Estrus synchronization and fixed-time artificial insemination alter calving distribution in  Bos indicus  influenced beef heifers

Oosthuizen, Nicola; Fontes, P. L. P.; Sanford, Carla D; Ciriaco, Francine M; Henry, Darren D; Canal, L. B.; DiLorenzo, Nicolás; Lamb, G. C.

doi:10.1016/j.theriogenology.2017.10.028

Cited by 8 publications

(6 citation statements)

References 13 publications

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“…Nonetheless, there are currently no definite GnRH-based protocols for estrus synchronization and fixedtime AI in B. indicus-influenced heifers. The use of a short-term GnRH-based protocol has been evaluated in B. indicus × B. taurus replacements (Oosthuizen et al, 2018). This protocol consists in 100 µg of GnRH + 25 prostaglandin F 2α (PGF) analogue injection + controlled internal P4 releasing insert (CIDR) on day 0, followed by 50 mg of PGF and CIDR removal on day 5, and 100 µg of GnRH and fixed-time AI 66 ± 2 h later.…”

Section: Management Of Bos Indicus-influenced Replacement Heifers In the United Statesmentioning

confidence: 99%

“…This protocol consists in 100 µg of GnRH + 25 prostaglandin F 2α (PGF) analogue injection + controlled internal P4 releasing insert (CIDR) on day 0, followed by 50 mg of PGF and CIDR removal on day 5, and 100 µg of GnRH and fixed-time AI 66 ± 2 h later. Oosthuizen et al (2018) reported that this strategy resulted in a greater proportion of heifers becoming pregnant within the first 21 d of the breeding season, whereas others have reported inconsistent results when utilizing a similar protocol for Brahman heifers (Yelich and Bridges, 2012). Hence, there is a need for the development of pharmacological strategies tailored specifically for B. indicus-influenced heifers in the United States that do not rely on estradiol-based products.…”

Section: Management Of Bos Indicus-influenced Replacement Heifers In the United Statesmentioning

confidence: 99%

“…Similar to replacement heifers, there are limited pharmacological alternatives specifically developed for cows with substantial B. indicus influence in the United States. A protocol similar to that described by Oosthuizen et al (2018) is the current recommendation for mature B. indicus-influenced cows. A PGF injection is given at the beginning of the protocol in conjunction with the first GnRH, and a second injection of PGF is administered 8 h after CIDR removal.…”

Section: Management Of Bos Indicus-influenced Cows In the United Statesmentioning

confidence: 99%

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Cattle adapted to tropical and subtropical environments: genetic and reproductive considerations

Cooke

Cardoso

Cerri

et al. 2020

Journal of Animal Science

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Efforts to understand biological functions and develop management schemes specific to Bos indicus-influenced cattle raised in tropical and subtropical environments are critical to meet the increasing global demand for protein. In the United States, B. indicus breeds are mostly used to generate B. indicus × B. taurus crosses with increased thermal and parasite tolerance, while retaining some productive characteristics of B. taurus cattle. Although crossbreeding represents a proven strategy to improve cattle adaptation almost immediately, research has also attempted to identify B. taurus genetics that can withstand subtropical and tropical climates. Reduced milk production and delayed reproductive maturation appear to be related with tropical adaptation of B. taurus breeds, as a means to conserve energy under stressful conditions and limited nutrition. Moreover, longevity may be the ultimate adaptation response to unfavorable environments, and retention of bulls and heifers from proven cows is the recommended strategy to improve longevity in B. indicus-influenced herds. Besides selection for longevity, other aspects should be considered when planning reproductive management in tropical and subtropical regions. Bos indicus and B. taurus breeds have multiple differences pertaining to reproductive function, including age at puberty, ovarian dynamics, and pregnancy development. Nutritional strategies such as the stair-step regimen, and use of exogenous progesterone (P4) inserts are options to hasten puberty attainment of late-maturing B. indicus-influenced heifers. Yet, limited pharmacological alternatives are available for reproductive management of B. indicus-influenced females in the United States, which rely on GnRH-based protocols not specifically designed to the reproductive function of B. indicus breeds. In contrast, hormonal protocols based on exogenous P4, estradiol esters, and equine chorionic gonadotropin are available for use in B. indicus females in South America. These include protocols tailored to prepubertal heifers, anestrous cows, and cycling nulliparous or parous females, which often yield pregnancy rates of 50% to fixed-time artificial insemination. The global dairy industry also faces similar challenges in increasing demand and production as the beef industry. Selection of cows capable of sustaining optimal milk yield, reproductive success, and health status in hot and humid conditions is essential for optimal dairy production in subtropical and tropical regions.

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Section: Management Of Bos Indicus-influenced Replacement Heifers In the United Statesmentioning

confidence: 99%

Section: Management Of Bos Indicus-influenced Replacement Heifers In the United Statesmentioning

confidence: 99%

Section: Management Of Bos Indicus-influenced Cows In the United Statesmentioning

confidence: 99%

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Cattle adapted to tropical and subtropical environments: genetic and reproductive considerations

Cooke

Cardoso

Cerri

et al. 2020

Journal of Animal Science

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“…Melatonin treatment has successfully been used to initiate ovarian cyclicity in anoestrous buffalo heifers 11 and increase plasma concentrations of GnRH and gonadotropins, promoting follicular growth and ovulation 12, 13 . The conception rate following AI is usually between 30% and 70% 14–22 . Early embryonic development may be negatively affected by insufficient progesterone (P4) production, with pregnancy failure attributed to insufficient luteal P4 production during early embryonic development 23 …”

mentioning

confidence: 99%

Two melatonin treatments improve the conception rate after fixed‐time artificial insemination in beef heifers following synchronisation of oestrous cycles using the CoSynch‐56 protocol

Gao

et al. 2021

Aust Veterinary J

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Objective This study investigated the effect of melatonin administration in combination with the CoSynch‐56 protocol on the conception rate after artificial insemination (AI) in beef heifers. Methods Eighty‐six beef heifers were allocated to four treatments in combination with CoSynch‐56 treatment. All heifers, excluding the control group (CTR = 25), were injected with melatonin on day 1. The melatonin (MT = 20) and MT + human chorionic gonadotropin (MT + hCG = 21) groups received no further treatment with melatonin. Each heifer was treated with gonadotropin‐releasing hormone (GnRH) on day 4, prostaglandin F2α (PGF2α) on day 11, and GnRH and AI 56 h later. The fourth group (2MT = 20) was injected again with melatonin concurrent with AI, and the MT + hCG group received hCG on day 19. Pregnancy diagnosis was performed using transrectal ultrasonography 45 days after AI and blood samples were collected via caudal venipuncture on days 0–1, 14–15, 24 and 59. Concentrations of progesterone (P4) and the activities of oxidative stress‐related enzymes were determined using enzyme‐linked immunosorbent assay. Results The conception rate was greater in the 2MT group (75%) than in the other groups, while there was no significant difference among the CTR (44%), MT (45%) and MT + hCG (38.1%) groups. Treatment with melatonin increased superoxide dismutase and glutathione peroxidase activities and decreased malondialdehyde concentrations but did not significantly affect the concentration of P4. Conclusion Our results indicate that the administration of melatonin twice during the CoSynch‐56 protocol may increase conception rates in beef heifers.

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“…Our first hypothesis was based on previous reports that described greater follicle size and better reproductive performance of postpubertal than prepubertal heifers [19,[27][28][29][30][31][32].…”

Section: Discussionmentioning

confidence: 99%

Hormonal combinations for fixed-time artificial insemination aiming to optimize fertility outcomes of Nelore cattle

Alves¹

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Hormonal combinations for fixed-time artificial insemination aiming to optimize fertility outcomes of Nelore cattle Two studies were performed aiming to evaluate reproductive outcomes, including ovarian dynamics and fertility, of Nelore heifers and cows submitted to estradiol (E2)/progesterone (P4)-based fixed-time artificial insemination (FTAI) protocols. The first study was performed using suckled Nelore cows and evaluated some adjustments in protocols with 7 days of P4 implant duration. Cows received an intravaginal P4 implant on Day 0, associated with E2 benzoate (EB) administration, and the implant remained for 7 days. At the time of P4 implant removal, all cows were treated with equine chorionic gonadotropin (eCG), E2 cypionate (EC) and prostaglandin F2α (PGF), and were inseminated 48 hours later. The first adjustment was made at the beginning of the protocol (Day 0) with or without PGF; the second adjustment was made at the time of P4 implant withdrawal (Day 7) and consisted of treating with either 0.5 or 1.0 mg EC. The third adjustment was administration or not of GnRH at the time of FTAI (Day 9). Regarding ovarian dynamics, multiparous had larger follicules than primiparous cows, on both Day 7 and at FTAI, in addition to a greater number of cows with CL at the initiation of the protocol. Overall, pregnancy per AI (P/AI) was high (~58%) and was not affected by PGF treatment on Day 0. Expression of estrus was higher in cows that received 1.0 mg EC, in addition to a tendency of greater P/AI. P/AI was greater when cows received GnRH at FTAI, particularly in cows not expressing estrus. Thus, GnRH improved P/AI especially in cows with lower expression of estrus, such as primiparous, thinner cows (BCS < 3.0), and cows treated with 0.5 mg of EC on Day 7. The second study evaluated the reproductive outcomes of Nelore heifers submitted to 7 or 9 d E2/P4-based FTAI protocols, with PGF administered at different times. An ultrasound evaluation was performed prior to the start of the experiment, to evaluate cyclicity. Heifers with CL were assigned to one of four experimental treatments, one with 7 days of P4 device, and PGF administered on Days 0 and 7, and the other with 9 days of P4 device, and PGF given at different times (Day 0 and 9, Day 7, or Day 9). Prepubertal heifers were submitted to a protocol for induction of cyclicity and, then, were randomly assigned to one of the four treatments, regardless of CL presence. Low number of heifers had CL at the first ultrasound evaluation (~17%), however, protocol for induction of cyclicity resulted in more than 80% of heifers with CL at the initiation of the synchronization protocol. The presence of CL on Day 0, overall, was positively affected by body condition score, although it did not influence expression of estrus and P/AI. There were differences on ovarian dynamics, with lower follicular diameter, at the time of AI, on animals from group 7 d. Expression of estrus was high (~90%) and did not affect P/AI, which also was similar between groups (~53%). Therefore, the st...

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Estrus synchronization and fixed-time artificial insemination alter calving distribution in Bos indicus influenced beef heifers

Cited by 8 publications

References 13 publications

Cattle adapted to tropical and subtropical environments: genetic and reproductive considerations

Cattle adapted to tropical and subtropical environments: genetic and reproductive considerations

Two melatonin treatments improve the conception rate after fixed‐time artificial insemination in beef heifers following synchronisation of oestrous cycles using the CoSynch‐56 protocol

Hormonal combinations for fixed-time artificial insemination aiming to optimize fertility outcomes of Nelore cattle

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