mvesnmnou or SOME DIGESTIVE
PARAMETERS OF THE WHITE~TAILED DEER
USING THE RADTOTSOTOPE Slennomum

Thesis for the Degree of Ph. D.
MICHIGAN STATE UNIVERSITY
WILUAM W. MAUTZ
1969

THHQIg

This is to certify that the

thesis entitled
Investigation of Some Digestive

Parameters of the White-Tailed
Deer Using the RadioisotoPe 5lCr

presented by

William Ward Mautz

-has been accepted towards fulfillment
of the requirements for

Ph.D.

   

/7
/
wfc‘xjg fl]

    

’0

|

LIBRARX ‘

Michigan Stat‘c
University

   

 
   

degree in Fisheries & Wildlife

7 _/
C) I at (/47

 

5/” Major professor

Date June 13; 1969

 

0-169

  
    

 
  
 

h IINDING IY
um I my
. not sum me.

 

,.‘

.— m‘.’___fAA

ABSTRACT

INVESTIGATION OF SOME DIGESTIVE PARAMETERS
or THE WHITE—TAILED DEER USING THE
RADIOISOTOPE SICHROMIUM

BY

William W. Mautz

Studies of the values of the radioisotope 51Cr as a

digestive marker in the white-tailed deer (Odocoileus

 

virginianus) were made. The role of the rumen as a mixing

 

organ, the relationships between food consumption and food
passage rates, the effects of new surroundings, new foods,
and starvation on digestive efficiency, and the relative
energy values to the deer of three natural deer foods were
appraised.

The major organ in which food mixing occurs is indeed
the rumen. Using a rumen-fistulated deer ingesting a
formulated standard diet, 5 to 50 minutes was required for
a single dose of 51Cr to become thoroughly mixed with food

I I 0 51
materials in the rumen. From studies of

Cr dilution,
rumen dry matter content varied between 521 and 821 grams,
with a mean of 547 grams.

Passage rates were studied mainly in animals fed ad

libitum. In this work, a small known quantity of 51Cr was

William W. Mautz

applied to 0.25 to 0.50 gram of food. Following ingestion
of this item, fecal materials were collected and analyzed
for 51Cr content until the isotope had been 100 per cent
excreted.

No significant correlation was observed between the
rates of food consumption and food transit. Natural foods
required somewhat longer to traverse the digestive tract
than did the standard diet, but the difference also was
not significant (P > .10).

As determined in an earlier study, spraying all foods
ingested with 51Cr allows calculation of digestibility
coefficients by comparing the 51Cr concentration in the
food with that of fecal materials. In an effort to test
a simpler method, a technique was tried in which only a
limited number of 0.25 to 0.50 gram food items were dosed
with radioactive materials. Unfortunately, this procedure
resulted in highly variable fecal isotOpe excretion. It
was concluded that a minimum of 2 radioactive particles
would have to be ingested per hour in order to achieve
success. This is impractical, hence all foods to be in-
gested should be sprayed evenly with the radioactive
material.

Although a starvation diet of only 22.57 per cent of
ad libitum ingestion caused a 17 per cent reduction in the
body weight of the test deer, it had no significant effect

on the digestibility of the standard diet.

William W. Mautz

51Cr, the time required before peak food utiliza—

Using
tion efficiency occurred was found to vary with different
foods and previous feeding history. Nine to 12 days of
confinement to the collection pen were required for animals
to become adjusted digestively. Digestibility coefficients
observed after this time were not significantly different
from coefficients determined when these animals were in
larger outdoor pens.

The 5 natural foods studied were aspen (Pogulus

tremuloides) leaves, sumac (Rhus typhina) inflorescences,

 

 

and bluegrass (Poa gratensis) clippings. They proved to
be digested to nearly equal extents. The average dry
matter digestibility coefficients for separate aspen,
bluegrass, and sumac diets were 50.70, 49.42, and 54.17
per cent, respectively and well below the average digest-
ibility coefficient of 65.68 per cent for the standard
diet. Of the natural foods, sumac inflorescences were
determined to provide the most energy. Animals consuming
this food gained weight. Separate diets of aspen leaves
and grass clippings yielded the deer near maintenance
levels of energy. Combinations of these foods showed that
interactions were present. Much more aSpen-sumac mixture
was consumed, for example, than would have been expected
on the basis of values determined for the 2 species

separately.

William W. Mautz

51Cr was also found to yield pertinent data concern-
ing the specific area of the gastrointestinal tract in
which dry matter absorption occurs. By means of autopsies
on 2 deer which had consumed a radioactive standard ration,
it was determined that a surprisingly high proportion of
materials leaving the small intestine enter the cecal

pouch (> 70 per cent).

INVESTIGATION OF SOME DIGESTIVE PARAMETERS
OF THE WHITE-TAILED DEER USING THE

RADIOISOTOPE 51CHR0MIUM

By \
W\
William W? Mautz

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

DOCTOR OF PHILOSOPHY

Department of Fisheries and Wildlife

1969

ACKNOWLEDGEMENTS

I would first like to express gratitude to my wife,
Sue, who served as a constant source of encouragement
throughout my doctoral program. She cheerfully helped in
the preparation of this thesis. I am also indebted to my
parents who exPressed confidence in me during my entire
graduate education. To them and my wife I am sincerely
thankful.

I wish to thank Dr. George A. Petrides, chairman of
my guidance committee, for his many suggestions during this
work and for carefully editing the manuscript. I am grate-
ful also to the other members of the guidance committee:
Drs. L. Dale Fay, Michigan Department of Natural Resources,
E. Paul Reineke, Physiology Department, Robert K. Ringer,
Poultry Science Department, and Duane E. Ullrey, Animal
Husbandry Department. These men all helped in the interpre—
tation of results and in editing the final manuscript.

Donald I. Inman, my colleague in the isotope study and
doctoral candidate, participated with me in frequent bene-
ficial discussions throughout the study.

In addition, I would like to thank the secretaries of
the Department of Fisheries and Wildlife for their kind
assistance in the typing of early drafts of this thesis.

I am also indebted to numerous other people on the campus
of Michigan State University who helped with many of the
physical problems concerned with this work.

This study was supported by U. S. Atomic Energy Commis-
sion Contract No. AT(11-1)—1554. The Michigan Department
of Natural Resources provided deer, deer feed, and some
equipment.

 

ii

TABLE OF CONTENTS

INTRODUCTION . . . . . . . . . . . . . . . . . . . .

METHODS.

Materials and Equipment . . . . . . . . . . . .
Passage Rate Studies. . . . . . . . . . . . . .
Digestibility Studies . . . . . . . . . . . . .

Adjustment to Confined Conditions. . . . .
Effects of Starvation. . . . . . . . . . .
Natural Diets. . . . . . . . . . . . . . .
Energy Values. . . . . . . . . . . . . . .

RESULTS AND DISCUSSION . . . . . . . . . . . . . . .

Passage Rate Studies. . . . . . . . . .

Comparison of Rumen and Fecal .51Cr Excre-
tion. . . . . . . . . . . . . . . . .
Rumen Dry Matter Content . . . . . . . . .
Rumen Turnover Time. . . . . . . . . . . .
Passage Time in the Alimentary Tract . . .
Comparison of Passage Rate of Standard
Diet and Natural Foods. . . . . . . .
Passage Rate Versus Food Consumption Level

Digestibility Studies . . . . . . . . . . . . .

DevelOpmental Results. . . . . . . . . .
Total Collection Method Versus Ratio
Method. . . . . . . . . . . . . . . .
Effects of Food Consumption Levels on Food
Digestibility . . . . . . . . . . .
Effect of New Surroundings on Digesti-
bility Coefficients . . . . . . . .
Effect of Rapid Introduction of New Foods
on Apparent Digestibility . . . . . .
Comparison of Dry Matter Digestibility
Coefficients of Various Foods . - . -
Energy Value of Several Diets to the Deer.

iii

Page

15
15
17
17
18
18
20
20
20
24
26
26

28
50

55
56
59
41
44

47
51

TABLE OF CONTENTS - continued Page

AutOpsy Results . . . . . . . . . . . . . . . . 52
~Amount of Digesta Entering Cecal Pouch . . 54
Absorption in the Small Intestine, Cecum,

and Large Intestine . . . . . . . . . 55

Behavior of Experimental Animals. . . . . . . . 60

SUMRY O O O O O O O O O O O O O O O O O O O O O O O 61

Evaluation of 51Cr as a Food Label in
Digestive Studies of Deer. . . . . . . . . 61

Digestive Parameters of Deer Investigated with
51

cr 0 O O O O O O O O O O O O O O O O O O 62
LITEMTUM CI TED O O O O O O O O O O O O O O O O O O 6 5

iv

TABLE

LIST OF TABLES

Percentage average hourly decline rates in 51Cr
concentrations of corresponding rumen and fecal
samples. Based on data from a fistulated deer
following ingestion of single doses of 51Cr

fed with a standard pelleted diet eaten ad
libitum (Deer II). Michigan State University,
1968. . . . . . . . . . . . . . . . . . . . . .

Ingested 51Cr levels, rumen isotOpe concentra-
tions, and calculated rumen volumes for a rumen—
fistulated white—tailed deer fed a standard
pelleted diet (Deer II). Michigan State Uni-
versity, 1968 . . . . . . . . . . . . . . . . .

Passage rate data of 51Cr labeled meals for

2 deer fed the standard pelleted diet and sever—
al natural summer foods ad libitum. Michigan
State University, 1968. . . . . . . . . . . . .

Level of food consumption as related to passage
rate of 5 white-tailed deer on a standard pel-
leted diet. Michigan State University, 1968. .

Variation in 51Cr concentrations between differ-
ent defecations from deer consuming various
numbers of radioactive food particles mixed
throughout the standard diet. Michigan State
University, 1968. . . . . . . . . . . . . . . .

Effect of restricted food consumption on fecal
51Cr concentrations in an animal consuming a
constant number of radioactive food pellets
mixed throughout the standard diet. Michigan
State University, 1968. . . . . . . . . . . . .

Dry matter digestibility coefficients deter-
mined simultaneously by the 51Cr ratio and
total collection methods. Data for a deer con-
suming the standard diet (Deer I, trial 1:9).
Michigan State University, 1968 . . . . . . . .

Page

25

25

29

52

54

57

58

LIST OF TABLES - continued

TABLE

8.

10.

11.

12.

15.

Gross energy digestibility and metabolizability
coefficients for a deer at 4 levels of food
consumption on the standard diet. Passage rate
data are included. Michigan State University,
1968. . . . . . . . . . . . . . . . . . . . . .

Dry matter digestibility coefficients of 2 deer
immediately preceding and after confinement to
collection pens. Both animals ingested an ad
libitum level of the standard, pelleted diet.
Michigan State University, 1968 . . . . . . . .

Dry matter and gross energy digestibility and
metabolizability coefficients for 2 deer when
first fed 5 natural foods. Michigan State Uni-
versity, 1968 . . . . . . . . . . . . . . . . .

Digestibility data for 7 diets fed to 5 deer
during evaluation of the 51Cr technique.
Michigan State University, 1968 . . . . . . . .

Count per minute per dry gram of samples of

digesta withdrawn from various areas of the gas-

trointestinal tracts of 2 deer sacrificed
while consuming a SJ'Cr labeled standard diet.
Michigan State University, 1968 . . . . . . . .

Percentage absorption of food by portions of
the digestive tract of 2 deer fed the standard
pelleted ration. Michigan State University,
1968. . . . . . . . . . . . . .-. . . . . . . .

vi

Page

40

45

45

49

55

58

FIGURE

LIST OF FIGURES

Page
Collection pen used in digestive studies with
white-tailed deer. Michigan State University,
1968. O O O O O I O C O O O O O O O O O O O O O 9

Collection apparatus used for separation of

hourly defecations of white—tailed deer. Gear
reduction unit shown. Michigan State Univer-

Sity, 1968. . . . . . . . . . . . . . . . . . . 11

Rumen and fecal isotOpe elimination pattern in

Deer II following ingestion of the standard

diet with a 5 uc single dose of 51CrCla (Trial

1, Table 1). Michigan State University, 1968 . 21

Percentage excretion curve of a single dose of

51Cr for a deer ingesting the standard, pel-

leted diet (Deer II, single dose trial 1,

Table 1). Michigan State University, 1968. . . 51

Feeding scheme used in digestibility studies of

several natural diets With 5 deer. ‘MiChigan
State University, 1968. . . . . . . . . . . . . 48

vii

INTRODUCTION

The rate and efficiency of energy transfer between
producer and consumer organisms are important aspects in
ecological studies of wild animals and in their adequate
management. Animal nutritionists, too, have long been con-
fronted with the need to measure the energy values of various
rations.

Only a limited number of digestive studies have been
carried out on wild species. Even though ungulates are one
of the more important wild-herbivore groups, including the
several deer species of economic significance, detailed
information is lacking on energy conversion in these animals.
The primary goal of this project was the further deve10pment
(see Mautz, 1967) and evaluation of 51chromium as a food
label in digestion studies with the white-tailed deer
(Odocoileus virginianus). In several of its phases, at
least, this was a feasibility study to determine further
suitable nutritional methodology. The nutritional data ob-
tained are somewhat incidental to this exploration of pro-
cedures.

Digestion trials are primarily concerned with the

extent to which a given diet is digested and absorbed and

with the length of time required for these to take place.

The extent to which a food is absorbed by an animal is

called the digestibility coefficient. This is normally
determined by either the total collection or the ratio method.
The total collection procedure involves determination of the
dry weights of food eaten and of feces excreted from that
food. With the ratio method, a constant level of an indi-
gestible indicator is incorporated throughout the food eaten
over a period of time, with the marker concentration in food
and feces being compared. The gastrointestinal transit time
is normally determined by marking a food sample with an indi-
gestible substance and then measuring the time required for
the marker to be defecated.

A number of different substances have been used in the
past as food labels in ratio digestibility coefficient cal-
culations and in passage rate analyses. Hoelzel (1950) made
use of rubber particles, cotton thread, beads, seeds, and
particles of aluminum, gold, silver, and steel in his study
of passage rates in the rabbit, dog, cat, guinea pig, rat,
mouse, hen, pigeon, monkey, and man. Other materials employed
have included ferric oxide (Bergeim, 1966; Moore and Winter,
1954; and Tuckey §£_al., 1958), barium sulfate (Henry §£_§l,,
1955), celluloid particles (Mueller, 1956), and monastral
blue (Lambourne, 1957). Several substances found naturally
in plants have also been used as indices of passage rates

and digestibility. These include oat hulls (Browne, 1922),

lignin (Forbes and Garrigus, 1948; Kane §t_al,, 1952; Balch,
1957; and Gray 2; al., 1958), and chromogen (Reid, t al.,

1952; and Kane §£__l,, 1955).

In 1918, Edin suggested the use of chromic oxide (Crgos)
as a food marker. Currently the most widely used food label,
chromic oxide has been successfully used in nutritional
studies of man (Krenla, 1947; and Irwin and Crampton, 1951),
poultry (Olsson and Kihlen, 1948; Dansky and Hill, 1952; and

Hill and Anderson, 1958), pigs (Schurch t 1., 1952; and

Moore, 1957) and sheep (Elam gt al,, 1962; and Johnson gt al.,
1964).

The use of a radioactive substance as a food marker has
many advantages over stable indicators in nutritional studies.
Even though radioisotOpes can eliminate much of the time and
labor involved in fecal analyses, until very recently they
have been used only to a limited extent as food labels.
Radioactive barium was used in digestive studies of the do-
mestic fowl (Imabayshi g£_§l., 1956), however, and Brandt
and Thacker (1958) employed radioactive chromic oxide to
study c0pr0phagy in rabbits.

Recent work has determined the radioisotOpe 51Cr to be
a generally useful food label in nutritional studies of wild
Species. Using 51Cr in 1964, Petrides (1968) studied pas—
sage rate and other digestive phenomena in the Opossum

(Didelphis virginiana), cotton rat (Sigmodon hispidus), bob—

cat (Lynx rufus), and other animals. Mautz (1967) and

Mautz and Petrides C1967)employed 51Cr as a food label in
nutritional studies of the white-tailed deer. Further work
with the cotton rat (Petrides and Stewart, 1968) has con—
firmed that 51Cr is a good food label for both passage rate
and digestibility studies. Work with avian species (Duke,
1967 and Inman, 1969) has shown that 51Cr is a valuable food
label in passage rate studies but is not fully accurate in
digestibility appraisals in birds.

There are several factors which make 51Cr an ideal iso—
tope for these types of digestive studies. Its half-life of
27.8 days is neither inconveniently short nor dangerously
long. The physical, chemical, or spectrophotometric analy-
ses required with stable compounds is eliminated since 51Cr
disintegrates with the emission of gamma rays allowing its
ready detection and quantification. Foster (1965) describes
51Cr as "one of the least hazardous radionuclides."

It is essential that labels used in digestibility and
passage rate studies be substances which are not appreciably
absorbed from the gastrointestinal tract. For CrCla admin-
istered orally to white rats, Visek §£_al, (1955) reported
that "less than 0.5 percent of the dose was absorbed from
the gastrointestinal tract as indicated by tissue distribu-
tion studies." Roche §£_al, (1957) demonstrated that

f 51Cr introduced into the

"practically negligible" amounts 0
human gastrointestinal tract were absorbed. Mautz and

Petrides (1967) found no detectable urine or tissue

radioactivity in white-tailed deer fed foods labeled with
51CrC13. Samples of tissues from experimental animals
used in the current work, furthermore, were analyzed by
Argonne National Laboratories and found to contain no 51Cr
at a level of 0.005 per cent.

The current study of the white-tailed deer was made in
order to determine the usefulness of 51Cr in ascertaining:

1. The particular role of the rumen in mixing, digest-
ing, and passing food materials through the alimentary
tract.

2. The relationship of the rate of food passage to food
consumption, diet, and digestibility.

5. The lengths of time required for deer to attain a
constant digestibility coefficient while changing from one
diet to another and while adjusting to new surroundings.

4. The effect of a limited food intake on digestive
efficiency.

5. The metabolizable energy of several deer browse
Species.

In addition, simplifications in technique were tested
so as to learn how limited the number of radioactive food
materials might be in order to yield the stable fecal iso-
tope concentration necessary for digestibility coefficient

measurements.

METHODS

Materials and Equipment

The compound 51CrC13 was the food marker used in this
work. A Nuclear Chicago Well—Scintillation Detector System
(DS-202V) with an 8725 Analyzer Scaler was employed to re-
cord the number of detectable disintegrations (counts)
occurring in a preset period of time. All counts were cor—
rected for decay and background radiation. Only those
counts which were greater than twice the background count
(normally 9-12 per minute) were used in computations.

Caloric values of all feeds and feces were determined
with a Parr Oxygen Bomb Calorimeter. To obtain samples
suitable for combustion, known volumes of urine were evap-
orated in petri dishes at 80-900 C.

Deer used in this work were provided by the Michigan
Department of Natural Resources. All were adult males and
ranged from 80 to 200 pounds.

One exceptionally-tame deer was chosen for rumen

f 51Cr movements through the upper di—

fistulation studies 0
gestive tract. The fistula was inserted in a two-part

surgical procedure by Dr. D. P. Purser of the Animal

Husbandry Department, Michigan State University. The pre-
liminary phase was designated to cause adhesion of the rumen
wall to the body wall. To do this, the abdominal wall was
slit and both it and the adjacent rumen wall were first
scraped to set Up an inflamatory reaction and then sutured

to each other. Care was taken at this stage not to puncture
the rumen. Twenty days were allowed for the fusion to become
complete. The second stage of the Operation involved Opening
the rumen in the center of the fused area and inserting the
cannula into the incision.

The cannula was of the sort commonly used in sheep and
consisted of a short rubber tube with an internal flange.

A rubber cork initially was used to plug the cannula.
Eventually, however, a threaded, 5/4 inch diameter aluminum
pipe with an easily-unscrewed plexiglass cap was fitted to
the cannula opening. The rumen was opened by merely unscrew—
ing the cap.

It is generally concluded that rumen fistulation has no
abnormal effect on digestive mechanisms. When speaking of
rumen fistulas in domestic animals, Hungate (1966; 176)
stated that "the animals heal readily with little disturbance
to their physiology." In deer, too, Hayes gt 3;. (1964)
reported that rumen fistulation does not significantly af-
fect digestion coefficients.

Various investigators (Smith, 1950, 1952; Bissel t al,,

1955; Deitz §£_§l,, 1962; and Cowan g; al., 1969) have used

collection pens for nutritional studies of deer. For the
present study, two collection pens were constructed similar
to the one described by Mautz (1967). They were refined,
however, with the addition of less-cumbersome collection
devices. Each pen consisted of a 4 x 4 x 4 foot box mounted
on stilts 4 feet tall (Figure 1). The walls of the pen were
completely closed to avoid undue disturbance of the test
animal by the attendant. A roof of boards placed approxi-
mately 1 to 2 inches apart admitted air and some light. The
floor was formed by 5/4-inch flattened eXpanded-metal which
allowed the ready passage of both feces and urine.

Beneath each pen, a large funnel of 1/4-inch hardware
cloth deflected fecal materials into a small aluminum funnel
located 50 inches beneath the pen floor and attached to the
hardware cloth at only 2 points so as to swing freely.

A sheet or polyethylene plastic film immediately beneath the
hardware cloth deflected urine into eavestroughs which de-
livered it to a collecting receptacle for each pen.

To facilitate hourly separation of fecal materials for
passage rate studies, a 5/4-inch plywood disc 4 feet in
diameter was constructed for each pen. Each disc was bordered
by 24 6-inch segments of 5—inch diameter stove pipe and was
mounted so that while turning, its rim was directly beneath
the aluminum feces-funnel (Figure 1). The aluminum funnel
extended 1/2 to 1 inch into any given stove pipe. The tops

of the stove pipes were notched on one side to allow easy

 

 

 

.47.
‘.~

Figure 1. Collection pen used in digestive studies with
white—tailed deer. Michigan State University,
1968.

10

entrance of the funnel. The fecal material dropped into
plastic bags fastened by rubber bands to the bottom of each
stove pipe. Each disc was rotated once per 24 hours, using
a continuous-duty electric motor. Gear boxes constructed
from a series of various sized lawn mower wheels and mounted
on 1/2-inch axles (Figure 2) reduced the motor speed and
supplied power leverage. As the discs moved, each hour the
aluminum funnel came above a new stove pipe and collection
bag.

In order to assure complete separation of urine from
feces it was necessary to keep the hardwood cloth free of
shed deer hair. To facilitate this, a 1-foot square Opening
was made in the floor of each pen. These Openings were
normally covered by slightly larger pieces of expanded metal.
During cleaning Operations a plywood sheet was lowered from
the ceiling of the pen, partitioning the test animal from
the area of the pen containing the opening. Through a small
door in the wall of the pen the opening was exposed and the
hardware cloth cleaned with a wire brush.

One of the pens contained a trap door on top which
allowed a man to enter to collect rumen samples. With the
other pen, it was possible to weigh the confined animal by
an attached 600-pound spring scale. Block and tackle was
arranged so that the pen could be hoisted Off the ground,
suSpended from the scale. This could be accomplished easily

by one person. By subtracting the weight of the empty pen,

Figure 2.

11

 

Collection apparatus used for separation of
hourly defecations of white-tailed deer.
Gear reduction unit shown. Michigan State
University, 1968.

12

it was possible to keep weight records of the animal housed
in this pen.

Each pen was found to be of sufficient size to hold a
white-tailed deer ranging from 80 to 200 pounds. Even the
largest animal had adequate room to turn around. All deer,
including the 200 pound animal which was previously kept in
a 40-acre enclosure, became surprisingly subdued during a
short period of time in the collection pens.

The 2 pens were kept indoors in a 8.5 x 16 foot room.
The light was controlled in this room to approximate outdoor
photOperiods. Adjacent outdoor pens of the same size were
used to hold additional animals.

A standard pelleted diet supplied by the Michigan
Department of Natural Resources was used for much of this
study. This diet, formulated by Dr. D. E. Ullrey, Animal
Husbandry Department, Michigan State University, contained

the following ingredients:

BE£_SEEE EQEEQE

Ground corn cobs 54.7 6,940
Ground shelled corn 29.5 5,900
Soybean meal 49 18.0 5,600
Linseed meal solution 10.0 2,000
Dehyd. alfalfa meal 17 5.0 600
Cane molasses 5.0 600
Corn oil 0.5 60
Regular Zn trace mineral salt 0.5 100
Ground limestone 0.5 100
Anhydrous sodium sulfate 0.25 50
Vitamin A, D and E premix* 0.25 50

’ 100.00 20,000

15

*Vitamin A, D and E premix

 

Pfizer 109 (10,000 IU vit. A/g) 6.62 lb.
Irradiated yeast 9F (9,000 IU vit. D/g) 0.5
Myvamix 125 (125,000 IU vit. E/lb) 5.2
Ground shelled corn 59.68
50.00 lb.

Calculated analysis

Crude protein 16.6%
Calcium 0.58
Phosphorus 0.29
Sulfur 0.27

Natural foods used in this work were asPen (Pogulus
tremuloides) leaves, sumac (Rhus typhina) influorescences
and bluegrass (Poa pratensis) clippings. The aSpen and
sumac foods were collected over a 5-week period in July,
1968, at the Rose Lake Wildlife Research Station, 10 miles
east of Lansing. Bluegrass clippings (Merion variety) were
obtained July 15th to August 15th from a research plot main-
tained and mowed bi-weekly by the Michigan State University
Turf Research Unit. These plant materials were stored frozen
in polyethylene bags. To facilitate handling and mixing,
the aspen and sumac were chOpped by hammer mill to a size

approximating that of the clipped grass.

Passage Rate Studies

Passage rates of each food were studied by feeding a

f 51Cr applied directly to the surface of a

single dose 0
0.25 to 0.50 gram food item. SJ‘Cr levels of approximately

2 to 10 microcuries per trial were employed using pipettes

14

calibrated in lambdas (0.001 milliliter). Passage rate
determinations in deer are independent of dose level in this
range (Mautz, 1967). Nonlabeled food identical with the
labeled item was fed ad libitum throughout the trial.

The fecal separation device was started at the time the
isotOpe was fed. All droppings were collected until no
further isotOpe was excreted. Two samples of 5 to 5 fecal
pellets each were taken from each defecation and placed in
tared test tubes. These samples were dried at 90-100o C to
constant weight. This normally took a minimum of 24 hours.
They were then weighed to the nearest thousandth gram and
counted in the scintillation detector. The data for sample
pellets were extrapolated to calculate the counts per minute
per dry gram (c/m/g) and per total weight of each defecation.

In single-dose trials with the fistulated animal, the
first rumen samples were taken immediately after ingestion
of the labeled food. Several samples were taken during the
first hour and hourly thereafter. On each occasion, the
fistula cap was removed and a Quinch diameter, 12-inch long
c0pper tube fitted with a bulb type suction device was in-
serted. Samples of rumen contents were placed in test tubes.
The animal readily submitted to collection procedures and
became surprisingly unconcerned. Each rumen sampling took
less than 5 minutes.

The average percentage reduction in 51Cr concentration

was determined for both rumen and fecal samples by least

15

squares regression analysis (Dixon and Massey, 1957:195).

The time of 95 per cent fecal 51Cr appearance was also re—
corded. This convention, which eliminates some of the
problems and uncertainties of indicator detection at low
levels, was first suggested by Castle (1956). This time was
derived from percentage excretion curves constructed by
plotting the accumulated percentage of indicator defecated
against time. Mean retention times were also determined

from these curves by summing the times of excretion of 10

per cent units of the marker, between 5 and 95 per cent, and
dividing the total by 10 (Castle, 1956). Mean retention time
is defined as the weighted average period that materials from
a given meal take to traverse the tract. All materials
present in the rumen at the time of isotOpe ingestion are
considered to be the meal.

The relationship of rumen and fecal passage of 51Cr was
investigated for the standard diet. This diet was also used
in the determination of effects of restricted food intake
on passage rate. The passage rates of natural diets were

investigated only at the ad libitum level of feeding.

Digestibility73tudies

Determination of digestibility coefficients using the
ratio technique required the feeding of a constant level of
indicator for a period of several days until the fecal in-

dicator concentration became stable. Then dry matter

16

digestibility coefficients were determined as:

_ counts/minute/gram food
(1 counts/minute/gram feces ) X 100

Mautz (1967) successfully used the labeling technique
of spraying deer foods with a uniform level of 51Cr. Feed—
ing food labeled in this manner yielded remarkably stable
fecal isotOpe concentrations. Because of the amount of food
involved with the present study, however, it was hOped that
a more convenient labeling technique could be developed by
feeding a limited number of individually-dosed food pellets.
It was hOped that this would result in stable fecal isotOpe
excretion and thus enable more ready calculation of digesti-
bility coefficients.

51Cr was distributed

To test this, the daily level of
over various numbers of food pellets. Radioactive pellets
were thoroughly mixed with nonlabeled portions of the daily
ration prior to presentation to the animal. Each labeled
pellet weighed approximately 0.25 to 0.50 gram. Normally 59
to 95 grams of feed were eaten by a deer per hour. Radio-
active pellets were eaten at average rates of 5.8 to 41.5
per day.

All labeled pellets were counted to ascertain the
amount of isotOpe being fed. The total dry weight of each
daily ration also was recorded.

The fecal separation device was used for all continuous-

dose trials and isotope concentration was measured in 2

samples from each defecation.

17

For comparative purposes, data for the calculation of
digestibility via the total collection method were obtained
simultaneously. This involved determining the dry weight
of all feces excreted as well as of the food consumed over
a period of 1 to several days. All feces excreted during
these trials were weighed fresh and converted to dry weight
by application of wet-dry correction factors. Total collection

digestibility coefficients were calculated as:

_ dry weight feces
(1 dry weight food ) X 100

Adjustment to Confined Conditions

The length of time required for an animal to become
adjusted digestively to the collection pen was investigated
for 2 animals on the standard diet. For these trials, a
continuous level of isotope was fed for 21 days. While the
animals were in collection pens, urine as well as fecal
output was measured. By comparison of food and fecal concen-
trations of 51Cr, it was possible to keep a record of di-

gestibility coefficients throughout the trials.
Effects of Starvation

The effect of decreasing food levels on digestibility
was carried out using the standard diet and a 200 pound

f 51Cr was fed for 28 days

animal. A continuous level 0
using 4 levels of food consumption: 80.8 grams/hour (ad

libitum), 57.2 grams/hour, 58.2 grams/hour, and 19.1

18

grams/hour. Each level of feeding was maintained for approxi-
mately 1 week. By comparing food and fecal levels of isotOpe,
any changes in digestibility coefficient between food consump-
tion levels were detected. Periodic weighings of the test

animal were carried out as described.
Natural Diets

Possible changes in digestibility caused by rapid intro-
duction of a new food was investigated for each of the 5
natural foods used. This involved mixing a constant level of
isotOpe throughout the food for several days beginning with
the time of first food introduction. All defecations were
collected and subjected to previously discussed procedures.
Three deer were used in this phase, 1 being kept outdoors.

Digestibility coefficients were determined for each of
the 5 natural foods and also for 5 mixed diets. The latter
consisted of 1:1 wet—weight mixtures of sumac and grass,

sumac and aspen, and grass and aspen.
Energy Values

In addition, gross energy digestibility values were
calculated for each diet. Caloric values were obtained from
bomb calorimetry of food and fecal samples and applied in
the following formula:

Gross energy digestibility coefficient:

1 _ (count/minute/gram food calories/gram feces) x 100
count/minute/gram feces calories/gram food

19

Metabolizable energy is defined as the amount of energy
available to the animal after deduction of gross energy of
the combined feces, urine, and combustible digestive gases.
The measurement of methane and other gaseous digestive by-
products was not possible in this study but the volume and
caloric content of urine was determined for test animals
held in the collection pens. With these data, the maximum

gross energy metabolizability coefficient was estimated as:

cal/hr.
excreted
(feces defecated/hr. x cal./q. feces + as urine x 100
food consumed/hr. x cal./g. food

The energy lost in gases may deduct considerably, however,

from this amount (Brody, 1945:82).

RESULTS AND DISCUSSION

Passage Rate Studies
Comparison of Rumen and Fecal 51Cr Excretion

The constant mixing action of the rumen has been ob-
served for many years in domestic ruminants. It is caused
by contractions of the walls of the rumen and reticulum.
Constant mixing serves to inoculate fresh ingesta with
microorganisms present in the rumen, to aid comminution, to
enhance nutrient absorption, and to assist passage of digesta
to other areas of the digestive tract (Hungate, 1966:170).

The present studies confirmed that the rumen is the
major site of digestive mixing in deer. Rumen samples,
withdrawn periodically from the fistulated animal following
ingestion of a single-dose of 51Cr, disclosed a regular
percentage decline in isotOpe concentration similar to that
observed in subsequent fecal eliminations (Figure 5).

There is no obvious explanation for this constant hourly
decline except that as materials pass from the rumen, un-
labeled foods are ingested which, upon mixing, cause a
unifOrm dilution of the radioactive rumen contents. The

rate of dilution shows some variation but nevertheless the

20

21

 

500

p.
O
O

J

50‘.

Counts per minute per gram of 51Cr in rumen
and fecal samples (logarithms)

 

10

 

 

Figure 5.

r I l l
5 10 15 20 25

Hours after ingestion of 51Cr

Rumen and fecal isotOpe elimination pattern in
Deer II following ingestion of the standard diet
with a 5 ac single dose of 51CrC13 (Trial 1,
Table 1). Michigan State University, 1968.

 

22

removal lepe is surprisingly constant during any one trial

(Figure 5). This shows that in general, food is consumed

on a regular and frequent basis, thorough mixing of digesta

occurs in the rumen, and materials are passed from the rumen
at a regular rate.

If no further dilution occurred beyond the rumen, the
fecal decline in 51Cr concentration should be at the same
rate as that observed in the rumen. In nearly all tests with
the fistulated specimen, however, the percentage hourly re—
moval of 51Cr from the rumen was higher than in the corres-
ponding marked fecal eliminations (Table 1). -A nonparametric
paired t-test disclosed a significant difference at the 0.05
level between the means of the rumen and fecal passage rates.

The lower fecal 51

Cr percentage excretion rate evidently was
caused by a constant percentage dilution of rumen materials
either with unmarked digesta or other materials in the
remaining stomachs, intestines, and cecum.

For a deer on the standard diet, maximum isotOpe concen-
tration in the rumen occurred 5 to 50 minutes after ingestion
of the labeled food (Table 1). Evidently, the peak concen-
tration of isotope occurs when it has become thoroughly mixed
with digesta already present in the rumen. Early rumen

k 51Cr concentrations apparently

samples showing lower than pea
were drawn prior to completion of the mixing process. True,
there was a chance of withdrawing an early sample containing

higher 51Cr concentration than would occur after complete

25

Table 1. Percentage average hourly decline rates in 51Cr
concentrations of correSponding rumen and fecal
samples. Based on data from a fistulated deer
following ingestion of single doses of 51Cr fed
with a standard pelleted diet eaten ad libitum
(Deer II). Michigan State University, 1968.

 

 

 

Trial Rumen Digesta Feces
1 15.69 12.14
2 16.06 10.66
5 50.25 24.45
4 25.65 *
5 15.12 8.54
6 11.92 5.29
7 25.78 5.05
8 6.01 6.89
9 * 7.46

 

Mean value

S

17.50

10.07

 

*-
Insuffici

ent data.

24

mixing but this seems unlikely where the ingested radio-
active materials represent 0.1 per cent or less of the
total rumen contents.

According to Hungate (1966), the physical state of the
digesta has much to do with the rapidity with which rumen
contents are mixed. He states (1966:175) that "the speed
of mixing decreases with increased particle size." As ex-
pected from this, the finely-ground pelleted ration did
become mixed more rapidly than any of the natural foods
used. Limited trials with aspen had a mean 'time of com-
plete mixing' of 48 minutes while 1 trial with grass showed

a mixing time of 55 minutes.

Rumen Dry Matter Content

By dividing the total count of the isotope ingested by
the count per gram of isotOpe in the rumen after thorough
mixing, the rumen dry matter content was calculated. Values
of dry matter rumen content during 6 trials with the same
fistulated animal on the standard diet varied from 521 to
821 grams, the mean being 547 grams (Table 2).

These data show considerable variation in the dry matter
content of the rumen for a deer feeding ad libitum. In
domestic ruminants, the minimal rumen content is reported
(Balch and Line, 1957) to be rarely less than 50 per cent of
maximum. The more variable results for deer could be due to
the noncontinuous monitoring system used or to a real dif-

ference between deer and livestock.

 

 

 

1-A

th4.

-n

Ve

25

Table 2. Ingested 51Cr levels, rumen isotope concentrations,
and calculated rumen volumes for a rumen-fistulated
white-tailed deer fed a standard pelleted diet
(Deer II). Michigan State University, 1968.

 

 

 

 

Times and Calculated dry
Amount of 51Cr concentrations of matter rumen
ingested early rumen samples content
(count/minute) minutes after c/m/g*
(=A) ingestion (=B) A/B (grams)
26,255 5 65 404
15 65
50 59
60 47
26,259 6 26
15 52 821
50 22
60 27
58,520 15 54
50 64 602
45 54
60 44
44,760 5 44
1O 75
15 76 589
50 68
60 60
66,200 5 **
10 105
15 92
20 206 521
25 64
50 142
45 165
60 200

 

*-
c/m/g Count (detectable disintegrations) per minute per dry

fram of digesta.
**
Non-significant count.

26

Two trials with aspen and 1 with grass yielded calcu-
lated rumen dry matter contents of 522, 700, and 655 grams,
respectively. The mean of these values (626 grams) is
higher than the mean observed when the animal was feeding on
the standard diet (547 grams). .Since the standard diet used
in the current study was more readily digested than any of
the natural foods used (see beyond), this observation agrees
with findings in domestic ruminants that rumen contents are

reduced in easily digested rations (Yadawa t a1., 1964).

Rumen Turnover Time

Hungate (1966:208) reported the turnover time of materi-
als in the rumen to be equal to the period required for
ingestion of an amount of dry matter equal to the dry matter
in the rumen. This represents the average time that particles
of digesta spend in the rumen. For the fistulated animal on
the standard diet, the mean rate of food consumption was 64.6
grams per hour. Dividing the mean rumen volume of 547 grams
(Table 2) by 64.6 yields an average time of 8.5 hours. So
far as known, these data have not before been estimated for
a wild ruminant. Castle (1956) working with the goat and
using stained hay as a marker found the time of rumen turn-

over to be 19.4 hours.

Passage Time in the Alimentary Tract

Balch (1950) reported that the average time that particles

of digesta Spend in the rumen-reticulum is equal to the time

27

of 80 per cent fecal-indicator excretion minus the time of
5 per cent indicator excretion. Substituting 21.1 and 11.2
hours, respectively, it is estimated that 9.9 hours was
required for the average food particle to pass through the
rumen-reticulum of the fistulated deer on the standard diet.
Balch also reported that the time of 5 per cent excretion
was a good approximation of the time required for digesta

to pass through the omasum, abomasum, and intestines. If
this is true for deer, then 11.2 hours is required for this
passage in the fistulated animal.

Natural foods, having a larger particle size and higher
fiber content, would be expected to have slower rumen turn-
over times than the finely-ground standard diet (Hungate,
1966:220). The mean 5 and 80 per cent excretion times for
the deer trials with natural foods were 12.5 and 26.6 hours
respectively. Thus, according to Balchs' theory, the time
of digesta passage through the rumen-reticulum and through
the remaining portions of the alimentary tract were 14.4 and
12.5 hours respectively.

If Balchs' theory is valid for deer, natural diets
required 4.2 hours longer to pass through the rumen-reticulum
than did the standard diet. An additional 1.5 hours was
needed for passage of natural foods through the remainder of
the tract. The reason why natural foods have a greater in-
crease in passage time through the rumen-reticulum than

through the remainder of the alimentary tract doubtless

28

relates to the facts that in ruminants, the major digestion
of dry matter occurs in the rumen and only food particles
of small size pass into the omasum (Hungate, 1966:225).

Comparison of Passage Rate of Standard
Diet and Natural Foods

Feeding a single dose of 51

Cr to animals consuming a
natural food yielded a fecal excretion pattern similar in
shape to that plotted for the standard pelleted diet (Figure
5) but showing the less-steep lep s indicative of less-
rapid transit times (Table 5). The average of mean retention
times for the natural diets eaten by Deer II was 21.4 hours
compared to 17.1 hours for the standard diet (Table 5).
Based on the nonparametric Mann Whitney U-test (Siegel, 1956:
119), however, this difference was Significant only at

P < 0.172. Similarly for Deer III, the average natural diet
mean retention time of 22.4 hours was significantly greater
than the 15.9 hours observed for the standard diet only at
the 0.154 level.

While these levels of significance are low they do indi-
cate that the natural diets, perhaps because of their more
fibrous nature, tend to require a greater time of passage
than does the more homogeneous standard mixture. Decreased
passage rates may be due mainly to increased transit times
through the rumen-reticulum as discussed. Two natural diet
passage rate studies with the fistulated animal yielded

rumen 51Cr passage rates of 5.84 and 12.45 per cent per hour.

29

 

 

 

Table 5. Passage rate data of 51Cr labeled meals for 2 deer
fed the standard pelleted diet and several natural
summer foods ad libitum. Michigan State Univer-
sity, 1968.

First 51Cr 95% Mean 1,
Percenta e appearance passage retention
hourly 5 Cr in feces time time

Deer Diet defecation (hours) (hours) (hours)

II Standard* 10.14 (5.0)“ 11.5 (1.2) 24.8 17.1 (1.7)
Aspen *** 16.0 29.0 25.1
Aspen 6.66 12.0 45.0 25.4
Grass 8.09 15.0 24.0 18.0
Grass 8.55 11.0 24.5 18.9

Average natural 15.5 (1.2

diets 7.69 (0.52) 15.5 (1.2) 50.1(4.4) 21.4 (1.9)

III Standard 14.90 (6.99) 11.0 (2.0) 19.5(2.0) 15.9 (2.0)
Aspen 8.00 11.0 40.0 21.0
Aspen 8.46 15.0 41.0 22.7
Sumac 6.68 17.0 52.5 26.1
.Aspen & 9.16 (0.52) 10.0 (1.2) 28.8(4.8) 19.6 (1.4)
Sumac
Average natural
diets 8.08 12.8 40.6 22.4

 

*

Average values for

**
Standard error.

**

*
Insufficient data.

standard diet Table 4

50

These are significantly lower than those observed for the

standard diet (Table 1) at P < 0.178.
ggssage Rate Versus Food Consumption Level

The relationship between food consumption and passage
rate was investigated for 5 deer on the standard diet.
Parameters studied included the time of first and 95 per cent
51Cr appearances, the percentage of isotope excreted per
hour, and the mean retention time. The time at which 95
per cent isotope passage occurred and the mean retention
time were calculated from percentage excretion curves (Figure
4). It is believed that the average time that food materials
from a particular meal spend in the tract, the mean retention
time, is the most important passage rate parameter.

For 1 of the animals used in these studies (Deer I)
the food intake was progressively decreased in several stages,
finally to a level 22.56 per cent of that normally consumed
at ad libitum levels of feeding. Other deer were fed only
ad libitum. No significant correlation (P >> 0.10) was
found between the SIOpe of isotope excretion or between the
mean retention time and the amount of food consumed per hour
(Table 4). 51Cr analysis revealed that, at least in these
studies, the rate of food passage was not affected signifi-

cantly by the amounts of food eaten.

51

.mema .s»amum>aeo menum cassava: .Aa magma .a Swan» mmoe
Imamcflm .HH noonv boat Umumaaom .OHMOSMDm ecu mafiummmcfl Homo
w you HUam mo mmoo mamcwm m mo w>usu codumuoxm mmmusoouwm

HUHm mo cowummmsfl umumm mnsom

mm mm em mm om ma ma «a Na 0H m e
b p . p . . _ p _ P L.

m
L‘

.e musmwm

”N

 

 

n.0H

..ON

1.0m

..oe

.uom

r.ow

r.0>

1.0m

.Iom

 

 

00a

paaeoegep IQIS go afiequaored aarqunmna

52

 

 

>.md m.HN o.m mm.> m.>m

d.¢d m.>a o.ma ww.am «.mm HHH

m.ma o.mm o.m mo.OH m.>¢

>.ma m.mm o.ma m¢.¢N N.om

m.md m.om o.m mm.m a.mm

m.NN o.mm o.>H em.m H.5m

m.md o.mm o.Na mo.m m.mm

m.aa o.mH 0.0a mm.w H.m> HH

«.me >.mm o.mN mm.m m.om

m.mm m.mm o.mm mm.m m.om

m.om o.m¢ o.mm mm.a o.>¢

o.mN m.>¢ o.¢m Om.¢ m.mm

m.mm >.>¢ o.¢N mm.m H.mm

m.om m.¢¢ m.mm mm.> H.mm H

Amusozv Amusocv Amusosv nmoom cw uson mom moowm cw oofismcou noon

mEHu SCH» TEA» soap mosmummmmm HUHm omumuuxw omouomw “SO£\mEMHO

ncmuwu one: louoxo Rmm umuflm mo mafia mo ucmo Hem

 

 

.mmmd .muHmHm>MSD wpmum cmmwsowz .umHv Umumaamm oumosmum m :0
meet Umawmulmuwz3 m Mom mumn wmmmmmm ou UmumHmu mm cofiumfismcou poem mo Hm>mq .w manna

Digestibility78tudies
DeveloEmental Results

The feasibility of employing a simplified dosing tech-
nique in digestibility studies of deer was investigated by
feeding 5 deer varying numbers of 51Cr labeled 0.25 to 0.50
gram food particles per day. Since the food material tends
to become thoroughly mixed, it was hOped that partial food
labeling thus would yield stable fecal isotOpe concentrations
similar to those observed when all ingested materials were
labeled (Mautz, 1967).

For different trials on the standard diet, the number
of radioactive items consumed per hour was varied between
0.16 and 1.72. Decreasing the number of radioactive items
consumed per hour normally resulted in an increase in the
variability of fecal isotope excretion (Table 5). This
trend was by no means constant, however, and much unpre-
dictable variability occurred within animals. When this
experiment was performed, Deer I diSplayed a defecation pat-
tern unlike that of the other animals used. While most
animals showed no change in defecation rate between night
and day, Deer I defecated only at night. This must have had
an effect on fecal isotope variation because when this animal
adopted a more typical defecation pattern the fecal isotope

variability decreased.

55

 

Ahmad . NquZ
.uomn N so mamauu mv MU

 

54

 

ma.o mm.fim mo DSDOEM Enomwss nuw3 commuwm
noon Ham so£3 mosam> mmmnm>¢
m>.d om.¢> no.0 m.mmd
mw.¢ m>.>dm «m.o m.mm
mm.m m>.mmd mm.o N.Nm
>m.a mm.mmd mm.a N.m¢ HHH
mN.H md.om Sm.o m.mma
mo.N mm.om 00.0 m.mm
am.m mm.mm mm.d «.mm
md.o m>.mm N>.d N.m¢ HH
mm.mm mm.mmma ma.o , m.oam
mo.m m¢.mwdd mm.o «.mmd
Ha.a¢ oo.maoa Hm.o w.>m
mm.0fi om.NN> am.a «.mm H
mCOHumummmo msoflumoomwp use H505 mom omummmSH Am om.oumm.ov HOOD
usmuommap ca luowwap cw HUam mo mEmufl OOOM o>wuom umaamm poom O>Hu
msowumuusoosoo mussflfi mom mucsoo Ioflomu UmumHDOHmu Iomoapmu mso £pa3
uUam How muouum smm3umn mosmwum> UmeE poom O>Huum
OHMUcmbm Iowomucos mo nEmuU

 

 

.mmma .wuflmnm>fis9 mumum smmfinofiz .umwc OHMUCMDn on»
uzonmzounu UmxHE mmaowunmm 000m m>wuumowpmn mo nquEss msoflum> mafiEsmcoo
Hemp Eoum msoHumommwp usmummmap smm3umn msoflumnucmusoo HUam SH nodumflum> .m magma

55

In work carried out previously using the spray tech-
nique of applying 51Cr to all food items ingested (Mautz,
1967), the variances of isotOpe concentration between dif-
ferent defecations ranged from 5.55 to 54.67, the mean being
21.62. The average standard error for these values was 0.16.
These data represent 6 trials on 2 deer. With variation of
this degree, it was found that accurate digestibility data
could be based on only a few fecal samples.

In the current study, however, concentrating the total
amount of isotope on a few food particles did not yield a
stable level of fecal isotope. In none of these trials
(Table 5) was variation between fecal isotOpe values observed
which resulted in a standard error as small as that seen when
all food materials were labeled. To be useful, this tech-
nique would require at least 2 radioactive food items to be
consumed per hour.

The feasibility of applying the isotope in this manner
rather than spraying all food items ingested would depend
on the amount of food eaten by the test animal. Individually
dosing 48 or more items per day would be less time consuming
than the Spraying method only perhaps, if an automatic
pipetting mechanism were available and if the total amount
of food ingested per day was great.

The variability of fecal isotOpe concentrations was also
determined for an animal fed a decreasing amount of food

per hour. Decreased levels of food consumption tended to

56

increase variability in fecal isotope concentration even
though a stable number of radioactive items was consumed
per hour (Table 6). The explanation for this is not known.
Possibly there is less digesta mixing at the restricted
consumption rates.

Thus, the level of food consumption as well as indi-
vidual variability must be considered in determining the
number of radioactive items per hour to feed. Reduced food
consumption requires Spreading the isotOpe over a greater
number of individual items to yield a constant fecal isotope

excretion.

Total Collection MethOd Versus Ratio Method

Because of increased variation in fecal isotOpe concen-
tration induced by labeling small numbers of food items, it
was not possible to obtain accurate digestibility coefficients
from a limited number of defecations. Accurate digestibility
coefficients were obtained, however, by lumping values from
several defecations.

Good correlations between total collection and lumped-
ratio values occurred only in trials on animals adjusted to
both the diet and collection pen (Table 7). For trials in
which test animals did not display constant levels of food
intake, passage rate, or digestion, there were poor correla-
tions between results of the 2 methods. This was due mainly

to the changing levels of food consumption.

57

.mumu Esuwnfla cm was
.x.

 

 

mm.» mm.>amd H¢.o «.ma

N@.N mm.mmm aw.o N.mm

mm.H mm.>ma ޢ.o N.>m

Ha.m mm.mmd w¢.o *m.om H
mcowumommmp macaumommmp H30: H50: noon

usmummwwv Eoum
mooHumuusmosou uUam
mo Houum Unmpcmum

pamummmae ea

cowumuusmucoo Roam
smm3umn OUSMHHM>

mom owfismsoo
muoaamm boom
m>auomowomm

Hmm-pmenmcoo
OOOM mo mamuu

 

 

.mwma .huwmum>flc9 mumum smmwnUflz
pmxfifi mumaamm poom m>auomoflpmn mo Hogans usmumcoo m mafiasmsoo HmEHcm
cm cw ncowumuusmosoo HUam Hmomw so soflumfismsoo noon pmuuwuunmu mo uoommm .m magma

.DOAU oumocmbm may usonmzounu

58

 

 

 

Table 7. Dry matter digestibility coefficients determined
simultaneously by the 5 Cr ratio and total col-
lection methods. Data for a deer consuming the
standard diet (Deer I, trial 1:9). Michigan
State University, 1968.

Period Ratio Total Collection
(days) Method Method

2-4.4 69.09%

0-4.6 71.95%
4.4-7.5 72.58

4.6-7.4 68.50
7.5-8.5 69.78

7.4-10.6 68.72

Means 71.92 70.06

 

59

The total collection method assumes a constant level
of food ingestion and excretion. This was not the case in
most trials carried out in this work, in which the animals
were subjected to a new environment or to new diets. The
51Cr ratio method does not require constant ingestion
levels and, unless noted otherwise, digestibility coeffi-
cients presented beyond represent lumped ratio data.

Effects of Food Consumption Levels
on Food Digestibility

An increase in digestibility with decreased food con-
sumption levels was observed in cattle and sheep by Blaxter
and Wainman (1961). The several levels of food intake in
the preseny study, however, had no effect on gross energy
digestibility or metabolizability coefficients for a deer
on the standard pelleted diet (Table 8). Nearly identical
digestibility coefficients were observed for the highest
and lowest levels of food consumption. The slight drop in
digestibility at the 2 intermediate levels of food intake
were not significantly different from the extreme values.

The animal tested in this study was under extreme
nutritional stress when its food was restricted. It lost
weight at each successive level of restricted feeding and,
by the end of the experiment, had lost 17 per cent of its
initial weight.

Ullrey g; l. (1969) found that feeding an amount of

food 50 per cent of that consumed at ad libitum ingestion

.oousmmmE uoz
*

.Honnm pnmocmum and;
*-

**

.x.

.mommm manwumDQEou How sowuomuuou unonuwz
*

 

 

A¢.>v m.am Am.¢v N.>m Amm.wv mm.¢ ma.>m am.wm mwa >.> «.mfi
m>.0m mo.mo Nma m.p m.mm
no

A. mm.mm v mm.mm *** m.m N.>m

A¢.av m.m¢ Aa.dv >.mm Awm.av md.m om.>w mm.mw oom o.O¢ m.om
**OEHu **OEHu **HMOE .mmoo.muos usowoammooo soHumEDmcoo soap H50: mom
cowumuoxm sofiucwuou omeQmH wmnmco wufiawnaumwmao mo Hm>ma ImEsmsoo mo poummmcw
usmu Hem cmmz Scam mo mmouw mmumcm mmouw cm>am mo Hm>0H sm>am poom mo
mm sowummoxm Use um Homo um mwmo manna mun

Hmomm mo mocsom mo HOQEDZ
356: 5 “seams.
womecooumm

 

 

.UOUDHOCH mum Mann mumu mmmnnmm

.mmmd .muflmum>wcb oumum smmflnowz
.umwo pumpsmum map so Seaumasnsoo Uoow mo
mHm>mH e um Homo o How mucmefimmmou hpwafinmuwaonmbmfi Use wuwawnwummmwo woumcm mmouw

.m wanes

41

levels caused no change in the dry matter digestibility
coefficients of deer.

There are mixed reports in the literature on the effect
of passage rate on digestibility. Blaxter _£__l, (1956)
and Derrickson (1965) suggest that the digestibility of a
food in ruminants can be predicted by its passage rate.
Shellenberger and Kesler (1961), however, found that the
digestibility of dry matter was not influenced by rate of
passage. In the present studies, a somewhat decreased rate
of passage resulted from low intake levels (Table 5) but
this did not have marked effects on digestibility. The
average mean retention times of the 51Cr labeled meals for
80.8 and 19.1 grams per hour levels of food intake were
29.7 and 57.2 hours, respectively. These means are Signifi—
cantly different at a level of P < 0.154.
Effect of New Surroundings on
Digestibility;Coefficients

The length of time required for an animal's digestive
mechanisms to adjust to collection pen conditions was
determined during trials on 2 deer consuming the standard
diet. For the first 4 days of the trial while the animals
were outdoors, the weather was mild and the temperature was
similar to that of the indoor collection pens. Deer II and
Deer III then had dry matter digestibility coefficients of

67.58 per cent and 64.17 per cent, respectively.

42

When first transferred to the small pens, both animals
Showed marked decreases in digestibility coefficients of
25.68 and 7.81 per cent. Tending to rise gradually, by the
9 to 12 day of confinement both animals had digestibility
coefficients approximating those observed at the outside
locations (Table 9).

Texter _£Hgl. (1968:111,119) said that some emotions
upset gastric secretions, gastric and intestinal motility,
and hence digestive processes. It is not surprizing, there-
fore, that food digestibility decreased when the deer were
first introduced to collection pens. They were visibly dis-
turbed when first so confined.

No permanent change in the digestibility coefficients
of a diet occurred between deer kept outdoors and those
housed in the indoor collection pens, but 1 of the animals
did Show a permanent change in the level of food consumption.
Deer III showed a transitory reduction in food consumption
but regained outdoor levels of intake in 21 days (Table 9).
Deer II had a significantly (P < 0.064) decreased level of
consumption even 55 days after it was placed in the collection
pen.

It may be that lack of exercise (Mayer t $1,, 1954,

1956) caused Deer II to undergo a more permanent reduction
in level of food intake than Deer III. Both deer were quite
active in the outdoor pens. Deer II became sedentary in the

collection pen, however, while Deer III remained fairly

active.

45

Table 9. Dry matter digestibility coefficients of 2 deer
immediately preceding and after confinement to col—
lection pens. Both animals ingested an ad libitum
level of the standard, pelleted diet. Michigan
State University, 1968.

 

 

 

Grams Dry matter
consumed digestibility
Deer Day of trial per hour coefficient
II 1-4 (outdoors) 86.1 67.58
5-8 (indoors on day 5) 45.70
9-12 50.90
15-16 66.00
17—19 79.4 66.65
20-25 65.2
III 1-4 (outdoors) 67.0 64.17
5-8 (indoors on day 5) 56.56
9-12 59.80
15-16 66.65
17-19 59.0 64.75

20-25 68.7

 

44

Effect of Rapid Introduction of New
Foods on Apparent Digestibility

Continuous digestion trials were run on 5 animals imme—
diately preceding, during, and after rapid changes from 1
diet to another. No attempt was made to Slowly introduce
the animals to new foods. Each food when first introduced
to the test animals had a markedly lower digestibility
coefficient than was observed after the animal had been con—
suming the food for several days (Table 10). This confirmed
that for deer, too, digestion trials must not be carried out
before the animal involved has had time to adjust to the new
diet. These delays probably ensue when a Shift in diet by
the host results in a subsequent change in the relative
numbers of different species making up the symbiotic rumen
community of bacteria and protozoa which digest the consumed
plant materials. Like any other ecosystem, the trend in
the rumen is toward stability, with those species most
adapted to the prevailing environmental conditions becoming
dominant over less well-suited species. To some degree the
various enzyme systems important in digestive processes also
become adjusted to a particular diet (Texter §t_al,, 1968:
185).

The deer used in this work and their symbionts, more
readily adjusted the digestive mechanism to the grass and
sumac diets than to the aSpen diet (Table 10). The aSpen

diet, however, was the first natural food fed to Deer II.

45

.mvmp powwoflmmsmsHull

 

 

uuu ae.me am.mm Se.me e.mum.m
nu- mm.ae me.me Ne.ae m.mum.m >H umSnm
In: eo.ae em.ee e.em o.m-o.>
In- mm.ae me.ee m.mm o.muo.m
-u- Se.o~ me.mm m.ma o.m-o.a >H mamas
oe.em fie.mm Se.em o.mm m.eaum.ma
oe.om ee.mm me.om m.om m.mdue.e
oe.mm me.mm me.mm m.ma o.e-o.n
ma.ea mo.mm so.ma m.em so.muo.m HH memeo
mm.me om.me em.am e.me m.mue.e
mm.mm «0.0m em.am m.em m.eum.m
Hm.m em.ea on.ea m.em m.m-m.m HH gamma
mucmfloflmmmoo musmfi0flmmmoo unmauflmmmou UmEDmsou umao Home umfln
Suaaaneuaaonmumz Suaaanaummmao Sphagnaummmae use: “we no mane

 

mmumsm mmouw Houume wan manna man no HOQESZ

 

 

.mmmd .muamno>fisb mumam smmflnuwz .mooom annoums m pom umuaw cm£3 Homo a
mom musmflowmmwou wuHHwQMNHHOQMDTE Ucm muflafinaummmflp >mumsm mmoum new umuume hum .oa manna

46

Both with the grass diet and with sumac, these foods were
preceded by another natural diet (of aSpen or sumac). This
may have been a significant factor in the shorter adjust-
ment period observed for these new foods.

While food digestibility appeared to stabilize in most
trials, the rate of food consumption continued to rise
(Table 10). The stabilization of digestibility coefficients,
therefore, is not necessarily the only factor involved in
the animal's adjustment to a new diet. It is difficult to
say if the final consumption levels for each diet (Table 10)
represent the maximum values that would be obtained if the
trials had been continued. It seems unlikely, however,
that consumption levels would rise much beyond the observed
maximum levels for each deer and diet. Several incidents
were observed where, after seemingly becoming adjusted to a
new diet, a deer decreased its level of consumption.

Most digestibility studies are ultimately concerned
with biotic productivity and the actual amount of food
energy utilized by an animal per unit time. To calculate
the amount of energy utilization occurring, it is necessary
to know the consumption rate as well as the digestibility
coefficients of the foods being tested. Ideally, trials
investigating productivity should not be initiated until
both of these parameters have stabilized. As these trials
with 51Cr Show, the time required for stabilization varies

with different foods and previous feeding history.

47

Comparison of Drpratter Digestibility
Coefficients for Various Foods

Two trials using different foods were conducted for
each of 5 deer using 5 natural foods. In addition, 5 combi-
nation diets were tested, 1 in each deer (Figure 5). The
combination diets consisted of 1:1 wet—weight mixtures of
2 natural foods.

The 5 natural foods proved each to be digested to nearly
the same extent. The average dry matter digestibility co-
efficients for the aSpen, grass, and sumac diets were 50.70,
49.42, and 54.17 per cent, resPectively (Table 11). These
were all below the average digestibility coefficient of
65.68 per cent for the standard diet (Table 11).

Digestibility data were calculated for the mixed diets
as if no synergistic or antagonistic effects were present
between the 2 foods used. The estimates were obtained by
taking the digestibility values for each food item as de—
rived separately and obtaining a weighted average (Table 11).
AS an example, the aspen-grass mixture for Deer II would be
expected to have a dry matter digestibility coefficient of
55.70 per cent if there were no interacting effects present.
This was obtained by multiplying the digestibility coeffi—
cient of aSpen 51.54 per cent, measured in Deer II, by its
dry weight prOportion of 0.56 in the aspen-grass mixture,
and adding this product to the product for grass in Deer II,

that is 56.47 per cent times 0.44.

48

 

 

 

 

 

DIET
Individual Foods Combinations
L Aspen 8c Aspen 8c Sumac 8c
eer Sumac Aspen Grass Grass Sumac (Grass
II X X X
III X X X
IV X X X

 

 

 

 

 

 

 

 

 

Figure 5. Feeding scheme used in digestibility
studies of several natural diets in
5 deer. Michigan State University, 1968.

 

 

H

 

 

 

 

 

 

 

49
Table 11. Digestibility data for 7 diets fed to 5 deer during
evaluation <1f the 51Cr technique. Michigan State
University, 1968.
Per cent of Kcalories
consumed digestibh
Grams Kcalories energy energy
consumed consumed excreted as: obtained
Diet Deer per hour* per hour* Feces Urine per hour*
Aspen leaves II 2 77 14.08 51.50 2.68 6.85
III 1.15 5.44 50.74 5.57 2.68
Mean 1.95 9.67 51.12 5.05 4.76
Grass clippings II 2.52 10.76 41.59 1.21 6.51
IV 1.65 7.57 58.96 *** 5.11
Mean 1.98 9.17 50.18 1.21 4.71
Sumac inflor— III 2.17 11.56 55.59 2.54 6.56
escences IV 2.02 10.75 50.56 *** 5.51
Mean 2.10 11.16 52.98 2.54 5.84
ASPen(56%) & Observed EXpected
Grass(44%) II 2.68 2.52 15.09 47.54 2.11 6.89
Aspen(44%) &
Sumac(56%) III 2.72 1.47 15.51 47.70 4.94 8.01
Sumac(59%) &
Grass(41%) IV 1.79 1.86 9.02 60.71 *** 3.43
Standard pel-
leted diet II 5.55 14.92 54.07 2.95 9.84
III 5.57 15.01 52.04 1.68 9.66
5.56 14.97 55.06 2.52 9.75

0.75

*-
All values standardized to kg body weight.

**
Expected values assuming no synerg1st1c or antagon1stic

effects present between the 2 foods.
***
Insufficient data.

50

 

 

 

 

 

 

Kcalories
metabolizable
energy Dry matter Gross energy Gross energy
obtained digestibility digestibility metabilizability
per hour* coefficient coefficient coefficient
6.45 51.54 48.50 45.82
2.50 49.85 49.26 45.89
4.48 50.70 48.88 45.86
6.18 56.47 58.61 57.40
<5.11 42.57 41.04 <41.04
<4.65 49.42 49.85 (49.22
6.07 55.12 55.05 52.51
<5.51 55.12 49.44 <49.44
(5.69 54.17 52.25 (50.98
(floserved Eercted Observed Exgected Observed Expected
6.62 6.27 55.54 55.70 52.66 50.55 50.92
7.25 5.66 52.80 52.80 52.50 47.56 44.21
(<5.54 *** 59.59 48.77 59.29 <59.20 ***
9.40 66.65 65.95 62.98
9.44 64.75 64.56 62.86
9.42 65.68 65.15 62.92

51

The only great deviation from expected values in the
mixed diets was in the much greater consumption level and
therefore in the calories derived by Deer III from the
aSpen-sumac mixture as compared with the 2 ingredients fed
individually. The dry matter digestibility coefficient for
the grass-sumac mixture in Deer IV was lower than expected,
indicating a possible antagonistic effect.

Evidently there are synergistic and antagonistic effects
involved with the food combinations used in this work.

Future digestive studies might include appraisals of the

total natural diet of the deer as determined by prior studies.
Accurate estimates of digestive parameters are not neces-
sarily obtained merely by lumping the appropriate data for

individual forages.

Energy Value of Several Diets to the Deer

The energy derived by deer from different foods can be
ascertained by comparing the consumption rate and dry matter
digestibility of the food with the caloric values of food,
feces, and urine.

Of the 6 natural diets tested, none provided the deer
with as much energy as the formulated standard diet (Table
11). Animals on that diet obtained above-maintenance levels
of energy as evidenced by continual weight gain. Of the
natural foods tested, sumac inflorescences evidently com-

prised the best source of energy. A mixture of sumac and

52

aspen also provided the deer with an excess of calories.
Periodic weighings of Deer III showed that this animal
lost weight while on the aspen diet and gained weight while
on the sumac and aspen-sumac diets. Although periodic
weighings were not possible, Deer II neither appeared to
lose nor to gain weight markedly during 16 days on the aspen
or 17 days on the grass diet. These deer required (Table 11)
approximately 6 kilocalories of metabolizable energy per

kilogram to the 0.75 body weight per hour.
Autopsy Results

To ascertain the areas of principal nutrient absorption,
several deer were sacrificed upon completion of digestion
trials. At the time of death, these animals had been consum-
ing a constant level of 51Cr on the standard diet. Since 51Cr
is not absorbed in the digestive process, it becomes increas-
ingly concentrated as foods are absorbed from the gut.

Samples of digesta were withdrawn from the rumen, reticu-
lum, omasum, abomasum, and cecum and from points every 12
inches along the small and large intestines of Deer I and V.
Three other deer autopsied for this purpose proved to have
digesta too scanty to allow adequate sampling.

As indicated by an increase in 51Cr concentration
(count/minute/dry gram) (Table 12), the major absorption of
nutrients from the digesta occurred in the distal 1/5 of

the small intestine, in the cecum, and in the proximal 1/5

55

Table 12. Count per minute per dry gram of samples of digesta
withdrawn from various areas of the gastrointestin-
al tracts of 2 deer sacrificed while consuming a
51Cr labeled standard diet. Michigan State Univer-

 

 

 

 

sity.
Deer
I* V
c/m/g ingested food 40 44
Portions of digestive tract c/m/g c/m/g
Rumen 49 54
Reticulum 46 52
Omasum 50 59
Abomasum 55 25
Small Intestine**

0-20% 11 1'
21-40 20 1
41-60 51 19
61-80 45 51
81-100 45 64

Cecum 115 115
Large Intestine

0-20% 92 95
21-40 97 100
41-60 107 105
61-80 90 97
81-100 105 105

Total lengths:

Small intestine 56 feet 55 feet
Large intestine 27 feet 19 feet
Cecum 16 inches ***

 

*
Chyme of the small intestine of this deer contained appreci—

able amounts of blood.
**
Due to differences in intestinal lengths between the Speci-
mens the data are expressed as percentages of total length
so as to enable ready comparison.
***
Not measured

1'Insignificant 51Cr levels.

54

of the large intestine. 51Cr concentrations lower than that
of the ingested food occurred in the proximal segments of

the tract and indicated a dilution, probably by digestive
secretions. In addition, some error was undoubtedly intro-
duced when withdrawing digesta samples from the proximal

area of the small intestine. In this area where only limited
amounts of digesta were present, mucosa and cells from the
intestinal endothelium diluted 51Cr concentrations beyond

that which normally exists.
Amount of Digesta Entering Cecal Pouch

The cecum of the deer is primarily a blind pouch 12 to
18 inches long and located at the junction of the small and
large intestine. 51Cr concentrations of digesta samples with-
drawn from this blind pouch and from the intestines showed
that a large proportion of digesta enters this organ. Chyme
from the small intestine which does not enter the cecal pouch
flows directly into the large intestine (Table 12), diluting
the materials which reenter the intestine from the pouch.

In Deer V, the isotope concentration in digesta samples
withdrawn from the tract immediately preceding the cecum,
from'the cecum, and from immediately after the cecal juncture
were 64, 115, and 95 c/m/g respectively. Since 95 c/m/g is
the weighted average of 64 c/m/g and 115 c/m/g, then the

prOportion of Chyme contributed by the small intestine and

that contributed by the cecum is:

55

let x = that portion of a gram contributed to the
95 c/m/g chyme of the proximal large intestine
directly by the small intestine.

let 1-x = that portion of the proximal large intestine
95 c/m/g/ chyme contributed by the cecum.

(64 c/m/g - x) + [115 c/m/g '(1-x)] = 95 c/m/g

0.451 grams
0.569 grams

x
1-x

Thus in order to obtain a final average of 95 c/m/g, 0.451
grams of small intestinal chyme bearing 64 c/m/g must be
mixed with 0.569 grams of 115 c/m/g cecal chyme. The 0.569
grams of cecal chyme represents a total of 0.569 grams times
115 c/m/g or 65.4 counts of 51Cr. Since this material origi-
nated from the small intestine at a concentration of 64 c/m/g
it represents 22°2/gjg' or 1.022 grams of original small

intestinal material. Therefore for every 0.451 grams plus

1.022 grams or 1.455 grams leaving the small intestine

1.022
1 .455

cecum. For Deer I, 85.98 per cent of the material leaving

x 100 or 70.54 per cent enters the blind pouch of the

the small intestine entered the cecal pouch.

Absorption in the Small Intestine, Cecum,
and Large Intestine

The prOportion of ingested dry matter absorbed from the
various areas of the gastrointestinal tract can be calculated
by multiplying the amount of original dry matter entering the

segment by the degree of absorption occurring there: In Deer

56

V the absorption occurring between the animals mouth and
the distal end of the small intestine was (1 - éfi-Eéfiég) x 100
(Table 12) or 51.25 per cent. Thus 68.75 per cent of the
original meal remained at the distal end of the small intes-
tine. The cecum of this animal absorbed (1 -1%%-§éaég) x 100
or 44.55 per cent of the dry matter which entered it.
However, as previously discussed only 70.54 per cent of the
dry matter leaving the small intestine entered the blind
pouch of the cecum. Because only 68.75 per cent of the
original meal reached the distal end of the small intestine
and 70.54 per cent of this actually entered the cecal pouch
then 68.75 per cent times 70.54 per cent or 48.56 per cent
of the original meal entered the cecum. .Since the material
entering this organ was absorbed 44.55 per cent then 44.55
per cent times 48.56 per cent or 21.45 per cent of the
original meal was absorbed in the cecal pouch of this deer.

The large intestine absorbed (1 -1%5_§§%é%) x 100
(Table 12) or 11.45 per cent of the chyme which entered it.
At the distal end of the cecum only 100 minus 51.25 less
21.45 or 47.50 per cent of the original meal remained. Since
this was absorbed to an extent of 11.45 per cent then 11.45
per cent times 47.50 per cent or 5.41 per cent of the
original meal was absorbed by the large intestine.

The total amount of material absorbed by Deer V was

therefore 51.25 per cent from the mouth to the cecum, plus

21.45 per cent from the cecum, plus 5.41 per cent from the

57

large intestine or 58.11 per cent. This agrees with the

figure arrived at by comparing the initial and final 51Cr

(1 - 13g :jfijg) x 100 or 58.11

per cent. The proportions of the total absorption contributed

concentrations, that is,

by the small intestine, cecum, and large intestine are 55.78
per cent, 56.91 per cent, and 9.51 per cent respectively.

The small intestine, cecum, and large intestine of Deer
I absorbed 6.98 per cent, 49.55 per cent, and 4.64 per cent
of the dry matter consumed by this animal. The total dry
matter absorption for this deer was 61.17 per cent. Thus
the proportion of the total absorption contributed by each
organ was 11.41 per cent, 81.00 per cent, and 7.59 per cent
for the small intestine, cecum, and large intestine respec-
tively. These results are presented in Table 15.

These calculations assume that all materials secreted
into the alimentary canal in the various segments of the
tract are absorbed prior to the distal end of the segment
in which they appeared. This is not always the case and
therefore the true dry matter digestibility for the various
areas of the tract may be slightly higher or lower than that
observed.

The rumen and small intestine are generally considered
to be the primary areas where absorption occurs. While this
was seen in Deer V (55.78 per cent of total), data from
Deer I indicate the proximal areas of the tract played only
a minor role in its absorption processes (11.41 per cent of

the total).

 

 

 

58

 

 

 

Table 15. Percentage absorption of food by portions of the
digestive tract of 2 deer fed the standard
pelleted ration. Michigan State University,
1968.

As percentage As percentage
of food of total food
entering organ absorbed

Deer I

Small intestine 6.98 11.41
Cecum 49.55 81.00
Large intestine 4.64 7.59

Total 61.17 100.00

Deer V

Small intestine 51.25 55.78
Cecum 21.45 56.91
Large intestine 5.41 9.51

Total 58.11 100.00

 

 

59

It seems unlikely that this could be the case in a
healthy animal and there was in fact, evidence of ulceration
of the gastrointestinal tract in Deer I. Chyme from several
areas of the small intestine appeared very dark, as if there
was much blood present. This disturbance could conceivably
cause absorption to be decreased in this area of the tract.
In addition, the blood entering the lumen of the intestine
would dilute the 51Cr of the chyme, thereby giving the
appearance of low dry matter absorption in the small intes-
tine. The absorption of much of this blood distal to the
area of ulceration would also add to the appearance of in-
creased cecal and large intestinal dry matter absorption.

It is not known what caused this intestinal disorder. Due
to malfunction of the counting device, rather large amounts
of isotOpe were fed to Deer I. The total isotope ingested
by this deer over a period of 67 days was 595 microcuries.
Whether these levels of 51Cr could cause the bleeding ob—
served is not known.

In all events, this 51Cr technique clearly discloses
the importance of the cecum in the digestive process of
white-tailed deer. Whether these findings also apply to
natural diets of the deer remains for future study. It was
unfortunate that data could not be obtained from 5 of the
5 deer used for these aut0psy studies.

The above described technique of detecting where dry

matter absorption occurs should also be of value in the

60

study of absorption of specific nutrients. By comparing
individual nutrient concentrations with the 51Cr indicator,
values could be obtained regarding the site of absorption
of Specific ingredients of a diet. This particular ratio
technique of studying absorption has been used for many
years with stable indicators such as Crgos, but the use of
51Cr simplifies indicator detection and makes possible the

easier analysis of many samples.
Behavior of EXperimental Animals

Emotional stress induced by confinement in some animals
introduced a source of variation into experimental results
which may not occur in wild populations. Collection-pen data
from the more relaxed animals probably provided data which
were more typical of wild deer than did results from excited
test animals.

Deer I and II seemed to accept captivity. They seldom
showed fear or apprehension and were the best suited of all
deer used. Only after periods of 5 to 4 months in the col-
lection pens did these animals show unrest. They would then
occasionally hit and scrape the grated floor with their hooves.
Even though raised as a fawn in captivity, Deer III constantly
displayed an apprehensive behavior. Deer IV displayed similar

behavior.

SUMMARY

Evaluatipn 9§A51Cr as a Food Label in

Digestive Studies with Deer fr

In the white-tailed deer 51Cr proved to be a useful
indicator for the study of many digestive parameters,

particularly those involving passage rate, rumen turnover

 

time, and the area of the tract where major nutrient absorp-
tion occurs. These are all areas of study which require
some type of food label. The radioisotope 51Cr has an
advantage over stable indicators in its simple detection

and quantification.

When SlCr was sprayed on all foods ingested, the degree
of total digestibility could be determined by comparing the
isotOpe concentration of the food with that of a few radio-
active defecations. The ingestion of only a limited number
of 51Cr labeled food items, mixed thoroughly with nonlabeled
food, however, yielded variable fecal isotOpe concentrations
in the deer which necessitated lumping values from several
defecations. When this must be done, there is little advan-
tage of the 51Cr ratio method over the total collection
method. Consequently, the method requires that all food or
at least a high number of individual food items be marked
with 51Cr.

61

62

The real advantage of the 51Cr ratio method will be in
digestibility studies on animals which do not allow severe
confinement, thus making the total collection of feces im-
possible. For studies such as these the effort and time
required for spraying all foods ingested with 51Cr or label-
ing many individual food items easily will be justifiable.
When this is done it will be possible to obtain digestibility
coefficients by collecting just a few fecal samples. 4

There are also certain types of digestibility studies

 

made on confined animals which are not possible with the

\ P’Ifi‘".hfi_ I

total collection technique. The 51Cr ratio method enables
calculation of short term changes in digestibility occurring
as results of stress, new diet, or other disturbances to the
test animal.
Digestive Parameters of Deer
Investigated withIBICr

The rumen was the major organ of the deer in which food
mixing occurred but significant mixing of digesta also
occurred in other areas of the tract. -While feeding on a
standard pelleted diet, 51Cr placed on a 0.25 to 0.50 gram
food pellet was thoroughly mixed with the rumen contents 5
to 50 minutes after ingestion. Rumen dry matter content
varied greatly even within 1 animal consuming the standard
diet. The mean rumen dry matter content for this animal

(Deer III) was 547 grams.

65

There was an inverse relationship between food consump—
tion level and passage rate. The relationship was variable,
however, and it was not possible to use one parameter to
predict the other.

A forced reduction of 25.62 per cent in dry matter in—
take had no effect on the digestibility coefficient of the r”?
standard diet even though the experimental animal studied 1
was in a state of negative energy balance, losing 17 per

cent of its body weight.

 

Two deer required 9 to 12 days to become adjusted to J
the collection pens in the amount of dry matter absorbed from
the standard diet. Digestibility coefficients thereafter
were the same as those observed when these specimens were
confined to larger outdoor pens. One animal showed a perman-
ent decrease in food consumption in the collection pen.

The 5 natural foods used in this study, aspen leaves,
sumac inflorescences, and grass clippings, had rather similar
dry matter digestibility coefficients (50.70, 54.17, and
49.42 per cent reSpectively). The standard pelleted deer
diet had an average dry matter digestibility of 65.68 per
cent. Of the natural foods tested, sumac inflorescences
appeared to be the best source of energy for the deer. An
animal which consumed only this food obtained above-
maintenance levels of energy as did a deer consuming an
aspen-sumac mixture. Aspen and grass when fed individually

yielded the deer near maintenance levels of energy.

64

The small intestine, cecum, and large intestine of a
deer consuming a standard ration accounted for 55.78, 56.91,
and 9.51 per cent respectively of the total dry matter
absorption occurring for this animal. For this deer 70.54
per cent of the material leaving the distal end of the small

intestine entered the blind pouch of the cecum. f——‘}

 

 

LITERATURE CITED

 

LITERATURE CITED

Balch, C. C. 1950. Factors affecting the utilization of
food by dairy cows. I. The rate of passage of food re
through the digestive tract. Brit. J. Nutr. 4:561. L

Balch, C. C. 1957. Use of the lignin-ratio technique for
determining the extent of digestion in the reticulo—
rumen of the cow. Brit. J. Nutr. 11:2154227. 5

Balch, C. C. and C. Line. 1957. Weight changes in grazing
cows. J. Dairy Res. 24:11-19.

 

Bergeim, O. .1926. Intestinal chemistry IV. A method for
the study of food utilization or digestibility.
J. Biol. Chem. 70:29-55.

Bissel, Harold D., Bruce Harris, Helen Strong, and Frank
James. 1955. The digestibility of certain natural
and artificial foods eaten by deer in California.
Cali. Dept. Fish & Game. 41(1):57-78.

Blaxter, K. L., N. McC. Graham, and F. W. Wainman. 1956.
Some observations of the digestibility of food by
sheep and on related problems. Brit. J. Nutr. 10:
69-91.

Blaxter, K. L. and F. W. Wainman. 1961. The utilization
of food by sheep and cattle. J. Agr. Sci. 57:419-425.

Brandt, L. S. and E. J. Thacker. 1958. A concept of rate
of food passage through the gastro-intestinal tract.
J. Anim. Sci. 17:218-225.

Brody, Samuel. 1945. Bioenergetics and growth. Reinhold
Publ. Corp., New York, 1025 pp.

Browne, T. G. 1922. Some observations on the digestive
system of the fowl. J. Comp. Path. and Thera. 55:12.

Castle, E. J. 1956. The rate of passage of foodstuffs

through the alimentary tract of the goat. Brit. J.
Nutr. 10:15-25, 115-125.

65

66

Cowan, R. L., E. W. Hartsook, J. R. Whelan, T. A. Long and
R. S. Wetzel. 1969. A cage for metabolism and radio-
isotOpe studies with deer. J. Wild. Mgt. 55(1):204-
208.

Dansky, L. M. and F. W. Hill. 1952. Application of the
chromic oxide indicator method to balance studies with
growing chickens. J. Nutr. 47:449-459.

Deitz, Donald R., Robert H. Udall and Lee E. Yeager. 1962.
Chemical composition and digestibility by mule deer of 4 m
selected forage Species, cache la Poudre Range, Colorado. F“
Colo. Game and Fish Dept. Tech. Pub. No. 14, 59 pp.

Derrickson, Charles M. 1965. Rate of passage of ingested
material through the digestive tract of steers. Ph. D.
Thesis. Mich. State University.

 

Dixon, W. J. and F. J. Massey Jr. 1957. Introduction to
statistical analysis. McGraw-Hill Book Co., Inc.,
New York. 488 pp.

'5'.

Duke, Gary E. 1967. Chromium-51 in metabolizability and
food passage rate studies with the ring-necked pheasant.
Ph. D. Thesis. Michigan State University.

Edin, H. 1918. Orienterande forsok over en paled kropps-
principen grundad metod att bestamma en toderblundnings
smaltburket. Medd. Nr. 105 Centralanstult. forso
ksuusendef jordbruks.

Elam, L. J., P. J. Reynolds, R. E. Davis, and R. D. Everson.
1962. Digestibility studies by means of chromic oxide,
lignin, and total collection techniques with sheep.

J. Anim. Sci. 21:189-192.

Forbes, R. M. and W. P. Garrigus. 1948. Application of a
lignin ratio technique to the determination of the
nutrient intake of grazing animals. J. Anim. Sci.

7:575-582.

Foster, R. F. 1965. Environmental behavior of chromium and
neptunium. In Radioecology, Reinhold Publ. Corp. and
AIBS, pp. 569-577.

Gray, F. V., A. F. Pilgrim and R. A. Weller. 1958. The
digestion of foodstuffs in the stomach of the sheep
and the passage of digesta through its compartments.

I. Cellulose, pentosans and solids. Brit. J. Nutr.
12:404-415.

67

Hayes, W.,

C. 0. Little and G. E. Mitchell, Jr. 1964.
Influence of ruminal,

abomasal and intestinal fistula-
tion on digestion in steers.

J. Ani. Sci. 25:764-766.
Henry, K. M., A. J. MacDonald, and H. E. Magee.

1955.
Observations on the functions of the alimentary canal
in fowls. J. Exp. Biol. 10:155.

Hill, F. W. and D. L. Anderson. 1958. Comparison of
metabolizable and productive energy determinations
with growing chidks . J. Nutr . 64: 587-605 .

Hoelzel. F. 1950.

The rate of passage of inert materials
through the digestive tract.

Am. J. Physiol. 92:466-
497.

Hungate, Robert E.

1966. The rumen and its microbes.
Academic Press,

New York. 555 pp.
Imabayashi, K., M. Kametaka, and T. Hatano. 1956.
on digestion in the domestic fowl.

Studies
Tokyo J. Agr. Res.
2:99. In Sturkie, P. D. 1965. Avian Physiology.
Cornell Univ. Press, 766 pp.

Inman, Donald L. 1968.

The use of chromium-51 in digestive
studies of avian Species. M. S. Thesis.
University. 40 pp.

Michigan State
Irwin, M. I. and E. W. Crampton.

1951. The use of chromic

oxide as an index material in digestion trials with
human subjects. J. Nutr. 45:77-85.

Johnson, D. E., W. I. Dinusson and D. W. Bolin. 1964. Rate

of passage of chromic oxide and composition of digesta

along .the alimentary tract of wethers. J. Ani. Sci.

25:499-505.

Kane, E. A.,

W. C. Jacobson and L. A. Moore. 1952.
Diurnal

variation in the excretion of chromium oxide
and lignin. J. Nutr. 47:265-275.

Kane, E. A., R. E. Ely, W. C. Jacobson, and L. A. Moore.
1955. A comparison of various digestion trial tech-
niques with dairy cattle.

J. Dairy Sci.

56:525-555.
Krenla, M. S.

1947. Absorption of carotene from carrots
in man and the use of the quantitative chromic oxide
indicator method in the absorption experiments.
Biochem. J. 41:269-275.

Q3!!!

.V r. Wrn‘xfl
f

p- “w. .1 . I." ..

 

’I.
“ “- fl‘:

68

Lambourne, L. J. 1957. Measurement of feed intake of
grazing sheep. I. Rate of passage of inert reference
materials through the ruminant digestive tract.

J. Agr. Sci. 48:275-285.

Mautz, William W. 1967. Determination of the usefulness
of chromium-51 in digestive studies of the white-tailed
deer. M. S. Thesis. Michigan State University. 50 pp.

Mautz, William W. and George A. Petrides. 1967. The useful—
ness of chromium-51 in digestive studies of the white—
tailed deer. Proc. N. A. Wild. and Nat. Res. Conf.
52:420-429.

Mayer, J., N. B. Marshall, J. J. Vitale, J. H. Christiansen,
M. B. Mushayekhi and F. J. Stare. 1954. Exercise,
food intake and body weight in normal rats and genetically
Obese adult mice. Amer. J. Physiol. 177:544-548.

Mayer, Jean, Roy Purnima, and Mitra Prasod Kamakhya. 1956.
Relation between caloric intake, body weight, and
physical work. Studies in an industrial male popula-
tion in west Bengal. .Amer. J. Clin. Nutr. 4:169-175.

Moore, L. A. and O. B. Winter. 1954. Rate of passage of
inert materials through the digestive tract of the
bovine. J. Dairy Sci. 17:297-505.

Moore, J. H. 1957. Diurnal variations in the composition
of the faeces of pigs on diets containing chromium oxide.

Mueller, W. J. 1956. Feasibility of the chromic oxide and
the lignin indicator methods for metabolism experiments
with chickens. J. Nutr. 58:29-56.

Olsson, N. and G. Kihlen. 1948. Edins indicator method in
digestibility experiments on poultry. Proc. 8th World's
Poultry Congress. p. 225.

Petrides, George A. 1968. The use of 51-chromium in the de-
termination of energy flow and other digestive character-
istics in animals. Proc. Symp. Recent Adv. Trap. Ecol.
pp. 25-51.

Petrides, George A. and P. Greig Stewart. 1968. Determina-
tion of energy flow in small mammals using 51-chromium.
Ekol. Volsta (in press). (Proceedings of the Oxford
IBP working party on small mammal productivity.)

Fit":
ti

 

"Viva.

69

Reid, J. T., P. G. Woolfolk, W. A. Hardison, L. M. Martin,
A. L. Brundage, and R. W. Kaufman. 1952. A procedure
for measuring the digestibility of pasture forage under
grazing conditions. J. Nutr. 46:255-269.

Roche, M., Marcel, Maria Enriguerta Peres-Gimenez, Miguel
Layrisse and Esteln DiPrisco. 1957. Study of urinary
and fecal excretion of radioactive chromium Cr51 in
man, its use in the measurement of intestinal blood loss
associated with hookworm infection. J. Clin. Inwest.
56:1185.

Schurch, A. F., E. W. Crampton, S. R. Haskell and L. E. Lloyd.
1952. The use of chromic oxide in digestibility studies
with pigs fed 3g libitum in the barn. J. Ani. Sci.
11:261-265.

Shellenberger, P. R. and E. M. Kesler. 1961. The rate of
passage of foods through the digestive tract of Holstein
cows. J. Ani. Sci. 20:416-419.

Siegel, Sidney. 1956. Nonparametric statistics. McGraw-
Hill, New York. 512 pp.

Smith, A. D. 1950. Sagebrush as a winter feed for deer.
J. Wild. Mgt. 14:285-289.

Smith, A. D. 1952. Digestibility of some native forages
for mule deer. J. Wild. Mgt. 16:509-512.

Texter, Clinton E., Ching—Chung Chou, Higino C. Laureta and
Gaston R. Uantrappen. 1968. Physiology of the gastro-
intestinal tract. C. U. Mosby Co., Saint Louis. 262 pp.

Tuckey, R., B. E. March and J. Biely. 1958. Diet and the
rate of food passage in the growing chick. Poult. Sci.
57:786-792.

Ullrey, D. E., W. G. Houatt, H. E. Johnson, L. D. Fay, B. L.
Schoepke, and W. T. Magee. 1969. Digestible energy
requirements for winter maintenance of Michigan white-
tailed does. J. Wild. Mgt. (in press).

Visek, W. J., I. B. Whitney, U. S. G. Kuhn III, and C. L.
Comar. 1955. Metabolism of Cr51 by animals as influ-
enced by chemical state. Proc. Soc. Exptl. Biol. Med.
84:610-615.

Yadawa, I. S., E. E. Bartley, L. R. Fina, L. L. Alexander,
R. M. Meyer, and E. L. Soreson. 1964. Rate of rumen
metabolism of Cl4-labeled alfalfa hay as determined by
Specific activity of rumen volatile fatty acids, blood,
urine and feces. J. Dairy Sci. 47:1546-1551.

.' n ':_W7-‘7