ULTRASONOGRAPHIC STUDIES ON PERIOVULATORY FOLLICULAR DYNAMICS AND RESPONSE TO GnRH THERAPY IN REPEAT BREEDING CATTLE WITH PROLONGED OESTRUS
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Date
2017
Authors
NIYAS, E.
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COLLEGE OF VETERINARY AND ANIMAL SCIENCES-MANNUTHY,THRISSUR
Abstract
The study was carried out with the objectives of ultrasonographic (US) assessment of follicular dynamics (FD), progesterone (P4) concentration and to determine the efficacy of GnRH administration on ovulation and fertility in repeat breeding (RB) cows with prolonged oestrus. Thirty healthy postpartum crossbred dairy cows maintained under identical conditions were selected from University Livestock Farm and Fodder Research and Development Scheme (ULF & FRDS). Ten cows with normal estrous cycle and exhibiting estrous period of less than 36 h formed the control group and twenty repeat breeding animals with history of prolonged oestrus (>36 h) was classified under Group II (n=10) and Group III (n=10). The study was conducted in two phases. In Phase-I, follicular dynamics and luteal growth and regression characteristics of all the animals were studied by transrectal ultrasonography (TRUS) for one complete oestrous cycle length. Blood samples were collected for serum progesterone estimation on day 0, 5, 10 and day of next oestrus. In Phase-II, cows exhibiting oestrus in Group I and III were inseminated when the follicle attained maximum size and re-insemination after 24 h carried out if ovulation did not occur. Cows in Group II were treated with 20 μg Buserelin acetate intramuscularly when the diameter of preovulatory follicle reached the persistent dominant size and inseminated 8 h after GnRH administration. Pregnancy was diagnosed by TRUS on day 25 after insemination and was confirmed on day 60 of pregnancy.
In the control group 70 per cent animals exhibited two waves per cycle and 30 per cent animals shown three wave cycles whereas in RB animals three pattern of follicular growth noticed, the patterns observed were three waves (50%), two waves (40%) and one wave (10%) respectively. The mean maximum diameter (mm) of preovulatory follicle for cows with 2 waves was 16.93± 0.63 and 14.78± 0.83 while it was 13.57± 0.96 and 14.92± 0.74 in 3 wave cycles in normal & RB respectively.
Duration of persistence of ovulatory follicle was found to be longer in RB animals (>24 h in 70% animals) whereas it was less than 24 h in all normally cycling animals in the control group. The luteal growth and regression pattern between the groups varied without significant difference. The mean serum progesterone value on day 5 & 10 in RB animals were lower (1.77± 0.19 ng/ml and 3.31± 0.29 ng/ml) when compared to animals with normal oestrus (2.17± 0.19 and 4.76± 0.29 ng/ml). A significant difference in the progesterone concentration on day 0 (0.36± 0.03 ng/ml in control group and 0.67± 0.03 in RB animals) was observed. Conception rate was higher in the control group (70 per cent) and it was 60 per cent in group II (GnRH treated) and 20 per cent in group III (non-treated) animals.
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