反芻胃の栄養生理学的研究

Nutritional physiological studies on the reticulo-rumen of ruminants

大谷 勲

広島大学水畜産学部紀要

Journal of the Faculty of Fisheries and Animal Husbandry, Hiroshima University

In view of the fact that the fore-stomach of ruminants plays a significant role in their digestive systems, nutritional and physiological studies were undertaken on the digestion in the rumen which has a close relation to the feeding of ruminants.

The results of those studies are as follows.

I Methods and Discussion on Collecting Rumen Contents
Experiments on the methods of collecting the contents of the rumen by permanent rumen fistulae and catheterization were tested with goats.
1) The rumen fistulae-operation was carried out as follows:
Along the lumbar from the last rip of the left side the abdomen was incised, and the skin, the muscle and the stomach wall were sutured. After the adhesion, the wall was incised and then the canula was inserted in the rumen wall.
2) Four catheters of size 12, 10, 6 and 5 mm. in outside diameter were inserted respectively to the rumen from the mouth. According to the results of X ray observations, the catheter of size 12 mm. showed a tendency to go near the rumen fluid level, size 10 mm. into the ventral sac and size 5 mm. and 6 mm. into the ventral sac and reticulum. That of 10 mm. was the most suitable for collecting the rumen contents.

II Studies on the Development and the Functions of the Reticulo-Rumen
1 Observations on the Normal Development of the Reticulo-Rumen
1) Five kids, from birth to 5 weeks of age, fed on a ration of milk, grass and concentrates, were used to investigate the development of rumen and reticulum by means of X ray observations and indirect photography.
2) In the goats at birth the structures of rumen and reticulum were very small and the rumen presented a globular or an oval shape. When a small dose of barium sulphate meal was administered through a catheter to them, the rumen swelled surprisingly and began a slight movement. The rumen moved more briskly as a result of introducing air into it. It is deemed that the air inhaled at sucking milk may be helpful for development of rumen.
3) At the age of I week the rumen extended downward and occupied about two-thirds of the abdominal cavity, but there was no solid food yet in it. Even a large amount of milk was sucked in, the milk did not enter the rumen in this stage.
4) At 2 weeks a little ingesta and weak movement were observed.
5) At 3 weeks the ventral sac was quite filled and the contraction of rumen and reticulum was noticed, but not strongly. It was deemed that some of the ingesta was swallowed into the rumen.
6) At 4 weeks the regular cycle of contraction was observed. After 4 weeks of age the digestive mechanism of fore-stomach seemed to be nearly full grown.
7) By measuring the increase in the sizes of parts of the stomach through the photographs of X ray observations, the following results were obtained:
The spindle of rumen developed until it occupied 90 per cent of the abdominal cavity in 2 weeks old kids and it reached the abdominal wall after 3 weeks. The growth rate of the spindle of rumen was such that at I week it was about twice the size of that at birth time, 3 times at 2 weeks of age, 4 times at 4 weeks and 4.3 to 4.7 times at 5 weeks. The development of the dorsal sac was relatively larger than that of the ventral sac.
8) The transversal axis of rumen to the pelvic cavity became at 3 weeks about twice the size of that at birth, 3 times at 5 weeks.
9) The major axis of the reticulum was about doubled at 3 weeks and tripled at 5 weeks. The minor axis was doubled at 3 to 4 weeks and quintupled at 5 weeks.

2 Experiments on the Reticulo-Rumen Dilation during the Suckling Period.
1) Comparative experiments were made using two normally developed goats and one with the stomach abnormally dilated, which condition the author found in many experimental goats. By X ray observations of the stomach dilation the following facts were ascertained.
2) At 2 weeks of age the rumen extended downward to the abdominal wall and showed greater development than did the control goats, and also strong contractions and ruminations were observed in this week of age.
3) The reticulum presented a shape like a walnut or a ball and the atrium of rumen took an abnormal form as if it were pressed.
4) From 2 to 9 weeks of age the same feeding was undertaken to the three experimental animals to investigate the differences in growth between them. It was found that the goat with the stomach dilation was much inferior to the others in growth and in weight increase. The body weight of the goat with the stomach dilation was 50 per cent of that of the control animals. However only the abdomen was observed to be dilated remarkably in the former.
5) Digestion experiments with milk and concentrates in 6 weeks of age, with concentrates and beet pulp in 8 weeks were carried out. In the digestibility no remarkable difference was noticed between them. In 6 weeks of age dry matter intake per 100 kg. body weight was 3.2 kg. in the one with the stomach dilation and 2.0 kg. in the control kids. In 8 weeks the former ingested 70 per cent more than the latter.
6) The rate figures of nitrogen retention were 28 per cent in 6 weeks of age, II per cent in 8 weeks in the experimental goat, and 62 per cent in 6 weeks, 46 per cent in 8 weeks in the controls.
7) In the daily amounts of excreted nitrogen the experimental one excreted about 4 times as much as the controls did.
8) From these observations it was suggested that the stomach dilation in the earlier age of suckling period, which brought about the heterotaxis and abnormally pressed other organs, caused functional disorder of the internal organs.

3 Experiments on Promoting the Dilation of Reticula-Rumen during the Suckling Period.
1) In order to investigate the effects of the stomach dilation in suckling period upon growth, digestion and nitrogen metabolism, the following experiments were undertaken by using 16 newborn goats.
2) To cause stomach dilation, the goats were divided into 4 experimental groups and managed as follows:
(i) Group I : were the fasting group for 2 or 3 days after birth.
(ii) Group II : were the underfeeding group for 10 days after birth. The amount of milk intake was limited to 1/5 or 1/10 of standard feeding.
(iii) Group III : were the group in which the animals were allowed 20 or 50 per cent of usual amount of milk through a catheter to the rumen from birth.
(iv) Group IV : were the control group of standard feeding.
3) The following results were obtained by X ray observations:
Stomach dilation, as compared with Group IV, was noticed in Groups I and II at 2 weeks of age. In Group III it had already been found at 2 weeks. In 3 to 4 weeks, however, their appetite failed entirely and they had violent scours and one of Group III died.
4) Groups I, II and III were observed to be slow growers compared with Group IV. The rate of body weight gain of these groups at the final week of experimental period ( 9 weeks) was 50 per cent of the latter and the~ growth of chest girth and body length were retarded, too.
5) On the other hand, no noticeable difference was found between groups in ability to digest food in these digestion trials in 2, 4, 6 and 8 weeks.
6) The amount of dry matter intake per 100 kg. body weight in the experimental goats was 1.7 times in 6 weeks, 1.7 times in 8 weeks as much as that in the control.
7) In the nitrogen balance experiments, the goats with stomach dilation showed low rate of retention. This effect corresponded to that report in the above-mentioned publication.
8) From these results of the experiments it is assumed that, without support by the abomasum which had been depleted by fasting or insufficient milk feeding, the reticula-rumen descended down relatively to the abdominal wall; furthermore, the emaciation which the goat with stomach dilation suffered affected remarkably not only the digestive organs, but also the whole growth of body.

4 Experiments on the Influence of Age and the Methods of Diet-Supplying on the Course of the Swallowed Bolus.
1) By means of X rays the course of the swallowed bolus was investigated with goats of various ages after birth on fluid and solid food.
2) In the first experiment using 8 kid goats aged 2 to 4 weeks the capsules (6.5 mm. in diameter and 20 mm. in length) were swallowed respectively and the following results were gained:
The rates of the capsules swallowed down into the rumen and reticulum were 27 per cent at 2 weeks of age, 33 per cent at 3 weeks and 38 per cent at 4 weeks. The rate of swallowing into the rumen af!d reticulum in the suckling period increased with age proceeding. But during the period from 2 to 4 weeks of age, the rate into the rumen and reticulum was relatively low: they deposited in the rumen at 20 per cent, reticulum at 14 per cent, omasum at 29 per cent and abomasum at 37 per cent.
3) In the second experiment 5 kids at I month of age which had been fed on milk alone were used. Various sizes of capsules and dumplings were administered and their courses in the stomach were observed. The dumpling of 20 mm. diameter was swallowed into the rumen and reticulum. The capsules of 5 mm. diameter, 5 mm. length and of 10 mm. diameter, 20 mm. length were swallowed into the abomasum in almost cases. In the test on the 5th day after weaning, nearly all of them, regardless of shape and size, were swallowed into the rumen and reticulum.
4) Comparative experiments were made in two cases; one with an animal on milk feeding, while the other was with a weaned one at I month of age. Offered wheat bran containing barium sulphate, the latter swallowed it into the rumen, but the former into the abomasum even at 7 weeks, but at 13 weeks of age the former as well as the latter swallowed it into the rumen.
5) In the third experiment 9 goats of ages varying from 2 weeks to 7 months were used to investigate how the method of administering liquids would affect the course into the stomach, by feeding milk in which barium sulphate suspension was contained. Following five experimental methods of feeding milk were employed:
(i) method I : feeding milk through a nipple;
(ii) method II : feeding milk from a bucket ;
(iii) method III : feeding thick gruel milk containing a large amount of starch from a bucket (barium gruel meal);
(iv) method IV : feeding milk by means of a sucking pail which was invented especially for this experiment;
(v) method V : feeding milk with hands which served to limit the swill.
Under the feeding of methods I, III, IV and V, milk was swallowed into the abomasum, but with method II, it entered into the rumen and reticulum in almost cases. When the amount of a milk deglutition was more than 8 mi., it flowed into the rumen and reticulum, about 4 mi., into the rumen, reticulum and abomasum. If the deglutition amount was within 3 mi., it entered into the abomasum. The amount of a deglutition at the time of swallowing milk or liquid is a significant factor in determining the course of flow.

III Studies on Digestion and Absorption in the Reticulo-Rumen
I Experiments on the Passage and Mechanical Digestion of the Ingesta in the Rumen
1) In the first experiment an adult goat on normal feeding was given stained oats to examine how long they would stay in the rumen and to what degree their chaffs would be crushed.
2) The percentage of remains of the oats intake in the rumen was 83.2 per cent at 6 hours after feeding; 77.4 per cent at 24 hours; 47.8 per cent at 48 hours; 16.7 per cent at 3 days; 2.6 per cent at 5 days; little or nothing at 6 days. It was deduced that the quantity of ingesta moving onward from the rumen was about 1/2or :1/3 of total content per day.
3) Concerning the rates of oat chaffs crushed in 24, 48 and 72 hours after feeding, the calculated data from the samples taken from the rumen were as follows:
(i) after 24 hours, 20 mesh and over: 56.6 per cent
30 mesh and over: 27.0 per cent
(ii) after 48 hours, 20 mesh and over: 29.8 per cent
30 mesh and over: 47.3 per cent
(iii) after 72 hours, 20 mesh and over: 14.2 per cent
30 mesh and over: 51.9 per cent
4) In the second experiment two adult goats fed stained oats and stained beet pulp comminuted to 50 to 60 mesh were used, to investigate the passage of rumen ingesta to abomasum. The samples of the rumen and abomasum contents were taken out by a catheter method.
5) In the abomasum there was a small amount of stained oat chaffs of 30 mesh and less noticed at 90 minutes after feeding, but the comminuted pulp was discerned in large amount even after 30 minutes. The passage of the finely crushed and ground ingesta from the rumen to the abomasum seemed to be fairly rapid.
6) The feed intake might be churned and crushed into pieces during their stay in the rumen, but not in the abomasum.

2 Experiments on the Changes of Composition of Foodstuffs in the Rumen
1) The first experiment on the changes of foodstuffs was made with a fistulated goat. The glass tubes (20 mm. in diameter, 40 mm. in length) covered with wire gauze in which some testing materials such as lupine hay meal and comminuted filte0 paper had been enclosed were put into the rumen, and after 12, 24, 36 and 48 hours they were taken out for chemical analysis.
2) The following degrees of digestibility of lupine hay meal were ascertained:
nitrogen free extract / crude fiber / crude protein
in 24 hours 28.2 per cent / 18.4 per cent / 63.6 per cent
in 48 hours 62.6 per / cent 29.5 per cent / 134.6 per cent
It is supposed that nitrogen free extract and crude fiber were fermented into some volatile fatty acids by the vigorous microbiological activities of microorganisms in the rumen.
3) Cellulose of filter paper disappeared to the amount of 13.0 per cent in 24 hours, 23.7 per cent in 48 hours.
4) The second experiment on the changes of foodstuffs was carried out with two goats which were fed the experimental diet concentrates with barium sulphate added as indigestible index substance. The result obtained by barium ratio calculation indicated that dry matter disappeared from the rumen at the rate of 40 to 44 per cent in 24 hours after feeding, crude protein 38 to 39 per cent, nitrogen free extract 51 to 56 per cent and crude fiber 28 to 34 per cent.

3 Experiments on Absorption from the Rumen, Especially the Effect of Feeding Methods
1) Experiments were carried out with 5 adult goats under three different experimental feeding methods; the jugular blood sugar and the blood urea concentration were determined in each case; glucose and urea were fed them together with concentrates in method I, together with water from a bucket in method 2, and with water from a nipple bottle in method 3.
2) When 3 g. glucose per kg. body weight was administered, remarkable rise of the blood sugar level was observed only in nipple feeding method. This response was in accord with that of the same experiment carried on with rabbits.
3) In the case of the administration of urea, on the other hand, there resulted a high level of blood urea concentration in every feeding method. Although a goat which had drunk urea solution (1 g. per kg. body weight) from a bucket got poisoned and died, no urea poison was caused in the case of nipple feeding.
4) The absorption of glucose through the wall of the rumen, of which contents had been removed completely, was observed when I or 2 g. of glucose solution alone was applied directly to the rumen wall. In I hour after administration, the blood sugar level rose !58 to 221 per cent; it returned to the normal value in 4 to 6 hours. From these observations absorption of glucose through the rumen wall is evident.
5) As for the blood urea concentration observed with the same experimental method, it increased immediately and presented 269 to 376 per cent in 6 hours after administration; that high level was maintained. It is suggested from those responses that the rapid absorption of urea through rumen wall occurs, and lasts for several hours.

4 Experiments on the Rumen Infusoria
1) An experiment on the separation of the infusoria from the rumen contents under the feeding wheat bran was made in order to study the usefulness of the rumen infusoria in the nourishment of the host animal. The infusoria was composed of 96.9 per cent of the organic matter, 42.8 per cent of the crude protein, 5.8 per cent of the crude fat, 48.3 per cent of the carbohydrate, 3.2 per cent of the crude ash and 40.8 per cent of the pure protein.
2) The artificial digestion coefficient of infusorial protein by pepsin was about 83.7 per cent.
3) If the population of Entodinium was assumed to be one thousand per I cubic mm. of rumen contents, the amount of protein of infusoria origin supplied to their herbivorous host animal should be about 0.16 g. per dl. of rumen content.
4) The amino acid pattern of the infusorial protein, separated by paper chromatograph, was alanine, valine, leucine, isoleucine, threonine, glutamic acid, cystine, lysine, arginine, tryptophane and serine.

IV Influence of Feeding on the Digestion of the Reticula-Rumen
1 Influence of Sucking Methods on Feed Intake and Digestibility

1) To investigate the amounts of the consumption of hay and its digestibility, observations were made using 2 suckling kids one month of age. Equal amounts of milk were supplied with an open bucket to the one and through a nipple bottle to the other, and Chinese milk-vetch hay was fed freely to them.
2) Feeding through a nipple bottle stimulated the consumption of hay, so that it was 27.4 to 37.2 per cent higher than the consumption by the bucket-fed animal.
3) As to the digestibility of milk and hay, the nipple feeding brought better results in crude fiber, but somewhat worse in nitrogen free extract and no difference in other nutrients.

2 Influence of Feeds upon Prehension and Deglutition
1) Two goats with rumen fistulae were fed on single feeding of wheat bran, rice bran, barley bran, soybean oil meal, ground corn, rice straw, rye grass or white clover. In each case, the feed intake, the time of prehension and mastication, and the number of mastications were measured. Also the swallowed boluses were collected by a spoon from the fistulae to investigate their weight, shape and moisture content.
2) Before reticulum contraction, the bolus was strongly casted out through the cardia to rumen. Rice bran and barley bran, however, did not take the shape of a bolus, but formed a pulpy mass which seemed to ooze out.
3) Soybean oil meal and corn were ingested better in amount but masticated less than the powdery concentrates such as wheat bran.
4) On feeding with rice straw cut in the length of 3 cm. and 30 cm., the latter was found to require longer time in phehension, besides, the number of mastications was greater but the intake amount was less.
5) On feeding of rye grass and white clover, the time of prehension was long and the number of mastications was great in rye grass, whether grass or hay. Green grass such as white clover was swallowed without good mastication.
6) The rate of secretion of saliva during eating was estimated from the water content of the bolus. The content of saliva in the bolus was 64 to 90 per cent in the case of feeding of soybean oil meal and corn, 120 to 127 per cent in wheat bran, 200 to 216 per cent in rice bran, 254 to 265 per cent in barley bran, 19 to 76 per cent in green grass and 136 to 172 per cent in hay. In the experiment on rice straw, 223 to 263 percent in "3 em.", 294 to 298 per cent in "30 em.". The production of saliva increased when the straw was cut longer.
7) The water content of the bolus was 46 to 55 per cent in coarsely ground concentrates, 61 to 76 per cent in finely ground concentrates, 65 to 68 per cent in hay, 74 to 79 per cent in rice straw and 88 to 90 per cent in green grass.

3 Influence of Cutting and Grinding of Roughage on the Amount of Feed Intake and Rumination
1) Rice straw cut 15, 5 and I em. long and comminuted straw were fed to 2 goats and the response difference between them was observed.
2) There was little difference of feed intake between the three kinds of cut straw. On comminuted straw, the intake amount was less than the others. Intake of dry matter per 100 kg. body weight was 2.7 to 3.0 kg. in cut straw, 2.1 to 2.2 kg. in comminuted straw.
3) No great difference was noticed between the times when the rumination occurred after feeding. It occurred in the shortest time on I em. cut straw, and in the longest time on comminuted straw.
4) No noticeable effect on the rumination was recognized in three cases of cut straw. However, on comminuted straw, the time and the number of mastications showed a tendency to decrease.

畜産業 [ 640 ]

日本語

広島大学水畜産学部

[ISSN] 0440-8756

[NCID] AN00213563