The effects of time of insemination on fertility in ...
|Title||The effects of time of insemination on fertility in beef heifers synchronized with prostaglandin F2 alpha|
|Author(s)||J. Manns, M. Wenkoff, W. Adams, G. Richardson|
|Journal||Canadian Journal of Animal Science|
|Abstract||Two injections of PGF2 alpha spaced 12 days apart were used to synchronise oestrus in Hereford heifers. Animals were inseminated at 75 h (group 2), 80 h (group 3) or 85 h (group 4) after the 2nd injection of PGF2 alpha . Untreated, control animals (group 1) were inseminated as detected in oestrus over an observation period of approx. 35 days. Immediately before, and 24 h after each PGF2 alpha injection, blood was collected for progesterone assay. Fertility expressed as calving rates was as follows: group 1, 33/77 (43%); group 2, 30/79 (38%); group 3, 29/79 (37%); group 4, 20/73 (27%). Fertility was significantly depressed in group 4 animals compared with controls, but there were no other significant differences. Progesterone assays showed that 65% of animals had progesterone-secreting corpora lutea at the 1st injection of PGF2 alpha . There was no relationship between fertility and either serum progesterone concentration or the day of the cycle at the 2nd injection of PGF2 alpha.|
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