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Treating cattle with progesterone as well as a GnRH analogue affects oestrous cycle length and fertility

Initiating the chronic administration of progesterone to cattle during metoestrus will produce shortened oestrous cycles containing one or two wave-like sequences of ovarian follicle development. Conception rates are reduced to inseminations at the oestrus preceding these shortened cycles. In contra...

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Bibliographic Details
Published in:Animal reproduction science 1999-08, Vol.56 (3), p.189-200
Main Authors: Lynch, P.R, Macmillan, K.L, Taufa, V.K
Format: Article
Language:English
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Summary:Initiating the chronic administration of progesterone to cattle during metoestrus will produce shortened oestrous cycles containing one or two wave-like sequences of ovarian follicle development. Conception rates are reduced to inseminations at the oestrus preceding these shortened cycles. In contrast, a single injection of the GnRH analogue, buserelin, around mid-dioestrus can lengthen the oestrous cycle by increasing the proportion of cycles with three waves of follicular development and may also increase conception rates. A series of trials was conducted to test the hypothesis that the adverse effects of progesterone on oestrous cycle length and conception rate could be prevented with a strategic injection of GnRH. In Trial 1, progesterone was administered per vaginum to heifers for 10 days from Day 2 or 3 (Oestrus=Day 0) and with ( n=42) or without ( n=46) an injection of a GnRH analogue (10 μg buserelin) on Day 12 or 13. Other heifers ( n=44) served as an untreated control group. The average inter-oestrous interval (IOI) for those heifers treated only with progesterone was 17.0 days and was less ( p
ISSN:0378-4320
1873-2232
DOI:10.1016/S0378-4320(99)00044-5