SOURCES OF VARIATION IN THE BIRTH WEIGHT OF
AYRSHIRE CALVES

Vappu Kossila and Pirkko Taskinen

Department ofAnimal Husbandry, University ofHelsinki

Received May 30, 1969

Beef producing cattle is very rare in Finland. Most of the beef in the Finnish meat
market originates from the native dairy cattle husbandry. Yet, only a few years ago, most
surplus dairy calves were disposed of at an age of a few days. Now, however, interest in
dairy-beef production has greatly increased. According to Hafez (1968, p. 239), dairy
cows give birth to larger calves than beef cows of similar weight. This phenomenon is
obviously largely due to the differences in the hormonal constitution of the two types of
cattle. Compared to the beef cow, the dairy cow is superior in milking ability and she
tends to convert the nutrients from the feeds into constituents of milk rather than into
flesh. However, it is possible that the hormonal efficiency of a dairy cow influences to a
certain degree the birth weight and viability of the calf. Presumably dairy cows that give
birth to large calves are better feed converters and milkers than those giving birth to small
calves. If this is so, the efficiency ofanimal production can be increased along these lines by
selecting dams of the former kind, since their offspring are usually not only more viable
and healthier, but also grow faster and yield more economic profits.

There are a number of factors such as the breed (ref. Nielsen 1964), season of calving
(Tyler et al. 1947), length of gestation (Mäkelä & Oittila 1955, Andersen 1962,
Mukerji & Ekka 1962), size of the dam (Knapp et al. 1940, Venoe 1948, Mäkelä 1959,
Now 1963), size of the sire (Foote et al. 1959, Nielsen 1964), number of calvings of the
dam (Venoe 1948, Braude & Walker 1949, Bennet 1959), nutritional factors, especially
during the last half of the gestation (Fitch et al. 1925), sex of the calf, and the number of
the fetuses (Roy 1955, Mäkelä 1959, Petcu & Calotoiu 1967) that are known to have
some influence on thebirth weight of the calves. It is possible, for instance, that an increase
in the length of the dry period in dairy cows increases the availability of nutrients for the
development of the fetus thus having a positive effect on the birth weight of the calf.
The number of services per gestation, an indicator of the reproductive capacity in cows,
on the other hand, may be assumed to be negatively related to the birth weight of the

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181

calf. If the growth rate of the calf in utero is parallel with the intensity of the development
of the milk secreting cells in the udder during the later part of gestation, a dam that
produces a large calf may also produce more milk as compared with one giving birth
to a small calf.

The object of the present study has been to find out whether and to what degree the
birth weight of the Ayrshire calf is related to the size of the dam, to the length of the dry
period prior to calving, to the number of services per gestation, and/or to the milk yield
of the lactation period subsequent to calving. At the same time also the effects of the
season of birth, the number of the dam’s calvings, and the sex of the calf have been
investigated.

Material and methods

According to the Finnish dairy cow testing system, a cow is considered a regular if her
calving intervals remain less than 15 months. Data comprising 56 regular, well-fed
Ayrshire cows in better than average condition and having from two to eight complete
consecutive lactation records were selected from the Viik Experimental Farm dairy herd
(Table 2). All cows had calved each time one fulltime, healthy calf. The following details
were listed for each cow: 1) date and 2) number of calving, 3) sex and 4) birth weight of
each calf, 5) live weight and 6) degree of fatness of the cow after five days ofeach calving,
7) number of services per the gestation from which the calf was born, 8) number of days
dry prior to calving (first calvers excluded), and 9) 4 % fat corrected milk (FCM) yield
during the complete lactation period subsequent to the birth of the calf in question. The
data consisting altogether of 225 calvings was grouped according to the sex of the calf,
the season of birth, and the number of dam’s calving (Tables 1 & 2). The statistical
calculations were made according to Croxton & Cowden (1955).

Results

The birth weight of the calves in this study ranged from 24 to 49 kg in males and from
23 to 46 kg in females. The live weight of the dams ranged from 378 to 680 kg, the degree
of fatness from normal to very fat, the number of services per gestation from 1 to 6 times,
the length of the dry period from 20 to 160 days and the FCM yield from 3953 to 9101 kg.

Effect of sex. As expected, the mean birth weight of all male calves (35.2 kg)
was higher compared with the corresponding value (33.4 kg) in females (Table 1), the
sex difference of 1.8 kg being significant at the level of P< 0.005.

Effect of season. Data consisting of 225 calvings was divided into four groups
according to the birth month: January-March, April-June, July-September, and October-
December (Table 1). The pasture season had begun approximately on May 20th lasting
from 100 to 120 days, but the cows calving in June were usually kept in the barn until
they had calved. Results in Table 1 show that the mean birth weight of both sexes of
calves was lowest (32.3 kg) in July-September and highest (35.5 kg) in April-June, the
difference between these two values being significant at the level P<o.ool. The mean live
weight of the dams was also lowest during July-September (Table 1).



182

When the birth weight of the calf was calculated as a percentage of the live weight of
the dam, the following results were obtained:

The birth weight of the calf as a percentage from
the live weight of the dam (N = number of cases)

Season of birth Males Females Both sexes

N % N % N %

January-March 37 6.83 31 6.70 68 6.78
April-June 33 7.13 40 6.52 73 6.80
July-September 22 7.38 32 6.40 54 6.80
October-December 31 6.08 26 6.58 57 6.80

All 123 7.05 129 6.55 252 6.80

The above results show that season had an opposite effect on the relative birth weight
of the males as compared with the females, but after both sexes were combined, the
seasonal effect was not observable. As a whole, the male calves were heavier (7.05 %)

in relation to their dam’s live weight than the female ones (6.55 %). It was also noted
that small cows produced relatively heavier calves than large cows, irrespective of age.

The cows that were bred during the first half of the year, ie. those bred to calve in
October-March, needed slightly more services per gestation than those bred during the
last half of the year (Table 1). The average length of the dry period was shortest in July-
September and longest in January-March, this seasonal trend being non-significant.
The season of calving had only a slight effect on the FGM yield, the lowest level occurring
during the lactation period following calving in April-June (Table 1).

Effect of calving number. The present material was also divided into
six groups according to the number of the calving of the dam. The birth weight of the
male calves increased from the first up to the sth calving, whereas in the females the
highest average birth weight occurred already at the 3rd calving (Table 2). In both sexes
significantly heavier calves were born from the 3rd to the sth calving as compared to the
calves born from the Ist, 2nd, and 6th or subsequent calvings.

The relative birth weight, again, tended to be higher at the first three calvings as

compared with later calvings. This can be seen from the compilation below;

The birth weight of the calf as a percentage of
the live weight of the dam (N = number of cases)

No. of calving Males Females Both sexes
N % N % N %

1. 29 7.44 27 6.69 56 7.08
2. 28 6.96 28 6.80 56 6.88
3. 21 7.07 31 6.77 52 6.89
4. 18 6.80 19 6.22 37 6.51
5. 17 7.05 10 6.26 27 6.76
6. or later 10 6.53 14 5.93 24 6.18

It shows also that the male calves at the first calving have been the heaviest in relation
to the size of their dam and the female calves at the 6th or later calvings have been the
lightest.



Table
I.
Seasonal
variations
in
birth
weights
of
the
calves
and
in

certain
characteristics
of
the
dam.

Males

Females

Both
sexes

Season

N

Xt
±

S

N

X,
±

S

N

X3±S

X,
±

S

X3±S

X,
±

S

X5±S

January—
March

34
35.7
±

4.26

28
34.7
±

4.94

62
35.2
±

4.94
519
±

49

1.8
±

0.88
56
±

23

6047
±

1292

April— June

26
36.6
±

5.24

31

34.6
±

3.97

57
35.5
±

2.11
516
±

65

1.5
±

0.28
51
±

11

5884
±

1027

July—September
21
33.9
±

4.72

30
31.2
±

4.25

51
32.3
±

4.42
476
±

45

1.5
±

0.64
50
±

1
1

5950
±llB4

October—
December
30
34.3
±

4.28

25
33.1
±

4.13

55
33.7
±

4.25
503
±

49

1.7
±

0.92
54
±

12

6019
±

1055

All

111
35.2
±

4.48
114

33.4
±

4.43
225
34.6
±

4.71

N

=

number
of

cases

5

=

standard
errorof

the
mean(if
distribution
is

regular
X
±

2
S
includes
95.45
%

of
cases)

X
;

=

meanbirth
weight
in
kg

X
s

=

»

live
weight
of
the
dam
in
kg
at
five
days
post
parlum

X3=»

number
of
services
per
gestation

X4=days
dry

on
an
average

prior
to

calving
(first
calvers
excluded)

X
5=FCM

yield
of
the

consequent
lactation
period
in
kg

Table
2.

Effect
of
the
number
of
the
dam’s
calving

on
the
birth
weight
of
the
calves
and
changes
in
the
live
weight,
fertility,
length
of
the
dry

period,

and
level
of
the

FCM
yield
with

age
in
the
dams.

Number
of

Males

Females

Both
sexes

calving
N

X3±S

N

X,
±

S

N

X,
±

S

X„±S
X3±S

X,
±

S

X5±S

1.

29
33.2
±

3.33

27
30.7
±

3.62

56
32.0
±

3.69

462
±39

1.6
±

0.98

5322
±

829

2.

28
33.7
±

4.63

28
33.5
±

4.37

56
33.6
±

4.51

488
±

41

1.5
±

0.76

57
±

10

5927
±

976

3.

18
36.1
±

3.73

27
36.1
±

3.69

45
36.1
±

3.71

525
±

68

1.6
±

0.76

54
±

23

6022
±

966

4.

16
37.4
±

4.70

16
34.1
±

4.07

32
35.8
±

4.70

540
±39

1.6
±

0.82

50
±

13

6295
±

1238

5.

12
39.2
±

4.84

9

33.6
±

5.93

21

36.5
±

6.02

547
±

49

1.8
±

1.14

49
±

13

6696
±

1232

6
or

over
8

35.4
±

5.63

7

31.7
±

4.89

15
33.6
±

5.60

555
±

39

2.0
±

0.52

47
±

17

6786
±

1513

See
footnotes
of
Table
I

183



184

The live weight as well as the level of the FCM yield of the dams has risen with
increasing numbers of the calvings (Table 2). Also, the number of services per gestation
tended to increase with age, whereas the length of the dry period prior to calving tended
to decrease correspondingly.

Statistical study. The relative importance of various factors on the birth
weight of the calves was ascertained by calculating the coefficients of simple and partial
correlations for the following variables: the birth weight in kg (X x), the live weight of the
dam in kg (X 2), the number of services per gestation (X 3), the length of the dry period
in days (X 4) (first calvers excluded), and the level of the FCM yield in kg during the
lactation period following the calving in question (X 6). The coefficients of correlations
thus obtained have been summarized in Table 3.

Coefficients of correlation in Table 3 demonstrate that, among the factors under
observation, the live weight of the dam had the greatest and the most highly significant
(P<0.001) influence on the birth weight of the calf (rl2 = 0.4081) even when other factors
were held constant (rl2 345 = 0.4022).

Number of services per gestation was hardly at all correlated with the birth weight
of the calves (rl3 = 0.0342, r l3 245 = —0.0260); the length of the dry period had a slight
positive, but non-significant effect on the birth weight (rl4 = 0.1210, rl4 235 = 0.1235),
and the FCM yield of the lactation period subsequent to calvings was hardly at all related
to the birth weight (rl5 = 0.0625, r l5 234 = 0.01 11).

Neither the number of services per gestation nor the length of the dry period were
significantly related to the live weight of the cows, whereas a fairly significant positive
correlation was obtained between the live weight of the cows and the FCM yield (r26 =

0.1734, r25 134 = 0.1474, PC0.05).
Other observable trends, even though non-significant, were the following: the length

of the dry period tended to increase with an increasing number of services per gestation
(r34 = 0.1121); the milk yield tended to be higher in cows with increasing number of
services per gestation (r 35 —O. 1250); the length of the dry period was negatively correlated
with the milk yield of the subsequent lactation (r45

= —0.1330).
The coefficients of simple correlation between the factors previously mentioned were

also calculated separately for the male and female calves:

Males Females Males Females

rla 0.4420»** 0.4162*** ra4 0.0980 0.0048
r l3 0.0125 0.0218 ras 0.2205* 0.0918
r l4 0.1109 0.0823

'

r 34 0.0996 0.1019
rl5 0.0737 0.0596 r 35 0.1250 0.0237
r23 0.1542 0.0824 r 46 —0.1061 —0.1510

The results in the above compilation indicate that the birth weights of the males as well
as the females were quite closely correlated with the live weights of the dam (rl2 = 0.4420 <J
and 0.4162 $) and that the live weights of the male-dams were more closely related to
the milk yield of the subsequent lactation (r25 = 0.2205, P<0.05) than those of the female-
dams (r 25 = 0.0918). The coefficients of simple correlation obtained separately for males
and females are similar to those obtained correspondingly for both sexes (Table 3).



185

Table 3. Coefficients of simple and partial correlations between the birth weight in kg {X!}, live weight
of the dam in kg (X 2), number of services per gestation (X 3), number of days dry prior to calving (X 4),

and level of FCM yield in kg during the subsequent lactation period (X 5).

rl2 = o.4oBl*** rl3 = 0.0342 rl4
r>2 . 3

= 0.4070*** rl3 .2 =—0.0112 r l4 . 2

rl2l
= 0.4082*** rl3. 4

= 0.0209 r l4. 3

rI2 .6 = 0.4042*** rl3 .5 = 0.0266 r l4 .6

ri2.34 = 0.4083*** rl3. 24 = 0.0248 rl4.23

ri2.35 = 0.4035*** rl3 . 26 = 0.0103 ri4.25
ri2.45 0.4017*** rl3, 46 = 0.0097 rl4. 35

ri2.345
“ 0.4022*** rl3 245 = 0.0260 rl4.235

= 0. 1210 rl6 = 0.0625 r 23 = 0.1088
1214 rl5 2 = —0.0091 r 23-1 = 0.1040
1180 rl6 3

= 0.0587 r 23

= 0.1067
1307 rl6 ,4 = 0.0797 r 23

= 0.0892
1233 rl6 23 = —0.0079 r 23

= 0.1074
1212 r l5 .24 = 0.0077 r 23

= 0.0858
1283 rl5 34 = 0.07 76 r2 3 = 0.0835
1235 r l6.234 = 0.01 11 r23 = 0.0868

= 0.
= o,
= 0.
= 0.
= o,
= o.
= 0.

r24 = 0.0252 r25 = 0.1734** r 34
r24il = —0.0265 r26-1 = 0.1623* r 34

r24
= 0.0132 r25

= 0.1620* r3 4
r2 0.0493 r25 4 = 0.1783** r34

r2 4.i3 = —0.0383 r 26
= 0.1515* r3 4

ra4.is 0.0035 r26 11
= 0.1602* r3 4

r24.35 = 0.03 82 r25
= 0.1658* r34

r24.i3s ~ 0.0148 r 26 134 = 0.1474* r34

= o. ,1121 r35 = 0.1250 r45 =—0.1330
1088 r35-1 = 0.1232 r46-1 = —0.1418
1100 r362 = 0.1084 rl6. 2 =—0.1394

.1308 r35 4 = 0.1420 r46
= —0.1491

,1121 r3 6
= 0,1084 rl6 . 12 =—0.1393

1284 r3614
= 0.1408 r45

= —0.1573
1270 r36 34 = 0.125 7 r 4 5 = —0.1532
1292 r36 121 = 0.1259 r 4S. 123 = —0.1533*

= 0.
= 0.
= 0.
= 0.
= 0.
= 0.
= o,

*** P<o.ool
�* P<o.ol

P<0.05

The equations for estimating the birth weight of the calf in kg (X 1), when the live
weight of the dam in kg (X 2) is known, were as follows:

Entire material
Both sexes (N = 225)
Males (N = 111)
Females (N = 114)

X t = 17.2 + 0.03447 X a

Xi = 19.5 + 0.03133 X 2
Xi = 12.9 + 0.04040 X 2

Material from which the first calvers have been excluded
Both sexes (N = 169) X, = 18.9 + 0.03089 X 2
Males (N = 82)
Females (N = 87)

Xi = 15.5 + 0.03919 X2
Xx = 21.0 + 0.02537 X2

According to the equation obtained from the entire material, the birth weight in both
sexes increased by 34.47 g (males 31.33 g and females 40.40 g) when the live weight of the
dam increased by 1 kg. After excluding the first calvers, the corresponding increase of
30.89 g in the birth weight obtained for both sexes was slightly lower and the extent of
increase in males (39.19 g) and females (25.37 g) was reversed, a phenomenon which can
be understood by examining the results presented in Table 2.

In addition to the above results, the birth weight of the calf was found to be more
closely correlated with the live weight of the dam at the Ist, 2nd, and 3rd calvings than
at the 4th and later calvings.

Discussion

According to Petraitis et al. (1967), female calves heavy at birth tended to be better
milk producers at an adult age than light ones. In dairy-beefproduction, the birth weight



186

of male calves is of special interest since the calves that are large at birth usually also
make the fastest gains. The birth weight (X,) in a group of 52 Ayrshire males was in a
significant (P<0.001) and positive correlation with the live weight (X 2) (rl2

= 0.5834)
and the carcass weight (X 3) (rl3 = 0.5129) attained by the age of six months. In another
similar study with 74 Ayrshire males the respective correlations were: r l2

= 0.5315 and
rl3 = 0.5468 (P<0.001) (writer’s observations). Mäkelä (1959) noted a similar correlation
(r i 2 = 0.55) in the female Ayrshires respectively.

Sex. The mean birth weight of the male calves (35.2 kg) in this study was significantly
(P<0.005) higher than that of the females (33.4 kg) (Table 1), the sex difference being
1.8 kg. Earlier in the same herd, Mäkelä (1959), noted that the mean birth weight of
299 male calves was 34.5 kg and that of 288 females 32.1 kg, the sex difference of 2.4 kg
being highly significant (P<0.001). The mean birth weight of 587 single calves was
33.3 kg in the study of Mäkelä, whereas in this study the mean value of 225 calves
was 1.3 kg higher, i.e. 34.6 kg. The proportion of calves born to the first calvers was
approximately % of all cases in both studies, but the age of the heifers at first calving has
decreased by I—21 —2 months during the last few years. This slight increase in the birth weight
of the calves in the said herd might be due to the fact that the heifers and cows have been
fed lately somewhat more intensively during few weeks prior to parturition compared to

the feeding practised several years ago. Moreover, only calves born to the regular cows
were included in the present study, whereas Mäkelä’s data included also calves born to

cows with calving intervals exeeding 15 months. In this study, the mean live weight of
the male-dams was 502 kg and that of the female-dams 507 kg. Since Mäkelä did not
mention the live weights of the cows in his data, it is not known whether the size of the
dams has been changed since 1950’5. In the present data the mean number of services
preceding the birth of a male was 1.71 and that of a female 1.54, the length of the dry
period was 55.51 and 50.08 days respectively. The mean FCM yield of the male-dams was
5958 and that of the female-dams 5993 kg during the subsequent lactation period.

Season. Season affected significantly the birth weight of the calves in this study
(Table 1), the highest mean value occurring in calves born during the first half of the
year. The mean birth weight was lowest in July-September when also the live weight of
the cows was at its lowest. The weight of the calf calculated as a percentage from the live
weight of the dam was not, however, influenced by the season of birth indicating that the
seasonal changes in the size of the calf at birth have been proportional to the changes
in the live weight of the dam.

Feeding of the cows in question has been very intensive during the stall-feeding period
(ref. Kossila 1967, p. 32—36). Even though the transition period has lasted from 1 to 2
weeks, and in addition to good quality pasture grass ad lib., the cows have received from 1
to 4 or 5 kg low protein concentrates (oats, barley) per day, according to their milk yield,
they have lost weight after being turned out to pasture. The mean live weight of the cows
in the present material was 516 kg in April-June and 40 kg less, i.e. 476 kg, in July-Sep-
tember. The milk yield of the last mentioned cows did not significantly differ from the
yield of cows that had calved during other seasons (Table 1). In the same herd, Mäkelä
(1962), noted lower peak yields during the grazing period than during the stall feeding
period. Apparently there has been an overall decrease in the productional efficiency of
cows during the summer months caused by the changes in the level of energy intake, in



187

the type of feed, in the amount of exercise, in the environmental climate, and in hormonal
functions. According to Kossila (1964), the level of protein bound iodine in the blood
serum of cows in the said herd was significantly influenced by the season, being at its
lowest during July-August and highest during the spring months.

Calving number. As far as the calving number is concerned, the results of
this study (Table 2) agree in general with some of those reported earlier (Fitch et al.
1925, Tyler et al. 1947, Venge 1948, Braude & Walker 1949, Mäkelä & Oittila 1955,
Mäkelä 1959, Nielsen 1964). The birth weight of Ayrshire calves at first calving was
31.19 kg (N = 100) in the study of Mäkelä (1959) and 32.0 kg in this study (Table 2),
and at the second calving 33.3 kg (N = 100) and 33.6 kg, respectively. Mäkelä & Oittila
(1955), reported a value of 34.16 kg (N = 49) at the fourth calving, the corresponding
value in this study being 35.8 kg. In several studies the change in the birth weights from
the Ist to the 2nd calving has been greater than the change from the 2nd to the 3rd., etc.
This was not the case with the present data, perhaps due to the limited number of cases.
Furthermore, it was noted that the birth weight, calculated as a percentage from the live
weight of the dam, tended to be higher at the first three calvings than thereafter.

Correlation studies. The live weight of the dam appeared to be the only
variable in the correlation studies which significantly affected the birth weight of the calf
(Table 3). Part of this effect was apparently due to the tendency for the birth weight to

increase with the number ofdam’s calvings, i.e. parallel with the increase in the live weight
of the dams due to age (Table 2), and partly to the parallel seasonal fluctuations in the
two variables (Table 1).

The corresponding correlations (rl2), calculated separately for the first-calvers, second
calvers, etc., were considerably closer at the Ist, 2nd, and 3rd calvings compared with
later calvings (writer’s observation). The first three calvings in the present study included
approximately 70 % ofall cases. In the study of Mäkelä & Oittila (1955), the correlation
between the birth weight of the calf and the so-called normal weight (effect of the degree
of fatness eliminated) of the dam was very low (rl2

= 0.113, N = 136). Probably the
birth weight of the calf is more closely correlated with the live weight than with this so

called normal weight of the cow, since, according to Mäkelä & Oittila, fat cows tended
to produce larger calves than lean ones.

In well fed, regular cows the length of the dry period and the number of services
required per birth of a calf cannot be expected to influence markedly the birth weight.
It might have been advisable to include also other variables, e.g. the length ofthe gestation
period, the degree of fatness of the cow at calving time, the calving interval, peak milk
yield, and/or persistency of lactation, into the correlation study. According to Mäkelä &

Oittila (1955), the length of the gestation, even though positively correlated with the
birth weight of the calf, was not influenced by the number of the dam’s calvings in the
said herd. The mean daily milk yield or 12 months’ yield would have been obviously a
more accurate indicator of the lactational ability of a cow compared to the FGM yield
of the entire lactation period used in this study, since the calving interval, even in normal
cows, may vary considerably in different individuals. Perhaps partly due to the method
used in estimating the FCM yield in this study, practically no correlation (rl2 346 = 0.01 11)
was noted between the birth weight of the calf and the milk yield of the dam (Table 3).

The negative correlation, noted between the length of the dry period and the milk



188

yield of the subsequent lactation period (r45123 = —0.1533) (Table 3), has probably been
partly due to the differences in the persistency of lactation in various individuals and
partly due to the tendency of the dry period to become shorter and the milk yield larger
with increasing calvings of the cows (Table 2).

Summary

Sources of variation in the birth weights of 225 single Ayrshire calves, born to regular
cows (calving interval less than 15 months) in the dairy herd of the Viik Experimental
Farm, were studied. The mean birth weight (35.2 kg) of 111 male calves was significantly
(P<0.005) higher than that (33.4 kg) of 114 females. The relative birth weight calculated
as a percentage from the live weight of the dam was 7.05 % in males and 6.55 % in
females, on an average.

The smallest calves were born in July-September (32.3 kg) and the heaviest in April-
June (35.5 kg), this seasonal trend being significant (P<0.001). However, the relative
birth weight of combined sexes remained constant throughout the year.

The number of the dam’s calvings affected significantly the birth weight, which was
low at the first calving (32.0 kg) and also at the 6th or subsequent calvings (33.6 kg).
Maximum birth weight of males (39.2 kg) was attained at the sth calving and that of
females (36.1 kg) at the 3rd calving. The relative birth weight was highest in the males
(7.44 %) at first calving and lowest in the females (5.93 %) at the 6th or subsequent
calvings.

The relationships between the birth weight of the calf (Xx), the live weight of the dam
(X 2), the number of services per gestation resulting in the birth of the calf (X 3), the number
of days dry prior to parturition (X 4), and the level of fat corrected milk (FCM) yield
during the lactation period subsequent to calving (X 5), were investigated by means of
calculating the coefficients ofsimple and partial correlations. The live weight of the dam was
the only variable which significantly affected the birth weight of the calf (r12 .3 45

= 0.4022,
P< 0.001, N = 225), the length of the dry period had a slight positive effect (rl4-235 =

0.1235). The correlations obtained separately for males were mostly of similar order as
those obtained for females. Regression equations demonstrating the relationship between
the birth weight of the calf and the live weight of the dam, are given.

Due to strong feeding of the cows, it is believed that the birth weights of the calves in
the dairy herd of the Viik Experimental Farm are somewhat larger if compared with
the overall values of the Ayrshire breed in Finland.

REFERENCES

Andersen, H. 1962. Sammanhaeng mellem draegtighedsperiodens laengde of kalvens fodelsevaegt. 11.
Sammanhaeng mellem moderensvaegt of kalvens fodelsevaegt. Arsberetning for Institut for
Sterilitetsforskning. 155.

Bennett, J. A. 1959. An analysis of birth, weaning and feedlot performance data on beef cattle. Anim.
Breed. Abstr. 27: 30.

Braude, R. & Walker, D. M. 1949.Mortality, weight and body measurements at birth of dairy Shorthorn
calves. J. Agric. Sci. 35: 156.



189

Croxton, F. E. & Cowden, D. J. 1955. Applied General Statistics. 2nd ed. Pitman, London, XVI +

843 pp. Chapt. 21.
Fitch, J. 8., McGillard, P. C. & Drumm, G. M. 1925. Untersuchungen iiber das Geburtsgewicht und

die Trächtigkeitsdauer von Milchvieh. Z. ftir Tier-Ziichtung & Zuchtungsbiol. IV.
Foote, W. D., Tyler, W. J. & Casida, L. E. 1959. Effect of some genetic and maternal environmental

variations on birth weight and gestation length in Holstein cattle. J. Dairy Sci. 42: 305.
Hafez, E. S. E. 1968. Reproduction in Farm Animals. 2nd ed. Philadelphia, XII + 440 pp.
Knapp, 8., Lambert, W. V. & Black, W. H. 1940. Factors influencing length of gestation and birth

weight in cattle. J. Agric. Res. 61: 277.
Kossila, V. 1964. Effects of season and stage of lactation on the protein bound iodine and total cholesterol

in serum of dairy cows. J. Sci. Agric. Soc. Finland 35; 81 —91.
—»— 1967. On the weight and basic structural components of the thyroid in dairy cattle. Acta Agral.

Fenn. 109, 2 pp. 57, 60—61.
Mukerji, S. K. & Ekka, S. T. 1962. Effect of some factors causing variation in the gestation period of

Bachaur cows in Bihar breed. Anim. Breed. Abstr. 30; 351.
Mäkelä, A. 1959. Havaintoja ja laskelmia lehmävasikoitten sekä hiehojen kasvusta Viikin koetilan kar-

jassa. J. Sci. Agric. Soc. Finland 31: 304—314.
—»— 1962. The lactation curve of the cow at the ascending phase. Ibid. 34: 173—186.
—»— & Oittila, R. 1955. Tiineysajan pituus Viikin opetus- ja koetilan Ayrshire-karjassa. Ibid. 27:

77—84.
Nielsen, E. 1964. Nogle factorer som har indflydelse pä kalvenes fodelsevaegt. Landbohojskol. beretn.

338: 12—31.
Novy, I. 1963. Study of the relations between the milk yield, the live weight of cows and the birth weight

of calves at the Slovak Spotted cattle. Acta Universitalis Agric., Nitra, Facultas Agronomica VII:
137—147.

Petcu, D. & Calotoiu, A. 1967. Twin calvings in dairy cattle. Lucr. stiint. Inst. Cere. Zooteh. 25:
363—371.

Petraitis, I. P., Zhal’nieryus, V. A. et al. 1967. The relation between the vitality of cows and their
birth weight. Vest, sel.-khoz. Nauki, Mosk. 12: 6: 66—68 (ref. D.S.A. 29 ab. 3351, 1967).

Roy, J. H. B. 1955. The calf. Its management, feeding and health. London. 79 pp.
Tyler, W. J., Chapman, A. B. & Dickerson, G. E. 1947. Sources of variation in the birth weight of

Holstein Friesian calves. J. Dairy Sci. 30: 483.
Venge, O. 1948. Forskellige faktorers invirkning pä fodelsvaegten of kalve. Nord. Jordbr. Forskn. 208.

SELOSTUS

AYRSHIRE-VASIKOIDEN SYNTYMÄPAINON VAIHTELUIHIN
VAIKUTTAVISTA TEKIJÖISTÄ

Vappu Kossila ja Pirkko Taskinen

Helsingin yliopiston kotieläintieteen laitos

Syntymäpainon vaihteluihin vaikuttavia tekijöitä tutkittiin 56:n 2—B kertaa perättäin säännöllisesti
poikineen lehmän 225 yksinään syntynyttä, täysiaikaista, tervettä vasikkaa käsittävästä aineistosta, joka
oli kerätty Viikin opetus- ja koetilan karjasta. 225;n vasikan syntymäpäino oli keskim. 34.6 kg, 111 tn

sonnivasikan keskim. 35.2 kg ja 114:n lehmävasikan keskim. 33.5 kg. Sukupuolien välinen painoero oli
merkittävä (P<0.005).

Eri vuodenaikoina syntyneillä vasikoilla havaittiin painoeroja; pienin keskim. syntymäpaino (32.3 kg)
oli heinä-syyskuussa syntyneillä (2 -)- (J) ja korkein (35.5 kg) vastaavasti maalis-kesäkuussa syntyneillä
(2 -)- (J) ko. keskiarvojen eron ollessa erittäin merkittävän (P < 0.001).



190

Emän poikimakertojen lukumäärä vaikutti vasikan syntymäpainoon merkittävästi. Ensikoilla (32.0 kg)
ja yli 5 kertaa (33.6 kg) poikineilla tavattiin pienimmät ja 3—5 kertaa poikineilla((35.36.48 —36.4 kg) suu-
rimmat syntymäpainot (£ + $). Sonnivasikoiden syntymäpainon todettiin kohoavan l.:stä (33.2 kg)
s.:teen (39.2 kg) ja lehmävasikoiden l.:stä (30.7 kg) 3.:teen (36.1 kg) poikimiseen.

Sonnivasikoiden emät painoivat 5. päivänä poikimisen jälkeen keskim. 502 kg ja lehmävasikoiden
507 kg. Vasikoiden syntymäpaino prosentteina emän elopainosta (= suhteellinen syntymäpaino) oli sonni-
vasikoilla keskim. 7.05 % ja lehmävasikoilla 6.55 %. Vuodenaika ei vaikuttanut lainkaan vasikan (<J + $)

suhteelliseen syntymäpainoon, mistä päätellen emien elopainon vuodenaikavaihtelut olivat olleet yhden-
suuntaisia vasikoiden syntymäpainovaihteluiden kanssa. Vasikan suhteellinen paino oli kolmena ensim-
mäisenä poikimakertana korkeampi verrattuna myöhempiin poikimisiin.

Aineistosta laskettiin tilastollisesti seuraavien tekijöiden väliset vuorosuhdekertoimet;vasikan syntymä-
paino (X,), emän elopaino 5. poikimisen jälkeisenä päivänä (Xt ), astutuskertojen lukumäärä sitä tiineyttä
kohden, josta ko. vasikka oli syntynyt (X 3), ummessaoloajan pituus ennen ko. vasikan syntymää (X 4) ja
poikimista seuranneen koko laktaatiokauden 4-prosenttiseksi muunnettu maitotuotos (X 5). Ko. tekijöistä
ainoastaan emän elopainolla oli merkittävä (P<0.001) vaikutus vasikan syntymäpainoon (r 12.345 =

0.4022). Astutuskertojen lukumäärällä oli varsin vähäinen vaikutus (r 13 . 245 = —0.0260). Ummessaoloajan
pidentyessä vasikan syntymäpaino pyrki kohoamaan (r 14.235 = 0.1235) joskaan ei merkittävästi. Vasikan
syntymäpainon ja syntymää seuranneen laktaatiokauden 4-prosenttisen maitotuotoksen välillä ei havaittu
juuri mitään vuorosuhdetta (rl6 234 = 0.01 1 1). Sonni-ja lehmävasikoille erikseen lasketuissa vuorosuhteissa
ei ilmennyt mainittavia eroja verrattuna koko aineistosta saatuihin vastaaviin vuorosuhdekertoimiin.

Tutkimuksessa on esitetty useita vasikan painon riippuvuutta emän painosta kuvaavia regressioyhtä-
löltä, joista koko aineistolle (N = 225) saatu oli seuraava:

X, = 17.2 + 0.03447 X 2
(X, = vasikan syntymäpaino, kg; X 2 = emän elopaino, kg). Yhtälön mukaan vasikan syntymäpaino
on kohonnut koko aineistossa keskim. 34.47 g emän elopainon kohotessa 1 kg:lla.