December, 1952 ]
ABSTRACT
327
With this possibility in mind statistical study has been made of published data
on a total of 27 feeds including dry roughages, silages and concentrates, involving
1912 trials by 386 authors. The data include proximate composition and the
digestion coefficients for organic matter, crude protein, crude fibre, nitrogen-free-
extract and ether extract and the contents of the total digestible nutrients in each
of the three feed classes. To make the comparisons fair covariance adjustment for
proximate composition was conducted. In case of dry roughages significant
differences between species of animals exist for the digestibility or organic matter,
crude fibre and nitrogen-free-extract and the contents of the total digestible nutrients.
In case of silages and concentrates, the differences for the two species were significant
only for ether extract. Thus the average differences for dry roughages are in favour
of cattle on all nutrients and for silages, although significant only for ether extract,
indicate that cattle tend to digest silage better than sheep. The average differences
in case of concentrates, however, favour sheep on all the nutrients. Significant
species-by-feed interactions were also observed for digestibility of proteins from
roughages and that of ether extract from concentrates.
In view of the non-interchangeability of the digestibility data for cattle and
sheep and the much larger consumption of feed by cattle, it is suggested that more
digestibility work be done on cattle rather than on sheep so that greater accuracy
may be attained in the application of the data.—[S.S.N.].
Factors Affecting the Utilization of Food by Diary Cows. 1. The Rate of Passage of
Food through the Digestive Tract. BALCH, C. C. (1950). Brit. J. Nutrit. 4, 361
T HIS work was undertaken to investigate factors that may influence the effici-
ency of digestive process in cows. Experiments were conducted to study the
relative rates of passage of hay, chaff, ground hay and concentrates and to find out
the causes and effects of different rates of passage.
The method for measuring the rate of passage of food consisted of feeding a
small meal of stained food and counting the stained particles in subsequent voidings
of faeces. The principal marked food was hay. Excretion curves were drawn to
show the percentage of the total residues voided at any time after feeding.
Excretion curves for hay were characterized by an initial appearance of marker
in the faeces varying from 12 to 24 hr. after feeding, a slow excretion of the first 10
per cent of the residues followed by a higher rate of excretion typically resulting in
the passage of 80 per cent of the residues within 70-90 hr. Excretion then proceeded
more slowly and was completed 7 to 10 days after feeding. These curves also showed
that in any one cow hay was excreted at a slower rate than any of the other foods
studied.
Ground hay given as a small addition to unground hay was invariably excreted
more rapidly than the unground hay. Ground hay in diets in which all the hay was
ground was usually excreted over a longer period than hay in a similar diet
in which the hay was not ground. These differences were due to changes in the move-
ment of the foods in the reticulorumen. Excretion curves for chaffed hay and
ground hay mixed with hay showed that finer particles were excreted more rapidly
than larger ones ; in some cows chaffed hay behaved like hay, in others like ground