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Oestrus detection techniques and insemination strategies in Bos indicus heifers synchronised with norgestomet‐oestradiol
Author(s) -
CAVALIERI J.,
FITZPATRICK LA
Publication year - 1995
Publication title -
australian veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.382
H-Index - 59
eISSN - 1751-0813
pISSN - 0005-0423
DOI - 10.1111/j.1751-0813.1995.tb03507.x
Subject(s) - estrous cycle , insemination , zoology , artificial insemination , pregnancy , pregnancy rate , chin , biology , dairy cattle , andrology , medicine , anatomy , genetics
SUMMARY Oestrus was synchronised in 57 Bos indicus heifers using norgestometoestradiol and pregnant mare serum gonadotrophin. Oestrus was detected by observations made at six‐hourly intervals, using oestrogen‐treated and chin‐ball harnessed steers, heatmount detectors, tail‐paint and visual observation. Heifers were inseminated once at either a fixed time of 49.2 ± 0.4 h (mean ± SE; n = 29) after implant removal or 12.6 ± 1.5 h (n = 28) after oestrus was detected. The mean (± SE) time to the onset of oestrus was 47.1 ± 1.9 h, while 90% of heifers recorded in oestrus were detected within 66 h of implant removal. Heatmount detectors were significantly more efficient at detecting oestrus than chin‐ball harnessed steers, tail paint or visual observation (P < 0.001). A higher pregnancy rate was obtained in heifers inseminated after oestrus detection compared with heifers inseminated at a fixed‐time (57.1 vs 34.5%; P = 0.043) and a higher pregnancy rate was obtained in heifers classified as easy to inseminate compared with heifers classified as difficult to inseminate (57.8 vs 0%, P < 0.001). We conclude that heatmount detectors are an efficient means of detecting oestrus in synchronised B indicus heifers and that pregnancy rates can be increased when insemination follows oestrus detection compared with a fixed‐time insemination regimen.