King Salman International University Veterinary Medicine Lecture Notes (PDF)

Faculty of Veterinary Medicine Level 4: Theriogenology (STG 411) LEC 2: Female Reproductive Physiology : Estrous Cycle in Farm Animals and Pets Dr. AHMED HASSANEEN Date: 13/10/2024 (AM) 1  B. Reproductive processes: 1. Follicular...

Faculty of Veterinary Medicine Level 4: Theriogenology (STG 411) LEC 2: Female Reproductive Physiology : Estrous Cycle in Farm Animals and Pets Dr. AHMED HASSANEEN Date: 13/10/2024 (AM) 1  B. Reproductive processes: 1. Follicular growth (folliculogensis) 2. Follicular dynamics (F. waves) 3. Ovulation 4. Luteolysis 5. Conception 1. Oocyte maturation 2. Fertilization 3. Maternal recognition of pregnancy 2 Oogenesis 3 Folliculogensis 4  1. Follicular growth: Thousands of primordial follicles exist in dormant state in the ovary. By unknown mechanism, the follicles are recruited into cohort that respond to rise in FSH. From the cohort, some follicles are selected. One or more selected follicles continue to grow until dominance The fate of the dominant follicle either 1.Ovulate in response to surge LH in absence of P4 2.Atresia in presence of P4 dominance and low LH 5 6  2. Follicular dynamics: It is the wave pattern of follicular growth and regression of a group of ovarian follicles that end by ovulation of preovulatory dominant follicle(s) The follicular dynamics continue throughout the cycle not only during estrus phase In cows, mainly 3 waves of 7 days each In mare, 2 waves of 10-12 days each 7 8  3. Oocyte maturation: It consists of: 1. Period of growth 2. Period of nuclear and cytoplasmic maturation The oocyte start to grow after selection of the primordial follicles After oogenesis, the nucleus remains in a resting state until preovulatory surge LH “oocyte maturation inhibitor; OMI effect” Preovulatory surge LH stimulate nuclear maturation “by meiosis” and cytoplasmic maturation as well 9  4. Ovulation: It is rupture of the mature graffian follicle(s) in response to preovulatory surge LH stimulated by threshold levels of estrogen Types of ovulation: 1. Spontaneous “Hormonal”: In cow, buffalo-cow, ewe, doe, and mare Ovulation occurs in respond to hormonal changes including estrogen peak and preovulatory surge LH. 2. Induced “reflex or neural”: In queen, she-camel, rabbit doe Ovulation in response to stimulation of cervix/vagina 10  4. Ovulation: Site of ovulation: 1. In mammalian ovary: In cow, buffalo-cow, ewe, doe, and she-camel Ovulation occurs in any site of the ovarian surface except hilus. 2. In mare: Ovulation occurs only through ovulation fossa. 11  PGE2 Preovulatory LH surge Increase Blood Flow Shift of Dominant to Ovary & Increase Follicle secretion Dominant Follicle PGF2α from E2 to P4 Contraction of Release of Smooth muscles Lysosomal Enzy. Edema Collagenase Follicular F. Wall Pressure Weakness Ovulation 12  Time of ovulation: Length of estrous Duration of estrus Time of ovulation Species cycle (Days) cycle (Hours) (Hours) Cow 21 – 23 10 – 19 10 – 12 after Buffalo-cow 18 – 22 17 – 24 end of estrus 30 – 36 from the Ewe 16 – 17 24 – 36 onset of estrus 18 – 24 from the Goat 21 20 – 25 onset of estrus Mare 19 – 25 4 – 8 days 1 – 2 days before end of estrus She-camel 24 5 days 30 – 40 hours after coitus 35 – 45 after Sow 21 48 – 72 13 onset  5. Luteolysis: It is destruction or decomposition of the CL followed by decline in the circulating P4. It begins with functional luteolysis as decrease in P4 which followed by structural regression with connective tissue scar deposition --------- corpus albicans It is initiated by uterine PGF2α ---------------- ovarian oxytocin and ovarian PGF2α -------------- vasoconstriction of the luteal tissue Uterine PGF2α transferred through utero-ovarian vein and artery. From ipsilateral uterine horn in cow “counter current passive diffusion” 14 5. Luteolysis: 15  5. Conception: B. Fertilization It begins with various maturational changes of the sperm-egg complex Because of the short life span of ova and sperms, the synchrony between ovulation and insemination is very critical for successful fertilization. Sperm capacitation: is associated with 1. Decrease intracellular pH 2. Influx of extracellular Ca++ ions 3. Removal of seminal plasma protein 16  6. Fertilization: Steps of fertilization: 1. Hyperactive motility of spermatozoa: It is fertilization dance that enable the sperm to make oocyte contact. 2. Binding to Zona pellucida “ZP”: It is species specific by receptor-ligand interaction 3. Acrosomal reaction: By fusion of inner and outer membranes of sperm acrosome - --------- acrosomal enzymes make tunnels in ZP 17  6. Fertilization: Steps of fertilization: 4. Sperm oocyte membrane fusion: It is fusion of oocyte plasma membrane with the sperm head membrane. 5. Cortical reaction : It prevent entrance of any additional spermatozoa 6. Formation of pronuclei: After formation of male and female pronuclei, the pronuclei fused forming syngamy and the zygote start to develop. 18  B. Maternal recognition: Following successful fertilization the conceptus maintain P4 production by sending signals about its presence to the maternal sys. In bovine and ovine, the conceptus secret some steroid hormones and proteins such as interferon Tau between day 12 and day 21 of pregnancy, such protein inhibit production of uterine PGF2α. Critical time for recognition from day 15 to day 16. In mare, the conceptus migrate within the two uterine horns 10-12 times/day between day 10 and day 16 of pregnancy. Critical time for recognition from 19 day 12 to day 14.  3. Estrous cycle: It is period between two successive heat which is defined as period of sexual receptivity, and it can be defined as repeated opportunity of the female to be pregnant Classification acc to frequency: 20  Phases of estrous cycle: A. Follicular phase: 20% of the cycle 1. Proestrus 2. Estrus B. Luteal phase: 80% of the cycle 3. Metestrus 4. Diestrus 21  Proestrus: Prepare the female tract to sexual receptivity and mating. It begins by destruction of the CL and end by the start of estrus phase. Duration: Lasts for 2-4 days. Hormonal: Major endocrine shift from P4 dominance to E2 dominance Cyclic Structure: Growing follicles with absence of CL. 22  Estrus/Heat: It is period of sexual receptivity Duration: Lasts for about one days. Hormonal: It is characterized by high threshold levels of E2 that stimulate more FSH, LH, ------ increase inhibin ------------ selective inhibition of FSH - ---------- Surge LH ----------- Ovulation Cyclic Structure: dominant mature Graafian follicles (MGF) with absence of CL. 23  Metestrus: It begins by ovulation until formation of full functional CL. Duration: Lasts for 2-5 days. Hormonal: Endocrine shift from E2 dominance to P4 dominance Structure: Corpus hemorrhagicum (softer than CL/mushy) due to the start of Luteinization of the follicular cells of after ovulation. Metrorrhagia: metestrual bleeding 48 h after estrus as a physiological phenomenon in cows “80% heifers” 24  Diestrus: It is defined as period of maximum luteal function begins by formation of full functional CL until luteolysis. Duration: Lasts for 10-14 days. Hormonal: P4 dominance Cyclic Structure: Full functional mature CL with presence of follicles of different size (small, medium, large). 25  Signs of heat: Early estrus: the cow mount other animals and refuse to be mounted Standing estrus: later, the cow accept to be mounted by other animals and showing lordosis Increase vocalization “bellowing” Decrease appetite Rosy red vaginal mucous membrane Decrease milk yield Increase movement and restlessness Estral mucous: as transparent viscous mucous discharge from the vulva and may soil/contaminate the tail and hindquarters The estral mucous is characterized by arborization in dry film 26 Signs of heat in cows: 27 Signs of heat in Buffalo: 28  Arborization The pattern of palm leaf/ferning/fernlike pattern or arborization occurs under the effect of high E2 from the preovulatory follicle, that the cervical mucus forms fern-like patterns due to crystallization of electrolytes especially sodium chloride on mucus fibers. When a dry film is made by the estral mucus. Just a thin layer of estral mucus on a glass slide and allowed to dry 29  Signs of heat in Mare: Introduction of teaser animal: Mare in estrus (heat): ❑ Standing back to face for stallion (calm and not kicking). ❑ Winking (rhythmic opening of the vulval lips with exposure and rhythmic contraction of the clitoris associated with drippling). ❑ Drippling (Frequent urination) and tail raising. ❑ Squatting (Abduction and opening of hind limbs). ❑ Swinging the rear quarter toward the teaser. Mare not in estrus: Stand face to face and may exhibit aggressive behaviour and kick the teaser. 30 Signs of heat in Mare: 31  Signs of heat in She-camel: 1.Restlessness, Seeking the camel-bull and close to him, tail wagging, and remain recumbent most of time. 2.Frequent squatting and straddling of hind limbs 3.She-camel secrets a characteristic pheromones from the pole gland behind the ear 4.Rutting phenomenon “Dulla/Gulla/Kolla/Pulla” (protrusion of soft palate) in camel-bull 5.The vulva becomes slight swollen with small amount of mucus 32 6.The cycle consists recruitment (4d), growth (6-10d), mature (7-9d), and regression (7-12d) Signs of heat in She-camel: 33  Signs of heat in ewe: 1. Male seeking behavior 2. Restlessness 3. Cervical mucous hidden under fatty tail 34  Signs of heat in doe/she-goat: 1. Male seeking behavior 2. Restlessness 3. Tail wagging. 4. Loud vocalization 35  Signs of heat in Queen: 1.Rubbing against human or objects 2.Restlessness and rolling on the floor 3.Loud vocalization 4.Lordosis 5.Licking of genitalia with occasional vaginal discharges 36 Signs of heat in Queen: 37 Stages and Signs of heat in Queen: 38 Estrus: > 50% of the cells (95%in Diestrus: Presence of small this smear) are cornified it may intermediate parabasal cells (Johnson, retain small pyknotic nucleus 2021)  Signs of heat in Bitch: 1.Swollen reddish vulva and bloody discharge 2.Restlessness and frequent urination 3.Attractive to male due to pheromones, both male & female show interest each other 4.Tail turning reflex (tail flagging one side) in respond to massage of perineal 39 Stages of heat in Bitch: 40  Stages of heat in Bitch: Fig. 1. Vaginal smear in Fig. 2. Vaginal smear in estrus: Fig. 3. Vaginal smear on first proestrus: 1. RBC; 2. Small 1. Superficial cell; 2. day of diestrus: 1. RBC; 2. intermediate cell; 3. Large Squamous cell Small intermediate cell; 3. intermediate cell; 4. Large intermediate cell; 4. Superficial cell; 5. Squamous Squamous cells; 5. Neutrophil cell. granulocyte 41 Stages of heat in Bitch: 42  Estrus detection: 1.Heat mount detector: to detect standing heat 2.Tail painting: to detect early-stage estrus 3.Chin ball device: detect standing heat 4.Teaser animals 5.P4 kits: undetectable milk P4 levels indicate estrus 6.Pedometer: Change in cow activity ✓Heat expectancy card 43 Heat mount detector  Estrus detection: Tail paint 44 Chin rest Estrus detection: Pedometer 45