god you been proved totally WRONG and u just keep postin your ignroant view fo fecal chemistry. just read this if u don’t get it:

E. W. Crampton and I. R. C. Jackson

Studies—XXVI)

Digestibility by Steers and Sheep. (Pasture

Pasture Herbage and the Relation to Its

Seasonal Variation in Chemical Composition of

J Anim Sci 1944. 3:333-339.

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SEASONAL VARIATION IN CHEMICAL COMPOSITION OF

PASTURE HERBAGE AND THE RELATION TO ITS DIGESTI.

BILITY BY STEERS AND SHEEP. (PASTURE STUDIES—XXVI)

E. W. CRAmPTON AND I. R. C. JACKSON

McGill University 1

T HE digestibility of the dry matter of pasture herbage under eastern Canadian

conditions may vary from 8o percent in the early spring to 6o percent

or less during mid-summer. The factors which cause these changes in digestibility

are not fully known, but there is reason to believe that changes in

digestibility reflect changes in nutritive value of feed. It is unlikely that

either amount or quality of protein limit the feeding value of pasturage to

grazing ruminants. The protein content of such material normally does not

fall below x S percent and ruminant digestion appears to be wholly independent

of amino acids in the diet. It is presumed that synthesis of necessary

amino acids may occur in the rumen from a variety of sources of dietary nitrogen.

Available energy, on the other hand, is correlated with the feeding value

of any ration. Since ration energy losses through incomplete digestion of the

potential energy yielding fractions are variable between different diets, it is

bumumed that seasonal trends in the digestibility of the energy-yielding portions

of pasture herbage indicate seasonal changes in the nutritive value of

such feed.

Critical examination of data from this station reveals that, excepting for

protein which shows little change in magnitude and none which follows

season, the seasonal trends in the digestibility of the several fractions of the

mixed pasturage involved in this study follow closely the trend of digestibility

of the total dry matter eaten. Therefore, the discussion following will

involve the digestibility of total dry matter only unless otherwise noted. It

may be of interest, however, to state the order of the digestibility of certain

of the feed fractions as determined from the past two years’ work on this

problem. The range covers the pasture season.

Range Average

Crude Protein 7~79~ 760”/0

Ether Extract ~5-6x 4 x

Crude Fibre 57-8~ 69

Nitrogen.Free Extract 68~78 75

Cellulose 4x-84 74

Soluble Carbohydrate 75-85 8o

“Lignin’” (Dif.) ~-58 34

Total Dry Matter .68-8o 7x

a C-~mtribution from Faculty of Agriculture, McGill University, Macdonald Cx~llege, Quebec, Canada. Journal

Series No. ~89.

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334 E. W. CRAMPTON AND I. R. C. JACKSON

If seasonal change in digestibility can be taken as an index of change in

feeding value of pasture herbage, then this figure should be useful as a basis

for studying the accuracy of schemes of chemical description intended to

depict or predict feeding value of such material.

For the past three seasons, the herbage from an experimental pasture has

been fed either to steers or sheep. In the case of steers, the material was cut

and fed at once to animals confined to digestion stalls on the area. During the

past season artificially dried clippings, taken every three weeks, were fed to

sheep in digestion stalls. During the 194i season but three digestion periods

were actually carried out. In i94~ our records give a daily digestion coefficient

throughout the full season. In this paper, the latter data have been

grouped into seven three-week periods.

The season trends in the digestibility of the dry matter for the three seasons

are shown in figure ~. It is not to be expected that these curves would

coincide, but it is noteworthy that their trends are similar from early spring

to mid-summer. During this period the decline in digestibility is marked,

X”’,; /

,%. ../

Figure I. Seasonal trends in digestibility of dry matter.

and coincides with the maturing of the plants. There may also be changes in

botanical composition during this time. (See table 3.)

After about July x, the digestibility may either continue to fall, or rise to

spring level.s, depending on climatic conditions. The season of i94i was exceedingly

dry, while I943 was the wettest season recorded for about 5o

years with no dry hot period during the summer.

Rate of gain of grazing cattle also followed roughly these trends in digestibility

of the dry matter of the forage.

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VARIATION IN COMPOSITION AND DIGESTIBILITY OF PASTURE 335

Presumably these seasonal changes in the digestibility of pasture herbage

are the result of changes in chemical composition. It is interesting to note.

the extent to which such changes in chemical make,up were correlated with

the trend in digestibility. Data are available for the I94~ season and i943

season only.

Table i gives the data for I94~. (The figures for daily feces output are of

no particular interest at present.)

TABLE i. SEASONAL TRENDS IN COMPOSITION OF MIXED PASTURE

HERBAGE TOGETHER WITH DATA FOR i) DIGESTIBILITY OF DRY MATTER,

~) AVERAGE DAILY FECES DRY MATTER OUTPUT

(x94 ~ SEASON—STEERS)

May

18

I

Dig. of dry matter (%) [ 76

Av. daily feces on I7. 5

lbs. D.M. intake (lbs.) 3.6

Composition of herbage

Crude protein (%)

Crude fibre (%)

N-Free extract (%)

Insoluble residue (%)

Lignin* (%)

Lignin** (%)

Soluble carbohydrate

I6.~

:z4.6

45.7

34.4

9.9,

7.4

41.6

June

1

75

4.3

I8.3

9`3.7

44.8

34.5

9.6

5.6

41.1

June June

17 ~7

7 ~ 65

4-7 5.7

I4.i 21.I

~7.6 ~I. I

46-7 45.6

36.7 3o.8

m.5 lO.6

19,.6 4.9,

4 ~.9 42.3

Correlation of

fractions

July Aug. Sept. with digesti,

~7 ~6 ~5 bility of dry

matter

7 ~ 7 ~

6. I 5.~

I7. 9 I8.3

20.0 I8.9

48.~ 5o.5

~9.9 3o.4

11.6 11.1

6.9` 9.4

43.4 4 ~.8

68

5.3

I9.7

I7.o

49.~

e9. I

9.9

9.3

41.1

— o. 696

o.59I

—o.4~ 5

0.737

—o.6*6

o.~3 I

-o.o8~

* Method of Crampton and Maynard, 1938.

** Method of Crampt,on and Whiting, i94~.

One of the first things to be noted in these data is the negative and high

correlation between crude protein and digestibility of the herbage. This is

strong evidence towards refuting the claim that treatment to pastures resulting

in increased protein correspondingly increases the nutritive value of

such pastures when their lowest level of protein was much above the needs

of the steers or sheep.

This is true also of crude fibre and insoluble residue3 These correlations

are positive but would be negative if increases in crude fibre or in cellulose

+lignin decreased nutritive value. The explanation obviously lies in the

high digestibility of cellulose by ruminants.

Insoluble residue, for practical purposes, may be taken as comparable to crude fibre obtained by omitting the dilute

alkali treatment. It differs from crude fibre, therefore, in that it contains the lignin as well as the cellulose. (See JOUr-

NAL OF ANIMAL SCIENCE, V. 9., No. 4, P. ~78, 1949..)

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336 E. W. C~a~x~ro~ AND I. R. C. JACKSON

Lignin, which it was believed might prove a useful index, is still an uncer-

.rain factor. Our studies have shown that “formaldehyde lignin” is probably

too high. Lignin by the method proposed by Crampton and Whiting (I94~)

(i.e. by difference) gives values more nearly in line with the 72 percent

sulphuric acid method. In the i942 results “formaldehyde lignin” was negatively

correlated, while “lignin by difference” was only slightly but posi,

tively correlated with digestibility of the dry matter.

The I943 data involving artificially dried clippings fed to sheep are shown

in table 2.

TABLE ~. SEASONAL TRENDS IN COMPOSITION OF MIXED PASTURE

HERBAGE TOGETHER WITH DATA FOR x) DIGESTIBILITY OF DRY MATTER,

2) AVERAGE DALLY FECES DRY MATTER OUTPUT

(~943 SEASON—SHEEP)

Dig. of dry matter (%)

Av. daily feces on 1r76

gins. D.M. iiltake (gins.)

Composition of herbage

Crude protein (%)

Crude fibre (%)

N,Free extract (%)

Insoluble residue (%)

Lignin* (%)

Lignin** (%)

Soluble carbohydrate

June

I

75

~89

17.9

~o. 9

48.

29.8

lO. 4

5.6

4~. 7

June

69

~67

I7.3

17.3

48. i

3~.8

11.4

6.6

4~.o

69

363

19.7

45”.3

31.8

8.9

38.7

Aug,

4

72

3~

I7,9

43.3

32.0

7.0,2`

7.5.

37- 3

I Correlation

of fractions

Aug. Sept. with digest,

~5 ~ ibility of

dry matter

73 75.

3r9 ~9 o

~5.8 2`6-3 0.337

~7-9 15.-4 —0.063

43.8 46.2` 0.075

3 ~ 3 “~5-7 —0.080

2o.0 16.9 —o.oo3

8.i 5..4 —o.663

36.8 41.8 o.3io

* Method of Crampton and Maynard, t938.

** Method of Crarapton and Whiting, 194~.

Here crude fiber shows no appreciable correlation in trend with digesti,

bility of dry matter; nor does insoluble residue or ”’formaledehyde lignin.”

Protein is slightly correlated. The “iignin by difference” shows a high and

negative correlation; but the change in lignin values during the season is

small.

In connection with these data, the change in botanical make,up of the

herbage is interesting. (Readings represent ground cover.)

Evidently change in clover content did not correlate with change in digestibility.

Indeed the highest digestibility was found in the periods when

the clover content was least. The influx of clover, however, undoubtedly

was a factor in the climb in percent protein in the mixed herbage from

spring to fall.

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VARIATION IN COMPOSITION AND DIGESTIBILITY OF PASTURE 337

The trends in the composition of the herbage for the two seasons x94~

and i943 are shown graphically in figures ~-5. There is no rhyme nor reason

to the crude fibre trends: the protein trends are influenced by change in

botanical composition; nitrogendree extract is naturally complementary to

protein as is soluble carbohydrate. Insoluble residue, which is really crude

fibre not treated with alkali, drops from spring to fall but fails to be low in

the spring as it would be if it were to serve as an index of digestibility. The

combined soluble carbohydrate and soluble protein, which might be taken

TABLE 3. DIGESTIBILITY OF ARTIFICIALLY DRIED CLIPPINGS OF

MIXED PASTURAGE BY SHEEP

(1943 SEASON)

Date Digestibility

of dry Notes re herbage as clipped

clipped matter

June I 75.4%

June zi

July 14

Aug. 4

Aug.~5

Sept. 15

68.8%

69. i%

71.8%

7~-9%

75.3%

Herbage about Io inches in height. Botanical make.up was:

Grbumes 65%— Timothy 4~%

Ky. Blue

Couch Grbum i:

Clovers 3o%— Wild White I4

Alsike I3

Red 3

Weeds x4%— Daisy, Dandelion.

Herbage 6-8 inches tall. Clovers now 5o% of ground cover.

Herbage 5 inches tall. Clovers about 55% of ground cover. Weeds

are few; grbumes chiefly timothy and red top.

Clovers now make up 65% of ground cover; grbumes 3o% and

weeds 5%.

No readings.

Clovers reduced to 4~%, mostly wild white; grbumes 55% with

90% of it timothy; weeds 3%.

in non-herbivors as an index of total energy value, does not follow the same

trend in the two seasons. “Lignin” as estimated by either of two methods

can not be relied on to indicate the trends in digestibility of dry matter in

this type of feedstuff.

General Observations and Conclusions

Under eastern Canadian conditions, mixed pasturage consisting principally

of timothy, red top, blue grbum, with or without wild white clover,

is the most important single feedstuff for dairy cattle. Through long neglect,

many pastures are badly run down and the nutritive value of the herbage

is obviously low. Fertilizer treatments restore such areas to increased carry-

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338 E.W. CRAM~O~q A~D I. R. C. JACKSO~q

.S,,~,.w x..,,a … c , , . e , ~ 4~tz~’~,,,, ~,~,.

N”,,,,.~:- ”~= :”~”: ~. . . . . . . . ~ ~,

,,/, ~u

,i

\

””“k

’, /

,.~,:...._:~: ....... .._/.:: ........

./: k ~__…...’”

j~ – j~$ ~ ~,~’~.

.~2

,70

___.. .,~-: ...... . ......... ~,: \

f

g/

/

.7::2.~ ,. .9 …/.f 4. .z ..~ .. . ... ... ..........

J /\

, i 7 ~ – ” ~j~”~ ~q~..-’. ”-~

Figure 2 (upper left). Seasonal trends in crude fibre and protein content of

mixed pasture herbage.

Figure 3 (upper right). Seasonal trends in insoluble residue and soluble carbohydrates

pins soluble protein.

Figure 4 (lower left). Seasonal trends in nitrogen-free extract and soluble

carbohydrate.

Figure 5 (lower right). Seasonal trends in lignin.

ing capacity, some of which is traceable to an improvement in the nutritive

value of the herbage and some to increase in yield of forage.

Improvement in nutritive value has been claimed for different treatments

in many pasture studies on the basis of a resulting increase in protein and/or

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VARIATION IN COMPOSITION AND DIGESTIBILITY OF PASTURE 339

decrease in fibre content of the herbage. In the light of the data above presented,

such conclusions are unwarranted. Neither of these proximate principles

differ significantly in their digestibility from each other or from that

of the total dry matter. Furthermore, changes in either fraction during the

season are either not correlated at all, or are correlated contrary to expectation

with the concomitant changes in the digestibility of the dry matter

eaten.

Protein and fibre fail as indices of nutritive value as do all other fractions

reported in this paper.

There appears to be a characteristic steady decline in the digestibility of

pasture herbage dry matter from values of ‘the order of 75 percent for early

spring grbum to 6o percent some six weeks later. Digestibility from this

time on may rise again, further decline, or remain at the mid-summer level,

apparently not depending on chemical changes indicated by standard feedingstuffs

analysis or its modifications herein described, but closely paralleling

local climatic conditions of moisture and temperature.

The authors believe it is much easier to predict, from observation of seasonal

conditions, the probable chemical make-up of the herbage than its digestibility.

The digestibility of mixed pasture herbage by steers and by sheep appears

to follow quite closely the leaf/stem ratio existing at the time. A wide ratio

means high digestibility which decreases as the material increases in propor,

tion of stems. This is not a new idea, but it is one which may hold the secret

of measurement of the nutritive value of such a highly variable feed as pasture.

Changes in the toughness of the stems noticeable in clipping, but too

small to be evident on casual observation, are promptly reflected in increased

feces output on constant levels of feed intake. It seems reasonable that these

changes are accompanied by or the result of some change in chemical composition

which could be easily measured.

It is possible that changes in the activity and nature of rumen flora of

microorganisms are occasioned by chemical and/or physical changes in the

herbage which in turn are reflected in “digestibility” of the ration.

These may include or consist of factors not now measured in the usual

feedingstuffs analysis. Certainly it is known that treatments of cellulosic ma.

terials with numerous chemicals, particularly alkal{, to partly do what bacteria

seem to do in the rumen, results in an increase in their digestibility and

nutritive value.

Literature Cited

Crampton, E. W. and L. A. Maynard, x938. The Relation of Cellulose and Lignin Content

to the Nutritive Value of Animal Feeds. J. Nutrition xS, No. 4: 383-397-

Crampton, E. W. and Frank Whiting, i94~.. A Proposed Scheme of Feedingstuffs Analysis.

JouR~qAt oF ANIMAL SCIENCE ~, NO. 4: 9-7~’~8A”

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