Estrous synchronization

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In agriculture, estrous synchronization is used (particularly in the dairy and beef industries) to facilitate breeding by artificial insemination.

Contents

Background

The term “estrus” refers to the phase of the estrous cycle in which a sexually mature, non-pregnant female is receptive to sexual advances from the male³. Ovulation occurs at approximately this time. [1] Estrous synchronisation is the process of targeting female mammals to come to heat within a short time frame (36 to 96 hours). This is achieved through the use of one or more hormones. Methods to improve our ability to synchronize the reproductive process and result in the ‘timed insemination’ without the detection of heat have been developed. These include the “Synch” protocols that involve the application of GnRH and PGF2α in various combinations. These “Synch” protocols may include: Select Synch, OvSynch, CoSynch, and Modified Select Synch [2] The synchronization of the estrous cycle is commonly used in different industries, such as Dairy and Beef cattle. Synchronization allows these industries to improve management and nutrition of the cattle, while also decreasing expenses. [3]

Method

Research has been conducted into different ways farmers can perform estrous synchronization such as progesterone injections or a Progesterone Releasing Intra-vaginal Device [PRID]. [4] The PRID is a sponge that is inserted into the vagina of a cow to stop the natural estrous cycle (for it acts as a corpus luteum), because progesterone is the hormone that signals the body to stop the cycle because fertilisation has occurred. When the sponge is removed the cycle restarts. This apparatus is useful in manipulating the cycle so that multiple cows can be ovulated around the same time. Other methods use injections of GnRH or PGF2a at certain points over the course of a few weeks to simulate the body’s natural production of these compounds. This is a more exact but time consuming way to manipulate the cycle of multiple cows to sync up the timing of A.I. [5] Estrus synchronisation has major advantages in making artificial insemination more practical. Increasing the productivity of embryo transfer and artificial insemination is economically profitable as the costs associated with veterinarian and semen services are reduced. The reduction of costs occur because vets are required for less time to do the inseminating because the period of ovulation of the herd is decreased to 2-5 days. There are many different injection methods that have been put into practise in order to manipulate the estrous cycle. These involve injections into each cow with a measured amount of progesterone or progestin and waiting 5-7 days, or until heat signals occur, before moving onto different impregnating methods such as joining the cows or heifers with a bull.

Agricultural applications

Milk is a product of great demand all year round. As a result of this demand, farmers have been given an incentive to produce milk during winter months. In order to achieve this public demand for milk, dairy farmers needed to change their breeding routines. estrous synchronization enabled this change in the herd’s breeding routine to allow dairy farmers to produce milk for human consumption year round. Case studies for the productivity of these incentives on dairy farms have shown to have positive results. [6] Oestrus synchronisation has proven to have many advantages in the dairy and beef industries. The application of estrous synchronisation enables the farmer to reduce costs involved in the hire of AI technicians and semen import. Concentrated calving and uniform weaning saves time and is cheaper than having individual cows in heat throughout the year. [7] However, there are also disadvantages with estrous synchronisation. It requires a high level of management and skills to be able to manage numerous calving operations at a synchronised time. [7] Furthermore, maintaining nutrition and herd health are major factors when it comes to the achieving optimum reproductive performance through estrous synchronisation. [8]

Related Research Articles

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<span class="mw-page-title-main">Dairy</span> Organization that processes milk

A dairy is a business enterprise established for the harvesting or processing of animal milk – mostly from cows or buffaloes, but also from goats, sheep, horses, or camels – for human consumption. A dairy is typically located on a dedicated dairy farm and milk or in a section of a multi-purpose farm that is concerned with the harvesting of milk.

<span class="mw-page-title-main">Artificial insemination</span> Pregnancy through in vivo fertilization

Artificial insemination is the deliberate introduction of sperm into a female's cervix or uterine cavity for the purpose of achieving a pregnancy through in vivo fertilization by means other than sexual intercourse or in vitro fertilisation. It is a fertility treatment for humans, and is common practice in animal breeding, including dairy cattle and pigs.

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<span class="mw-page-title-main">Corpus luteum</span> Temporary endocrine structure in female ovaries

The corpus luteum is a temporary endocrine structure in female ovaries involved in the production of relatively high levels of progesterone, and moderate levels of estradiol, and inhibin A. It is the remains of the ovarian follicle that has released a mature ovum during a previous ovulation.

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In mammalian species, pseudopregnancy is a physical state whereby all the signs and symptoms of pregnancy are exhibited, with the exception of the presence of a fetus, creating a false pregnancy. The corpus luteum is responsible for the development of maternal behavior and lactation, which are mediated by the continued production of progesterone by the corpus luteum through some or all of pregnancy. In most species, the corpus luteum is degraded in the absence of a pregnancy. However, in some species, the corpus luteum may persist in the absence of pregnancy and cause "pseudopregnancy", in which the female will exhibit clinical signs of pregnancy.

<span class="mw-page-title-main">Estrous cycle</span> Ovulation cycle occurring in most mammalian therian females

The estrous cycle is the set of recurring physiological changes that are induced by reproductive hormones in most mammalian therian females. 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. Some animals may display bloody vaginal discharge, often mistaken for menstruation. Many mammals used in commercial agriculture, such as cattle and sheep, may have their estrous cycles artificially controlled with hormonal medications for optimum productivity. The male equivalent, seen primarily in ruminants, is called rut.

<i>Tritrichomonas foetus</i> Species of protozoan parasite

Tritrichomonas foetus is a species of single-celled flagellated parasites that is known to be a pathogen of the bovine reproductive tract as well as the intestinal tract of cats. In cattle, the organism is transmitted to the female vagina and uterus from the foreskin of the bull where the parasite is known to reside. It causes infertility, and, at times, has caused spontaneous abortions in the first trimester. In the last ten years, there have been reports of Tritrichomonas foetus in the feces of young cats that have diarrhea and live in households with multiple cats. Tritrichomonas foetus looks similarly to Giardia and is often misdiagnosed for it when viewed under a microscope.

<span class="mw-page-title-main">Australian Charbray</span> Breed of cattle

The Australian Charbray is an Australian breed of cattle derived from a cross between the French Charolais cattle and American Brahman cattle. The charbray breed was first conceived in the United States of America in the 1930s and later introduced into Australia in 1969. In Australia, Australian charbray breeders are concentrated in the tropical Northern regions of Queensland. As of 1977, the official breeder society of Charbray cattle in Australia and New Zealand is the Charbray Society of Australia Limited, responsible for recording Charbray cattle in herd books, fostering improvement, enhancement and sales of Charbray cattle.

<span class="mw-page-title-main">Cattle</span> Large domesticated cloven-hooved herbivores

Cattle are large, domesticated, cloven-hooved, herbivores. They are a prominent modern member of the subfamily Bovinae and the most widespread species of the genus Bos. Adult females are referred to as cows and adult males are referred to as bulls.

<span class="mw-page-title-main">Bull</span> Male individual of cattle

A bull is an intact adult male of the species Bos taurus (cattle). More muscular and aggressive than the females of the same species, bulls have long been an important symbol in many religions, including for sacrifices. These animals play a significant role in beef ranching, dairy farming, and a variety of sporting and cultural activities, including bullfighting and bull riding. Their use in herd maintenance is part of their monetary value.

Controlled internal drug release (CIDR) devices are used in livestock for the synchronization of estrus. They are T-shaped devices with a silicone-coated nylon core. The silicone coating is impregnated with progesterone. CIDRs are inserted intra-vaginally using a specialized applicator. The flexible wings collapse for facilitated insertion and expand once placed appropriately within the vagina. The expansion of the wings retains its position; CIDRs have very high retention rates that may exceed 97%. A thin nylon tail remains exteriorized and is used for removal.

Progesterone devices are broadly used in the control of reproductive management in livestock. They work by increasing circulating plasma progesterone levels with the following consequences:

  1. Progesterone suppresses the secretion of gonadotropin-releasing hormone (GnRH) from the hypothalamus. This is done via a negative feedback to the hypothalamus neuroendocrine cells, by inhibition of KiSSpeptin KiSS1-derived peptide receptor, a protein needed for the release of GnRH.
  2. Low levels of GnRH prevent the emergence of a dominant follicle by reducing the release of LH and FSH hormones. Current follicular waves cease and a new wave emerges 3–5 days after implant.
  3. A dominant follicle develops but there is no ovulation as LH release is prevented by suppression of GnRH.
  4. Removal of progesterone device produces a surge of GnRH, generating a pulse of LH that induces ovulation.
<span class="mw-page-title-main">Cow–calf operation</span> Method of raising beef cattle

A cow calf operation is a method of rearing beef cattle in which a permanent herd of cows is kept by a farmer or rancher to produce calves for later sale. Cow–calf operations are one of the key aspects of the beef industry in the United States and many other countries. In the British Isles, a cow–calf operation may be known as a single-suckler herd. The goal of a cow–calf operation is to produce young beef cattle, which are usually sold. A rancher who works within such a model is often called a "cow–calf operator" in the United States.

Menstruation is the shedding of the uterine lining (endometrium). It occurs on a regular basis in uninseminated sexually reproductive-age females of certain mammal species.

<span class="mw-page-title-main">Induced ovulation (animals)</span>

Induced ovulation is when a female animal ovulates due to an externally-derived stimulus during, or just prior to, mating, rather than ovulating cyclically or spontaneously. Stimuli causing induced ovulation include the physical act of coitus or mechanical stimulation simulating this, sperm and pheromones.

Vaginal cytology is a microscopic examination of cells from the vaginal epithelium. In veterinary medicine, it helps differentiate the stages of the mammalian estrous cycle because the vaginal epithelium changes in response to sex hormone levels; practically, it is used to distinguish when a female canine is at a particular point in the estrous cycle. In a normal vaginal smear, lactational cells, navicular cells, endocervical cells, endometrial cells, trophoblastic cells, and leucocytes may be present.

References

  1. ↑ Government of Alberta, Alberta Agriculture and Forestry, Food and Value Added Processing Division, Rural Development Branch, Agriculture Grant Programs Section. (2016, August 23). Synchronizing Estrus. Retrieved December 11, 2017, from http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/beef4894
  2. ↑ Hopkins, F. M., & Schrick, F. N. (n.d.). Estrous Synchronization . Retrieved December 7, 2017, from https://beef.unl.edu/reproduction/benefits-of-estrous-synchronization
  3. ↑ University of Nebraska-Lincoln | Web Developer Network. (2014, March). Benefits of Estrous Synchronization. Retrieved December 09, 2017, from https://beef.unl.edu/reproduction/benefits-of-estrous-synchronization
  4. ↑ Walsh, R., Leblanc, S., Vernooy, E. and Leslie, K. 2008. Safety of a progesterone-releasing intravaginal device as assessed from vaginal mucosal integrity and indicators of systemic inflammation in postpartum dairy cows. Canadian Journal of Veterinary Research, 72 (1), p. 43
  5. ↑ Nebel, Ray; M. DeJarnette. Dairy Cow Synchronization Protocols (2017). Select Reproductive Solutions.
  6. ↑ Dpi.vic.gov.au. 2013. Farmer Case Studies - Department of Environment and Primary Industries. [online] Available at: http://www.dpi.vic.gov.au/agriculture/dairy/handling-and-management/extended-lactation/farmer-case-studies [Accessed: 28 Oct 2013].
  7. 1 2 Hopkins, F. and Schrick, F. n.d. ESTROUS SYNCHRONIZATION. [e-book] pp. 1-2. Available through: http://animalscience.ag.utk.edu/Beef/Publications-Beef.html http://animalscience.ag.utk.edu/beef/pdf/EstrousSynchronization-FMH.pdf [Accessed: 28 Oct 2013].
  8. ↑ Dejarnette, M. 2004. ESTRUS SYNCHRONIZATION: A REPRODUCTIVE MANAGEMENT TOOL. [e-book] p. 7. Available through: selectsires.com http://www.selectsires.com/resources/fertilitydocs/estrus_syn_reproman.pdf [Accessed: 28 Oct 2013].
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