observations on the functions of the alimentary canal in fowls by miss km henry, aj macdonald

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153
OBSERVATIONS ON THE FUNCTIONS OF THE
ALIMENTARY CANAL IN FOWLS
BY MISS K. M. HENRY, A. J. MACDONALD
AND
H. E. MAGEE.
(Rowett Research Institute, Aberdeen.)
{Racnvtd 12th August, 193a.)
(With Twelve Text-figures.)
THE work recorded in this paper is a continuation and amplification of the study of
alimentary function in the fowl begun by MacOwan and Magee (1931) and, like it,
deals with the passage of food through, and the absorption of carbohydrates from,
the digestive tract. The technique employed in the study of these questions was
varied, and it has, accordingly, been found convenient for descriptive purposes to
divide the paper into two parts.
PART I. THE MECHANICS OF THE ALIMENTARY CANAL.
The data obtained from the previous study of the progress of food through the
alimentary canal was so limited that further research on the problem was essential,
and the experience gained from the X-ray observations enabled us to continue these
in greater detail and with greater precision. This work, although it brought to light
many interesting findings in regard to the rate of onward propulsion of food, added
but little to our knowledge of the intimate nature of the contractility of the crop and
gizzard. From nnflt"f"»f*1 considerations alone, these viscera must be regarded as
capable of playing important roles in alimentary function and, to understand these
properly, some information concerning the movements of the organs was considered
desirable. Experiments were accordingly carried out in which the contractions of
the viscera were recorded graphically.
X-RAY OBSERVATIONS.
The fowls were placed in a specially constructed wooden box containing a
movable perch and a fixed feeding trough, and just wide enough to accommodate a
full-grown bird so that turning was impossible. Irradiation was carried out in
various directions, but most frequently from side to side. Photos were taken when
considered desirable.
Deglutition.
Fowls which had fasted 24 hours were placed in the box, given a meal of their
usual ration pbu BaSO and screened. The first three or four boluses usually passed
4
directly across the dorsal portion of the crop into the gizzard. The remainder of the
Jll-xii 11
154 K. M. HENRY, A. J. MACDONALD and H. E. MAGEE
meal seemed to lodge entirely in the crop, from which it was discharged at very
irregular intervals in the manner already described (MacOwan and Magee). Boluses
required 5-30 sec to pas* from crop to gizzard and the mean of 43 observations was
14 sec. No constant individual variations were observed.
Movements of the gixxard.
The gizzard was observed to assume, at regular intervals, an elongated shape with
long axis parallel to the long axis of the body. As this change in form was easily
seen when the rays were diaphragmed down sufficiently, it served as a means of
running the rate of contraction of the viscus.
The number of seconds which elapsed between successive appearances of the
elongated form of the viscus was determined at different times after feeding diets of
varying degrees of coarseness. The foodstuff chosen to bring out these differences
was oats, which is obtainable as (1) the whole grain, (a)" crushed oats," in which the
husk is split longitudinally and the kernel is flattened or broken into coarse pieces,
(3) a fine flour of the entire grain," Sussex-ground oats " (to be called " ground oats "
for brevity). Differences attributable to the nature of the diet were not observed, the
intervals varying from 11-5-27-9 sec., with an average of 16-3 for 54 observations.
Furthermore, the rate of contraction did not show any constant variation with time
after administration of food. The duration of a complete contraction-relaxation
cycle, ascertained from tracings of the gizzard obtained as described below, was
about 24 sec in the fasting state and slightly less in the fed state. It is clear then,
that the elongated form of the gizzard as seen by X-rays maAfH one phase in the
cycle of movements, but whether contraction or relaxation it is impossible to say.
Time of arrival of food m duodemtm.
The observation of MacOwan and Magee, mat boluses were shot off from the
gizzard into the duodenum at intervals of about a second, was confirmed 00 several
occasions; but sometimes longer intervals were noted. The rate of discharge did not
appear to be affected by varying the nature of the food; but, as in the former
experiments, these observations could only be made for a few minutes after shadow
began to appear in the duodenum owing to dispersal of barium all through the
intestine. The influence of the physical state of the food on the interval which
elapsed between the commencement of pecking and the arrival of the first bohis of
food in the duodenum was determined by feeding to fowls whole, crushed or ground
oats mixed with a constant proportion of BaSO . The crushed and ground-oat
4
meals were administered as pastes containing 30 per cent of water and 16 per cent
of BaSO , whereas the only successful way in which BaSO could be incorporated
4 4
with whole oats was to mix the grains in gum acacia containing the requisite
quantity of BaSO in suspension, and when the oats were dried a film of barium
4
remained adherent to the husk. The interval with the crushed and ground oats
varied from 1 to 5 min. and with whole oats from 3 to 11*5 min. The •igntfipym^ of
these findings will be discussed in Part II.
Observations on the Functions of the Alimentary Caud in Foals 155
Rate of progrtu of food through the ahmentary canal.
Fowls which had been fasted 24 hours were allowed to eat ad Ub. a meal consist-
ing of their usual ration pbu barium and enough water to form a stiff paste. The time
between the commencement of peeking and the arrival of shadow in the cloaca was
noted, X-ray observations being made half-hourly and then more frequently as the
barium approached the cloaca. In six experiments the following results were
obtained: 145, 160, 83, 390,150,175 min. between the commencement of pecking
and the arrival of shadow in the cloaca. Although these results showed that food
passes through the alimentary canal in about i\ hours, they threw no light on the
rate of progression of an entire meal. Experiments were therefore undertaken to
determine the time required for an entire meal of normal size to pass out of the body.
Fowls, which had received their usual feeds during the day, were given, in the
evening, barium meals of which the basal portions were the foods detailed below.
The size of the meals was such as to just fill the crop; it varied slightly for different
fowls but generally weighed about a oz. The interval of time which elapsed between
the commencement of feeding and the disappearance of barium from the digestive
tract was noted, no food being meanwhile given.
Time m hours between beginning 0} meal and disappearance of
shadow from alimentary canaL
Stock ration Ground oat* Crushed oata Whole oata
as 16 16 16
24 20 19
17 20 ao 33
17 17 16 M
«9 18 19
as as
The results show that, irrespective of the state of division of the diet, the digestive
tract empties itself in 16-26 hours after ingestion.
Nature of the movements of crop and gixxard.
The movements of the crop and gizzard were recorded in different experiments
by means of a balloon fastened on to a rubber catheter which was connected with a
manometer and tambour system. The balloon was inserted into the viscus by means
of a blunt probe passed down the catheter. For the crop a toy balloon was found
most suitable, and for the gizzard two strong rubber fingerstalls, one inside the
other, were employed in order to withstand the grinding action of this organ.
Pressures of about 10-15 cm- CHClg were found most suitable for both viscera. In
order to rule out the influence of respiratory movements simultaneous records were
made in some of the experiments by means of a simple stethograph made from a
piece of cycle tubing. During the taking of the records the fowls were held in a
mflpnar which experience showed to be the most conducive to quietness on their
part, and all noise and disturbance in the experimental room and in its vicinity were
eliminated so far as possible.
n-a
i|S K. M. HENRY, A. J. MACDONALD andH. E. MAGEE
The experiments described under mis heading are to be regarded merel/as a pre-
liminary study of the subj ect, especially those on the effect of drugs on gizzard motUity.
Crop.
The movements of the crop did not conform to any particular type of rhythm,
the contractions being, as a rule, irregular both in rate and in amplitude. Very
often attempts to record movements ended in failure, because of efforts made by the
fowl to get rid of the catheter and balloon. On these occasions the pressure changes
were due merely to the struggling or to the accompanying rapid and deep respira-
tions. These experiments gave the impression that the fowl in the fasting state is
very sensitive to pressure changes in the crop. This observation is in agreement with
Fig. i. Above, crop; below, respirations. Fig. 3. Effect ot" excitement on Contraction*
In *h« and in all other tracings time inter- of giaaard: slowing and diminution of am-
Tab — 30 seconds, upatrofce — contraction; plitude. At f the fowl was obviously ex-
records read from left to right. cited but not before.
that of Ashcroft (1930). A typical tracing is shown in Fig. 1, from which it will be
seen that when the fowls were at rest the respiratory movements had no effect on the
crop records. The contractions of the crop appeared to be markedly influenced by
impulses from the higher centres of the central nervous system. Thus, visual or
auditory stimuli frequently caused complete cessation of movements even although
struggling was completely absent Attempts made to determine how the move-
ments reacted to drugs which influence the autonomic nervous system were un-
successful because of the uncontrollable voluntary and emotional factors.
GtMxard.
The presence of the balloon in the gizzard rarely elicited struggling movements
of any significance, and the fowl would therefore appear to be much less sensitive to
Observations on the Functions of the Alimentary Canal in Fowls 157
pressure changes in the gizzard than in the crop. Nor was the contractility affected
by the emotions to anything like the same extent as that of the crop. The movements
always continued during periods of great excitement accompanied or not by violent
struggling, although some degree of inhibition was usual in these circumstances
(Fig. 2).
Fig. 3a. Gizzard. Effect of atropine 0-5 mg.: slowing and finally inhibition, contractions
being replaced by respiratory movements. All drugs were given subcutaneously.
Fig. 3 A. Above,gizzard sixminutes Fig. 3 c. Gizzard, six minutes after
after injection of 1 mg. atropine injection of 1 mg. atropine showing
showing respiratory movements relaxation becoming less and less
in prolonged relaxation interval: complete.
below, respiratory movements.
The records of the gizzard movements, as can be seen from Figs. 2-7 indicate a
fairly constant type of rhythm. The variations which occurred probably depended
on the location of the balloon in the gizzard; for it was frequently observed that the
movements were generally of small amplitude when the balloon was driven some
distance into the duodenum, as judged by the fact that it was exceptionally difficult
to withdraw at the conclusion of the experiment. The rate of contraction was very
constant (about 2-5 per minute) in different fowls in the fasting state. These
sp K. M. HENRY, A. J. MAC0ONALD andH. E. MAGEE
observations support those of Ashqroft (1930) After the ingestion of food the rate
quickened to about 3 per minute and the increase was independent of the nature of the
food, being about equal after skim milk, ground and crushed oats or green stuff.
Influence of drugs. With a view to throwing some light on the nervous control of
the gizzard movements the effects of atropine, pilocarpine, ergotoxine and adrena-
line were investigated. They were all given hypodermically in the following doses,
as a rule: atropine sulphate 0*5-1 mg., pilocarpine nitrate 10-20 mg., ergotoxine
(B. and W.) 0-05-1-3 mg., and adrenaline hydrochloride 1-2 mg.
The effects of atropine were roughly of two types. The more frequent was a
marked slowing and diminution in amplitude, the contractions being finally
replaced by short rapid movements (Fig. 3 «), which were found to be chiefly, if not
entirely, respiratory in origin. These were usually well marked during the prolonged
Fig. 4. Gizzard: a, nonnal, rate 2-75 per minute, b, three minute* after 10 mg. pilocarpine, rate
3*75 per minute, e, tweoty-two minute* after first injection and five minute* after fresh injection
of 10 mg. pilocarpine, tetany almost eatablfched.
relaxation period (Fig. 3 b). The other effect of atropine was one in which the
amplitude was diminished on account of incomplete relaxation, the rate being little
influenced (Fig. 3 c). It appears, therefore, that this drug can act in two opposing
fashions on the tonus of the gizzard musculature, the ultimate effect of each mode of
action being cessation of movement These results demonstrate an interesting
parallelism between the effects of atropine on the gizzard of the bird and the stomach
of the mamma.1; for, as cited by McSwiney (1931) in a recent review, this drug
sometimes inhibits and sometimes excites contractility of the mammalian stomach.
Pilocarpine caused either (1) a transient increase in amplitude with no definite
alteration of rate, or (2) an increase in rate with at first no alteration in amplitude,
which, after a variable time, generally diminished gradually, the final result being
short tetany-like contractions (Fig. 4).
Fowls seemed to vary widely in their sensitivity to ergotoxine. Thus, the drug
Observations on the Functions of the Alimentary Canal in Fowls 15.9
often produced its effects in less than 2*5 min., slowing of the contractions rapidly
passing into complete inhibition (Fig. 5); while in other experiments cessation of
movement did not set in until 10 min. or more after injection (Fig. 6). Whether the
drug acted rapidly or slowly, the records always showed the respiratory movements
shortly before and during quiescence of the organ.
The effects of adrenaline were very constant—distinct slowing accompanied by
an increase in amplitude (Fig. 7). This drug resembled pilocarpine in its action, in
Fig. 5. Gizzard. Effect of 1-3 mg. ergotoxine injected at | .'Rapid inhibition
and replacement of contractions by respiratory movements.
Fig. 6. Gizzard: a, normal. 6, twelve minutes after 1-3 mg. ergotoxine: slowing
and replacement of contractions by respiratory movements.
that respiratory movements were rarely shown on the tracing, and in this respect
both these drugs differed from atropine and ergotoxine. Because of the density of
the musculature it is reasonable to suppose that the balloon inside the gizzard would
be affected by the respiratory movements only when the organ is completely re-
laxed. If this is correct it would appear, since atropine and ergotoxine block im-
pulses via the vagus and splanchnic nerves respectively, that the maintenance of
tone in the gizzard musculature depends on the integrity of both nerves. This con-
ception is strengthened by the fact that the tone of the musculature was apparently
ife K. M. HENRY, A. J. MACDONALD and H. E. MAGEE
not abolished by pilocarptne or adrenaline, which intensify the activity of the vagus
and sympathetic nerves respectively. Furthermore, it would appear from this,
admittedly incomplete, study of the effect of these drugs on gizzard contractility
and from their well known actions on the autonomic nervous system that the
extrinsic nervous control of this organ is, as in the case of the mammalian stomach,
exerted by the vagus and splanchnic nerves, the former being in the main excitory
and the latter inhibitory.
Fig. 7. Ginard: a, normal, b, four minute* after 1 mg. adrenaline, c, eight minute* after b and
7-5 minute* after aa additional 1 mg. adrenaline, amplitude increased, rate decreased.
PART II. THE FASTING BLOOD-SUGAR AND ITS RELATION TO
INGESTION OF CARBOHYDRATES.
The objectives of the experiments described under this heading were to de-
termine (1) the influence of fasting on the blood-sugar level, (2) the relation between
the blood-sugar and digestion and absorption of carbohydrates, and (3) the in-
fluence of concentration of the solution on the rate of absorption of glucose. It was
hoped that from the results obtained under (2) some light would be thrown on the
rate of onward progress of food, which could be correlated with the X-ray observa-
tions and, along with these, be considered in regard to the probable mode of
functioning of the gizzard, aa suggested by MacOwan and Magee. The deductions
to be made from study of the blood-sugar level in relation to ingestion of food
depended, as in the case of the preliminary work of these authors, on the assumption
that the blood-sugar level can be regarded as an index of the rate of absorption of
glucose from the intestine. The only published experimental evidence we knew of
which would strengthen this hypothesis is that provided by the work of Magee and
Reid (1931). Their results refer to anaesthetised animals; but, as additional support-
ing data referring to unanaesthetised fowls have been obtained in our experiments
described under (3), there is good reason for believing in the accuracy of deductions
we have made.
It is true that Cori (1931) has made a statement which might be interpreted as
directly opposed to the above view. He has, however, informed us (1932) that his
Observations on the Functions of the Alimentary Canal in Fowls 161
criticism was directed more against experiments in which adequate precautions
were not taken to control factors capable of altering the blood-sugar level by
affecting the intrinsic regulators of carbohydrate metabolism. As our methods do
not fall in this category, in so far as we can see, Cori's criticism does not appear to
be applicable,
Blood-sugar was determined by the Hagedorn-Jensen method. All other sugar
analyses were carried out by the Shaffer-Hartman method. For the estimation of
liver glycogen the modified Pflliger method described by Osterberg (1939) was
employed. The fowls experimented on were all pure-bred White Leghorns.
The fasting blood-sugar.
MacOwan and Magee found that the blood-sugar of fasting hens fell on the first
day, but rose again on the third or fourth to levels as high as the initial, non-fasting
220
210
6 200
8 190
t 180
I 170
1 160
160
140
130 _J I I I 1
10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170
Time in houn
Fig. 8. Blood-sugar of fowli (cocks) during fatting.
value. As no extrinsic cause of this increase could be found, an unspecified en-
dogenous one was postulated. The fact that their experimental animals were hens in
the egg-laying season -suggested the possibility that the alteration in Wood-sugar
might be related in some way to the function of egg-laying. The blood-sugar of
three cocks was accordingly determined daily for 7 days during which water only
was administered, but since all three curves (Fig. 8) showed well-defined peaks on
the fourth day of fasting, this hypothesis proved to be untenable. The increase in
blood-sugar is, therefore, believed to be an indication of a change in the type of
energy metabolism—perhaps from that in which carbohydrate catabolism plays a
major part to that in which breakdown of fats and proteins predominates. Although
there can be little doubt that the original glycogen reserves were exhausted by
4 days' starvation, it is not clear why fat or protein catabolism should be ushered in
162 K. M. HENRY, A; J. MACDONALD and H. E. MAGEE
by a transient rise in blood-sugar. It is also noteworthy that the blood-sugar of
goats has been found to rise gradually from the second until the seventh day of
fasting (Magee, 1932). While the phenomena in the fowl and the goat are not
completely similar they have so many points in common that analogous exciting
causes are probable. Experiments, which it is hoped will throw some light on the
problem, are in progress.
In view of the above-discussed results it was considered that a preliminary fast of
48 hours would afford steady blood-sugar values, which could be used as a standard
for comparison with the hyperglycaemia following carbohydrate ingestion. As will
be seen below, however, this did not always prove to be the case, although the X-ray
observations have shown that less than 30 hours suffice for the digestive tract to
empty itself after a full meal.
Relationship between alimentary hypergfycaemia and the function of the gixzard.
The experiments under this head were carried out to test more fully the con-
ception of MacOwan and Magee that the gixzard is capable of acting as a filter BO
that the coarser ingesta are retained and ground by the powerful contractions of the
vi8CU8, while the fine particles pass rapidly into the intestine. The experimental
procedure employed to test this opinion was of the same nature as in the work just
quoted, viz. a comparison was made between the effects on the fasting blood-sugar
of meals of the same food material in different states of division. Before commencing
these experiments two preliminary investigations had to be conducted. These had to
do with (1) the basal blood-sugar value and (2) the influence of the water content of
the meal on alimentary hyperglycaemia.
Table I. Blood-sugar in mg. per 100 c.c. of fowls1 blood after 48 hours' fasting:
(2) from a sample taken at zero time and (i)from a sample taken 30 mm. earlier.
I a a-i I a a-1
an aoi — 10 179 17? 0
173 157 - 16 aos 188 - 17
190 17a - 18 171 180 + 9
37a -45 170 184
ai7 aio - 7 J96 168 — ao
160 '54 - 6 aao aio — 10
17a 17a 0 aia aio — a
168 17a + 4 164 158 - 6
z'i
163 — n
173 «67 + 15
(1) In the previous study it was noticed that the blood-sugar of some fowls after
fasts of 48 or 72 hours was unexpectedly high, amounting to 220 mg. per 100 c.c. or
more. It was thought that these high fasting values might be due, either to an
abnormally early increase in the blood-sugar as observed in starving fowls, or to
excitement Fowls which behaved in this way were rejected as experimental
animals. In the present study cocks were used and not more than one experiment
was done on each for reasons of economy. The initial blood-sugar values of some of