Recent developments in animal breeding programmes
K.L. Macmillan, W.W. Thatcher and M. Drost
MAFTech, Ruakura Agricultural Centre, Hamilton; Dairy Science
Department, IFAS, University of Florida, Gainesville, Florida, USA and
Department of Reproduction, Collage of Veterinary Medicine, University
of Florida, Gainesville, Florida, USA
Proceedings of the New Zealand Society of Animal Production.
1989, 49: 91-96
A single intramuscular injection of 10g of Buserelin (Bus), a
potent analogue of gonadotrophin releasing hormone (GnRH) was
administered to non-lactating Holstein cows (Experiment 1) or Brangus
cross animals (Experiment 2) on cycle day 12 (oestrus + cycle day 0).
This treatment altered normal patterns of ovarian follicle development,
causing atresia or premature luteinisation especially in follicles of 6
to 9 mm diameter. Injecting 8 or 10g Bus every third day from cycle day
12 to cycle day 48 (Experiment 3), extended the average inter-oestrous
interval to 56.2 days, maintained diaoestrous concentrations of plasma
progesterone (5 to 12 ng/ml), and increased corpus luteum lifespan to at
least 49 days in 5 of 6 Holstein cows. This 3 day interval was also
used with 18 cows and heifers which were embryo recipients when they had
been in oestrus from 2.5 to 7.5 days before their contemporary embryo
donors (Experiment 4). The average pregnancy rate following these
asynchronous transfers was 38.9%, varying from 20% when morulas were
transferred to 62.5% with blastocysts. Inserting a CIDR-B into heifers
12h after the onset of oestrus for 3 to 15 days produced alterations in
inter-oestrus intervals which indicated that progesterone treatment
during metoestrus could potentiate the capacity of the uterus to
synthesise and release prostaglandin F2a (Experiment5).
The results from these five experiments showed that manipulating ovarian
follicle development with Bus, or altering normal follicle-uterine
interactions could be utilised as forms of oestrous cycle control which
may be applied after insemination or embryo transfer.
Keywords: NZSAPAB;
Gonadotrophin releasing hormone; Buserelin; follicle
development; corpus luteum; embryo transfers; CIDR; progesterone;
metoestrus
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Last Updated 18-03-1997
