78
Four Times Milking in Cows of Tharparkar Breed
The cows named in column 2 of Table II were milked four times throughout, i.e., in their pre-
experimental first lactations and experimental second, third and fourth lactations. It will be noted
that bigger yields are recorded in the case of all these animals, except 'Machkani', who aborted
at her second calving and that the increase ranges up to 82.23 per cent. It will be seen that there
is an increase in each lactation averaging 19.54 lb. in first, 21.24 lb. in second, 25.29 lb. in third and
27.14 lb. in fourth lactations. Cows named in column 1, were milked four times in the pre-experi-
mental first lactations and two times in their experimental second, third and fourth lactations. It
will be noted that in the second lactation there was a distinct decrease in the case of each cow vary-
ing from 5.01 to 19.57 per cent and that the range of decrease increased with subsequent lactations.
The average percentage decrease of six cows in each lactation over their first lactation being 12.16
in the second, 12.52 in the third and 14.24 in the fourth lactations. Here, the difference between
the average values of columns 5A, 7A and 9A and of columns 6A, 8A and 10A represents the average
percentage decrease due alone to decreasing the frequency of milking from four to two times. The
increases from first to fourth lactations recorded in the case of four times milking represent the aver-
age expected behaviour of normal lactating cows. The decrease shown by the cows under two times
milking represents behaviour which is at variance with what is considered normality.
As before, the difference between the average yields of the 'four-time milkers' and 'two-
time milkers' was estimated from columns 6, 8 and 10 and columns 5, 7 and 9 respectively.
Finally, in Table III are given the means with their standard errors and co-efficients of varia-
tion for (a) total milk yield per lactation, (b) average milk yield per day for wet period, (c) average
over all milk yield per day, (d) length of wet period, (e) length of dry period and (f) length of service
period for all the cows under two times and four times milking separately.
MILK YIELD AND LIVE-WEIGHT GRAPHS
Graph I shows the average milk yields of eleven 4-week periods of cows under two and four
times milking in six consecutive lactations. Curve A represents the average first lactation yield
of 11 cows under four times milking and Curve B represents the average first lactation yield
of seven cows under two times milking. Of the 11 cows in Curve A, five went under four times
milking and six under two times milking in the subsequent lactations and of the seven cows in Curve
B, four were under two times milking and three under four times milking. The first lactations in
both cases covered the pre-experimental period. They are both normal in type for first lactations,
with the only difference, that the yields under the four times milking are on a higher level than under
two times milking. A definite flush period is usually not well developed in the first lactation under
either four times or two times milking. It has been our experience, working with two Indian breeds,
that even in the case of good milkers there is a tendency to flatness throughout the length of the
first lactation curve as compared with subsequent lactations. The daily yield at the end of the first
lactation of good milkers is about half that given at the time of maximum production during the
lactation.
The difference in the effects of the two systems of milking is clear from the form of the curves
obtained when the subsequent yields are graphed. Four times milking shows a definite and steady
upward trend with each succeeding lactation. It is the development of the flush period under the
four times milking which contributes to the increases in the yields, though each lactation finishes
at about the same level as the first lactation. Under the two times milking, on the other hand, no
development of the flush period takes place. Although yields in the early part of the subsequent
lactations are somewhat higher than those of the first lactation, the drop in yield in the course of
the lactation is sudden, and this rapid downward trend results in daily yields below those of the
first lactation and a lower final total lactation yield. There is also a tendency to a shortening of
the lactation period. Regardless as to whether the cows were milked four times or two times in the
first lactation, there was a definite fall under two times milking in the subsequent lactations and
similarly there was an increase in each subsequent lactation under four times milking.