Manipulating Patterns of Ovarian Follicle Development in Cattle
with Progesterone and Gonadotrophin Releasing Hormone to Produce
Oestrous Cycles with Two or Three Follicle Waves
B.A. Clark, F.M. Rhodes, C.R. Burke, S.R. Morgan and K.L. MacMillan
A: Dairying Research Corporation, Private Bag 3123, Hamilton.
Proceedings of the New Zealand Society of Animal Production. 1998,
58: 85-87
This study tested the hypothesis that oestrous cycles with two
follicle waves created using progesterone, could be converted to
oestrous cycles with three follicle waves using gonadotrophin releasing
hormone (GnRH). Oestrus (Day 0) was synchronised in 24 Friesian cows. On
Day 2, a progesterone containing device (CIDR) was inserted into the
vagina of 16 cows for 10 days. Eight of these animals received 8µg of
buserelin (GnRH) at device removal. Eight untreated animals formed the
Control group. Daily transrectal ultrasonography showed that the
oestrous cycles of the cows treated only with a CIDR device had two
ovarian follicle waves compared to 1/8 in CIDR+GnRH and 3/8 in Control
groups (p<0.01). The average length of the oestrous cycle was shorter
in the CIDR-only group (19.3 ± 0.5 days), compared to the CIDR+GnRH
(20.9 ± 0.2 days) and Control (22.3 ± 1.1 days) groups (p<0.05). These
results demonstrate that strategic administration of GnRH can convert
progesterone induced two-wave oestrous cycles into a three-wave pattern.
Keywords: NZSAPAB;
cattle; progesterone; gonadotrophin releasing hormone;
oestrous cycle; ovarian follicle.
Last Updated 12-09-1998
