Reproductive Physiology and Artificial Insemination (AnSc 321) PDF

# Reproductive Physiology and Artificial Insemination ## (AnSc 321) Sep, 2024 Bale-Robe, Ethiopia ### 1. What is Reproduction? - The process by which organisms produce more of their own kind offspring are reproduced. - Offspring are produced by male and female parents. - It involves heterose...

# Reproductive Physiology and Artificial Insemination ## (AnSc 321) Sep, 2024 Bale-Robe, Ethiopia ### 1. What is Reproduction? - The process by which organisms produce more of their own kind offspring are reproduced. - Offspring are produced by male and female parents. - It involves heterosexual mating, conception, pregnancy, parturition and lactation. - Reproduction involves close coordination of various physiological events to be successful. #### Types of Reproduction - Two types of reproduction: - Sexual reproduction (sperm + egg) - Asexual reproduction no fusion of gametes #### Sexual Reproduction (male gamete+ female gamete= offspring) - Cells of the offspring have 2 sets of chromosomes (one from each parent) - Sexual reproduction involves two stages: - Meiosis- special cell division - Fertilization- fusion of 2 gametes #### Types of fertilization - External - fish - Internal (all mammals and birds) #### Incubations - External incubation - birds - Internal incubation – mammals #### Asexual Reproduction - Perpetuation without sex (parthenogenesis) - Only one parent is involved (no males) - Offspring are genetically identical to their parents - Faster population growth ##### Types of Asexual reproduction - Mitosis - Binary fission - Budding - Sporulation - Regeneration ##### Mitosis (Somatic Cell Division) - Exact duplication of the nucleus of a cell so as to form two identical nuclei during cell division. ##### Binary Fission - Occurs in one celled organisms like ameba, paramecium - Nucleus divides via mitosis and the cytoplasm divides, forming 2 new daughter cells of equal size. ##### Budding - Occurs in hydra and yeast - The division of cytoplasm is unequal, one daughter cells is larger than the other. - Daughter cells can separate or remain attached. ##### Sporulation - Occurs in molds, etc. - Spores produced in large numbers by mitosis. - Spores are surrounded by a tough coat to help them survive harsh environmental conditions. ##### Regeneration - The replacement or re-growth of lost or damaged body parts. #### Parthenogenesis - Is the development of an unfertilized egg into a new individual that is a clone of the parents. - Animals that are parthenogenetics include bees, wasps, ants and some species of birds and lizards. #### Role of Male and Female in Reproduction - **Role of males** - Produce mature spermatozoa >* Store spermatozoa until needed. >* Discharge spermatozoa in to female tract and fertilize the egg. - **Role of females** >* Provide ova(eggs) >* Provide proper environment for fertilization >* Nurture the embryo/fetus(gestation) >* Deliver immature individual >* Provide for proper behavior patterns >* Attracting males and mating. #### Maternal functions ### 2. Male Reproductive Tracts and Physiology - The male reproductive organ can be viewed as: >* Primary sex organs (testes and scrotal sac suspended by spermatic cord) >* Secondary sex organs (duct tissues, which transport sperm from the testes to the externa and include the efferent ducts within the tests, epididymes, ductus deferens (vas deferens), the urethra and penis). >* Accessory sex organs (prostate gland, seminal vesicles and bulbo-urethral (cowper’s) glands). - But, all the sex organs work together to form, mature & transport spermatozoa. #### Primary Organs of Reproduction of male animal Testes (plural) - testis (singular) - Sperm producing organ - Held in the scrotum - Testicle include testes and scrotum #### Purpose of Suspension from the body (Scrotum) - As heat regulating mechanism (for normal sperm formation) - At 4 to/or 5 °C below body temperature is essential for spermatogenesis (growth and maturation of the sperm) #### Functions of Testes - Testes has 2 vital functions: >* Produce testosterone (Leydig (Interstitial) cells or gonads) >* Site of spermatogenesis (sperm production) - within seminiferous tubules ### Regulation or Coordination of 3 Structures: 1. **External Cremaster muscle within the spermatic cord** - Consists of Cremaster muscle, Ductus deferens, Testicular artery, Pampiniform plexus 2. **Temperature-sensitive layer of muscle** - The scrotum is lined internally by muscle (Tunica dartos). 3. **Counter-current temperature exchange** - Regulated by pampiniform plexus (a complex network of veins, around the spermatic artery, in the base of the card). #### Cremaster muscle within the spermatic cord - Muscle from internal abdominal oblique - Can only sustain short periods of contractions (does not work well to pull up testis) - Primarily a pumping action on the pampiniform #### The Interior of the Testis - Divided into compartments (lobules) by fibrous membranes (septa). #### Each Lobule Consists of: - Semniferous tubules (up to four) - They are embedded in tissue that consists of: >* Blood vessels, >* Nerves and >* Leydig cells #### The Testis Contains: - Long, tiny, coiled tubes - Known as seminiferous tubules #### Seminiferous Tubules - In the seminiferous tubules sperm formed & begin to mature. - Seminiferous tubules are surrounded by Leydig cells >* Highly specialized cells >* Produce testosterone. #### Semniferous Cells - Are of 2 types >* Spermatogenic cells (Spermatogonia) divide and differentiate to from spermatozoa. >* Sertoli cells (provides a microenvironment for normal spermiogensis) #### Functions of spermatogenic and Sertoli cells - **Spermatogenic cells (spermatogonia)** >* Give rise to spermatozoa - **Sertoli cells** >* Supply nutrients to spermatogonia #### The Secondary Sex Organs: - Epididymis - Vas deferens - Penis #### Epididymis - Flat and convoluted structure - Attached to one side of the testicle ##### General functions of epididymis - Mature sperm: release of protoplasmic droplet from sperm. - Store sperm: mainly in the tail (up to 60 days motile and fertile) (sperm collecting ducts) - Transit sperm : 10-12 Days - Absorb sperm: in prolonged sexual rest - Secrets glyceryl-phosphorylcholine which is metabolized by sperm in female genitalia for gaining more energy during capacitation #### Parts of Epididymis - Epididymis is divided into 3 regions. - **Body of Epididymis** - Caput Epididymis (head) >* Sperm maintain mobility. - Corpus Epididymis (body) >* Sperm maintain mobility. - Cauda Epididymis (tail) >* Principal storage of sperm >* Contains ≈ 70% of total epididymal sperm #### Vas Deferens (Ducts deferens) - Cord like structure and it joins ducts of seminal vesicles. - Emerges from tail of epididymis to pelvic urethra. - Passes as part of spermatic cord. - Its Ampulla secrete fructose and citric acid (branched tubular glands, which in the stallion, are highly developed and contribute ergothionine to the ejaculate). ##### Function of Vas (ducts) deferens: - Transport sperm from epididymis to the urethra at the time of ejaculation. - May contain large number of sperm equal ejaculate. - Nutritive to stored sperm. - Sperm stayed alive, motile & fertile for 3 days then loose its fertilizing capacity. - May absorb dead sperm. #### Penis - The organ of insemination. - Consists of 3 parts: >* Root >* Body >* Glans penis - Mainly composed of erectile tissue. - Forms s-shaped curve (sigmoid flexure) behind scrotum. #### Urethra - Begins at the opening of bladder and is continuous with the penis. - Posterior portion of the urethra is S-shaped (Sigmoid flexure). #### The Sigmoid Flexure - An S-shaped curve behind scrotum. - It extends the penis outside of the body and into the vaginal cavity of the female so that the semen can be deposited. - Strong retractor muscles hold the penis in the S shaped configuration. >* Retractor muscle retracts the penis into the protective sheath. >* Straightened during erection. >* If these muscles are too weak portion of the penis protrude at all times. >* If Sigmoid flexure doesn’t work the male is sterile. #### Prepuce - Tubular integument that covers the free portion of penis (30-40 cm long). - Tubular glands secrete smegma that modulate the condition of prepuce >* Function is to protect the penis - Has an orifice with long tough hair and supported by protractor muscles for closure. #### Accessory Glands of Male Animal (accessory sex organs) - Prostate gland (1) - Seminal vesicles (2) - Bulbo urethral (Cowper’s) gland (2) ##### Secretions from the three glands: - Make up most of the liquid portion of semen (add volume). - Provide medium for the transport of sperm from testes to vagina. - Provides nutrients for the sperm. - Clean and flushes out urinary tract. #### The Prostate Gland - The only gland common to all mammals. - Located at the neck of the urinary bladder. - Relatively small in the bull than other species. ##### Functions of prostate gland. - Doesn’t produce very large volume secretion. - Secrete large amount of minerals that regulate buffering system of seminal plasma. - Secrete amino acids for sperm nutrition. - It is alkaline in reaction to neutralize the acidic sperm coming from the Cauda epididymis. - Participate as a vehicle media for sperm with the seminal glands #### Seminal Vesicles - Lie on either side of the neck of the bladder. - Each has excretory duct. ##### Functions of seminal vesicles. - Secrete main volume of seminal plasma (>50%) which act as a vehicle to sperm activity. - Secrete Fructose for energy to sperm. - Secrete citric acid as buffer to sperm. - Secrete K and iron to control equilibrium of osmotic pressure. - Secrete flavin which give yellow coloration to normal ejaculate in few bulls #### Bulbo-Urethral (Cowper’s) Glands - Small, firm glands. - Located on either side of the urethra, behind the prostate. - Has secretory duct to pelvic urethra. ##### Function of bulbo-urethral glands (Cowper’s glands). - Flush, clean and neutralize the urethra of any urine residue (may be harmful to spermatozoa) - The clear secretion that often drips from the penis during sexual excitement prior to service is largely produced by these glands ##### Accessory gland fluids contain: - Sodium chloride - Potassium chloride - Nitrogen - Citric acid - Fructose - Several vitamins ##### Purposes of Accessory Gland Fluids: - Add volume to the ejaculates - Enhance sperm survival - Enhance sperm movement - Provision of nutrients for sperm. - Provision of electrolytes for sperm. - Lubrication for mating process. - Neutralization of urinary acid residues in urethra ### 3. The Female Reproductive Tracts and Their Physiologies #### The Female Genitalia Consist of: - Vulva - Vestibule - Vagina - Cervix - Uterus - Fallopian tubes (oviducts) - Ovaries - Supporting structures #### The Overall Functions of Female Reproductive tract: - Transport sperm - Produce oocytes - Facilitate fertilization - Provide environment for embryo & fetus - Give birth to fetus - Recycle to become pregnant again. - Provide nutrients to young. #### Female Bovine Reproductive tract: 1. **Vulva (lips)** >* External vertical opening of genital tract just below anus. >* Allow the entry of bull’s penis (AI gun) at service. >* Allow the expulsion of calf at birth. >* Exit point of urine from the body. 2. **Vestibule** - Part of the reproductive tract shared with the urinary system. - The common duct for urine & reproduction. - Glands of Bartholin( lubricating gland) contribute to lubrication during estrus 3. **Vagina** - Located between cervix & vulva - Copulatory organ - Responsible for secretion of mucus - Admits male organ during copulation. - Transport & temporarily store sperm. - Serves as a birth canal. - Line of defense against invasion by bacteria. >* Epithelium of the vagina secretes fluids which combine with cervical fluids to inhibit growth of undesirable bacteria. >* Protection from infections may not be sufficient when there is unsanitary housing conditions, or dirty AI equipment is used. #### The Vagina wall - Tough and highly elastic - The lining (epithelium) changes with the stage of the oestrous cycle 4. **Cervix** - The organs near to the vagina: >* Produce mucus >* Active around the time of estrus #### Cervix Uteri - Neck of the womb. - Lies between the vagina and uterus. - Forms a barrier between the vagina and uterus. - Has a very thick fibrous wall in comparison to the walls of the vagina. ##### Function of the cervix: - Acts as a reservoir for semen - Selector of viable sperm >* Prevents transport of nonviable and defective sperm (trap non-viable sperm, sperm filter) >* Prevent large number of sperm from reaching oviduct in cow and ewe - Dilatation to permit parturition & expulsion of fetal membrane #### Cervical Canal (lumen) - Tightly closed and dilate at parturition and at estrus (dilate slightly). #### Secretions of the cervix: - Normally thick, but thin at the time of estrus ( to facilitate transfer of sperm to the uterus). #### The Thick Plug: - Act as a physical barrier - Blocks access to the pregnant uterus: >* From any foreign material >* From bacteria **Note:** During AI semen is deposited in the anterior cervix. 5. **The Uterus** - Hollow muscular organ - Consists of ‘body’ and two ‘horns’ - Suspended in the pelvic cavity by the broad uterine ligaments on either side. - Body of uterus is adjacent to cervix. #### Layers in wall of uterus: - Has three layers. >* Outer – Perimetrium (Outer serous layer continuous with peritoneum. It blocks adhesions or linkages) >* Middle – Myometrium (Inner circular layer of smooth muscle. Outer longitudinal layer, peristaltic contractions) >* Inner – Endometrium (Provides point of placental attachment, glands provide secretions for embryo development (Estrogen and Progesterone)) ##### Functions of uterus - **Transport of sperm - when female is in heat:** >* Estrogen stimulates myometrial contractions so that sperm move to site of fertilization >* Viable sperm (motile) are important so that they are not absorbed. >* Muscle contractions >* Towards oviduct during estrus (heat) but >* Following ovulation towards cervix until progesterone increases from CL ##### Functions of uterus … - Absorption and phagocytosis occurs by uterine epithelium: >* Leukocytes fight infection - Partially prepares sperm for fertilization: >* Estrogen stimulates uterine secretions which capacitate sperm(in endometrium Provides environment for embryo till birth >* Secrete fluid (uterine milk) which provide nutrients to developing embryo before & after its attachment. >* Secretion is stimulated by estrogen & progesterone - Expels fetus at birth - Recovers from pregnancy & makes corpus luteum regress #### Components of the uterus - **Horn & Body** - Horns (Two cornua) - Body >* Fusion between horns. >* Allows trans uterine migration in ewe, mare, pig. >* Site of semen deposition in mare, sow 6. **The Oviduct (fallopian tubes)** - Lie between ovary & tip of uterine horn. - End of the oviduct is funnel shaped - called infundibulum. >* Consists of 3 segments ( Isthmus , Ampulla , Infundibulum ) ##### Functions of the Fallopian Tubes - Oocyte retrieval after ovulation - Site of fertilization. - Oocyte/ovum transport to uterus. - Egg travels from ovary to uterine horn in 3 - 4 days. - **Oocyte retrieval after ovulation:** >* Removes oocyte from surface of ovary. - **Site of fertilization:** >* Transport oocyte and sperm to site of fertilization >* Reduce sperm number to prevent polyspermy. >* Provide proper environment for Oocyte, sperm & fertilization. - **Oocyte/ovum transport to uterus:** >* Transport & facilitate development of early embryo. #### The Isthmus (narrow proximal portion) - Extends from the tip of the uterine horn for about half the length of the oviduct #### The Ampulla - A slightly wider section opening into the peritoneal cavity via the funnel like third portion ( infundibulum) #### The Infundibulum - The funnel shaped portion of the fallopian tube near the ovary that catches. - Serve to capture the ovulated egg as they shed from ovary at ovulation. - Pushes the ovum into the fallopian tube during ovulation. - Facilitate their passage down the oviduct. 7. **Ovaries** - Primary reproductive organ of female. - Suspended from the broad ligament. - Ovarian structure is not static. - Appearance of the surface changes: >* Follicle growth, ovulation or regression >* Corpus luteum growth (regression) #### The Ovary is Responsible for the: - Production of the female egg or ovum: - Gamete production..gametogenesis - Production of hormones….steroidogenesis >* Estrogen and progesterone >* Inhibin, relaxin, oxytocin - The ovaries contain thousands of ova - All ova are surrounded by a **special layer of cells in the ovary**. - The growth of these cells produces **blister like structures**, called follicles that are visible on the surface of the ovary. - As follicle enlarges, it appears as a large blister on the surface of the ovary and can be easily detected by **rectal palpation**. #### The Ovary is Responsible for: - Development of ovulatory follicles begins at **puberty**. - They develop continuously throughout the life of the cow & the vast majority regresses without releasing the ova. - Following ovulation, the walls of the follicle collapse & develop into corpus luteum (CL) or yellow body. - The CL reaches its maximum size 10-12 days after ovulation & is the dominant structure on the ovary. - If pregnancy does not result, CL regresses 3 to 4 days prior to the next ovulation. - The presence of embryo in uterus prevents this from happening. - Development of the follicle and subsequent formation of the CL are associated with the production of estrogen and progesterone. #### Reproductive tract in male poultry: - The male poultry anatomy consists of two testes (each with an epididymis and vas deferens) that lead to papillae and a rudimentary copulatory organ. - Unlike other livestock species, the testes of poultry are located within the abdominal cavity along the backbone. - The epididymis, which still functions in sperm storage, is relatively small in relation to the testes. - The vas deferens extend from the epididymis to the cloaca are located on each side of the vertebral column. - The vas deferens function in transportation of sperm and as sperm reservoirs. #### Cloaca: - The lower end of the avian digestive tract that provides a passageway for products of the urinary, digestive, and reproductive tracts. #### Papillae: - Located at the end of the vas deferens and on floor of the cloaca, the papillae emit semen into the cloaca of the female. #### Phallus: - A rudimentary copulatory organ that becomes engorged with lymph during mating, which allows semen to be deposited onto the female’s everted cloacus; the phallus is more developed in ducks and geese. #### Androgen: - The male sex hormone produced by the testes. ##### Functions of androgen include: - Directing sexual activity and production of sperm, - Controlling secondary sexual characteristics of the male, and - Influencing social rank or “peck order.” ##### Secondary sexual characteristics include: - Comb growth, crowing or gobbling, spur development, and male feathering. #### Reproductive tract in female poultry: - The female reproductive system in *fowl* is quite different from that of the mammals. - Only the left ovary and oviduct of the hen are functional, although the right is found in an underdeveloped state. - The oviduct has five parts:- the infundibulum, magnum, isthmus, uterus, and the vagina. - A cloaca and vent are located at the end of the oviduct. ##### Functions of the parts: - **Ovary**: The ovaries produce the female sex cells, called eggs or ova, and sex hormones. - The ova are released from follicles on the ovary. - **Infundibulum**: The infundibulum receives the egg from the ovary. - **Oviduct**: The oviduct, or fallopian tube, is a tube-like structure that carries the egg from ovary to the uterus. - It is also the site where sperm and egg meet during fertilization. - **Uterus**: The fertilized egg develops in the uterus before birth. - **Magnum**: Magnum secretes albumen, which is the white of the egg. It surrounds the yolk. - **Isthmus**: Two shell membranes are added to the egg yolk and white in the isthmus. - **Uterus**: Also known as the shell gland, the uterus adds a thin white, shell, and pigment to the egg. - **Vagina**: The egg is temporarily stored in the vaginan before it is laid. It also produces the cuticle, the exterior coating of the shell. - **Cloaca**: The cloaca, which is the junction of the digestive and reproductive systems, receives the male’s semen. - The egg passes through the cloaca during laying. - **Vent**: The vent is the opening through which the egg passes out of the body during laying. ### 2. Reproductive Hormones - Organic substances secreted by certain specialized cells (glands) - They are diffused to some other body part and bring about certain changes. #### Reproductive hormones are produced from: - Hypothalamus - Pituitary - Gonads - Uterus - Placenta ##### Cause: - Release of other hormones (releasing hormones) Stimulate gonads (gonadotropins) - Sexual promotion (steroids) - Pregnancy maintenance #### Hormones involved in reproduction can be classified as: - Primary hormones - Secondary (metabolic) hormones #### 1. Primary Hormones - Directly involved in various aspects of reproduction - e.g. spermatogenesis, oogenesis, & ovulation #### 2. Secondary Hormones (metabolic hormones) - Are hormones that indirectly influence reproduction. - They are needed for normal functioning of organs which makes it possible for reproduction to occur. #### 1. Primary Hormones of Reproduction - They are involved in spermatogenesis, ovulation, sexual behavior, fertilization, implantation, maintenance of gestation, parturition, lactation, maternal behavior. ##### Primary Hormones of Female Reproduction: - Estrogen - Follicle stimulating hormone - Luteinizing hormone - Gonadotropin releasing hormone - Oxytocin - Progesterone - Prostaglandin #### 1. Estrogen - Produced by the cells lining the wall of the follicle and responsible for: - Changes in behavior of cow - Adjust the production of fluids by the vagina, uterus and cervix - Trigger/activate the release of LH (luteinizing hormone) ##### As a result of these synchronized events: - Cow comes into estrus and can be mated. - Fluids of the tract provide a favorable environment for survival of the sperm and ova, and - Ovulation occurs at the time when sperm will be available to cause fertilization. ##### Sites of Production of Estrogen: - Ovary - Placenta - Adrenal cortex #### Functions of Estrogens: - Stimulate follicular growth and maturation. - Induce females to display estrous behavior. - Contribute to growth & development of mammary tissue. - Prepare the uterus for parturition: - Secretory glands enlarge & thickening of tissues. - Significantly increase blood flow. - Increased uterine muscle tone and stimulate mucus secretion in the cervix and vagina. #### 2. Progesterone - It is produced by corpus luteaum and placenta which is essential for pregnancy. ##### During Pregnancy: - Concentration of progesterone high and inhibits secretion of GnRH - Prevents ovulation of follicles during luteal phase ##### Concentration of progesterone: - Increases after ovulation then decreases near term. - Altering ratio between progesterone and oestrogen Stimulates myometrial activity. - Prepares the uterus for parturition. #### Functions of Progesterone: - Prepares uterus for reception of fertilised oocytes. - Stimulates growth of glands in endometrium to increase secretion of mucin & carbohydrates. - Nourish embryo prior to implantation. - Stabilizes smooth muscle cells of endometrium to ensure that they do not contract during foetal development. - Prepares mammary tissues for milk production. - Prevents cow from coming into heat. #### 3.Prostaglandin (PGF2α) - Secreted by the uterus. - Causes regression of CL and decrease in progesterone levels. - If cow is pregnant, embryo will block the release of PGF2α and allow CL to continue to secrete progesterone. #### 4. Gonadotropin releasing hormone (GnRH or LH-RH): - In male and females, stimulates the anterior pituitary to secrete FSH and LH which control ovarian function. - Causes ovulation of the dominant follicle. #### a. Luteinizing Hormone (LH): - Secreted from the pituitary gland. - Its secretion is regulated via the secretion of GnRH i.e. travels through the blood to signal the ovary for release.. #### a. Luteinizing Hormone (LH) ... in males - Stimulates interstitial cells of testis. - Stimulates the production and secretion of testosterone from the testes via leydig cells. - Stimulates interstitial cells of ovary. - Stimulates production of oestrogens & progesterone from the ovary via theca interna cells and luteal cells - LH is responsible for: >* Rupture of follicle wall of dominant follicle and >* ovulation Stimulate the CL to secrete progesterone. >* Luteinisation of granulosa & thecal cells. #### b. Follicle stimulating hormone (FSH) - Secreted by the pituitary gland. - Regulated by GnRH from the hypothalamus - Target tissue of FSH >* In males - Sertoli cells (within the testes) >* In female - Granulosa cells of the ovary ##### FSH in males - Stimulates maturation of sperm cells. ##### FSH in females - Stimulates follicular development and oestradiol synthesis i.e. stimulates growth & maturation of the ovarian (Graafian) follicles. - Does not cause secretion of estrogen from ovary by itself; instead, it needs the presence of LH to stimulate estrogen production. - Travels through blood to the ovary after being signaled for its release by GnRH. | Hormone | Function | |---|---| | Follicle stimulating hormone (FSH) | Spermatogenesis; ovarian follicular growth. | | Luteinizing hormone (LH) | Androgen release; ovulation | | Oxytocin | Parturition; uterine contractions; Milk letdown | | Testosterone | Maintenance of male reproductive duct system and secondary sexual characteristics; Male sexual behavior; Spermatogenesis | | Estradiol | Maintenance of female reproductive duct system and secondary sexual behavior; Mammary gland stimulation | | Progesterone | Implantation; pregnancy maintenance; mammary gland stimulation | | Relaxin | Relaxation of uterine cervix, pubic symphysis; Inhibition of uterine contractions. | #### 2. Secondary Hormones of Reproduction - Indirectly influence reproduction. - Regulation of reproduction. ##### The main elements of regulation are: 1. **Nervous system:** Fundamental responsibility in translating or transducing external stimuli into neural signals. 2. **Endocrine system:** Pathways are neural reflex and neuroendocrine reflex. #### Hormone - Physiologic organic/chemical substance synthesized and secreted by ductless endocrine gland. - Passes into the circulatory system for transport and bring about certain changes. #### Functions of hormones: - Inhibit, stimulate, or regulate the functional activity of the target organ or tissue. - Regulation of hormone secretion is by nervous system. #### Regulation of gonadal activity is by: - Endocrine feedback mechanism - Neuro endocrine reflex (neural pathways) - Immuno endocrine control #### 1) Endocrine feed back mechanism: - Feedback control occurs at hypothalamus & pituitary gland level - Depending on their concentration in the blood, steroid hormones may exert stimulatory (positive) or inhibitory (negative) feedback ##### Gonad: - Inhibitory (negative feedback) - Stimulatory (positive fed back) - Hypothalamic hormones ##### Inhibitory (negative)feedback - This system involves reciprocal interrelationships between two or more glands and target organs. - e.g., As stimulation of the ovary increases estrogen secretion, FSH levels declines. - These two events are precisely synchronized, because LH surge is necessary for the rupture of the follicle wall of the dominant follicle and ovulation. ##### Stimulatory (positive) feedback - In this system, an increasing level of hormone(s) causes subsequent increase of another hormone. - e.g., Increasing levels of estrogen during the pre ovulatory phase trigger an abrupt release of pituitary LH - Stimulate LH Receptor. Tonic LH release maintains CL. ##### Hypothalamic hormones - Pituitary & Steroid hormones regulate the synthesis, storage, & release of hypothalamic hormones through two feedback mechanisms: - Long feedback mechanism - Short feedback mechanism ##### 1. Long feedback system - Involves interaction among the gonad, pituitary, and hypothalamus. ##### 2. Short feedback system - Pituitary gonadotrophin influences secretory activities of releasing hormones without mediation of the gonads. - Graafian Follicle Increase Estrogen Production will stimulate LH surge. Negative Feedback to inhibit FSH release. Positive Feedback. #### 2) Neuroendocrine reflex - The nervous system may release hormones through neural pathways, e.g., Oxytocin in milk let down, LH release following copulation. #### 3) Immuno endocrine control - Endocrine and immune systems interact extensively to regulate each other. - Several endocrine organs are involved in some aspects of regulatory process: - Hypothalamus, pituitary, gonads, adrenals, pineal, thyroid, thymus. - Many of these organs are themselves affected by immune function. ### 5. Reproductive Behavior in Farm Animals - Mating behavior is very strong drive & can take *precedence/priority* over other activities. #### Purpose: - Promote copulation. - Assure sperm and Oocyte meet. - To achieve pregnancy & parturition. #### From mating point of view - Males competing for access to females - Females being selective in their choice of mates #### Cattle - As ovulation approaches, cow behaves in an agitated manner to attract bulls. - Cow to cow mounting is common in dairy herds without bull. - For sexual stimulation of bull vision appears more important than smell. - When bull is present there will not be cow to cow mounting: - The bull will guard the cow from approaches by all other cattle. - The bull will chase off other bulls, prevent her from rejoining the herd. - Cow remains behind with him as the herd moves on. - The bull position: - Stands in the inverse polar position - Parallel and close to the cow - His head by her rump - **When cow becomes receptive (stands still) the bull serve the cow about 5 times.** #### Bull Detects the Estrous Cow By: - (Smelling) around genital - Licking - Curling upper lip in characteristic manner “Flehmen” behavior #### Sheep and Goats - Similar with bull. - Courtship display is comparatively simple. - In the temperate zone. - They are seasonally polyestrous, breeding season is in Autumn. - Libido of both sexes is low outside breeding season, males are aggressive during mating. #### Pigs - Come into heat at any time of the year. - Every 21 days interval. - Each heat period lasts 3 days. - Maximal receptivity period is about 12 hours. #### Factors Affecting Expression of Estrous Behavior: - Housing, temperature, day variation, arrangement where cattle are crowded, cow density, feet and leg problems, number of herd mates in proestrus (estrus) and nutritional factors ##### The stages of reproductive behavior are: - **Pre-copulatory stage** - Search for sexual partner (sexual arousal), Courtship (sexual display) - Erection - **Copulatory stage** - Mounting - Intromission - Ejaculation - **Post-copulatory stage** >* Dismounting >* Memory #### Search for Sexual Partner (sexual arousal/provocation) - In female limited to estrus >* Increased physical activity - In male it can occur at any time >* Involves all of the senses : - Sight - Smell - Hearing - Tactile/tangible - Sexual arousals >* Female: lordosis, presents hindquarters to male >* Male: erection, penile protrusion #### Courtship/Sexual display: - It is species specific events. #### Types of courtship: - **Male courtship** >* Sniffing (suggesting an important chemical communication through olfaction) >* Licking, Flehmen reaction. >* Nuzzling of rump & back ( in ruminants) >* Biting neck (in stallion) >* Noses flanks. >* Grind teeth. >* Foams at mouth (boar) >* Increased vocal and motor activity. >* Increased phonation. >* Male checks for female lordosis - **Female courtship** >* Restlessness, increased vocal activity , sniffing of male genitals (sniffing other female vagina), circling, mock fighting, frequent urination, mount other females (in cows, goats, pigs) >* Tail wagging ( in sheep & goats) >* Vulva “winking” (in horses) #### Erection - Erection of the penis requires: >* Elevated arterial blood inflow >* Restricted venous outflow >* Elevated intrapenile pressure >* Relaxation of the retractor penis muscle - Copulatory stage: >* Mounting >* Intromission >* Ejaculation #### Copulatory Behaviour - Varies among species. >* Short copulators (1 - 3 seconds) Bull and Ram >* Intermediate (20 to 60 seconds) Stallion >* Sustained copulator (5 - 20 minutes) Boar #### Refractoriness - Refractory period: is period of time during which copulation will not take place. - Dependent on Sexual rest prior to copulation - Age of male - Degree of female novelty/virginity - Number of previous ejaculates - All males have refractory period #### Estrus and Estrous Cycles - Puberty is the stage of sexual maturation as a desire to mate and abil to fertilize an egg in males and; - In female production of ova by follicles, development of the reproductive tract. - Puberty is marked by the first estrus in female while estrus (heat): period of sexual receptivity #### Estrous cycle: - Interval from beginning of one estrus to the beginning of the next. - Interval between 2 consecutive heat periods. - Average length is 21 days (18-22days in heifers; 18-24 days in cows). #### Mono estrous (seasonal breeders): - Animals that have only one estrous cycle/year. #### Polyestrous: - Animals that have several estrous cycles per year. #### Oestrous cycle - Cattle and swine >* No seasonality of breeding - Sheep and goats >* In tropical countries no seasonality of breeding