P. V.
SUKHATME
171
TABLE IX
Common year lactation comparison
48M
49M
Foundation stock . .
First progeny . .
t
Foundation stock . .
First progeny . .
t
Average . . .
Standard error .
Average . .
Standard error .
Average . . .
Standard error .
. Average . . .
Standard error . .
No. of
lactations
15
33
12
12
Total
milk
yield
oz.
5178.7
721.0
6627.8
378.1
2.0
4450.7
596.0
4670.7
530.1
0.3
Average milk
yield per day
of lactation
oz.
34.6
2.4
36.5
2.2
1.0
30.9
7.4
32.1
5.3
0.5
Average milk
yield per day
of kidding
interval
oz.
18.2
3.0
20.9
1.5
0.9
19.0
3.0
18.3
1.8
0.2
earlier lactations of the first progeny and the later
ones of their dams. The results of these compari-
sons are shown in Table IX, for bucks 48M and
49M. Buck 50M does not provide sufficient
material for such a comparison. It will be seen
that the first progeny of sire 48M gives a signifi-
cantly larger total milk yield per lactation. When,
however, the total milk yield is corrected for the
length of lactation and the kidding interval, the
difference disappears. The progeny of sire 49M
does not show a significant difference in any of
these characters. Table IX-A shows the results of
the separation of the common year lactation com-
parison for the progeny of buck 48M into summer
and winter kiddings. It will be seen from the table
TABLE IX-A
Separation of the common year lactation comparison
for the progeny of buck 48M into summer
and winter seasons
Summer
Foundation stock .
First progeny .
t
Winter
Foundation stock .
First progeny .
t
Average
Average
Average
Average
No.
of
lacta-
tions
8
11
7
22
Total
milk
yield
oz.
3952.0
5004.8
1.14
6580.8
7440.0
0.93
Average
milk
yield
per day
of lac-
tation
oz.
32.8
34.9
36.0
37.3
Length
of
lacta-
tion
days
120.4
143.4
183.0
199.9
that there is no significant difference between the
performance of the first progeny and of their
mothers within a season, but all the three charac-
ters give a significantly higher value for the winter
than for the summer lactation. As the differences
are very large, the values of t have not been given.
The preponderance of winter lactations in the
common period in the first progeny observed in
Table VIII thus at once partly explains their
superiority over the foundation mothers. We
may, therefore, conclude that while breeding may
have had an effect, the better performance of the
first progeny might also to an extent be due to
better feeding and management at the farm, to
differences in the years in which the majority of
the lactations of the foundation stock and the first
progeny were completed and to the preponderance
of winter kiddings in the first progeny.
While bucks No. 48M and 49M are by themselves
not proved it is of some interest to compare their
relative worths as transmitters of milk yield.
This is done in the last row of Table VII giving the
values of t for the comparison of the transmitting
abilities of the two bucks, transmitting ability
being measured by the difference in the perfor-
mances of the progeny and their mothers. It
will be seen that these comparisons are free from
consideration of the order of lactation or seasonal
effects. The table shows that none of the three
values of t is significant, though the value of t for
total milk yield is high and approaching the 5
per cent level of significance. While, therefore,
there is a slight suggestion that buck 48M is pro-
bably superior to 49M, there is no adequate
evidence to establish his superior worth.