Table Of ContentThis thesis, having been approved by the
special Faculty Committee, is accepted by
the Graduate School of the
University of Wyoming,
in partial fulfillment of the requirements
for the degree of Master oX Science__
__________
Dean of the Graduate School.
Date August 1?, 19^0
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
MAMMARY GLAND DEVELOPMENT
OF DAIRY CALVES
by
Donald C. Brown
A Thesis
Submitted to the Department
of Animal Production and the Graduate School
of the University of Wyoming in Partial
Fulfillment of Requirem ents for the Degree of
M aster of Science
LIBRARY
QF THE
University of Wyoming
LARAMIE 82070
University of Wyoming
Laram ie, Wyoming
August, 1950
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UMI Number: EP20474
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ACKNOW LEDGM ENTS
The author is grateful to Dr. H. S. W illard for his assistance
during the initial stages of the experiment, and to Dr. Carl Roubicek
for aid in the statistical analyses of the data. Further acknowledg
ment is made of the cooperation of M r. George McCue for the use of
additional experim ental anim als.
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TABLE OF CONTENTS
ACKNOWLEDGMENTS.......................................................................................... ii
LIST OF T A B L E S................................................................................................... iv
INTRODUCTION......................................................................... I
EXPERIMENTAL PROCEDURE ...................................................................... 2
Palpation exam in ation .................................................................................. 2
Gland s ta g e s ....................................................................................................... 3
RESULTS AND DISCUSSION.............................................................................. 4
Correlation of gland s iz e s .......................................................................... 5
Correlation of gland size and body w eight......................................... 6
Gain in gland size and body w eight.......................................................... 7
Average size of g lan d s.................................................................................. 8
SUMMARY AND CONCLUSIONS...................................................................... 14
REFEREN CES........................................................................................................... 16
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LIST OF TABLES
Table Page
I. Summary of correlation coefficients (r) of mean width
of front and rear glands and mean width and length
of g lan d s....................................................................................................... 4
II. Summary of correlation coefficient (r) and linear
regression (b) of mean width of glands and body weight
and mean length and body w e ig h t.................................... 5
III. Summary of correlation coefficients (r) and linear
regression (b) of gain in mean width and length of
m am m ary gland and gain in body w e ig h t................................. 7
IY. Summary of gain in body weight and gain in gland size
from 3 to 6 months of a g e .................................................................. 9
V. Summary of m easurem ents and stage of growth for calves
grouped as norm al and above norm al size on a weight
basis ........................................................................................................... 10
VI. Comparison of growth of sm all and large glands from
3 to 6 months,, grouped independently of body weight . . . 12
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INTRODUCTION
The stage of m am m ary-gland development in young heifer calves
may be a fairly reliable index to their future milk-producing ability.
Swett (6) has dem onstrated that the m am m ary development of the heifer
calf at 4 months of age has a direct relationship with her later produc
tive ability. He found that the calves that were advanced in m am m ary
development have subsequently produced from 2, 500 to 4, 000 pounds
m ore milk than those that were retarded at the same age.
Since it seemed desirable to obtain additional information on
various stages of m am m ary-gland growth and because published data
on the subject are m eager, the present study was undertaken. This
basic research problem, as the initial step in a long-time study, will
be lim ited to udder growth of young dairy heifers from 3 to 6 months
of age. When m ore data become available further studies will be made
to find the relationship between the size of gland and later producing
ability. Information on the effect of environment, breeding, and
nutrition on m am m ary development will also be obtained.
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EXPERIMENTAL. PROCEDURE
Data were collected during the period from November 1947 to
April 1950 at the University of Wyoming dairy farm and a nearby com
m ercial dairy. A total of 35 Holstein heifer calves from 3 to 6 months
of age were studied. Not all of the data were used because of death
losses and culling to barn capacity and also because some initial data
were taken at the wrong age for comparisons.
The calves were weighed and m am m ary gland m easurem ents
taken for each calf at monthly intervals from 3 to 6 months of age.
Weights for the 9 calves from the com m ercial dairy were estim ated by
taking chest-girth m easurem ents, since numerous experim ents (1) (3)
have shown their method to differ from the actual live weight by not
over 7 per cent. Age data used in the sum m aries varied by 4 7 days
in a few cases at the 3, 4, 5 and 6-month stages; however, a m ajority
of the m easurem ents were taken at 3 or 4 days.
-
Palpation examinations were made by using the method developed
by Swett (7). With the thumb and second finger serving as two arm s
of a caliper, the extrem e lateral surfaces of a front or rear quarter
were located. Holding fingers rigid, the hand was brought out, and the
distance between the ball of finger and thumb was m easured by using
a common scale graduated to l/l6 of an inch. A sim ilar procedure
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3
was used for m easuring gland lengths. Three m easurem ents were
taken of each width or length, using averages for records. Repeated
m easurem ents usually checked, within l/l6 to l/8 of an inch; the
m easurem ents were then recorded in decimal equivalents.
In addition to weight and palpation, data were also recorded for
stage of growth. M ammary glands of heifer calves pass through a
number of changes during their first six months. These stages were
identified as early quarter, late quarter, early half, and late half at
the 3- to 6-month level. Glands are in the quarter stage when each
one can be felt separately and at the half stage when the front and rear
glands on each side of the udder are attached. Length m easurem ents
were taken only at this stage. At the 6-months stage and older the
glandular tissues of well-conditioned calves was found to be covered
by varying degrees of fatty tissue; hence the individual stages were
difficult to determ ine. G reat difference was also observed between
calves as to the age at which their glands reached a given stage and size;
this accounts for the differences in calf numbers used when sum m arizing
the data.
All o£ the calves used in the study, with the exception of the 9
com m ercial heifers, were on feeding experim ents. Several planes of
nutrition were tried during the period in which m easurem ents were
taken.
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