230 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ IV, III

by what figures a given yield should be multiplied in order to reduce it to a yield
for 300 days. An example is given at the foot of the table which explains how the
Table may be made use of in practice.

                                                      SUMMARY.

How yields may be predicted from known portions of the lactation are dealt
with. A complete lactation from an incomplete one may be predicted either by
computing the area under the curve or by arithmetical calculation by multiplying
the yield at maximum successively by the rate of decline, and summing up the
products. This requires a knowledge of the rate of decline, and the average value
obtained for the decline in parts I and II may be utilised. A ready reckoner table
(Table II) is given by means of which complete lactation may be obtained by multi-
plying the monthly yield at any stage of the lactation by an appropriate ratio given
in the table.

The peak of lactation is generally reached between the 3rd and 6th week after
calving, and if the yield for these four weeks is known, the yield for a lactation of

Military Dairy Farms, Northern Circle, for the year 1932-33, Table 13, page 21, shows the lactation
yields as under :—

Breed

Av. milk yield
in lb.

Average number
of days in milk

Ferozepore Pedigree . . . . . . . .

7,912

330

¾ Foreign . . . . . . . . . . . .

6,885

335

⅝ „ . . . . . . . . . . . .

6,851

310

In order to see how these herds compare it is necessary to know how much they yield during the
The figures in the table show how lactation yield of any length from 200 to 400 days may
be converted into yields for identical periods, namely, 300 days. For conversion that figure should be
employed which is below the rate of decline appropriate to the breed to which the herd belongs. Thus
for the Pedigree Sahiwal it has been found that the rate of decline is nearly 8 per cent., and the correc-
tion factor is obtained from the column headed 8.0. Similarly for the cross-bred the correction is ob-
tained from the column headed 10.0. The yields for 300 days will be:—

Ferozepore Pedigree . . 7,912 × .8,632 or 6,830 lb.

¾ Foreign . . . . 6,885 × .9,400 or 6,472 lb.

⅝ „ . . . . 6,851 × .9,813 or 6,723 lb.

(N.B.—In the case of ¾ foreign where the number of days is 335 the average of the figures against
330 and 340 is taken.)

When the yields are thus expressed the order of merit of the herds can be readily appreciated.