MVSc

With the object of evaluating the e f f i.ca cy of
gonadotrophin releasing hormone (GnRH) and prostaglandin F2
alpha (PGF2 alpha) for induction of early postpartum oestrus
and reduction of calving to conception interval, 30 crossbreds
cows which had normal parturition, selected from Livestock
Research Station, Thiruvazhamkunnu were allotted to three
different treatment groups. Ten cows each in gro~p I, II and
I I I were administered intramuscularly 5 ml Receptal, 5 ml
Dinofertin and 5 ml Saline respectively on 14th day of
calving. The time taken for regression of pregnancy corpus
luteum averaged 14.5 ± 0.37, 14.9 ± 0.45 and 15.3 ± 0.87 days
respectively in the three groups. Uterine involution was
complete in 25.3 ± 0.47, 25.0 ± 0.77 and 34.6 ± 1.79 days
respectively. Analysis of data revealed significant variation
in the uterine involution between experimental and control
groups. The interval from treatment to onset of oestrus was
18.1 ± 1.69, 19.5 ± 1.93 and ~0.7 ± 3.37 days respectively for
the three groups and the interval from calving to first
exhibited oestrus was 32.1 ± 1.69, 33.5 ± 1.93 and 46.11 ±
3.19 days respectively. Statistical analysis revealed
significant variation in the interval from calving to first
oestrus and treatment to onset of oestrus between treatment
and control groups. Percentage of cows that evinced oestrus

within 45 d of calving were lOO, 90 and 50 respectively in the
three groups. This variation between treatment and control
groups was statistically significant. A higher proportion of
cows from group I and 11 showed medium to high intensity of
oestrum when compared to control. The ovulation rate in cows
that exhibited oestrus upto 45 d of calving wa$ 90, 77.77 and
60 per cent respectively in group I, 11 and Ill. There was
significantly higher progesterone level in the ovulated cows
of the treatment groups than that of control. The interval
from calving to first insemination in group I, 11 and III
were 56 ± 1.99, 52 ± 1.24 and 65.77 ± 2.90 days respectively
and the interval from calving to coneption were 69.77 ± 3.70,
75.87 ± 5.62 and 95.0 ± 6.04 days respectiyely. The
variations in service period and calving to conception
interval between treatment and control .groups was
statistically significant. The first insemination conception
and overall conception rate with three or more A.I. were 30
and 90 per cent for group I, 20 and 70 per cent for group 11
and 11.1 and 55.5 per cent for group Ill. The A.I. index was
1.7, 2.25 and 2.8 for the three groups respectively.
Eventhough, there was no significant difference in the first
insemination conception and A. I. index between the three
groups, there was apparently better conception rate in the
treatment groups with reduction in A.I. index. However, no
'.
significant variation in any of the reproductive parameters
between the two treatment groups was noticed. The accuracy of



prediction of pregnancy by progesterone assay on day 20 was
only 70 per cent as against 100 per cent for non-pregnant
animals. The accuracy of pregnancy diagnosis by this method
can be improved by a second assay on day 30, which will cover
loss of pregnancy due to early embryonic death.
It is concluded that GnRH er PGF2 alpha administered on
the fourteenth day of calving will help early induction of
oestrum and conception and is therefore cost-effective.