EVALUATION OF FERTILITY IN POSTPARTUM DAIRY COWS BY INDUCING OVULATION USING HCG IN PROGESTERONE-BASED OESTRUS SYNCHRONISATION
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Date
2019-08-20
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COLLEGE OF VETERINARY AND ANIMAL SCIENCES, POOKODE WAYANAD
Abstract
The study was conducted to evaluate and compare the efficacy of 3000 IU of hCG
for induction of ovulation in five day and seven day CIDR-based oestrus synchronisation
protocols in postpartum crossbred dairy cows. Twenty-four apparently healthy, cyclic
cows, which had completely involuted uterus were selected and randomly allotted into two
treatment and one control groups (n=8 each). On day 40 postpartum, animals of Group I
(5 day CIDR group) were inserted with CIDR followed by administration of GnRH on the
same day. The CIDR insert was removed on day 5 and PGF2α was administered. After 36
h of CIDR removal, 3000 IU of hCG was given followed by TAI at 50 - 56 h after CIDR
removal. In Group II (7 day CIDR group), similar protocol was followed as in group I,
with the difference that CIDR was kept for 7 days. Animals in Group III (Control) were
observed for occurrence of natural postpartum oestrus from day 40 to 90 postpartum and
inseminated at detected oestrus. CIDR based oestrus synchronisation resulted in 100 per
cent oestrus response in postpartum animals whereas only 37.5 per cent oestrus response
was observed in control animals. Higher per cent of animals exhibited high intensity
oestrus in both 5 day (75 per cent) and 7 day (62.5 per cent) CIDR protocols with 3000 IU
hCG whereas oestrus signs of high intensity could not be observed in the natural
postpartum oestrus. There was no significant difference in the mean time taken (h) for the
onset of oestrus after removal of CIDR between two synchronisation protocols but the
mean duration of oestrus (h) observed in treatment animals were significantly (p<0.01)
higher than that observed in control animals. Pregnancy diagnosis was carried out by
transrectal ultrasonography on day 25 post AI and later confirmed by rectal examination
on day 60. The first service and overall conception rate after three consecutive AI were
higher in 5 day CIDR group than in 7 day CIDR and control group. Days open was also
higher in animals treated with 5 day CIDR treatment. There was no significant difference
in serum progesterone concentration between the groups on the day of CIDR insertion or
on day 40 postpartum, at the time of hCG injection, at the time of AI and at day 10 post
AI. However, the serum progesterone concentration on the day of CIDR removal was
significantly higher (p ≤ 0.05) in animals of 5 day than that of 7 day CIDR groups. Higher
conception rate was found in the animals having serum progesterone concentration above
1 ng/mL at the time of CIDR insertion or on day 40 postpartum, below 0.5 ng/mL at the
time of AI and above 4 ng/mL on day 10 post AI in all the groups.
The present study can be concluded that interms of first service and highest overall
conception rate, the five day CIDR-based protocol was superior to seven day CIDR-based
protocol when 3000 IU of hCG was used to induce ovulation in oestrus synchronisation
protocols. But both protocols gave better oestrus response with more high intensity of
oestrus resulting in improved conception rates compared to control group