ROLE OF OXYTOCIN IN ANIMAL REPRODUCTION AND PRODUCTION
Oxytocin word is derived from Greek which means “quick birth”. Oxytocin is made in magnocellular neurosecretory cells in the supraoptic nucleus and paraventricular nucleus of the hypothalamus and is released into the blood from the posterior lobe of the pituitary gland. Oxytocin is also produced in the corpus luteum of the buffalo and cow (Wathes et al 1983). Oxytocin is secreted into the blood at orgasm – in both males and females. Half-life of oxytocin in blood is 0.55 to 3.6 minutes. Synthetic oxytocin is sold as generic oxytocin. Injected oxytocin analogues are used to induce labor and support labor in case of non-progression of parturition to facilitate birth. Physiologically important for cervical dilation before birth and causes contractions during the second and third stages of labor. Oxytocin release during calf-feeding causes mild but often painful uterine contractions during the first few weeks of lactation. This also serves to assist the uterus in clotting the placental attachment point postpartum.
Increase in oxytocin concentration over a threshold level and milk ejection occurred simultaneously and was closely correlated. The stripping yield was higher and fat content in the stripping yield significantly lower. Thus buffaloes are easily disturbed even by small changes in milking routines. (Thomas et al 2005). In India , unfortunately oxytocin is using by the owner to increase milk production without knowing any problem occur to the animal. Oxytocin is usually injected intra-muscularly in a dose of 10-20 IU immediately before each milking. The purchase of oxytocin does not require any prescription and is easily available even on a general store of a village although it is a Prescription drug..
Due to the rapid modernization and renewal happening in the society, we are facing many problems, some new diseases and new things are emerging day by day. The way it is increasing, due to that we need more amount of resources and production, due to which we are crossing any limit to increase the production capacity of anything, we are not seeing that Changes in the capacity of this thing can have serious consequences in the future. Man is using new chemicals and catalysts to produce more variety of food items, due to which production is increasing but its quality is being affected greatly. Such as tampering with natural things to produce more quantity of fruits, vegetables and milk can have fatal consequences. OT is a peptide hormone released from the posterior pituitary gland. The release of OT from the posterior pituitary is regulated by sensory stimuli rising from the cervix, vagina and the reflux of milk from the mammary glands. Stimulation of the cervix in pregnant animals triggers neural signals to the hypothalamus, causing secretion of OT, and nipple/nipple suction stimulation along the same pathway he releases OT. It is also known as Pitocin. Large amounts of milk are stored in the alveoli and ducts of the breast and are transported by neuroendocrine reflux through her OT to the cisternal space to produce milk. Oxytocin is released from the pituitary gland upon nipple stimulation. It contracts the myoepithelial cells around the alveoli and ducts of the breast. The milk is then transferred to the ducts, the cisterna of the gland and the nipple . Synthetic OT is used all over the world and in my country (India) approved by the Food and Drug Administration. It is commonly used to prevent postpartum haemorrhage, termination of treatment, and induction of labour, thereby providing postpartum lactation. This is now increasing daily. In the United States (USA), OT was used in 18.4% of all births, a rate reported as 20% in 2000. OT is injected into animals before or during milking. This removes all residual milk, as not all milk is removed from the breast. With OT, up to 90% of the milk is removed from the breast during normal pumping . Prolonged use of Exotic OT reduces milk yield. The effect of OT injections on milk yield varies between 10-15.5%. The dose and timing of OT injections control breast milk production.
It is a peptide hormone synthesized in magnocellular-neuro-secretory-cells in supraoptic and para ventricular hypothalamic nuclei while stored in posterior pituitary lobe then released in the blood as a result of a neuroendocrine reflex. OT is packaged in granules, then transported-down with posterior- pituitary-glandaxon and excreted to the systemic circulation with carrier protein, the neurophysins. It is related to the reproductive process causing the womb to contract. Similarly, an estrogen dominated myometrium such as is found at ovulation and at parturition, seems more responsive to OT, and as a result it causes greater contraction of the uterus. Release of OT at that time is associated with subsequent myometrial contractions and appropriate stimuli that assist the transportation of sperm to the oviduct at copulation and helps in the expulsion of the fetus at parturition; hence plays important role in completion of the fertilization process. OT is also secreted into the blood in both females and males also at the sexual orgasm. In cow/buffalo OT is secreted in brain and few other tissues along with ovaries, testes and corpusluteum (Wathes et al., 1983). In all the mammals OT is secreted endogenously for induction and maintenance of labor at birth process and for milk letdown in lactation. It causes uterine contraction as well as milk-ejection through promotion of myoepithelialcell’s contraction which surrounds milk alveolus. Natural OT causes milk to be ejected from the breasts during lactation: the amount of OT produced naturally, however, does not stimulate labor. For induction of labor at birth there is a need for administration of exogenous oxytocin. In order to duplicate the hormone and create an artificial drug OT (Syntocinon) was developed in 1953 by Vincent du Vigneaud (Bruckmaier, 2003). In case of the nonprogression of parturition, generic oxytocin analogues (synthetic OT) are used to facilitate the birth by induction and support of labor. It is very important physiologically for cervical dilation before the birth and contractions in 2nd and 3rd stage of labor during delivery process. The half-life of the OT in blood is 0.55 to 3.6 minutes, so it rapidly disappears from blood stream through the action of various enzymes only within 2-6 minutes (Ijaz and Aleem, 2006). OT causes contractions of the smaller ducts and myoepithelial-cells around the alveoli of mammary gland. After discovery of OT and studying it’s role in neuro-hormonal-milk-ejection process, it was recognized as a pharmacologic agent to facilitate and allowed the managing of milking-process with an exogenous-OT administration; Thus it ↑ the yield of milk in dairy animals (Kiran, 2001).
As a developing country, India depends mostly on agriculture and its livestock population. In India the livestock sector employs about 8 percent of the total population. India ranks one in terms of total livestock population as well as total milk production in the world. India contributes about 22 percent of the total global milk production. The increase in the demand for milk, has resulted in rampant use of various exogenous chemicals. One such incidence is the increase in the oxytocin supplementation. Oxytocin has been derived from the Greek word, which means quick birth. It is a peptide hormone synthesized in magnocellular-neuro-secretory-cells in supraoptic and paraventricular hypothalamic nuclei and stored in the posterior pituitary lobe then released in the blood as a result of a neuroendocrine reflex. It is transferred to the posterior pituitary after proteolytic processing and disulphide bond assembly Oxytocin is packaged in granules, then transported down with posterior-pituitary-gland axon and excreted to the systemic circulation with carrier protein, the neurophysin. Oxytocin, a neuropeptide, has 125 amino acid precursor. Apart from brain, Oxytocin is also synthesized in various other tissues and organs, including the uterine epithelium, ovary, testis, vascular endothelium and heart. It is now known that Oxytocin elicits its biological actions by binding to G-protein coupled receptor. In structural terms, oxytocin is a nano-peptide wherein the first cysteine residue is disulphide bonded to the 6th cysteine, thus creating partial cyclic peptide. The disulphide bridge in Oxytocin is essential for its interaction with the receptor and thus for biological activity.
Functions of Oxytocin
The oxytocin acts as the primary hormone for the ejection or let down of milk. Oxytocin is also involved in the process of parturition and in the management of post parturient uterine prolapse. It is used for the management of inevitable abortions and for the induction of abortions therapeutically. It is used for the treatment of cases like breast engorgement and mastitis, in the cases of agalactia and retention of fetal membrane. The release of oxytocin during suckling is to reinforce maternal behaviour. Oxytocin has insulinlike activity in that it stimulates lipogenesis and increases pyruvate dehydrogenase activity. Oxytocin released during milking or suckling is to increase peripheral concentrations of lipids as part of a mechanism designed to replenish the lipids “lost” during milking or suckling. Moreover, prolactin and oxytocin are released during suckling and milking, and both prolactin and oxytocin have been implicated in regulation of fluid and osmotic balance.
Exogeneous Oxytocin Analogues
In order to duplicate the hormone and create an artificial drug Oxytocin (Syntocinon) was developed in 1953 by Vincent du Vigneaud. Other analogues used are Pitocin, carbetocin etc. The dose rate for Oxytocin in case of cattle for uterus inaction, milk ejection, mastitis, uterus involution is 40IU(I.M./S.C.) or 2.5-10 IU(I.V.). While in case of sheep and goat , exogenous oxytocin is used for milk ejection and uterus involution at the dose rate of 10-20 IU (I.M./S.C.) or 0.5-2.5 IU(I.V.), and in the case of uterus inaction, it is 10-20 IU (I.M./S.C.) or 0.5-2.5 IU(I.V.).
Milk Production and Oxytocin
Lactation consists of two phases: milk secretion or synthesis, which is controlled inpart by a hormonal complex originating in the anterior pituitary, and milk removal or (ejection), which is controlled primarily by oxytocin release from the posterior pituitary. The receptors for oxytocin are present in the smooth muscle cells and myoepithelial cells. The contraction of the myoepithelial cells result in the ejection of milk from mammary ducts. The receptors for oxytocin are also present in the myometrium and endometrium which gets activated at the end of pregnancy. The half-life of oxytocin is given by 2-8 minutes. Basal concentrations of oxytocin decreased from early to middle lactation, increased from middle to late lactation, and further increased from late lactation to the dry period.
Advantages of Oxytocin Injection
Effect on milk production:
There is an increase in milk production. There is increased gland milk output rather than residual milk removal. It is obvious that total evacuation of the udder during milking so that there is no-residual milk reduced production-losses which occur when using once a day milking, while ↑ the rate of milking was found ineffective in reduction of losses. Exogenous oxytocin injections at non-milking times ↑ the milk yield and improved galactopoiesis (maintainance of milk production). Thus, oxytocin influences cell maintenance and mammary metabolism in addition to its traditional role of facilitating milk let-down. The use of oxytocin to promote milk let-down, in particular when the glands are engorged with milk, can prevent udder damage and promote udder health.
Effect on milk composition:
Chronic oxytocin administration has also been shown to increase electrical conductivity and SCC of milk as well as lactose and K levels in the systemic circulation.
Effect on reproductive health:
Oxytocin is related to the reproductive process causing the womb to contract. Similarly, an oestrogen dominated myometrium such as is found at ovulation and at parturition, seems more responsive to oxytocin, and as a result, it causes greater contraction of the uterus. The release of oxytocin at that time is associated with subsequent myometrial contractions and appropriate stimuli that assist the transportation of sperm to the oviduct at copulation and helps in the expulsion of the foetus at parturition; hence plays an important role in the completion of the fertilization and parturition process. Oxytocin is also secreted into the blood in both females and males also at the sexual orgasm.
Disadvantages of Exogenous Oxytocin
Effect on milk production:
Milk let-down without administration of oxytocin seems to be difficult in the animals which regularly exposed to oxytocin injections as they become habitual to the drug. While repeated administration of oxytocin injections therefore interferes with the normal mammary epithelium milk secretary activity thus inhibits the normal milk ejection process and affect reproductive health. Thus a disadvantage of oxytocin injection was that its continuous usage could lead to addiction and lack of response to normal milk ejection stimuli.
Effect on reproduction:
It is believed that the prolonged use of oxytocin injections also causes fertility disorders like poor oestrus signs, reduced lactation period, lower conception rate and high embryonic mortalities. Delayed puberty, lower conception rates, increased abortion rates, lower pregnancy chances, delays in the duration of placenta expulsion, ovulation interval, shortened postpartum oestrus interval and calf death soon after the delivery because of poor quantity and quality of milk have also been observed.
Effect on human health:
Oxytocin produces its desired effects in minutes and then is readily metabolized in inactive products. It is mostly secreted and ingested along with the milk, it is efficiently degraded by gut enzymes so can’t reach the blood circulation in biologically active form. However ,it has been believed to have harmful effects when milk with oxytocin is consumed by humans. For example, oxytocin in milk and dairy products, the age at which girls attain menarche has come down drastically from 16 years of age to 10 years of age. Gynaecomastia (breast enlargement) is diagnosing even in boys due to oxytocin affects. Due toIt is clear to have imbalance hearing and weak eyesight in children due to oxytocin. Pregnant women should avoid such milk or don’t use milk without proper boiling. The use of such milk by the pregnant women may lead to abortion. And babies may born with deformities and low immunity levels. Use of such milk also increases the risk of haemorrhage in mothers after birth.
Since oxytocin is mostly known for let-down of milk , extensive use of oxytocin to increase the milk yield has let to harmful effects on the animals. There has been reduction in response to natural stimuli for let -down of milk. Moreover, the action of hormone causes the uterus of the cattle to contract, causing immense pain. Due to these reasons of extensive unethical use of oxytocin injection, Oxytocin is banned under Section 12 of the Prevention of Cruelty to Animals Act (1960). According to Food and Consumable Substances Adulteration Act and the Drug Control Laws cannot be sold without a prescription from a registered medical practitioner. Thus, judicious use of exogeneous oxytocin supplements with proper consultancy can be helpful in terms of milk production as well as animal health
OT Applications
The synthetic OT is used in veterinary and human medicine practice. OT is the drug of choice to augment and induce the rhythmic contractions of the uterus during the desultory labor both in human and veterinary treatment. It is used to prevent and control the bleeding after abortion and childbirth. It is also used for the management of inevitable abortions and for the induction of abortions therapeutically. Clinical use of OT for promotion of the milk-ejection in lactating women which experience breast feeding difficulty is also equally important. Moreover, it is used for the treatment of cases like breast engorgement and mastitis. OT is used universally for expulsion of retained placenta after delivery and to induce the letdown of milk in veterinary practice. OT is also used to aid the delivery when female has been in labor for an extended period in young animals. Furthermore, OT is also very helpful in the management of post parturient uterine prolapse. It is employed frequently as an adjunct to the antibiotic-therapy for the treatment of mastitis in lactating animals (Ijaz and Aleem, 2006). It is often administered in dairy practice to reverse any failure in milk ejection caused by a lack or reduction in endogenous OT release. It is also administered in the cases of agalactia. However, the effect of its injection on milk ejection efficiency and blood flow pattern is unclear. Although genetics, hormonal status, environment, milking frequency and nutritional status are the main factors which regulate the milk yield in dairy animals (Bruckmaier, 2003; Lollivier et al., 2005). In addition, long term treatment of OT in cows reduces the spontaneous milk-ejection upon cessation of the treatment. Meyerhoff (2016) reported that in dairy farming exogenous administration of OT helps to release milk by simultaneously stimulating and calming the animal. So, it is very useful to the farmer if the animal is stressed-: examples include when animals are milked for the first time or experience a difficult birth. In the uterus OT plays its role by binding to specific receptors which are present on smooth muscle cells. At the point of parturition or when babies are delivered prematurely, the number and affinity of OT receptors increases. During fetal expulsion OT is secreted by the posterior pituitary and by intrauterine tissues in a pulsatile manner. While in mammary tissues myoepithelial cells have OT receptors which performs bindings, contract in response to their activation by OT resulting in ejection of milk from milk ducts (Rogers, 2016).
Effects on milk production
OT administration to cattle for whole lactation resulted in ↑ milk yield by 11.6% over control animals (Nostrand et al., 1991). Similarly, ). Similarly, milk production ↑
What is oxytocin?
Oxytocin is a natural hormone that manages key aspects of the female and male reproductive systems, including labor and delivery and lactation, as well as aspects of human behavior. Your hypothalamus makes oxytocin, but your posterior pituitary gland stores and releases it into your bloodstream.
Hormones are chemicals that coordinate different functions in your body by carrying messages through your blood to your organs, muscles and other tissues. These signals tell your body what to do and when to do it.
Your hypothalamus is the part of your brain that controls functions like blood pressure, heart rate, body temperature and digestion.
Your pituitary gland is a small, pea-sized endocrine gland located at the base of your brain below your hypothalamus.
Synthetic forms of oxytocin
Healthcare providers use synthetic (manufactured) forms of oxytocin — Syntocinon® and Pitocin® — to induce labor in childbirth if it hasn’t started naturally or to strengthen contractions. Healthcare providers also use synthetic oxytocin to speed up delivery of the placenta (the third stage of labor) and reduce the risk of heavy bleeding (postpartum hemorrhage).
What is the function of oxytocin?
The two main physical functions of oxytocin are to stimulate uterine contractions in labor and childbirth and to stimulate contractions of breast tissue to aid in lactation after childbirth.
Oxytocin also acts as a chemical messenger in your brain and has an important role in many human behaviors and social interactions, including:
- Sexual arousal.
- Recognition.
- Trust.
- Romantic attachment.
- Parent-infant bonding.
The effects of oxytocin on your brain are complex. Scientists are currently researching the role of oxytocin in various conditions, including:
- Addiction.
- Anorexia.
- Anxiety.
- Autism spectrum disorder.
- Depression.
- Post-traumatic stress disorder (PTSD).
Oxytocin and uterine contractions
During labor, when the fetus’s body (usually head) pushes against your cervix, the nerve impulses from this stimulation travel to your brain and stimulate your pituitary gland to release oxytocin into your bloodstream. The oxytocin travels to your uterus and stimulates contractions.
These uterine contractions, in turn, cause your pituitary gland to release more oxytocin, leading to an increase in both the intensity and frequency of contractions. Oxytocin also increases the production of prostaglandins (a group of lipids with hormone-like actions), which move labor along and increase the contractions even more. This enables you to carry out vaginal delivery completely.
Oxytocin and lactation
Once your baby is born, oxytocin promotes lactation by causing contractions of the myoepithelial cells in the alveolar ducts of your breasts. These contractions move milk through your breast tissue.
When your baby sucks at your breast, oxytocin secretion causes the milk to release so your baby can feed. As long as your baby keeps sucking, your pituitary gland continues releasing oxytocin. Once your baby stops feeding, the release of oxytocin stops until the next feeding.
Oxytocin in people assigned male at birth
In people assigned male at birth (AMAB), oxytocin plays a part in ejaculation. The hormone contracts the vas deferens to push sperm and semen forward for ejection. Oxytocin also affects the production of testosterone (a sex hormone) in the testes.
How are oxytocin levels controlled?
Oxytocin is one of a few hormones that have a positive feedback loop. This means that the release of oxytocin leads to actions that stimulate your pituitary gland to release even more of it.
Most hormones create negative feedback loops after they’re released, meaning your body releases less of the hormone after it has its effect on your body.
With uterine contractions in childbirth, pressure on your cervix from the fetus baby stimulates your pituitary to release oxytocin. The release continues until your baby is born. With lactation and breastfeeding (chestfeeding), your baby’s sucking stimulates your pituitary to release oxytocin to push milk through your breast tissue. The release continues until your baby stops feeding and will restart when your baby feeds again.
What happens when oxytocin levels are low?
Having lower-than-normal levels of oxytocin is rare.
Low levels of oxytocin could stop uterine contractions during the birthing process and prevent milk ejection after giving birth. Although it’s rare, the most common cause of lower-than-normal oxytocin levels is panhypopituitarism, a condition in which all the levels of hormones your pituitary gland releases are below normal.
Low oxytocin levels have been linked to autism spectrum disorder and depressive symptoms. Scientists are still researching the connection between oxytocin and these conditions, and the potential of using synthetic oxytocin as a treatment.
What happens when oxytocin levels are high?
Having higher-than-normal oxytocin levels is very rare for people assigned female at birth (AFAB) and is called oxytocin toxicity. It results in an overactive uterus, causing an increase in uterine muscle mass (hypertrophy), which limits pregnancy due to not being enough space in your uterus to hold your fetus.
For people assigned male at birth, high levels of oxytocin have been linked to benign prostatic hyperplasia (BPH). BPH is a condition in which the prostate, a walnut-sized body part made of glandular and muscular tissue, grows in size.
The prostate surrounds part of the urethra, which is the tube that carries urine and sperm out of the body. BPH can make it difficult to pee (urinate). It affects more than half of people assigned male at birth over the age of 60.
FREQUENTLY ASKED QUESTIONS
Why is oxytocin called the love drug?
As oxytocin is associated with trust, sexual arousal and relationship building, it’s sometimes referred to as the “love hormone” or “cuddle chemical.” Oxytocin levels also increase when you’re hugging someone and when you’re experiencing an orgasm.
Compiled & Shared by- Team, LITD (Livestock Institute of Training & Development)
Image-Courtesy-Google
Reference-On Request.
