174
RUMEN
DIGESTION
[Vol. XXVIII, Pt. IV,
In the new-born calf the rumen and reticulum together are about half as large
as the abomasum. At four months of age, the rumen and reticulum together become
four times as large as the omasum and abomasum taken together. At the age of
about a year and a half, according to Sisson [1914],the four compartments reach their
permanent relative size, the rumen accounting for about 80 per cent of the total
stomach capacity, reticulum 5 per cent, the omasum 7 to 8 per cent and the abomasum
8 to 7 per cent.
Conditions in the rumen are most suitable for bacterial fermentation. The
rumen works at 39°C, with neutral pH and under anaerobic conditions.
b. Temperature. The temperature of the rumen remains more or less constant
except when a slight rise occurs during and after feeding and a slight drop during
fasting and after drinking of water. However, variations do not exceed 39.3 to
40.7°C [Krazywanek, 1929 ; and Lampe, 1931]. Recently Dale et al. [1954] has found
more or less similar results.
c. Gases. Washburn and Brody [1937], Lugg [1938], Dougherty [1940, 1941]
and Quin [1943] all have reported anaerobic condition, in rumen with the following
gases: N, H 2 , H 2 S, CO 2 , and CO and O 2 . Quin [1943] reports that the presence
of nitrogen and oxygen is due to air swallowed. Pilgrin [1948] has confirmed the
finding of the above authors for hydrogen.
d. pH. Cole et al. [1945] has reported a pH of 6.9 in the rumen. Electro-
metric measurements of pH of rumen ingesta have been made by Monroe and Perkins
[1939], Hale et al. [1940], Smith [1945] and Phillipson [1942]. Factors affecting pH
in rumen have also been studied. Slight variations occur due to the kind of ingesta
and lapse of time after feeding. According to Phillipson [1942] and Myburgh and
Quin [1943] diets like lucerne hay, maize and starch have a tendency to make the
pH more acidic (5.6) while fresh, green, flowering lucerne or matase veldt grass hay,
which produces urea, create slightly alkaline reaction (7.7). According to Ammerman
et al. [1955] blue grass creates 0.2 unit higher pH than alfalfa and lardino.
According to Smith [1941], the pH of rumen ingesta becomes acidic after feeding
and rises to the level of saliva pH when fasting. Phillipson [1942] and Myburgh
and Quin [1943] have reported that the maximum fall of pH in the rumen occurs
after four hours of feeding. Variations in pH from 6 to 7.14 have been reported
by Olson [1941], Hunt et al. [1943] and Lardinois et al. [1944].
According to Lamphia [1956], the pH of rumen varies from the uppermost
part, where it is highest, to the bottom part, where it is lowest.
Products responsible for acid pH of rumen content have also been studied.
According to Phillipson [1942], Elsden [1946] and Lamphia [1956] volatile fatty
acids, the by-products of cellulose fermenation are responsible for maintaining acidic
pH of rumen contents. According to Dukes [1955] CO 2 also contributes to acidic
pH of rumen contents. The stability of ingesta to pH is due to saliva [Collin, 1886 ;
Scheunert and Traulmann, 1921 and Scheunert et al., 1930], due to neutralizing
effect of NH 3 produced by proteolysis [Schuphan, 1943 ; and Pearson and Smith,
1943] and due to permeability of the epithelium which lines the rumen [Danielli,