144
Candling Appearance of Eggs and their Thick White Percentage
TABLE I
Test of significance
Breed
White Leghorn
Rhode Island
Red
Desi . .
All breeds .
Candl-
ing
grade
{ I
II
{ I
II
{ I
II
{ I
II
Size of
sample
364
178
453
123
474
276
1,291
577
Mean
percentage
thick white
and its
standard
error
51±0.405
52±0.567
48±0.392
47±0.742
50±0.346
53±0.534
49±0.223
51±0.365
S. E.of
differ-
ence of
means
}0.697
}0.840
}0.637
}0.429
Differ-
ence of
means
S. E. of
differ-
ence
1.43
1.19
4.71*
4.66*
*Highly significant
TABLE II
Percentage distribution of poor, average and high
quality eggs in the two grades of eggs of different
breeds
Breed
White Leghorn
.
Rhode Island Red .
Desi . . .
All breeds . .
Candling
grade
{ I
II
{ I
II
{ I
II
{ I
II
Poor (less
than 40
per cent
thick
white)
5.0
3.9
16.1
22.0
8.4
4.0
10.1
7.8
Average
(45-55
per cent
thick
white)
57.1
53.4
42.8
49.6
56.3
43.8
51.8
48.0
High
(over 60
per cent
thick
white)
11.7
14.6
6.4
4.1
6.5
18.8
7.7
14.4
It will also be seen that, in all breeds other than the
Rhodes, the proportion of poor quality eggs was
higher in grade I than in grade II, and that of the
high quality eggs was greater in grade II than
grade I. With Rhode Island Reds, the reverse
was noted in both cases. The mean percentage
thick white of eggs (Table I) was about the same in
all the breeds as well as between the two grades
in each one of the individual breeds. The figures
for the Rhodes were slightly lower than those of
the other two breeds. Even in this factor, the grade
II eggs had the higher figure, except in the case of
the Rhode Island Reds.
DISCUSSION
In spite of the fact that the mean percentage
thick white of the eggs of the Rhodes was some-
what lower than those of the other two breeds, a
much larger proportion of the eggs of this breed
was classed as grade I in candling. Since all birds
of the different breeds were fed the same ration,
candling appearance could not have been materially
affected by yolk colour. The brown shell of the
egg of the Rhode Island Reds gives a reddish
colour in candling which causes some difficulty
in properly assessing the intensity of the yolk
shadow. The latter is a factor of considerable
importance in deciding the candling grade. Though
allowance for this factor was made while candling,
it seems to have influenced the grading to some
extent as shown by the higher percentage of eggs
of this breed classed as grade I. Hence shell
colour appears to interfere with candling appear
ance.
The grading of eggs by candling was carried out
with the object of grouping the better class of
eggs in grade I and the poorer in grade II. If
candling appearance were a true index of percent-
age thick white, the proportion of the better class
of eggs in grade I, i.e. having a thick albumen
percentage greater than 60, should be high, and
that of the poorer ones, with less than 40 per cent
thick white, very low. Similarly in grade
II, the great majority of the eggs should belong to
the latter category and hardly any to the former
class. From the experimental results of the com-
bined breeds as well as those of the Leghorns and
desis, however, it will be seen that the proportion
of the poorer quality eggs in grade II was not only
very low but also considerably less than in grade 1.
Also, the percentage of eggs of the higher quality
was decidedly more in grade II than in grade I.
Further, it was found that grade II contained a
higher proportion of better quality eggs than of low
quality ones. It would, therefore, seem that the
grading of day-old eggs by candling was not
very successful in accurately sorting them out
according to their percentage thick white.
Among the Rhodes, however, the proportion of
the poorer quality eggs in grade II was higher than
that of the other breeds in the same grade. But
in this same breed the percentage of eggs having
less than 40 per cent thick white, in grade I, was
nearly twice that found among the desis, and
over three times that in the Leghorns in the same
grade. Further, the percentage of the higher
quality eggs among Rhodes, in grade I, was the
lowest among the different breeds investigated.
It was also found that the actual average interior
quality of the eggs of the Rhode Island Reds was
the lowest of the three breeds studied. The
relationship of candling appearance to thick white
percentage in eggs of this breed, therefore, does not
seem to be any better than in the others.
The statistical analysis of the results, given in
Table I, aslo confirms this view. The data show