FERTILITY MANAGEMENT IN CROSSBRED CATTLE DURING HEAT STRESS BY FORTIFYING LUTEAL FUNCTION
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Date
2016
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COLLEGE OF VETERINARY AND ANIMAL SCIENCE-MANNUTHY,THRISSUR
Abstract
A study was conducted among crossbred cattle with the objective to assess
the effect of heat stress on fertility and also to evaluate the effect of fortifying luteal
function by using hCG, on fertility.
Apparently healthy cycling crossbred cows detected in oestrus were utilized
for the study. The experiment was carried out at ULF & FRDS, Mannuthy in two
phases viz. period of the year with average low THI (November- January) and period
of the year with average high THI (March –May). In each phase animals were
divided randomly in to treatment and control groups of 10 animals each. Cervical
mucus was collected during oestrus for study of rheological properties and BCMPT;
artificial Insemination (AI) was done in all the animals and those in treatment groups
were administered 1500 IU hCG on day 6 post AI. Blood samples were collected on
day 6, 12 and 24 post-AI for progesterone assay and pregnancy was confirmed by
rectal examination on day 45 post AI in non-returned animals.
The average THI of the station was calculated as per LPHSI (1990) formula
using meteorological data from CAADECCS, Mannuthy. Average values during low
and high THI phase were 79 and 83.5 respectively. Mean duration of standing oestrus
in low THI period and high THI period did not differ significantly (24.67 ± 0.98 vs
24.70 ± 1.17 h). Contrary to the previous reports, intensity and duration of oestrus
was not affected by heat stress. Transparency of oestrual mucus was not affected by
heat stress Mean spinbarkeit value during heat stress was significantly higher, which
was contrary to previous reports. Mean spinbarkeit value was significantly higher
among conceived than non-conceived animals. Majority of animals had typical fern
pattern in both the phases and heat stress did not seem to influence the fern pattern.
Per cent of animals exhibiting typical fern pattern was more among conceived
animals than non-conceived animals. Cervical mucus penetration distance was not
affected by heat stress, but it was significantly higher among conceived animals than
non-conceived. Though there was no significant difference between phases regarding progesterone level on 6th and 12th day post AI, concentration on 12th day during
comfortable period was higher than that recorded during heat stress. Administration
of hCG had no significant effect on subsequent luteal function Mean serum
progesterone level in both the phases was significantly higher in conceived animals compared to non-conceived animals on 6th , 12th and 24th day post The pregnant
animals in both phases had mean serum progesterone levels of >2ng/ml on day 24.
The conception rate was better in low THI phase than during high THI phase (37.7 vs
25 per cent). Conception rate was higher in treatment group than control (40 vs 25 per
cent).
Even though hCG administration did not significantly increase progesterone
level in treated animals, better conception was recorded among treated animals.
Also, better conception was recorded during low THI phase (comfortable period).
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