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Locke JWC, Thomas JM, Knickmeyer ER, Ellersieck MR, Yelich JV, Poock SE, Smith MF, Patterson DJ. Comparison of long-term progestin-based protocols to synchronize estrus prior to natural service or fixed-time artificial insemination in Bos indicus-influenced beef heifers. Anim Reprod Sci 2020; 218:106475. [PMID: 32507258 DOI: 10.1016/j.anireprosci.2020.106475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Revised: 04/04/2020] [Accepted: 04/21/2020] [Indexed: 11/26/2022]
Abstract
This experiment was designed to evaluate breeding strategies involving natural service or fixed-time artificial insemination (FTAI) in Bos indicus-influenced beef heifers (n = 1456) when there were field-type management conditions. Body weights and reproductive tract scores (RTS; Scale 1-5) were obtained for heifers before assignment to one of five treatments: 1) Non-synchronized control exposed for natural service (NS), n = 299; 2) melengestrol acetate + natural service (MGA + NS; 0.5 mg/heifer/d), n = 295; 3) 14-d controlled internal drug release insert + natural service (CIDR + NS), n = 289; 4) 14-d MGA-prostaglandin F2α (PG) + FTAI, n = 295; or 5) 14-d CIDR-PG + FTAI, n = 278. Fertile bulls were placed in pastures with heifers of the three NS treatment groups for a 65-day period which began 10 days after progestin treatments (MGA or CIDR) ended. Heifers in FTAI treatment groups were administered PG (25 mg, IM) 16 days after CIDR removal or 19 days following MGA withdrawal, respectively, and FTAI was performed at 66 (CIDR-PG) or 72 h (MGA-PG) after PG. Gonadotropin-releasing hormone (GnRH; 100 μg, i.m.) was administered at FTAI. Pregnancy status was determined at the end of a 65-day breeding period. Pregnancy rates on Days 21 and 65 of the breeding period differed among treatment groups based on pre-treatment pubertal status (P ≤ 0.02) and body weight (P ≤ 0.05) but did not differ by group. These data highlight the need for continued research efforts to improve reproductive management of Bos indicus-influenced females.
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Affiliation(s)
- J W C Locke
- Division of Animal Sciences, University of Missouri, Columbia, MO 65211, United States; College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, United States
| | - J M Thomas
- Division of Animal Sciences, University of Missouri, Columbia, MO 65211, United States
| | - E R Knickmeyer
- Division of Animal Sciences, University of Missouri, Columbia, MO 65211, United States; College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, United States
| | - M R Ellersieck
- Agriculture Experiment Station Statistician, University of Missouri, Columbia, MO 65211, United States
| | - J V Yelich
- Department of Animal Sciences, Institute of Food and Agriculture Sciences, University of Florida, Gainesville, FL 32611, United States
| | - S E Poock
- College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, United States
| | - M F Smith
- Division of Animal Sciences, University of Missouri, Columbia, MO 65211, United States
| | - D J Patterson
- Division of Animal Sciences, University of Missouri, Columbia, MO 65211, United States.
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Evaluation of the hypothalamus–pituitary axis response to exogenous GnRH, estradiol benzoate, and LH during the postpartum period in Nellore cows. Theriogenology 2013; 79:797-802. [DOI: 10.1016/j.theriogenology.2012.12.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2012] [Revised: 12/11/2012] [Accepted: 12/11/2012] [Indexed: 11/23/2022]
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Brar PS, Nanda AS. Postpartum Ovarian Activity in South Asian Zebu Cattle. Reprod Domest Anim 2008; 43 Suppl 2:207-12. [DOI: 10.1111/j.1439-0531.2008.01163.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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