NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
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[Vol. XXVIII, Pt. IV,
protein, have been thoroughly reviewed by Marston [1939], Goss [1943], McAnally
and Phillipson [1944], Owen [1947], Baker et al. [1947], Elsden and Phillipson
[1948], Owen [1951], Reid [1953] and Gallup [1956]. Bohstedt [1949] has specially
reviewed the importance of rare minerals in ruminant digestion. Alexander
[1954] has recently reviewed the available knowledge about herbivorous digestion.
The most recent discussion on the biochemistry and microbiology of rumen digestion
is by Edwards [1955].
Prehension
In the digestion of ruminants the first step is prehension. In cows the chief
organ of prehension is the tongue. However, in goats and sheep the incisors and
the tongue are the principal prehensile structures.
Grazing habits of ruminants have been studied by Atkeson et al. [1942]
Johnstone et al. [1944] and Tribe [1949]. According to Fuller [1928], Schalk and
Amadon [1928], Bergman and Dukes [1925], Johnstone et al. [1944] and Hughes
and Reid [1951] cattle spend equal amounts of time in grazing, ruminating and
lying down. Tribe [1950] has recently reviewed the present knowledge of the
behaviour of the grazing animals.
Kick [1937] has studied the time spent by steers in mastication and Fuller
[1928] has observed the number of jaw movements in cows while eating [10,530]
and rumination [26,400] per day.
Mastication
Ruminants have no incisors in the upper jaw. Preliminary mastication
therefore, is incomplete and food passes almost completely unchanged into the
rumen [Schalk and Amadon, 1928]. The bolus, which is later regurgitated and
returned to the mouth for chewing during rest, contains primarily roughage.
Saliva
a. Amount. In the mouth both during preliminary and final mastication
the food gets mixed with saliva. According to Collin [1852] the amount of saliva
secreted in 24 hours in cattle is 50 to 60 kg. He has also studied the factors affecting
saliva secretion. According to him, with green and hay fodder, the amount of
saliva secretion is one-half and four times the weight of fodder respectively. With
cereals the amount of saliva secreted is equal to its weight. Smith [1890] has also
studied the amount of saliva secretion in cattle. According to Scheunert and
Traulman [1921] and Scheunert et al. [1930], in small ruminants the volume of
saliva secreted from one parotid gland is 5 to 42 cc/10 mins.
b. pH and composition. Ruminant saliva is alkaline. Schwarz and Hermann
[1924] and McDougall [1949] have reported that in dairy cows the pH of saliva is
8.1 and 8.3 respectively. Weyers [1937] has reported that pH of saliva varies from
8.23 to 8.54 and that the alkalinity of saliva is due to the presence of sodium and
potassium carbonates. Similar results were also reported by Collin in [1852]. Recent-
ly, however, McDonald [1949] has reported that the alkalinity of saliva is due to its
higher content of urea. The composition of saliva has been studied by different
December, 1958]
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AGARWALA
173
workers. Markoff [1913], Scheunert et al. [1930] and Trautmann and Albrecht
[1931] have reported that saliva contains Na, K, carbonates, phosphates and
chlorides. According to Scheunert et al. [1930] the ash from saliva contains 30
per cent Na, 2.4 per cent K, 9.2 per cent phosphate and 1.9 per cent chloride.
Lenkeit [1933] has recently reviewed the chemical composition of saliva of
different animals.
c. Functions of saliva. The main function of saliva is to moisten the feed
to facilitate easy fermentation, to neutralize the organic acids in the rumen and to
prevent the frothing of the rumen contents. Koebner [1931] has reported lipolytic
action by ruminant saliva. According to Scheunert and Trautmann [1921] and
Dukes [1942], because of the mucin content of saliva the food particles are easily
formed into bolus for swallowing and swallowing passages are lubricated.
Almost all the investigators [Carlson and Crittenden, 1910 ; Markoff, 1913 ;
Scheunert and Trautmann, 1921 ; Steintechner and Schwartz, 1925 ; Schwartz
and Rasp, 1926 ; Trautmann and Albrecht, 1931 and Gall et al., 1947] have reported
that ruminant saliva is free from the enzymes ptyalin and cellulose.
Rumen
a. Movement. In ruminants the act of deglutition of food and movement of
stomachs during digestion and its control by vagi have been studied by Cannon
and Moser [1898], Schalk and Amadon [1928], Czepa and Stigler [1929], Magee
[1932], Krazywanek and Quast [1937], Quin and Vanderwath [1938], Clark [1938],
Phillipson [1939], Duncan [1951] and Rushmer and Hendron [1951]. Recent
studies by Dougherty et al. [1955] and Grau [1956] in this respect are also worth
mentioning. These authors more or less agree that food in the rumen is kept in
continuous motion by rhythmic contractions of this organ the frequency of which
according to Schwartz, as quoted by Dukes [1955], runs as follows :—
While
(a) Eating
(b) Ruminating
(c) Resting
2.8 contraction/min.
2.3
do.
do.
1.8
do.
do.
Regurgitation is caused by an inspiratory effort with a closed glottis. The
bolus, after being remasticated, returns to the fermentation chamber. The passage
of ingesta from the rumen is very slow, giving enough time for microbiological
activity. The rumen communicates freely with the reticulum over the rumen-
reticular fold. The mucous membrane of the rumen is nonglandular and is covered
with papillae which are well developed in the ventral sac.
b. Capacity. According to Sisson [1914] the capacity of the rumen varies
according to the size and age of the animal and he gives the following variations
in small, medium and large sized cattle.
small size
medium size
large size
25-35
30-40
50-60
gallons
„
„
December, 1958]
O.
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AGARWALA
175
1945]. According to Danielli [1945] when pH falls towards acid, the+ions are
absorbed quicker than -ions and when pH rises, the—ions are absorbed quicker than
+ions, thereby maintaining the pH.
Digestion in the rumen is accomplished by agents of external origin, since no
secreting glands have been found therein and as already mentioned, saliva apparently
contains no enzyme. The known agents at work are bacteria, protozoa and enzymes.
Bacterial fermentation is most important in the rumen. The composition of rumen
bacteria has been studied quantitatively and qualitatively by different investigators.
e. Bacteria. According to Kohler [1940] and Gall et al. [1947] the bacterial
count in rumen ingesta varies from 12.8×10° to 9.2×10 9 per gm. of ingesta. The
count changes with the diet. For instance Gall et al. (1947, 1948) have demonstrated
that winter ration tends to increase the bacterial count from 92×10 9 to 150×10 9
per gm. of ingesta, while summer ration tends to decrease it from 92 ×10 9 to 52×10 9
per gm. of ingesta. Gall et al. (1947) has also reported increase in bacterial count by
cobalt in ration.
Qualitatively, rumen bacteria consist of iodophilic bacteria [Baker, 1939 ;
1942 ; Asher, 1942 ; Hungate, 1947 ; and Gall and Huhtanen, 1951]; Clostridium
cellubiopasus and Micromono spova propionici [Hungate, 1944]; Bacterium succino-
genes [Hungate, 1950]; Flavobacterium vitarumen [Bachdet et al., 1926]; Strepto-
coccus lactis [Ball and Huhtanen 1951]; Ruminococcus flavefaciens (Sypestyn, 1949,
1951]; Oscellospera guillermondi [Baker, 1942]; Amylococcus, Amylosarcine, Amy-
lobacterium and Amylo spirillum genera of iodophilic bacteria [Smith and Baker,
1944] and the Schizosaccharomycete group, which though looking like yeast in shape
and fission are different because of absence of alcohol production [Quin, 1943].
Qualitative changes in rumen bacterial flora also occur due to changes in
diet [Quin, 1943 ; Elsden, 1945 ; Gall et al. 1948 ; and Pounden et al., 1950].
f. Enzyme. Enzymatic activity in rumen is not important. The enzymes
either find their way into the rumen by way of ration or are secreted by bacteria.
Brown [1892], Karrer and Staub [1924], Woodman and Stewart [1928], Iwata
[1935], Sym [1938] and Sym et al. [1939] have isolated cellulase, licheninase,
xylanase, proteinase, amylase and lipase, respectively, from rumen contents.
g. Protozoa. According to Vanderwath [1942] protozoa in the rumen play no
vital part.
Cellulose Digestion
Cellulose digestion in the rumen is carried out mostly by bacteria of iodophilic
nature producing volatile acids and gases as end-products as stated above.
Hale et al. [1940] and Gray [1947] have demonstrated that in cattle 85 per cent
to 70 per cent of total digestible cellulose is digested by the rumen alone. Because
of maximum digestion of cellulose occurring in the rumen, Owen [1951] has deve-
loped the following regression equation to find out the digestibility of crude fibre
in ration :
Y=87.8-0.83X
(where ' y ' is the estimated digestibility per cent and ' X ' is the percentage
of fibre in ration).
December, 1958]
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177
Protein synthesis
Rumen bacteria, in addition to breaking down complex cellulose, synthesize
animal protein from vegetable protein and as well as from non-protein nitrogenous
material; these bacteria are utilized by the host when they die. [Axelsson, 1943
and Pounden et al., 1948]. The whole question of disintegration of bacteria in the
rumen has been discussed by Cuthbertson and Phillipson [1953].
1. Substitutes.—Soluble amides and urea can be most effectively used to replace
protein diet in ration, as has been shown by Zuntz [1891], Hagemann [1891], Armby
[1911], Steintechner and Schwartz [1925], Barlett and Cotton [1938], Lankeit and
Becker [1938], Smith and Marias [1940], Wegner et al. [1940], Owen et al. [1941],
McElsoy and Goss [1941a and b], Harris and Mitchell [1941], Klein and Muller [1942],
Johnson et al. [1942], Mills et al. [1942], Pearson and Smith [1943], Archibald [1943],
Elsden [1943], Phillipson and McAnally [1942, 1943], Smith and Baker [1944],
Briggs et al. [1944], Barcroft et al. [1944a and b], Mills et al. [1944], Marshall and
Phillipson [1945], Loosli et al. [1949], MacNaught and Smith [1947] and Duncan
et al. [1953]. However, Scheunert et al. [1922], Honcam and Schneller [1923],
Krebs [1937] and Smith [1945] doubt that urea can be utilized as a source of protein
supplement.
2. Aids.—Burroughs et al. [1951] has reported that iron and phosphorus are
important for urea utilization in rumen. Pearson and Smith [1943] have reported
fall in urea utilization due to inclusion of blood, casein and gelatin. Wegner et al.
[1941a and 1941b] has studied the protein content in diet and its effect on urea
utilization. They have found that non-protein nitrogen conversion to protein is
retarded after 12 per cent protein in diet.
Loosli and Harris [1945], Lofgreen et al. [1947], Klosterman et al. [1950, 1951]
and Gallup et al. [1952] have reported that methionine in diet increases urea utiliza-
tion.
Sulphur increases urea utilization. This has been demonstrated by Thomas
et al. [1951].
Fat synthesis
Fat synthesis, though not important, has been reported by Kraus [1927] and
Krazywanek and Quittek [1936].
Vitamin synthesis
It is now an accepted fact that ruminants can synthesize most vitamins of the
B complex group in rumen.
Theiler [1915] observed that ruminants can be maintained on diet poor in
certain vitamins. However, he was not able to name these vitamins. Bachdel
et al. [1927, 1928] however, observed that vitamin B complex can be synthesized
in rumen. This was later confirmed by Thompson [1942], Burkholder and McVeigh
[1942], Peterson and Peterson [1945] and Owen [1947].
178
RUMEN
DIGESTION
[Vol. XXVIII, Pt. IV,
A number of investigators have studied the synthesis of different members of
the vitamin B complex group in the rumen of cattle and ruminants in general,
as summarized below:
Vitamin
Thiamin (B 1 )
Riboflavin (B 2 )
Nia. cin
Vitamin B 6
Pantothenic acid
Biotin
Folic Acid
Vitamin B 12
Nicotinic acid
Investigators
McElroy and Goss [1941a], Wegner et al. [1940] and Johnson el al. [1941]
MoElroy and Goss [1939, 1940a], McElroy and Jukes [1940], Wegner et al.
[1940] and Johnson et al. [1941]
Wegner el al. [1940]
McElroy and Goss [1939, 1940b], McElroy and Jukes [1940] and Wegner
et al. [1940]
McElroy and Goss [1939, 1941b], McElroy and Jukes [1940], and Wegner
et al. [1940]
McElroy and Jukes [1940], Wegner et al. [1940]
Lardinois et al. [1944]
Zucker and Zucker [1948], Lillie et al. [1948] Abelson and Darby [1949]
and Hale et al. [1950]
Wegner et al. [1940]
In calves, the rumen does not function. Workers at Illinois showed that
thiamin [Johnson et al., 1948 ; Draper and Johnson, 1951], riboflavin [Wiese et al.,
1947], vitamin B 6 and pantothenic acid [Johnson et al. 1950], biotin [Wiese et al.,
1946], folic acid [Draper and Johnson, 1952b], B 12 [Draper et al., 1952] and choline
[Johnson et al., 1951] are essential vitamins and omission of any of these results
in poor growth and continued deprivation can result in death. However, Brisson
and Sutton [1951] and Kesler and Knodt [1952] have demonstrated that even in
calves vitamin B 1 and riboflavin are manufactured.
Synthesis of vitamin K in the rumen has been demonstrated by McElroy and
Goss [1940a, 1940b, 1941a, 1941b] and Owen [1947].
December, 1958]
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Factors in vitamin synthesis
Diet is responsible for changes in vitamin synthesis in rumen. Starch inclusion
in diet increases synthesis of members of the vitamin B complex in rumen, as demon-
strated by McElroy and Goss [1939], Lardinois et al. [1944] and Hunt et al. [1952].
Urea increases synthesis of vitamin B complex group members except B 6
[Lardinois et al., 1944]. However, Wegner et al. [1940] think that synthesis of
thiamin, riboflavin, pantothenic acid, B 6 and biotin is not affected by changes in
diet.
Inclusion of cobalt in diet increases the synthesis of vitamin B 12 as shown by
Moinuddin et al. [1951, 1953], Hasper et al. [1951], Hoekstra et al. [1952], Collins
et. al. [1953], Shrimpton and Duckworth [1953].
Role of antibiotics
Recently the effect of antibiotics in diet on protein and vitamin synthesis and
digestion of cellulose has been studied by different investigators.
According to Hungate et al. [1955] aureomycin in diet changes the rumen
flora and thus, according to Bell et al. [1951], Kester et al. [1952b], Murley et al. [1952],
Horn et al. [1953] and Pritchard [1955], decreases cellulose digestion. Decrease in
cellulose digestion due to streptomycin and Chloromycetin has been reported by
Wassermann et al. [1952]. They are of the opinion that the amount of antibiotics
in the diet is the factor that determines its effect and have demonstrated increase in
cellulose digestion at low levels of penicillin and streptomycin.
Antibiotics at higher levels of feeding decrease vitamin synthesis [Colby et al,
1950, Cunningham and Washermann, 1951 and Rusoff et al., 1954], However,
Chance et al. [1953a and 1953b] have shown that synthesis of riboflavin, vitamin
B 6 , biotin and vitamin B 12 is not affected by feeding antibiotics. Smith and Allen
[1953] are of the opinion that only thiamin, riboflavin, pantothenic acid, niacin are
not affected by inclusion of antibiotics in diet.
Rumen absorption
Until recently it was usually categorically stated that no absorption occurs
in the rumen. However, Trautmann [1933], Rankin [1941] and Phillipson and
McAnally [1942] have shown absorption of atropine, glucose and volatile fatty acids
respectively in rumen. Davey [1936] has shown that osmotic pressure of the fluid
in the various parts of the rumen is equal to that of blood and he gives this as a
proof that absorption results in rumen. Barcroft et al. [1944a] have shown that
rumen epithelium is more favourable to absorption than skin epithelium. Barcroft
et al [1944] have also demonstrated that absorption of lower fatty acids takes
place in rumen. Danielli [1945] has followed the work of Barcroft et al. and found
that absorption of fatty acids is influenced by pH of rumen ingesta. At lower pH,
according to him, more fatty acids are absorbed than at higher pH.
Mason and Phillipson [1951] and Kiddle et al. [1951] have further studied the
absorption of acetic, propionic and butyric acids in rumen. Absorption of K, Na
and chlorides in the rumen has been shown by Parthasarathy and Phillipson [1953].
78 AR/58
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180
RUMEN DIGESTION
[Vol. XXVIII, Pt. IV,
SUMMARY
1. The ruminants differ from non-ruminants herbivores in that the stomach
consists of four chambers—rumen, reticulum, omasum, and abomasum.
2. The saliva of ruminants is alkaline and contains no cellulase, amylase or
proteolase. Its main action is to keep the pH of rumen more or less uniform.
3. The temperature of the rumen is maintained at 40°C, with a variation of 1°C.
The rumen has slightly acidic pH and works under anaerobic conditions.
4. The gases in the rumen consist of N, H 2 , H 2 S, CO and CO 2 .
5. The average bacterial count in the rumen varies from 12.8×10 9 to 150×10 9
depending upon diet.
6. The most common bacteria in the rumen are iodophilic.
7. Enzymes and protozoa, though present in the rumen, play no important
part in rumen digestion.
8. Bacteria are responsible for cellulose digestion in the rumen and their activity
can be effectively improved even on poor roughage by mineral supplements.
9. Urea can be effectively substituted for proteins in the diet of ruminants.
10. Vitamin K and most of the members of the vitamin B complex group are
synthesized in the rumen.
11. Inclusion of antibiotics in diet has no effect on cellulose digestion and on
the synthesis of protein and vitamins.
12. Absorption of volatile fatty acids, glucose, certain drugs and minerals takes
place in the rumen.
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