The mean thyroid weight of the growing (under 60 months old) and full-grown (over 60 months old) cows slaughtered from the Ayrshire herd of the Viik Experimental Farm during the years 1958—59 (I), 1960—65 (II) and 1966—69 (III) was as follows: 24.46 and 43.10 g (I), 21.02 and 30.16 (II) and 18.16 and 27.01 g (III) respectively. Decrease in the thyroid weight from (I) to (III) was believed to be due to the adding of iodine as a component of a mineral salt mixture into the ration of the herd in 1959. The thyroid weights of young cattle and bulls showed trends similar to those observed in cows

Vappu Kossila

Agricultural and Food Science

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ON THE DEVELOPMENT OF THE THYROID WEIGHT
IN THE DAIRY HERD OF THE VIIK EXPERIMENTAL
FARM
Vappu Kossila
Department of Animal Husbandry, University ofHelsinki
Received Feb:uary 25, 1969
The results of an earlier study indicated that the weight and the epithelial tissue content
of the thyroid were significantly smaller in cows and young cattle discarded from the dairy
herd of the Viik Experimental Farm during the years 1960—65 (group II) than correspond-
ingly in those discarded during 1958—59 (group I) (Kossila 1967 b). These differences in
the thyroid characteristic between the groups I and II were believed to be due mainly
to the addition of supplementary iodine into the ration of the herd since the year 1959.
In the cow, the fetal period is evidently the most critical in iodine deficiency. Possible
malformations in the thyroid, developed during this period, are obviously not completely
reversed back to what we call normal by the addition of sufficient amounts of iodine into
the diet during the later periods of life. Since most of the cows in group II were born before
the iodized mineral salt mixture was introduced to the ration of the herd, it seemed that
a further reduction, especially in the thyroid weight of the cows, could be quite possible.
In order to find out whether this was so thyroid studies were carried out in the same herd
for nearly four more years.
Material and methods
Details concerning the feeding and management of the Ayrshire herd of the Viik Ex-
perimental Farm have been described earlier (Kossila 1967a, p. 32—36), and so far these
conditions have remained more or less unchanged. The few nutritional details that have
been introduced since 1965, have been as follows: (a) The cows approaching parturition
have received two vitamin injections, each consisting of 5 million units of vitamin D 3,
1.5 million units of vitamin A, and 250 mg of vitamin E. This treatment has been applied
in order to prevent parturient paresis and to improve the nutritional status of the cows
at calving. Before 1965, only vitamin D 3 was used correspondingly, (b) Propylenglycol has
150
Table
1.
The
weight
of
the
thyroid
gland
in
various
groupsof
cattle
slaughtered
during
the
years1958—59
(Group
I),
1960
65
(Group
II),
and
1966
69
(Group
III)
from
the
dairy
herd
of
the
Viik
Experimental
Farm.
Group
I
Group
II
Group
111
N
X,
X2X2aX3NX2X 2X2aX3NX3X 2X2aX3
Young
cattle
1
to
6
months
old
6
15.87
130
4.4
20
11.55
97
3.3
25
10.61
118
3.6
6
to
12
months
old
4
21.75
228
10.3
6
12.25
242
9.3
9
13.30
245
9.7
over12
months
3
21.67
385
23.0
16
13.76
325
15.2
20
16.00
383
20.1
Bulls
I
95.00
770
40.0
2
30.29
793
34.8
2
24.65
735
27.5
Cows (growing) under40
months
8
19.63
443
426
34.5
19
18.75
444
419
34.3
17
16.55
465
429
34.0
40
to
50
months
old
7
27.79
478
463
45.0
16
22.03
490
460
44.9
10
20.75
512
462
44.7
50
to
60
months
old
6
27.02
512
485
53.7
16
22.69
479
452
53.3
4
18.54
557
518
55.5
All
growing
cows
21
24.46
475
455
43.5
51
21.02
469
443
43.6
31
18.16
492
451
40.4
(full-grown)
60
to
80
months
old
6
31.07
553
499
71.8
20
27.92
543
506
67.6
9
25.23
463
512
67.8
80
to
100
months
old
3
51.70
565
519
90.3
13
29.41
513
483
89.9
6
25.67
612
550
91.5
100
to
120
months
old
3
49.47
544
500
109.0
16
29.06
521
496
109.6
6
27.04
542
501
110.0
over
120
months
2
56.75
508
536
167.0
6
42.17
521
500
135.3
2
38.95
494
474
165.5
All
full-grown
cows
14
43.10
547
509
97.4
55
30.16
527
497
92.5
23
27.01
564
515
93.5
All
cows
35
31.91
504
477
65.0
106
25.76
499
471
69.0
54
21.93
523
479
62.9
N
number
of
cases
X3=meanvalueofthethyroidweight,g2 »»»»liveweight,kg X2a»»»»correctedbody
weight,
kg
3 »ageinmonths
151
been used lately in order to prevent acetonemia in post parturient cows exhibiting signs
of this metabolic disturbance, (c) Wheat bran formerly used in the concentrate mixture
has been replaced by oat- and barley-meals.
The thyroid samples were handled as previously described (Kossila 1967a, p. 36).
Altogether 49 thyroid samples had been obtained from animals slaughtered during the
years 1958—59 (group I) and 150 from those slaughtered during 1960—65 (group II).
110additional samples were obtained from animals slaughtered during 1966—69 (group
III) (Table 1). Live weight and, for cows, also corrected body weight, were determined
in a manner previously described (Kossila 1967 a. p. 37—38). The ages of the animals
varied from 1 month to 208 months. The animals were divided into several subgroups
according to their age as shown in Table 1. The age-groups of animals 1 to 6 months old
and 6 to 12 months old included both sexes, whereas the age-group of young cattle over
12 months included only heifers.
Results
The results obtained for the groups I, 11, and 111 have been summarized in Table 1.
The effect of age on the thyroid weight of the animals belonging to the groups I, 11, and
111 has been illustrated graphically in Fig. 1. It shows that the animals in group I had
the heaviest thyroids, on an average, irrespective of age. The difference in thyroid weight
between group I and group II was highly significant in young cattle (P < 0.001) (see
Table 1), the difference was not significant in growing cows, but it was again significant
in full-grown cows (P < 0.001) as well as in all cows (P «< 0.005).
Young cattle in the groups II and 111 had quite similar thyroid weights (Fig. 1). On
the other hand, in growing and in full-grown cows, i.e. as from about 30 months of age,
the thyroid weight has been consistently lower in group 111 than in group 11. Even though
this difference between the two groups is relatively small, it nevertheless shows that the
tendency for the thyroid weight to decrease since 1960—65 has persisted.
In all cows, the mean thyroid weight was 31.91 g in group I, 25.76 g in group 11, and
21.93 g in group 111 (Table 1). Thus the decrease in the thyroid weight of cows has been
6.15 g from the first to the second phase of the study and 3.83 g from the second to the
third phase of the study, on an average. Furthermore, the values in Table 1 show that the
thyroid weight has decreased more in full-grown than in growing cows.
In groups II and 111, there appears to be a tendency for the thyroid weight to remain
constant after the cows have completed growth, i.e. approximately from the age of 65
months on. However, the cows over 120 months old have still had rather high thyroid
weights (Fig. 1) in spite of the fact that they have received supplemental iodine in some
cases during several years.
Discussion
The results of this study show that the thyroid weight of the cows belonging the dairy
herd of the Viik Experimental Farm has continued to decrease during the last few years
even though the rate of decrease has somewhat slowed down. Obviously the decrease in
the thyroid weight has occurred as a result of the addition ofan iodized mineral salt mixture
into the ration of the herd since 1959 (Kossila 1967 a, p. 34—35). This theory is also sup-
ported by the results obtained from histological studies, which revealed significantly more
epithelial tissue in grams per thyroid gland ofthe animals belonging to group I as compared
with those belonging to group II (Kossila 1967 a, p. 78 —79). It is well known that iodine
deficiency results in an increase of the weight and the epithelial tissue content of the
thyroid. It should be emphasized that hardly any such feeds, as are known to contain con-
siderable amount of goitrogens (rutabagas, swedes, marrowstem kale), have been fed to
the cows in question. An exception to this rule was made during the winterfeeding period
1967—68, when silage, which contained marrowstem kale and beet tops in a ratio of 1:1,
was fed at a rate of approximately 20 kg/cow/day during a four month period. If this
silage has had any effect on the thyroid weight, it has affected only the animals in group
111.
Most of the thyroids of the full-grown cows in group I exhibited signs of struma hypo-
epithelialis medio- & macro]ollicularis according to the classification of Uotila (1957), whereas
most of those in group 111 examined so far could be classified correspondingly as stiuma
normoepithelialis mediofollicularis. Obviously the iodine prophylaxis, applied since 1959, has
been beneficial in preventing the development with age of colloid goiter in cows. The
fact that the oldest cows in groups II and 111 have still had rather high thyroid weights
is not surprising since these cows were already born before the feeding of supplemental
iodine was begun.
The absolute weight of the thyroid is related to the body weight of the cows. Further-
more, the weight of the gland appears to be more closely related to the corrected body
weight than to the live weight of the cows (Kossila 1967 a, p. 73—74). Results presented
in Table 1 show, however, that the mean corrected body weight of all cows has been ap-
proximately the same in groups I, 11, and 111.
There is no direct evidence so far that would indicate that the various treatments,
introduced since 1965 in order to improve the nutritional status of the cows, would have
exerted any influence on their thyroid weights. On the other hand, there is reason to
believe that at least the propylenglycol treatment has been beneficial in improving the
lectational performance of especially such cows that otherwise would have suffered from
acetonemia.
It is well known by now that the growth (Turner 1965) and secretion of milk (Turner
1963) of the mammary gland are largely controlled by endocrine factors including thyroid
function (Turner 1968). It has been noted that the capacity of milk production of the
Fig. 1. Effect of age on the thyroid weight
in cattle slaughtered during the years
1958—59 (group I), 1960—65 (group
II), and 1966—69 (group III) from the
dairy herd of the Viik Experimental Farm.
152
153
herd in question has increased markedly since 1958. According to the herd records, the
cows produced an average of 4738 kg milk and 223 kg butterfat during the control year
1958—59 and 6268 kg and 285 kg respectively during 1967—68. Judging by the above
observations and by results obtained earlier (Kossila 1967 b), a thyroid with weight and
structural characteristics close to what we consider normal ( glandula thyreoidea normoepilhe-
lialis medio/ollicularis) is obviously an indicator of higher hormonal efficiency from the
point of view of maintaining the milk secretion in cows at an optimal level than a thyroid
with weight and/or structural characteristics deviating considerably from normal ( struma
hypoepithelialis medio- & macrofollicularis or struma hyperepithelialis micro- & mediofollicidaris).
Summary
The mean thyroid weight of the growing (under 60 months old) and full-grown (over
60 months old) cows slaughtered from the Ayrshire herd of the Viik Experimental Farm
during the years 1958—59 (I), 1960—65 (II) and 1966—69 (III) was as follows: 24.46
and 43.10 g (I), 21.02 and 30.16 (II) and 18.16 and 27.01 g (III) respectively. Decrease
in the thyroid weight from (I) to (III) was believed to be due to the adding of iodine as
a component of a mineral salt mixture into the ration of the herd in 1959. The thyroid
weights of young cattle and bulls showed trends similar to those observed in cows.
REFERENCES
Kossila, V. 1967a. On the weight and basic structural components of the thyroid in dairy cattle. Acta
Agr. Fennica 109, 2 pp. 115.
—»— 1967b. Jodintarpeen tyydyttämisen merkitys lypsylehmien ravitsemuksessa. Summary: The role
of iodine in the nutrion of dairy cows. Maata), ja Koetoim. 21: 228—233.
Turner, C. W. 1963. What causes high production? Study of the role endocrine glands play in milk
secretion. Mo. Agr. Exper. State Bull. 795.
—»—- 1965. What causes high production? Story of the role of the endocrine glands in udder growth.
Ibid. 793.
—»— 1968. What causes high production? Story of the role of the thyroid glands in milk secretion. Ibid.
871.
Uotila, U. 1957. Thyreoideas histofysiologi. Nord. Med. 57: 809.
SELOSTUS
KILPIRAUHASPAINON KEHITTYMISESTÄ VIIKIN OPETUS- JA KOETILAN
LYPSYKARJASSA
Vappu Kossila
Helsinginyliopiston kotieläintieleellinen laitos
Vuosina 1958—59 (I), 1960—65 (II) ja 1966—69 (III) Viikin opetus- ja koetilan Ayrshire-karjasta
alle 60 kk;n ikäisenä eli kasvavana ja yli 60 kk:n ikäisenä eli täysikasvuisena poistettujen lehmien kilpi-
rauhasten paino oli keskimäärin (I) 24.46 ja 43.10 g, (II) 21.02 ja 30.16 g, (III) 18.16 ja 27.01 g vastaa-
vasti. Kilpirauhaspainon alentuminen I:stä III;een uskotaan johtuneen lähinnä siitä, että ko. karjalle
ryhdyttiin vuonna 1959 syöttämään jodisoitua kivennäissuolaseosta. Nuorella karjalla ja sonneilla on
todettu samansuuntaista kehitystä kilpirauhaspainossa kuin lehmilläkin. Tutkimuksessa on kiinnitetty
myös huomiota kilpirauhasen mikroskooppiseen rakenteeseen.


On the development of the thyroid weight in the dairy herd of the Viik experimental farm

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On the development of the thyroid weight in the dairy herd of the Viik experimental farm

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