Reproduction Physiology: Key Terms

Physiology of Reproduction: Common Terminologies

• Andrology studies the physiopathology of the male reproductive system.
• Gynaecology studies the physiopathology of the female reproductive system, focusing on the health of female reproductive organs and associated diseases.
• Veterinary Obstetrics is an area of veterinary science that deals with necessary aid for parturition in animals, encompassing the management of pregnancy and labor.
• Embryology is the study of the physiological development and growth of the antenatal (pre-birth) individual.
• Teratology studies abnormal development and malformations in antenatal individuals, bridging embryology and pathology.
• Fertility in males refers to the desire to mate and the ability to produce viable spermatozoa.
• Fertility in females includes the desire to mate, the ability to conceive, the capacity to nourish the conceptus, and the power to expel the fetus and fetal membranes at the normal gestation length.
• Artificial Insemination introduces semen into the female uterus through artificial means.
• Capacitation is a stage in sperm maturation that enables sperm to undergo the acrosome reaction, an important step for fertilization.
• Cryoprotectants, ex: Glycerol, DMSO, Etylene glycol, are used in freezing solutions to protect semen during cryopreservation.
• Germ cells are defined as spermatozoa or oocytes.
• Long-day breeders' reproductive activity and cyclicity peaks during spring and summer due to long photoperiods.
• Short-day breeders such as certain females begin estrous cycles during periods of short photoperiods (short days).
• Luteinizing hormone (LH) is a glycoprotein hormone secreted by the anterior pituitary lobe that triggers ovulation and the development/maintenance of the corpus luteum; LH causes leydig cells to produce testosterone in males.
• The Pampiniform plexus is a specialized venous plexus in the spermatic cord that cools arterial blood, providing a countercurrent heat exchange for the testes.
• Semen is a viscous, whitish secretion from the male reproductive organ that contains spermatozoa and seminal plasma.
• Seminal plasma is the noncellular liquid portion of semen produced by accessory sex glands.
• Sertoli cells, found in the seminiferous epithelium, are believed to control spermatogenesis.
• Theriogenology is a specialty in veterinary medicine focusing on the normal function and pathology of animal reproductive systems.
• An embryo is an organism in the early stages of development before it has gained anatomical features recognizably of a specific species.
• A fetus is a potential offspring still inside the uterus but generally recognizable as a member of its species, considered a more advanced form of an embryo.
• A conceptus is the product of conception.
• Abortion is the expulsion of a living fetus before it can survive or a dead fetus at any gestation stage.
• Libido is innate sexual desire.
• The hilus is a region housing blood and lymphatic vessels and nerves that serve an organ.
• Luteinisation is the transformation of granulosal and thecal cells into luteal cells, stimulated by LH.
• Luteolysis is when luteal tissue is rendered non-functional.
• The Zona pellucida is a thick layer mostly made of mucoprotein surrounding the oocyte and early embryo.
• A zygote is the diploid cell resulting from the fusion of male and female pronuclei.
• Primipara refers to animals that have conceived and completed one gestation period.
• Pluripara refers to animals that have conceived and completed more than one gestation period.

Puberty

• Puberty is the stage in life when reproductive organs develop and sexual and innate interests become prominent.
• Animals become able to produce spermatozoa, and the female is able to copulate, resulting in pregnancy.
• Puberty does not indicate full reproductive capacity; maturity is attained later.
• In females, first ovulation or first estrus is an indicator of puberty.

Average Age at Puberty (months)

• Sheep: 5-9
• Pigs: 3-7
• Cattle: 10-20
• Horses: 15-24
• Bull: 12-18 (exotic), 18-24 (zebu)
• Buffalo: 24-30
• Stallion: 18
• Ram: 7-8
• Boar: 6-7
• Dog: 8-10
• Cat: 9-10

Factors Affecting Age at Puberty and Sexual Maturity

• Genetic factors significantly influence the age at puberty.
• Nutritional factors are very important; TDN, protein, calcium, phosphorus, copper, cobalt, iron, and iodine deficiencies can prevent gonadotropin secretion.
• Hormonal factors are important; testosterone and gonadotropin balance is essential for proper functioning.
• Social and climatic factors influence puberty age; presence of females can hasten puberty in males.
• Body weight influences due to nutrition; recommended body weight for bulls for service is around 240 kg at 18 months; for buffalo bulls, around 280 kg.

Estrus Cycle Intro and Definition

• In all domestic animals that have reached puberty, a physiological rhythm of the reproductive system known as the estrous cycle exists.
• The term for one cycle interval is from the start of sexual receptivity to the next, or between successive estrus phases.
• The estrous cycle is a period of sexual receptivity in females at regular intervals.
• Hormones from the ovary (directly) and the adenohypophysis (indirectly) control the estrous cycle.
• The basic pattern of the cycle is the same across species, but there are stage differences.

Estrus Cycle Types

• Monoestrus: animals have one estrous cycle per year -dogs, wolves, bears
• Polyestrus: animals have multiple estrous cycles per year; cattle/pigs/humans, Cows/sows
• Seasonal breeders: animals that have one or more estrous cycles during certain periods of the year.
• Seasonally polyestrus: animals exhibit many cycles of estrousduring certain periods known as breeding season - ewes, does, mares
• Seasonally polyestrus can be short-day or long-day breeders

Estrus Cycle Type Details

• Short-day breeders estrous cycle occurs as days get shorter in winter and cause anestrus in Spring/Summer e.g. sheep, goats, deer.
• Long-day breeders estrous cycle occurs as days get longer in Spring/Summer and cause anestrus in winter - horses and hamsters.
• Seasonally monoestrus animals are only in estrus once and then enter anestrus - bitches
• The queen will undergo a series of ovulatory estrus in Spring, Summer, and early Autumn.

Estrus Cycle Phases

• The estrous cycle has four main phases: Proestrus, Estrus, Metestrus, Diestrus
• Based on changes occurring in the ovary, the estrous cycle consists of the follicular stage or proliferative/oestrogenic phase
• The estrus cycle also consists of the Luteal phase or secretory stage.

Estrus Cycle, Follicular and Luteal Phases

• The follicular or oestrogenic phase where the oocyte matures and ovulation occurs and includes both proestrus and estrus phases.
• The luteal phase is when the corpus luteum forms, leading to fertilization and embryo development.
• Progesterone from the CL is generally dominant and includes metestrus and diestrus.

Proestrus: Follicular Growth

• Proestrus is a period of rapid follicular growth under gonadotrophic stimulation where, in polyestrous species, the CL (Corpus Luteum) regresses from the previous cycle.
• GnRH, FSH, and LH all influences follicle growth, also known as folliculogenesis.
• Follicle growth occurs through small, medium, and large sized follicles with Follicle Stimulating Hormone initiating growth.
• Luteinizing Hormone converts C-27 steroid cholesterol to C-19 steroid androgen in the theca interna.
• FSH favors C-18 steroid estrogen from androgen by the granulose cells.
• Estrogen concentration Progressively increases, resulting in simultaneous decline in progesterone level.
• PGF2a triggers the luteolytic action which causes the regression of the corpus luteum of the previous cycle by PGF2a in polyestrus species.
• Folliculogenesis is depressed during pregnancy, except in mares, because of high levels of progesterone.
• there is increased growth of reproductive tract epithelial tissues, musculature action, mucus secretion, and Endometrial/vaginal mucosa vascularity.
• In cows and mares sticky, dry mucus changes during proestrus into a milky, less viscid discharge (serous), then to clear transparent, stringy mucus late in the proestus period.
• Proestrus is not clinically evident in most domestic species and lasts ~2-3 days.
• In the bitch, Proestrus lasts for 7-9 days and is clearly identifiable by well-defined changes in the external genitaila and behavioral signs due to increasing sexual excitement.
• increased Endometrial vascularity is characterized by bleeding.
• The vulva becomes edematous and swollen.
• There is a gradual relaxation of the cervix and an increased secretion of viscid, slimy mucus from the goblet cells of the cervix and anterior vagina and from the uterine glands.

Estrus: Sexual Receptivity

• Estrus is the period of sexual receptivity during which most species mate, ovulation occurs, and the corpus luteum begins to form.
• The graafian follicle is large and mature which leads to maturation changes when the ovum goes under estrogen production.
• Increasing level of estrogen is produced by synergistic effects of theca and granulosa cells.
• The hormones Inhibin and increasing level of estrogen secreted from the graafian follicle inhibit hypothalamic and pituitary gonadotrophin secretion, thus inhibit FSH release by negative feedback effect.
• Increased estrogen levels trigger hypothalamic LHRH release via the positive feedback mechanism that results in greater ovulatory LH surge before ovulation.

Estrus: Oviducts

• The oviducts are tonic, the epithelium mature, and cilia are active resulting contract to a close affinity from the Graffian follicle.
• There is increased number of secretions which happens when the oviduct increase.
• The uterus is erect and turgid resulting higher Mucosa growth in blood supply and increased edema and mucus secretions.
• The vagina, vulval and cervical mucosa is congested/pink due to increased vascularity.
• greatly increased mucus secretion is shown by strings of mucus discharge.
• Increased leukocytes towards the uterine lumen.
• Most species rupture mature ovisacs or ovulate towards the end of the estrum period.
• The Estrus duration varies such as 14-18 hours in cow, 7-10 days in mare and bitch.
• additional signs are mounting, bellowing, frequent urination, discharge, reduced feed intake/milk yield.

Species and Signs of Estrus

• Cow Bellowing, mounting, Cervical mucus discharge, Frequent urination, Swollen vulva, Reduced milk yield and Reduced feed intake.
• Mare Frequent urination, Exposure of clitoris (winking of clitoris).
• Doe Edema and hyperemia of vulva, Frequent and rapid tail wagging.
• Sow Watery vulval discharge, Standing quietly while pressing loin (lordosis).
• Bitch During proestrus, bleeding from vulva and vulva swelling; during estrus diminishing of vulval swelling, Less turgid vagina.
• Queen Characteristic call and Roll over on its back.

Specific Behavioral Signs

• Buffalo cows show less signs of estrus, only frequent urination, teat swelling, a reduction in milk yield and bellowing.
• Mare may act different to other horses as well as nastiness, vicious temper, frequent urination, brownish yellow discharge as well as mucous exposure
• Cattle show restlessness, frequent bellowing and mud after the estrous cycle.

Metestrus phase

• Metestrus is a transitional period when ovulation happens and progesterone is produced.
• The Granulosa and thecal cells grow together, reorganizing into the corpus luteum (CL), corpus lutem hemorrhagicum.
• CL grows quickly from granulosa cells.
• Hormone levels also play a large role in metestrus.

Diestrus phase

• It is a long lasting period with cows, sheep goats and others.
• is largely affected by Progesterone since it prepares growth for the feus.

Anestrus phase

• Happens when the breeding season has ended and the animals dont breed.
• Uterus is very small and inactive.
• Follicles may develops, but not many are mature.

Estrous cycle details

• Estrous cycle is regulated through GnRH hormones.
• These hormone help follicle growth maturation.
• In non pregnant animals, the lysis starts to die and triggers the cycle once again where new GnRh and gondatrophin triggers the process.

Photoperiods

• Light is the simulator for cycling in the estrous period.
• Animals react to lighting by the pinel gland and hypothalmus.
• The increasing secretion of melatoin triggers the decreasing photo-period.

Chapter 4: Reproductive Hormones

• Hormones are organic substances, the secretion of which is essential for successful reproduction.
• Primary hormones are directly involved in spermatogenesis, oogenesis, and ovulation.
• Secondary hormones are needed for organisms to reproduce to occur.

Gonadotrophin Releasing Hormone (GnRH)

• GnRH, secreted by the hypothalmic surge and tonic centres, influences the anterior pituitary gland.
• GnRH in males and females secretion influences Follicle Stimulating Hormone (FSH) and Leutinising Hormone (LH) which come from the anterior pituitary gland.
• GnRH triggers the release of a surge due to estrogen as well as regulates LH which stimulates ovulation.

Luteinising Hormone (LH)

• LH stimulates production/secretion of testosterone from the testes through leydig cells
• It is a type of Glycoprotein, produce from the Anterior pituitary.
• Concentration for LH increases during ovulation.
• There are 4-12 GnRH Pulses and LH Peaks in Males.

Follicle Stimulating Hormone (FSH)

• This helps Germ cell's maturation and is secreted by GnRH.
• In males, FSH also triggers Inhibin.
• Cycles such as seasonal activity are controlled by this pulsatile system. In male animals there are generally 4 to 12 GnRH pulses per day.
• FSH stimulates the maturation of germ cells within the testes and ovaries.
• In the female it also stimulates follicular development and oestradiol synthesis.

Prolactin (PRL)

• Exerts a stimulatory effect on milk synthesis within mammary glands.
• Regulated by the hypothalamus (dopamine, prolactin).
• PRL-RH) that is an intracellular tyrosine kinase.

Oxytocin (OT)

• Synthesised in the Hypothalamus.
• Upregulating of the activity of smooth muscle cells of the uterus.
• Contraction From the myometrium.

Estradiol (E2)

• Part of the Estrogen Hormones and a Steroid Hormone.
• Principle estrogen in females, chemically similar to Estrone and Estriol.

Progesterone (P4)

• Hormones that is based on a Cholesterol molecule produced by the corpus luteum.
• It is designed for nourishment of the embryo, stabilises muscles to be contracted.

Testosterone (T)

• The male sex hormone and is required for spermatogenesis
• Steroid hormone that is made by leydig cells
• Primary action is anabolic growth.

Prostaglandin F2a

• A fatty acid and lipid soluable.
• The target tissue in the female is the corpus luteum.

Chapter 5: Conception and Gestation

• Conception refers to fertilization. It is the successful fusion of gametes to form a new organism.
• the important factor that governs the gestation length in animal is mainly genetically determined.

Species RANGE of Gestation length in Days

• CATLLE 275-290
• SHEEP 145-155
• GOAT 145-155
• SWINE 112-115
• MARE 325-345
• MOUSE 19-20
• RABBIT 30-32
• ELEPHANT 630-660
• WOMAN252-274
• LION 110-112
• TIGER 103-110
• LEOPARD 93-105
• CHEETAH 91-95

Factors Affecting Length of Gestation:

• Genetic: pregnancy duration varies between species and breeds
• Material: age of the dam affects gestation length
• Fetal: size and sex of the fetus influences gestation length
• Physical Season of the year may be a modifying influence on gestation length.

Chapter 6: Sign of parturition in Difference Species

• Parturition is the act of giving birth, labor is the act of moving the fetus out of the females’ body.
• General sign of parturition in all females animal is a is a swollen udder and discharge from the vulva.

Other physical signs

• swollen vulva, sunken hips, leaking milk.
• The animal may move restlessly.

Chapter 7: Methods of Collection of Semen

• Insemination is a breeding method that contributes to improvement of farm animal populations,.
• Three most common methods are Artificial Vagina and Electro Ejaculation and Massage Method

Additional Information

• For Collection the temperature should steady between 45-46°C, The bull should be backtracked.
• The voltage should be gradually increased from zero to 10 to 15 volt with an increase of two volt.

Chapter 8: Method of Semen Extension and Preservation

• Semen collected from farm animals and used for Al is either extended and used "fresh" within several days of collection or extended and frozen for use at a later date.
• The freezing method contains temperatures at -196° c.

Chapter 9: Transportation of Semen

• Transportation may be done by thermos flask or insulated cartons and should be minimized with Jerks.

Chapter 10: Introductions - Artificial Insemination

• Artificial insemination (AI) is the single technique that has been most popular in veterinary practice.

Additional Info

• Used in 1939 by Kumaran at Palace Dairy Farm and can be loaded at Al gun.
• Animal should be in Estrum

Chapter 11: Precaution of Handling Liquid Nitrogen

• Avoid high concentrate of escaping gas.
• Wear safety equipment
• Use label as living biology