12

0~-- 2

'

(~1'0

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, 2'2 ~ 2 ' 6

Figure 4. Dry matter intake of cows fed complete diets of various moisture contents, trial 2 (78% DM .... ;64% DM . . . ; 5 2 % D M - - . - - ; 4 0 % D M ). Journal of Dairy Science Vol. 66, No. 9, 1983

1898

LAHR ET AL.

40 38 36 34 32 30

~

28 26 24

22 2O o.

.2 .

.

6.

.

10

1' 4 ~ 7 ~ -

'

~2

' - - 2~6

WEEKS

Figure 5. Milk production of cows fed complete diets of various moisture contents, trial 2 (78% DM , 6 4 % D M . . . . ; 5 2 % D M --.--.; 40% D M --).

.08) as ration DM c o n t e n t decreased. Cows fed the 52% DM diet p r o d u c e d milk of higher total solids (P<.05) than cows fed the 78% DM diet. Orthogonal contrasts revealed a linear increase (P<.05) of percentage of total solids with decreasing ration DM content. No differences of p r o d u c t i o n of total solids occurred. Initial and final b o d y weight and b o d y weight change (Table 7) were n o t different a m o n g treatments. R u m e n fluid pH and V F A are in Table 8. No differences in r u m e n fluid pH or in acetic or butyric acid were observed among the f o u r

TABLE 8. Influence of dietary dry

matter content

on

treatments. Ruminal p r o p i o n a t e of cows fed the 78% DM diet was 2.4 percentage units higher (P<.05) than that of cows fed the 52% DM diet. Isobutyric, valeric, and isovaleric acids were higher (P<.05) for cows fed the 52% DM diet than for cows assigned to the o t h e r diets. A l t h o u g h slightly higher p r o p o r t i o n s of propionic, isobutyric, valeric, and isovaleric acids were in r u m e n fluid f r o m cows fed the 52% DM diet as contrasted to others, no specific trends indicate that moisture c o n t e n t was influencing rumen f e r m e n t a t i o n . Daily eating time, r u m i n a t i o n time, or total chewing time did n o t differ a m o n g treatments (Table 9). A m o n g the cows observed for chewing time, cows fed the 78% DM diet c o n s u m e d m o r e DM ( P < . 0 0 5 ) than cows fed the other diets, which was the same occurrence among all cows in the lactation trial. Cows fed the 78% DM diet had less chewing time per kilogram of DM intake (P<.05) than cows fed the 64 and 40% DM diets as a result of greater DM intake and n o t because of less chewing time. The less chewing time per kilogram of DM intake p r o d u c e d lower milk fat content. The equation of Sudweeks et al. (20) suggested fat c o n t e n t s f r o m 3.44 to 3.66%, but fat contents of only 3.20 to 3.38% were observed. Our results contrast with those of Thomas et al. (22) in which addition of water to hay did n o t reduce dry m a t t e r intake of heifers. Neither changing the moisture c o n t e n t of haylage by

rumen fluid pH and volatile fatty acids, trial 2. a

Dry matter content

Item

pH

78%

6.65

Acetic acid Propionic acid Butyric acid Isobutyric acid Valeric acid Isovaleric acid

63.71 22.49 c 11.35 .71 c 1.30 c .44 c

64%

6.59

64.59 21.07 cd 11.93 .69 d 1.3 lC .41 c

52%

SD b

6.63

6.41

.41

(mol/lO0 mol) 65.40 20.09 d 11.54 .86 d 1.54 d .57 d

64.38 21.52 cd 11.57 .68 c 1.42 c .42 c

2.73 2.81 1.40 .15 .17 .16

aLeast square means. bx/Error mean square. C'dMeans in the same row without a common superscript differ (P<.05). Journal of Dairy Science Vol. 66, No. 9, 1983

40%

MOISTURE CONTENT OF COMPLETE DIETS

1899

TABLE 9. Influence of dietary dry matter (DM) content on chewing time, trial 2. a Dry matter content Item

78%

64%

52%

40%

No. cows Eating time, min/day Rumination time, rain/day Chewing time, rain/day c Dry matter intake, ky/day Chewing time/DM intake, min/kg

6 250 460 711 25.1 d 28.8 f

6 220 460 679 20.0 e 34.3g

6 219 445 664 20.2 e 33.1 fg

6 245 444 690 18.8 e 37.3g

SDb

46 41 65 5.4 1.8

aLeast square means. bx/Error mean square. CEating + rumination. d'eMeans in the same row without a common superscript differ (P<.005). f'gMeans in the same row without a common superscript differ (P<.05).

drying nor addition of water affected intake by heifers. Also, in that trial (22), addition of water directly into the r u m e n did n o t influence the a m o u n t of DM consumed. Gharib et al. (7) f o u n d that f e e d l o t steers had the highest DM intake when fed all-concentrate diets that were 55% DM and reduced intake when fed diets that were 40% DM. Intake of 88 and 70% DM diets was intermediate. M a x i m u m DM intake for feedlot steers is predicted w h e n diets are 66% DM (15). When diets are lower or higher than 66% DM, reduced intake is predicted (15). In our trials, cows fed the driest diets had the highest DM intake. It is possible that high producing lactating cows, with greater intakes and energy outputs than heifers or feedlot steers, are influenced m o r e easily by moisture c o n t e n t o f their diets. Some feeds e x t r e m e l y high in water m a y reduce intake w h e n added to diets in large quantities. Grenawalt et al. (11) showed that inclusion of w e t brewer's grains (20% DM) as 40% of DM in diets for lactating cows decreased intake and milk p r o d u c t i o n whereas there was no effect if the wet brewer's grains were limited to 20 to 25% of DM. These data indicate t h a t diets b e l o w a p p r o x i m a t e l y 50% DM and high in wet brewer's grains w o u l d depress intake severely. Results f r o m the t w o triaIs r e p o r t e d herein suggest that diets below 60 to 65% DM tend to reduce intake by lactating cows w h e t h e r the DM c o n t e n t is lowered by ensiled feeds

(trial 1) or by addition of water (trial 2). Many o t h e r trials have shown similar results (3, 9, 10, 11, 12, 13, 16, 18, 21, 22); however, o t h e r trials have n o t (7, 22). Proposed factors causing r e d u c t i o n of intake include organic acid c o n t e n t and silage pH (14), silage f e r m e n t a t i o n products (22), and moisture c o n t e n t (11). The results of our trials did n o t show an adverse effect on milk p r o d u c t i o n w h e n high m o i s t u r e diets were fed, but these m o d i f y i n g factors m a y affect milk p r o d u c t i o n of cows fed high moisture diets low in pH or high in certain silage ferm e n t a t i o n products. REFERENCES

1 Association of Official Analytical Chemists. 1975. Official methods of analysis. 12fla ed. Washington, DC. 2 Baumgardt, B. R. 1970. Control of feed intake in the regulation of energy balance. Page 235 in Physiology of digestion and metabolism in the ruminant. A. T. Phillipson, ed. Proc. 3rd Int. Syrup., Cambridge, England. Oriel Press, Newcastle, England. 3 Burgess, P. L., J.W.G. Nicholson, and E. A. Grant. 1981. Effect of level of alfalfa pellets on intake of early and late harvested timothy silages of different dry matter content by dairy cows. Can. J. Anim. Sci. 61:633. 4 Campling, R. C. 1970. Physical regulation of voluntary intake. Page 226 in Physiology of digestion and metabolism in the ruminant. A. T. Phillipson, ed. Proc. 3rd Int. Syrup., Cambridge, England. Oriel Press, Newcastle, England. 5 Conrad, H. R., A. D. Pratt, and J. W. Hibbs. 1964. Regulation of feed intake in dairy cows. I. Change Journal of Dairy Science Vol. 66, No. 9, 1983

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