STATISTICAL STUDIES, INDIAN DAIRY CATTLE
93
quickly, but that the total extent of increase in their milk yield as measured by the
difference between the 1st lactation yields and the yield for the lactation of maxi-
mum productivity is very low. Roughly our average cow does her best perform-
ance at her 3rd lactation, and maintains this yield during the 4th lactation,
whereas in no other case the maximum is reached before the 6th lactation ; further-
more whereas our cows increase to the extent of only about 10 per cent. of their
1st lactation yield till their maximum production ages the foreign cows increase by
as much as 30 to 60 per cent. the variation depending upon the data used, i.e.,
short period milk records, or lactation period milk records. All this goes on to prove
the very poor quality of our Indian cows as milkers, for a good cow is a persistent
milker not only in every lactation but throughout her life so that her average yield
per lactation for whole life be high. This fact becomes all the more striking when
it is borne in mind that the results as have been given above as representing the
behaviour of Indian cattle are for the best Indian milch cattle, cows whose lactation
yields are as high as 4,000 lbs. on the average and that much worse results would be
got with the average Indian cows.
Of course, the peculiarity about the attainment of maximum production at a
comparatively earlier age (as measured in lactations) in Indian cattle can be
explained away by the fact that Indian cows calve about a year later than foreign
ones, and the total period as covered by their 4 lactation periods is equal in length
to that of 5 lactations of foreign cows, so that the actual age of maximum produc-
tion (about 7-8 years for both) is more or less the same for both classes of animals ;
but the other peculiarity, i.e., the very low increase of yield of the lactation of
maximum production over that of the 1st lactation, seems to the author to merit
further consideration. However, it is not desired just at present to enter into the
cause of this queer phenomenon. This, therefore, is left off for the present to be
taken up in detail some other time though to check these results and to see if they
truly represented the behaviour of all the cows of our data, the records as used
above were divided into separate classes according to the number of lactations for
which a cow was maintained in these herds, and the mean variation of milk yield
was worked out separately for every class. No peculiarity however was observed
in the behaviour of these various age classes as compared with the average results
given above for all cows, except that the cows that were maintained for more than
8 lactations in these herds showed a higher increase till the age of their maximum
productivity over the 1st lactation yield although they too increased till their 4th
lactation only. This slight peculiarity, however, can be explained away by the fact
that the animals included in these higher age classes are only selected ones ; and
therefore the results already given in Table XVI seem quite correct and truly re-
presenting the underlying physiological relationships of the variations of milk yield