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Abstract

This is a review of the physiology and endocrinology of the estrous cycle and how ovarian physiology can be manipulated and controlled for timed artificial insemination (TAI) in beef and dairy cattle. Estrus detection is required for artificial insemination (AI), but it is done poorly in dairy...

Author(s)
Colazo, M. G.; Mapletoft, R. J.
Publisher
Canadian Veterinary Medical Association, Ottawa, Canada
Citation
Canadian Veterinary Journal, 2014, 55, 8, pp 772-780
Abstract

The objective was to determine the effect of plasma progesterone concentration and the duration of proestrus during growth of the ovulatory follicle on fertility in beef cattle. Heifers (N=61) and postpartum cows (N=79) were assigned randomly to four groups in a two-by-two design involving...

Author(s)
Dadarwal, D.; Mapletoft, R. J.; Adams, G. P.; Pfeifer, L. F. M.; Creelman, C.; Singh, J.
Publisher
Elsevier, New York, USA
Citation
Theriogenology, 2013, 79, 5, pp 859-866
Abstract

The objective was to determine the effects of the duration of progesterone exposure during the ovulatory wave on fertility (pregnancy rate) in beef cattle. We tested the hypothesis that short-progesterone exposure during the growing and early-static phase of the ovulatory follicle (analogous to the ...

Author(s)
Dias, F. C. F.; Mapletoft, R. J.; Kastelic, J. P.; Adams, G. P.; Colazo, M. G.; Stover, B. C.; Dochi, O.; Singh, J.
Publisher
Elsevier, New York, USA
Citation
Theriogenology, 2012, 77, 2, pp 437-444
Abstract

The objective of this study was to determine the effects of low versus physiologic plasma progesterone concentrations during the ovulatory wave on fertility in cattle. Suckled beef cows (Bos taurus; n=129) and pubertal heifers (Bos taurus; n=150) at random stages of the estrous cycle were given a...

Author(s)
Pfeifer, L. F. M.; Mapletoft, R. J.; Kastelic, J. P.; Small, J. A.; Adams, G. P.; Dionello, N. J.; Singh, J.
Publisher
Elsevier, New York, USA
Citation
Theriogenology, 2009, 72, 9, pp 1237-1250
Abstract

The objective was to synchronize follicular wave emergence among cattle for synchronization of oestrus and ovulation, and to determine pregnancy rate after AI at observed oestrus. At random stages of the oestrous cycle, a controlled internal drug release device (CIDR-B) was inserted intravaginally...

Author(s)
Martinez, M. F.; Adams, G. P.; Kastelic, J. P.; Bergfelt, D. R.; Mapletoft, R. J.
Publisher
Elsevier Science Inc., New York, USA
Citation
Theriogenology, 2000, 54, 5, pp 757-769
Abstract

56 cows received a norgestomet implant and an injection of norgestomet and oestradiol valerate; half (n = 28) received 500 IU equine chorionic gonadotropin (eCG) at implant removal, 9 days later. A third group (n = 25) received 2 injections of cloprostenol (500 µg) 11 days apart. The percentage of...

Author(s)
Kastelic, J. P.; Olson, W. O.; Martinez, M.; Cook, R. B.; Mapletoft, R. J.
Citation
Canadian Veterinary Journal, 1999, 40, 3, pp 173-178
Abstract

Estradiol cypionate (ECP) was used in beef heifers receiving a controlled internal drug release (CIDR; insertion=Day 0) device for fixed-time AI (FTAI) in four experiments. In Experiment 1, heifers (n=24) received 1 mg ECP or 1 mg ECP plus 50 mg commercial progesterone (CP) preparation i.m. on Day...

Author(s)
Colazo, M. G.; Kastelic, J. P.; Mapletoft, R. J.
Publisher
Elsevier Science Inc., New York, USA
Citation
Theriogenology, 2003, 60, 5, pp 855-865
Abstract

The objective of this experiment was to compare two progestins and three treatments for synchronizing follicular wave emergence and ovulation in protocols for fixed-time AI in beef heifers. On day 0 (beginning of the experiment), Angus and Angus-Simmental cross beef heifers at random stages of the...

Author(s)
Martinez, M. F.; Kastelic, J. P.; Adams, G. P.; Mapletoft, R. J.
Publisher
American Society of Animal Science, Savoy, USA
Citation
Journal of Animal Science, 2002, 80, 7, pp 1746-1751
Abstract

Two experiments were conducted to compare pregnancy rates when GnRH or estradiol were given to synchronize ovarian follicular wave emergence and ovulation in an MGA-based oestrus synchronization programme. Crossbred beef cattle were fed melengestrol acetate (MGA, 0.5 mg per day) for 7 days...

Author(s)
Martinez, M. F.; Kastelic, J. P.; Adams, G. P.; Mapletoft, R. J.
Publisher
Elsevier Science B.V., Amsterdam, Netherlands
Citation
Animal Reproduction Science, 2001, 67, 3/4, pp 221-229
Abstract

The objective was to determine reproductive performance following AI in beef heifers given estradiol to synchronize ovarian follicular wave emergence and estradiol or GnRH to synchronize ovulation in a two-dose PGF-based protocol. In Experiment 1, 561 cycling (confirmed by ultrasonography), Angus...

Author(s)
Martínez, M. F.; Kastelic, J. P.; Mapletoft, R. J.
Publisher
Elsevier Science Inc., New York, USA
Citation
Theriogenology, 2004, 62, 1/2, pp 363-372

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