March, 1954] S. S. PRABHU AND P. BHATTACHARYA 39
was taken to see that the other teaser cow was not on heat during the experiment.
The six bulls were divided at random into two lots of three bulls each. Collections
were taken on alternate days for a period of two weeks. At each collection two
ejaculates were taken and these were analysed separately. Reaction times for the
different ejacualtes were recorded separately. Bulls in the first lot were shown
the on-heat teaser cow to begin with, while the bulls in the second lot were shown
the non-heat teaser cow. The treatments were interchanged at subsequent collec-
tions following the 'switch-back' design of experimentation. At the end of two
weeks, the bulls were rested for a week and second set of observations were taken
for a further period of two weeks, following the same procedure as detailed for the
first two weeks. In this way a complete replication of the entire experimental
series was provided.
Experimental series II. The procedure adopted was identical with that followed
in the first experimental series, except that instead of making collections on alternate
days, once a week collections were made. The experiment was run for six weeks.
There was no replication of the experimental series.
Experimental series III. The general procedure followed was the same as for
the first two experimental series. Instead of six, twelve bulls were used, and instead
of two, four ejaculates in rapid succession were taken per collection. The first two
ejaculates were taken with one type of teaser cow, say one 'on heat', while for the
subsequent two ejaculates the 'non-heat' teaser cow was used. The treatment
was interchanged at subsequent collections. Thus, a bull which had its first two
ejaculates taken on 'on heat' teaser cow for a given collection, had 'non-heat'
cow for getting the first two ejaculates in a subsequent collection and so on. The
collections were taken once a week and the experimental series was run for a period
of eight weeks. There was no replication of the experimental series.
Details of observations made
In each ejaculate, reaction time and the semen characteristic detailed under
each experimental series were studied.
Experimental series I. (i) Volume (ii) Initial motility (iii) Sperm concentration
(iv) Percentage of abnormal sperm (v) Total Sperm in the ejaculate (vi) Initial pH.
(vii) Percentage of dead sperm (opal-blue-eosin method) (viii) Percentage of non-
motile sperm (ix) Percentage of weakly motile sperm (x) Percentage of progressively
motile sperm (xi) Percentage of total motile sperm.
Experimental series II. Items (i) to (vii) and (xi) as detailed under the first
experimental series. In addition, total number of live-sperm in an ejaculate was
studied.
Experimental series III. Items (i) to (iii), (v) and (vi) as detailed in the first
experimental series.
The number of items of semen characteristics studied in the first experimental
series were cut out in subsequent experimental series, in the light of the progressive
results got from the experiments. Minimum items consistent with the efficient
study of the problem under scrutiny were retained in the last experimental series,
so that the time thus saved could be profitably utilised in studying a larger number
of bulls.