Does the amount of progesterone in intravaginal implants used to synchronise oestrus affect the reproductive performance of brahman heifers artificially inseminated at a fixed time

Phillips, N. J., Fordyce, G., Burns, B., Williams, P., Mayer, D., Bo, G. O. and McGowan, M. R. (2010) Does the amount of progesterone in intravaginal implants used to synchronise oestrus affect the reproductive performance of brahman heifers artificially inseminated at a fixed time. Reproduction In Domestic Animals, 45 6: e392-e397. doi:10.1111/j.1439-0531.2010.01585.x

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Author Phillips, N. J.
Fordyce, G.
Burns, B.
Williams, P.
Mayer, D.
Bo, G. O.
McGowan, M. R.
Title Does the amount of progesterone in intravaginal implants used to synchronise oestrus affect the reproductive performance of brahman heifers artificially inseminated at a fixed time
Journal name Reproduction In Domestic Animals   Check publisher's open access policy
ISSN 0936-6768
1439-0531
0940-5496
Publication date 2010-12
Sub-type Article (original research)
DOI 10.1111/j.1439-0531.2010.01585.x
Volume 45
Issue 6
Start page e392
End page e397
Total pages 6
Place of publication Berlin, Germany
Publisher Wiley-Blackwell
Collection year 2011
Language eng
Formatted abstract
The study tested the hypothesis that reduced intravaginal implant progesterone (P4) concentration to synchronise oestrus would increase pregnancy rates to fixed-time artificial insemination (FTAI) in Bos indicus heifers. Brahman heifers (n = 294; 2 year) were body condition scored (BCS), weighed and scanned for presence of a corpus luteum (CL). Only cyclic heifers were selected and allocated randomly within BCS and 25 kg bodyweight category to one of three P4 treatment groups. On day 10, heifers received a P4 implant (CueMate-1-pod, 0.78g P4; CueMate-2-pod, 1.56g P4; or CIDR-B, 1.9g P4), 2 mg oestradiol benzoate (ODB) intramuscularly (IM) and 250 ug cloprostenol IM. At day 2, the implant was removed, 250 ug cloprostenol was injected IM and tail paint applied. The heifers received 1 mg ODB 24 h later and were FTAI 48–54 h after implant removal (day 0). Ten randomly selected heifers per group were blood sampled and scanned at days 10, 2, 0 and 6 to define the P4 profiles pre- and post-FTAI. Heifers were heat-detected 18–20 days post-FTAI and oestrous heifers AI’d by the AM/PM rule. Bulls joined the heifers on day 27 post-FTAI. Transrectal ultrasonography estimated conception date on day 72. Statistical analysis examined the effects of treatment, technician, semen, ovarian status, BCS and liveweight, on pregnancy rate (PR) to FTAI. There was no significant difference (p = 0.362) in PR between treatment groups (CueMate 1-pod, 36.4%; CueMate 2-pod, 39.6%: CIDR-B, 28.3%), but PR was higher in those heifers with increased BCS between FTAI and pregnancy diagnosis (p = 0.005). Thirty-three per cent of monitor heifers had plasma P4 concentrations of <1 ng/ml on day 6 after FTAI; only 20% of these conceived vs 60% of heifers with P4 ≥ 1 ng/ml. In summary, no significant difference in PR was identified between treatments but good BCS and a rising plane of nutrition were critical to PR of these pure grade Brahman heifers in northern Australia.
© 2010 Blackwell Verlag GmbH.
Keyword Lactating dairy-cows
Bos-indicus
Follicle
Endocrine
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2011 Collection
Queensland Alliance for Agriculture and Food Innovation
 
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Citation counts: TR Web of Science Citation Count  Cited 3 times in Thomson Reuters Web of Science Article | Citations
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Created: Sun, 02 Jan 2011, 00:06:32 EST