Animal experiment -vegan rats die early and have low energy

"The ratio of omnivorous to the vegetarians in regard to efficiency would be 100 : 20.9, or about 5 : 1."

"After the third month the general average of the vegetarians falls below that of the omnivorous."

"We must not lose sight of the fact that this difference in ability to do work is caused by the presence of animal food in one diet and the absence of it in the other, this being the only difference in the environment."

"The vegetarians were emaciated and skinny. Their back arched and more or less stiffened. The fur was harsh and ruffled, and the tail and nose inclined to be more or less covered with dry scale and sores. The attitude presented extreme lassitude and indifference. They remained in a crouched position most of the time, their legs appearing too weak to support their weight for only a short while. They lacked energy..."

The study of dietetics today occupies one of the most important places in the field of physiological investigation. Many popular articles have appeared in the past few years advocating this or that diet as best adapted to the needs of man. The argument is usually based on the personal opinion of the writer or the effects a certain diet may have had upon him. The personal idiosyncrasies which appear in these articles are too numerous to mention. Such writings are of no scientific value, and only show the trend of a certain class of people.
In contrast to these popular articles appear the writing of various scientific men giving the results of their investigations. These results are based on the comparative digestibility and absorption of the different foods and upon their ability to maintain nitrogenous equilibrium in the animal experimented upon.
The tendency of humanity is to go to the extremes, and nowhere is this more manifested than in dietetics. One class, vegetarians, maintains that man should abstain exclusively from animal foods, the other class claims that the human alimentary tract is more adapted to omnivorous food than to a strictly vegetable diet.
Vegetarianism as used by most people is a misnomer. The larger proportion of the so-called vegetarians partake freely of such animal foods as milk, eggs, butter, cheese and the like. A few, the fruitarians, live wholly on nuts and fresh fruits Another small group live on nuts, fruits, legumes and vegetables, either in the raw or cooked state. The much larger number of vegetarians (?) live on a mixed diet which differs from the ordinary mixed diet in only one respect - the absence of meat.
Most investigators have studied the effects of a certain diet on the animal for a limited time, which in most cases is insufficient to warrant such sweeping conclusions. Because an animal is able to maintain its weight and health for a limited time, is no argument that it could do so for its entire life. Neither has the effect on the offspring been ascertained. Such results can only be obtained by continuing the experiment during the lifetime of the animal and succeeding generations. The present experiment was undertaken to determine as fully as possible the comparative effect of a strictly vegetable diet, and an omnivorous diet, upon the spontaneous energy of the animal as manifested by its voluntary activity, the effect on its growth, and on the length of its life. An experiment is now under way to study the effect on the progeny. No attempt has been made to study the income and outgo of nitrogen.

In order that such an experiment may be of value a number of similar animals must be used, and the environment of these must be the same in every respect, with the exception of diet.
In this experiment sixteen rats were used To secure these as nearly alike as possible, sisters were mated to the same male. After numerous trials, lasting more than a year, two sister rats of approximately the same size, which had been mated to the same male, gave birth to eight each, just a day apart. Previous observations have shown that the young of a litter of three not only averaged heavier at birth than those of a litter of ten, but also gained more rapidly during the nursing period and had a better start at the weaning time than those of the larger litter. Also the age of the mother had an effect on the size of the litter and the average weight of the young. Very young mothers were less prolific than older females.
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Minot (3) found in his observations on the guinea pig that the average young of a litter of one weighed 85.5 grams, and the average of a litter of eight 52.2 grams. Also that the males averaged heavier (71 grams) than the females (70.2 grams). A similar condition exists between the sexes of the albino rat. This difference in weight of the two sexes becomes much more marked as the animals grow older. One should therefore have rats of the same age, of as nearly as possible the same parentage, the same number in the litter, and the same number of each sex. Owing to the fact that it is difficult to determine the sex of the young rats with accuracy, the sexes were not distributed as I would have wished.
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These sixteen young were arranged and designated as follows:
No. 1 and No. 2 from litter A, and No. 3 and No. 4 from litter B, were put into revolving cages to be used as omnivorous feeders in determining their activity; No. 5 and No. 6 from litter A, and No. 7 and No 8 from litter B, were put in revolving cages to be used in ascertaming the amount of work the vegetarian feeders would perform; No. 9 and No. 10 from litter A, and No. 11 and No. 12 from litter B, were put in stationary cages for omnivorous controls; and No. 13 and No. 14 from litter A, and No. 5 and No. 16 from litter B, were placed in stationary cages for vegetarian controls. Thus each litter was equally and uniformly distributed. Unfortunately the sexes were not ideally grouped. The following table illustrates the manner in which the young were distributed.

Each rat was thus confined in a cage by itself, which served as its home for its entire lifetime, and from which it was taken at intervals of about two weeks for a time sufficient to weigh the rat and clean its cage.
The apparatus for recording the activity has already been described, (4) but may be briefly given again. It consisted of a series of eight cylindrical cages which revolved on stationary axles to which were attached the nest boxes. The food and water boxes were attached to the ends of the nest boxes. The cage thus revolved about the stationary nest box whenever the rat ran. Automatic devices were attached to register the number of revolutions and to record them on paper kept moving by a continuous roll kymograph. The first device being read in the morning and in the evening gave the daily and nightly run of each rat through its lifetime. The second arrangement showed the distribution of the activity of each rat for each twenty-four hours during its whole life. These records were of great assistance in showing the peculiarities of activity which occurred at different ages.
This apparatus was therefore only adapted to recording the running activity of the animals. Previous observations (2) have shown that the running activity of the rat is proportional to the other activities.
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No. 1 and No. 2 from litter A, and No. 3 and No. 4 from litter B, were put into revolving cages to be used as omnivorous feeders in determining their activity; No. 5 and No. 6 from litter A, and No. 7 and No. 8 from litter B, were put in revolving cages to be used in ascertaining the amount of work the vegetarian feeders would perform; No. 9 and No. 10 from litter A, and No. 11 and No. 12 from litter B, were put in stationary cages for omnivorous controls; and No. 13 and No. 14 from litter A, and No. 15 and No. 16 from litter B, were placed in stationary cages for vegetarian controls. Thus each litter was equally and uniformly distributed. Unfortunately the sexes were not ideally grouped. The following table illustrates the manner in which the young were distributed.
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Each rat was thus confined in a cage by itself, which served as its home for its entire lifetime, and from which it was taken at intervals of about two weeks for a time sufficient to weigh the rat and clean its cage.
The apparatus for recording the activity has already been described, (4) but may be briefly given again. It consisted of a series of eight cylindrical cages which revolved on stationary axles to which were attached the nest boxes. The food and water boxes were attached to the ends of the nest boxes. The cage thus revolved about the stationary nest box whenever the rat ran. Automatic devices were attached to register the number of revolutions and to record them on paper kept moving by a continuous roll kymograph. The first device being read in the morning and in the evening gave the daily and nightly run of each rat through its lifetime. The second arrangement showed the distribution of the activity of each rat for each twenty-four hours during its whole life. These records were of great assistance in showing the peculiarities of activity which occurred at different ages.
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This apparatus was therefore only adapted to recording the running activity of the animals. Previous observations have shown that the running activity of the rat is proportional to the other activities.
Changes in the amount of the running activity are correct indicators of similar fluctuations in the other activities of the animal.

No attempt was made to give a definite amount of protein food in the diet nor to try to maintain nitrogenous equilibrium. The diet was varied as much as possible, and the amount of food given was more than was eaten before the feeding time on the following day. The feed and water boxes were then cleaned and a new supply given. Cracked corn was always given. The young were weaned at the age of 28 days and placed in their respective cages, as already described. A rich mixed diet, consisting largely of bread and milk with an occasional feed of baked beans and meat hash, was given all to prevent any disastrous effects resulting from the sudden change in environment and methods of feeding. This mixed diet was continued for twenty-eight days. At this age (fifty-six days) all appeared perfectly healthy and normal in every respect. They had each made a normal gain. The males averaged 70.1 grams and the females 59.3 grams.
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The difference in the character of the food was introduced at this time, the one group being designated vegetarians, and the other, omnivorous feeders. These two groups were fed exactly the same food each day, with the exception of meat and other animal foods which were given about three times a week to the omnivorous feeders in addition to the vegetable food. The vegetable foods were as rich in protein as it was possible to obtain from this class of foods, and consisted of such articles as the following: fresh vegetables, such as lettuce, kale, cabbage, cauliflower, clover and celery; cooked vegetables, such as white, corn, brown and graham bread, biscuits, buckwheat cakes, doughnuts, crackers, cookies, oatmeal mush, fried cornmeal mush, dumplings, corn, rice, baked beans, potatoes, carrots and onions; nuts, fruits and grains, such as almonds, English walnuts, apples, cracked corn, wheat, and corn meal. Occasionally, when the vegetarians seemed to be losing ground too fast, a feed of cheese, milk, or some other animal food was given. This was done only a few times soon after the vegetarians were first put on their exclusive diet.
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As can be readily seen, the above articles composing the vegetarian diet are either found on our tables or can readily be procurred from shops. Some of them contained small portions of animal food, i.e., graham muffins usually contain an egg and milk, bread often contains milk, doughnuts and several other articles contain animal fat. As only very small amounts of animal food were present as compared to a large quantity of vegetable food, I have called this a strictly vegetable diet, at the same time realizing it is not absolutely such a diet.
The amount of food given to each rat was not weighed, but measured as accurately as possible with a spoon, or by pieces of equal size.

In studying the characteristics of the activity one needs to refer to the kymograph records. Figures 1 to 10 inclusive are reproductions of such records, and show the activity of each rat for twenty-four consecutive hours at different ages. By comparing these figures a great difference is noticed in the activity at different ages.
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Figure 1 represents the activity of each rat at the age of thirty-two days, and just four days after they had been weaned and placed in the revolving cages. There is no regularity in the distribution of the activity and periods of rest. Neither is there any apparent tendency to be more active at one time in the twenty-four hours than at another. They were restless, playful and filled with a spirit of investigation. Since they were all fed at this time on the same diet, any differences in the character of the activity may be attributed to individual variation.
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In Figure 2, which shows the distribution of the activity, at the age of six months, two important things are noticed. First, the great bulk of the activity occurs during the evening and early night time; second, the omnivorous rats (O) are more active than the vegetarians (V). There is more or less random running for an hour or so before and after the feeding time (4 p.m.), but the most is done during the night.
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At the age of eleven months (Figure 3) the periods of activity and rest are more sharply defined. Also the difference in the amount of voluntary activity of the two classes is very obvious. The activity of the vegetarians is approaching closely in appearance that of old age. (2)
In Figure 4 the activity at the age of sixteen months is seen. Some days previous to this record the feeding time was changed to the morning to see what effect it would have on the distribution of the activity. The main bulk is seen to remain constant, but the usual random running which occurs at the feeding time has shifted to the morning. At this age two of the vegetarians have died and the other two compare very unfavorably with the work of the omnivorous.
Figure 5, which represents the activity at the age of twenty-one months, shows that when the feeding time is returned to the afternoon the periods of activity and rest are sharply defined. The omnivorous feeders are still quite active when compared to the remaining vegetarians.
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At the age of twenty-five months all the vegetarians were dead (Figure 6). The records of the omnivorous rats show a marked tendency toward old age. Especially is this true in No. 1 and No. 4.
The remaining figures (7, 8, 9 and 10) represent the records for the ages twenty-six, twenty-eight, thirty-one and thirty-four months respectively. No. 4 in Figure 7 shows the death struggle of this rat, which ended a little before 10 p.m.
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In comparing these different records of activity, one notices that in the young rats the periods of activity and rest are of short duration and have no definite arrangement so far as the time of the day is concerned. As the rats grow older the activity becomes greater and occurs more and more during the night time, the periods of rest being confined to the daytime. This continues until the rats reach the prime of life. After some months of almost uniform activity there is a gradual reduction, and the distribution and amount of work done approaches that of youth. It also shows that the vegetarians are not as active, that they age more early, and that their duration of life is shorter than the omnivorous rats.
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Since all the animals were fed on a mixed diet for twenty-eight days after commencing the experiment, any difference in activity during this period must he considered due to individual variation. This variation is sometimes very noticeable, as seen in Table I. This table represents the average number of revolutions of five consecutive days of each rat at the ages indicated. There is not a gradual and regular increase in the amount of running done by each, but fluctuations - now greater, now less. At first this was thought to be due to making the average from too small a number of days. Therefore another table (Table II) was made, by taking the average run of each sex of each group for a whole month. The figures in the column of the omnivorous males thus represent the average of thirty days' run of three individuals. But here again we see the lack of a uniform increase. In other words, the activity manifests itself rhythmically. No doubt if the number of individuals had been greater the results would have been more uniform. In a former paper I have discussed the causes of these fluctuations. (2)
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Table II is put in the form of curves in Figure II. The rhythmical variations are very conspicuous. These fluctuations also correspond in many cases both in regard to time and appearance. For example, from the beginning to, the third month there is a rapid rise in the curves. showing a great increase in the daily activity. This was, no doubt, due to the feed, for they were all fed on a strong mixed, diet for almost a month, and on rich food for almost two months. The effect of this food carried them over apparently till the end of the third month, when they began to feel the effects of the lack of it. This was followed in a general reduction of amount of daily activity in all except the omnivorous female, which remained practically unchanged. Then, with the exception of the vegetarian female, there was another general increase up to the fifth month. Again, at the tenth month, all show an increase, excepting the vegetarian male, which shows a slight decrease.
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It is especially noticeable that the curves representing the two sexes of the omnivorous feeders correspond much more closely in their fluctuations than those of the vegetarian feeders. In fact after the third month similarity in the character and time of these fluctuations of the omnivorous and vegetarian feeders grows rapidly less and less. The same may be said regarding the amount of daily activity of the two classes. The omnivorous female far surpasses all others. The omnivorous male comes next in order. Then follows the vegetarian female, closely followed by the vegetarian male. The females of each class thus surpass the males of the same group in average daily activity.
When we consider the time in life at which these rats do the greatest amount of daily running we see, on consulting the curves of Figure II, that it occurs in both classes at an early age in life, usually between the seventh and twelfth month. In the omnivorous feeders it is a little later than in the vegetarians. In a former experiment (2) it was ascertained that the greatest average daily run of the normal male and female occurred when they had reached a trifle more than one-third of their natural lifetime. In this experiment the vegetarians seem to have done their best day's work when about one-fourth of their life had passed. This was equivalent to about one-sixth of the lifetime of the normal omnivorous rat.
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Let us now consider the total amount of work, as indicated by the number of revolutions which each of the exercised rats voluntarily made during its lifetime.
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Table III represents the total number of revolutions of each rat at the ages indicated. To give a better idea of the amount of work equivalent to these revolutions, the actual distance in miles has been computed and shown in Table IV. By consulting these tables it is readily seen that the work done by all the rats corresponds rather closely during the first three or four months. This corresponds closely to the average daily work shown in Figure II. As a matter of fact the vegetarians average a trifle more at the end of the third month than the omnivorous. This is seen by consulting Table V, which represents the averages of each sex of these two groups.
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From this I think one of two conclusions may be reached. Either the sudden reduction in the rich protein food of the omnivorous rats to almost a vegetarian diet (meat being given only two or three times a week) has had the effect of checking the activity of all alike, or a strictly vegetarian diet at this age is conducive to a slightly greater activity. If the latter is true it may be explained in this manner: The omnivorous rat had a satisfying diet; the vegetarians did not, and ran a great deal, apparently in search for what they desired. The behavior of the vegetarians strongly supports this supposition. When they were fed they ate ravenously, as if they had been starving. This was not so manifest in the omnivorous. It was true that both classes of exercised rats always appeared more hungry than the control rats of the same group.
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After the third month the general average of the vegetarians falls below that of the omnivorous. This is shown in the curves of Figure 12. Here we see that the omnivorous female rapidly surpasses the omnivorous male in the amount of work done. The female vegetarian also excels the male of the same class in the distance run, but only to a small extent. The females are thus voluntarily more active than the males. We also note that the omnivorous male is much more active than either sex of the vegetarians. At the time of the death of the vegetarian rats (twenty-five months) the omnivorous female had voluntarily done almost nine and one-half times as much work as the female vegetarian, and the omnivorous male almost three and one-half times as much as the male vegetarian.
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When the total amount of work voluntarily done by each class is considered, a still greater difference is observed. The omnivorous female ran a total distance of 5447 miles, while the vegetarian female ran only 492.1 miles, or a ratio of about 11 : 1. The omnivorous male ran 1588 miles, compared to 450.9 miles for the vegetarian male - a ratio of 3.5 : 1. The average run for both sexes was, for the omnivorous rats 3517.5 miles, and for the vegetarians 471.5 miles, or a ratio of almost 7.5 : 1.
We thus see that when the initiative and ability to do work - are considered, the result is decidedly in favor of the rats that had received animal food in their diet, and overwhelmingly against the vegetarians.

GROWTH

We have just considered what a marked effect on the efficiency of the rat these two diets had. Let us now consider the effect on growth.
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The rats were weighed before feeding about once each two weeks. Weighings made approximately a month apart were selected in making Table VIII. This shows the individual weights of each of the sixteen rats at intervals of about a month during their entire lifetime. The young at the age of thirty days thus appear to be nearly uniform in size. The advantage is slightly in favor of the vegetarians, the males averaging 42 grams and the females 39 grams, while the omnivorous male averaged 41 grams and the female 38 grams. Twenty-eight days later, when the two groups were put on the omnivorous and vegetable diets, the sexes averaged approximately the same. Eleven days later a difference in the rate of growth is already noticed. This is more obvious in Table IX, which represents the averages of each sex in the different groups. As the rats became older this difference in weight was more and more noticeable, becoming greater as age advanced.
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It was previously noted (2) that the control rats surpassed the exercised ones in weight. The same is observed here in both groups of rats. This is especially noticeable in the curves of Figure 13, which represent the data of Table IX. The heavy lines are the averages of the omnivorous rats, the light lines the vegetarians. The male in each case is decidedly heavier than the female of the same group. Also the control and exercised males excel both the control and exercised females of the omnivorous group. This relation does not exist in the vegetarian. The heaviest omnivorous female exceeds the heaviest vegetarian male by 9 grams and the heaviest vegetarian female by 36 grams. The maximum weight in each of these tables is shown in bold type.
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A glance at Tables VIII and IX shows that, with the exception of the exercised vegetarian female, the exercised rats reach their maximum weight at an older age than the control rats, regardless of the diet. In Table X these facts are in a more accessible form. It shows the individual weights and the age of each rat, and the average weights and ages of each sex in each group, at the beginning of the experiment, as the maximum weight, and at death. As already stated, the average weights of the young were about as uniform as could be gotten. When the maximum weights are considered a marked contrast is noted. In every case the average weight of each sex is decidedly in favor of the omnivorous rats.        
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Considering the exercised rats in regard to the maximum weights and weights at death, we find the following ratios:
This last ratio is not reliable, as the control female had to be killed on account of sickness. There is no doubt had it been normal it would have reached a much heavier weight, since other omnivorous females did not reach their maximum weight until a much later age.
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In regard to growth, we must conclude that the data is decidedly in favor of the omnivorous rats and against the vegetarians.
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The appearance and attitude of the two groups is also in marked contrast. Figures 14, 15, 16 and 17 are photographs of eight of these rats, all being of the same age. Those on the left of each figure are omnivorous rats; those on the right are vegetarians. Figure 14 represents females. The other three figures are of males.
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These photographs show the marked difference in appearance and attitude referred to above. The vegetarians were emaciated and skinny. Their back arched and more or less stiffened. The fur was harsh and ruffled, and the tail and nose inclined to be more or less covered with dry scale and sores. The attitude presented extreme lassitude and indifference. They remained in a crouched position most of the time, their legs appearing too weak to support their weight for only a short while. They lacked energy and would stay "put" when placed ready for photographing.