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User:Samsmith428/Estrous cycle

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Notes

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  • lead section: wikipedia flags it as too short. add a couple more sentences?
  • distinctions from the menstrual cycle probably doesnt belong at the top; possibly rearrange in article?
    • sentence about human females having more sexual thoughts during ovulation have nothing to do with estrous cycle

3/11 I edited a few sentences, added a few tidbits of info, and added some citations to the wiki page

Lead

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[my edits in bold]

The oestrous cycle or estrous cycle (derived from Latin oestrus "frenzy", originally from Greek οἶστρος oîstros "gadfly") is the set of recurring physiological changes that are induced by reproductive hormones in most mammalian therian females.[1] Estrous cycles start after sexual maturity in females and are interrupted by anestrous phases, otherwise known as 'rest' phases, or by pregnancies. Typically, estrous cycles repeat until death. These cycles are widely variable in duration and frequency depending on the species.[2] Some animals may display bloody vaginal discharge, often mistaken for menstruation.[3] Many mammals used in commercial agriculture, such as cattle and sheep, may have their estrous cycles artificially controlled with hormonal medications for optimum productivity.[4][5] Naturally, estrous cycles are complimented by a rutting period of male counterparts within a species[2].

Cattle

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Female cattle, also referred to as "heifers" in agriculture, will gradually enter standing estrus, or "standing heat," starting at puberty between 9 to 15 months of age. The cow estrous cycle typically lasts 21 days.[5] Standing estrus is a visual cue which signifies sexual receptivity for mounting by male cattle. This behavior lasts anywhere between 8 to 30 hours at a time.[6] Other behaviors of the female during standing estrus may change, including, but not limited to: nervousness, swollen vulva, or attempting to mount other animals.[6] While visual and behavioral cues are helpful to the male cattle, estrous stages cannot be determined visually by the human eye. Rather, the stage can be estimated from the appearance of the corpora lutea or follicle composition.[7][8]

Estrous Control

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[see estrous synchronization]

Due to the widespread use of bovine animals in agriculture, cattle estrous cycles have been widely studied, and manipulated, in an effort to maximize profitability through reproductive management.[6] Much estrous control in cattle is for the purpose of synchronization, a practice or set of practices most often used by cattle farmers to control the timing and duration of estrus in large herds.[4]

There is variation between the available methods of cattle estrous synchronization. Treatment depends on herd size, specific goals for control, and budget.[4] Some of the FDA-approved drugs and devices used to mimic natural hormones of the estrous cycle include, but are not limited to, the following classes:

  • Gonadorelin: There are currently five available gonadorelin products that are FDA-Approved.[9] Usually, gonadorelin is used in conjunction with another estrous control drug (typically, prostaglandin).[9][10] This drug is used to mimic gonadotropin releasing hormone (GnRH) and may also be used to treat ovarian cysts.[5]
  • Prostaglandin: Mimics the prostaglandin F2-alpha hormone released when no pregnancy has occurred and regresses the corpus luteum.[5] This drug is used to achieve more consistent results in artificial insemination.[10] Typ
  • Progestin: Used to suppress estrus and/or block ovulation[5]. Most commonly, it is administered via an intravaginal insert comparable to an IUD, which used in controlling menstrual periods.[11] It is also available as a medicated feed, but this method is not yet approved for cattle crop synchronization.[5]

There is variation between the available methods of cattle estrous synchronization. Treatment depends on herd size, specific goals for control, and budget.[4]

While estrous management is deemed safe by the FDA and may provide added monetary gain[12], repeated cycles of gestation and constant lactation causes dairy cattle to exhaust their bodies leaving them with a shortened lifespan of approximately 4 years. In comparison, the average captive lifespan ranges from 15-20 years.[13] Bovine estrous cycles may also be impacted by other bodily functions such as oxytocin levels.[14] Additionally, heat stress has been linked to impairment of follicular development, especially impactful to the first-wave dominant follicle.[15] Future synchronization programs are planning to focus on the impact of heat stress on fertilization and embryonic death rates after artificial insemination.[16]

Additionally, work has been done regarding other mammalian females, such as in dogs, for estrous control; However, there are yet to be any approved medications outside of those commercially available.[17]

  1. ^ Hill, M.A. (2021, April 6) Embryology Estrous Cycle. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Estrous_Cycle
  2. ^ a b Bronson, F.H., 1989. Mammalian Reproductive Biology. University of Chicago Press, Chicago, IL, USA.
  3. ^ Llera, Ryan; Yuill, Cheryl (2021). "Estrous Cycles in Dogs". VCA Hospitals. Retrieved April 6, 2021.{{cite web}}: CS1 maint: url-status (link)
  4. ^ a b c d "Synchronizing Estrus in Cattle - How does estrus synchronization work?". Texas A&M AgriLife Extension Service. Retrieved 2021-03-22.
  5. ^ a b c d e f Medicine, Center for Veterinary (2021-03-05). "The Cattle Estrous Cycle and FDA-Approved Animal Drugs to Control and Synchronize Estrus—A Resource for Producers". FDA.
  6. ^ a b c Perry, George (2004). Salverson, Robin (ed.). "The Bovine Estrous Cycle" (PDF). SDSU Extension.
  7. ^ Ireland, James J.; Murphee, R.L.; Coulson, P.B. (1980). "Accuracy of Predicting Stages of Bovine Estrous Cycle by Gross Appearance of the Corpus Luteum". Journal of Dairy Science. 63 (1): 155–160. doi:10.3168/jds.s0022-0302(80)82901-8. ISSN 0022-0302.
  8. ^ Ginther, O. J.; Kastelic, J. P.; Knopf, L. (1989-09-01). "Composition and characteristics of follicular waves during the bovine estrous cycle". Animal Reproduction Science. 20 (3): 187–200. doi:10.1016/0378-4320(89)90084-5. ISSN 0378-4320.
  9. ^ a b Medicine, Center for Veterinary (2018-11-03). "Fertagyl® (gonadorelin acetate) - Veterinarians". FDA.
  10. ^ a b "LUTALYSE® Injection (dinoprost injection)". www.zoetisus.com. Retrieved 2021-04-06.
  11. ^ "Hormonal Control of Estrus in Cattle - Management and Nutrition". Veterinary Manual. Retrieved 2021-03-22.
  12. ^ Larson, Daniel; Musgrave, Jacqueline A.; Funston, Richard N. (2010-01-01). "Estrous Synchronization Increases Early Calving Frequency, Which Enhances Steer Progeny Value". Nebraska Beef Cattle Reports.
  13. ^ "Market Cows: A Potential Profit Center - Dairy Cattle". livestocktrail.illinois.edu. Retrieved 2021-03-22.
  14. ^ Armstrong, D.T.; Hansel, William (1959). "Alteration of the Bovine Estrous Cycle with Oxytocin". Journal of Dairy Science. 42 (3): 533–542. doi:10.3168/jds.s0022-0302(59)90607-1. ISSN 0022-0302.
  15. ^ Wolfenson, D.; Thatcher, W. W.; Badinga, L.; Savi0, J. D.; Meidan, R.; Lew, B. J.; Braw-tal, R.; Berman, A. (1995-05-01). "Effect of Heat Stress on Follicular Development during the Estrous Cycle in Lactating Dairy Cattle1". Biology of Reproduction. 52 (5): 1106–1113. doi:10.1095/biolreprod52.5.1106. ISSN 0006-3363.{{cite journal}}: CS1 maint: numeric names: authors list (link)
  16. ^ Santos, J. E. P; Thatcher, W. W; Chebel, R. C; Cerri, R. L. A; Galvão, K. N (2004-07-01). "The effect of embryonic death rates in cattle on the efficacy of estrus synchronization programs". Animal Reproduction Science. Research and Practice III. 15th International Congress on Animal Reproduction. 82–83: 513–535. doi:10.1016/j.anireprosci.2004.04.015. ISSN 0378-4320.
  17. ^ Kutzler MA. Estrous Cycle Manipulation in Dogs. Vet Clin North Am Small Anim Pract. 2018 Jul;48(4):581-594. doi: 10.1016/j.cvsm.2018.02.006. Epub 2018 Apr 27. PMID: 29709316.
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