ECAR prep Flashcards

Question

What are the primary causes of retained placenta in cattle, and how is it managed?

Answer 1

Frequency of ejaculation (if increased can dramatically reduce the number of spermatozoa in the tail of the epididymis, if decreased the number of spermatozoa in the tail is at its highest, although prolonged storage time can alter the morphology and function of spermatozoa); also actions of sexual preparation (false mounting, restrain from mounting increase the amount of spermatozoa ejaculated from the tail)

Answer 2

Acts in minutes, relatively short half-life, binds to specific receptors, regulate intracellular biochemical receptors

Answer 3

4-8 pulses

Answer 4

Blulbospongiosus (overlaps the root of the penis, covers the bulbo-urethral glands - if present - empties the extrapelvif part of the urethra), ischiocavernosum (paired muscles, relatively short, located in the area of the root of the penis. These muscles insert broadly on the lateral parts of the penis above the sigmoid flexure - if present. These muscles attach the penis to the ischiatic arc), uretralis (striated muscle surrounding the pelvic urethra, responsible for the movement of the semen.

Answer 5

An ovarian follicle are structures located within the ovarian cortex and containing immature oocytes. Ovarian follicles can be classified as primordial, primary, secondary, and antral (or tertiary). A dominant antral preovulatory follicle can also be refferred to as 'Graafian follicle'. Females are born with a lifetime reserve of primordial and primary follicles. Primordial follicles are the earliest stage of development and the smallest structures. The oocyte is surrounded by a single layer of flattened squamous epithelium. These evolve into primary follicles, that are small structures in which the oocyte is surrounded by a single layer of cuboidal follicular cells. Primary follicles cannot divide into other primary follicles, but either evolve to secondary follicles or degenerate. Secondary follicles have 2 or more layers of follicular cells and the oocyte is surounded by a zona pellucida. Finally, antral follicles (or tertiary follicles) are the largest stuctures, ranging from 1 mm to some cm, these possess an antrum filled with follicular fluid. Each follicle has multiple layers. Specifically, the theca externa is made of connective tissue supporting the follicle, the theca interna is made of cells producing androgens under the influence of LH. The theca interna is divided by the granulosa cell layer by a thin basement membrane. The cells of the granulosa layer present FSH receptors and produce estrogens, inhibin, follicular fluid. Once ovulation of antral follicles occurs, small blood vessels rupture causing an hemorrage, moreover the follicular fluid is lost causing the collapse of the follicle ('in-folding'). In this process, some theca and granulosa cells are pushed to the apex of the follicle. All this causes the formation of a 'corpus hemorragicum' (NB the follicular fluid of mares contains an heparin-like substance that prevents clots formation). After the formation of the corpus hemorragicum, the theca and granulosa cells differentiate into luteal cells forming the corpus luteum. Specifically, the theca cells become small luteal cells, whereas the granulosa cells become large luteal cells.

Answer 6

Cattle, Horse, Camel. In large gilts and sows it is possible to palpate the uterine artery pulse for pregnancy diagnosis after day 40 (increased tone and fremitus).

Answer 7

Inguinal herniation is common in boars (1/200 males) because the inguinal canal is located more dorsally compared to other species. In this conditions, abdominal organs (mostly the gut) is herniated within the vaginal process, which is in direct communication with the peritoneal cavity. Usually, the visceral vaginal tunic and the parietal vaginal tunic can be sutured in order to prevent further herniation.

Answer 8

The proliferation phase is the first phase of spermatogenesis, it takes place in the basal compartment of the seminiferous tubules. It consists of mitotic divisions of spermatogonia until the stage of primary spermatocytes. The number of mitotic divisions depends on the species. In general, there are multiple generations of spermatogonia A, then spermatogonia I, and finally spermatogonia B, that will divide into primary spermatocytes, that do not divide by mitosis but immediately enter the first meiotic division, passing from the proliferation phase to the meiosis phase of spermatogenesis.

Answer 9

Equine ovaries present an inversion of the cortex and medulla, therefore ovulation can only take place at one location, which is the ovulation fossa (a depression located on the ventral surface of the ovary). Follicles can be palpated per rectum at the ovulation fossa. However, normally palpation of the corpus luteum is not possible as it tends to penetrate the ovarian tissue intead of protruding from the surface of the ovulation fossa.

Answer 10

The flagellum consists of a middle piece, a principal piece, and a distal piece. (i) The middle piece consists of a capitulum that inserts within the implantation socket (a depression of the posterior nucleus of the spermatozoon), laminated columns (that provide flexibility during flagellar beat), and the mitochondrial helix (which is the engine allowing the motility of the flagellum). The juncture between the middle and the principal pieces is the annulus. The principal piece is formed by the axoneme, that originated from the distal centriole and is formed by a 9+9+2 arrangement of microtubules, with 9 pairs of microtubules radially arragend around two central filaments. The microtubules terminate in the (iii) distal piece.

Answer 11

Increased lordosis, phonation, physical activity

Answer 12

The oviduct (or salpinx, or Fallopian tube) is a paired hollow organ of the female reproductive tract. It is responsible for receiving the ovulate oocyte/oocytes, being the location of fertilization, and conveying the early embryo to the uterus. It can be divided into three parts. The infundibulum is the cranial end of the oviduct, it is funnel-shaped and the mucosa possessess finger-like projections ('fimbriae') increasing the surface area (6-10 cmq in sheeps, and 20-30 cmq in cows) and protruding towards the ovary and increasing the chances to capture the ovulated oocytes. An ostium marks the passage from the infundibulum to the ampulla, which represents more than 50% of the lenght of the oviduct and it is the site of ovulation. It presents fern-like mucosal folds with ciliated epithelium. An ampullary-ishtmic junction separates the ampulla from the caudal portion of the oviduct, which is the isthmus. The ampullary-isthmic junction is poorly defined, although in mares represents an important control point for the passage to the isthmus (only fertilized oocytes forming viable embryos producting PE2 normally pass into the isthmus). The isthmus is smaller, although presents a thicer muscolaris layer and fewer mucosal folds compared to the other parts of the oviduct. It is connected to the uterus through a utero-tubal junction which represent a control point: specifically, in cows it forma a kink when estradiol is high, the it straightens when estradiol decreases, allowing the passage of the embryo into the uterine horn. In sows, constriction of the utero-tubal junction prevents excessive amounts of spermatozoa to reach the ampulla, therefore it is a mechanism for polyspermy prevention in this species. The muscolaris of the oviduct is importat to guarantee contractions fro gamete transport in opposite directions so they can meet in the ampulla. The mucosa provides the optimal environment for oocytes, spermatozoa, and for the development of early embryos.

Answer 13

Hormone secretion can follow an episodic pattern (with sudden release of high levels of hormones, e.g., GnRH by the surge center of the hypothalamus). When episodic secretion of hormones follow a predictable pattern, this is defined as pulsatile. Pulsatile patterns are those of GnRH, LH, and FSH and are key to manain cyclicity. There second type of hormone secretion pattern is the basal secretion of low amoun of hormones, which blood concentraction fluctuate with low amplitude (e.g., GnRH released from the tonic center in the hypothalamus). Finally, sustained secretion is another pattern of hormone secretion. This consist of continuous production of the hormone that remain elevated for long periods (e.g., steroids, as P4 during pregnancy and diestrus).

Answer 14

Mesoderm (gonads, salpinx, uterus, cervic, cranial vagina, epididymis, ductus deferens, accessory sex glands); ectoderm (mammary glands, portions of the vagina and vestibule, also hypothalamus and both lobes of the pituitary)

Answer 15

Alpha-ferroprotein is a protein secreted by the embryonic yolk sac and later by the liver that binds estradiol and prevents it from crossing the blood-brain barrier

Answer 16

The mare will not show a normal response to changes in the photoperiod, whereas ewes keep exhibiting normal seasonality, indicating that environmental factors other than melatonin are involved in seasonality

Answer 17

Milk ejection by mammary alveoli. This involves oxytocyn produced by the paraventricular nucleus of the hypothalamus and stored in the posterior pituitary. Once sensory receptors in the nipple or tit are mechanically stimulated, an afferent sensory nerve convey the information to the spinal cord, where it synapses with an interneuron, that synapses with an efferent nerve conveying the information to the brain, making another synapsys with neurons in the hypothalamus and causing the release of oxytocyn. Oxytocin causes the myoepithelial cells of the mammary alveoli to contract. Another example is the Ferguson's reflex, with mechanical stimulation of sensory terminals within the cervix by the fetus, leading with a similar mechanism to the release of oxytocin that will act on the myometrium causing uterine contractions. Finally, another example of neuroendocrine reflex is that leading to production of gonadotropins in the anterior pituitary.

Answer 18

The mesonephric ducts are paired ducts conveying the urine produced in the mesonephros (the first functional kidney of the fetus that replaces the pronephros that was not functional and that is replaced when the metanephros is developed; the metanephros will develop into the definitive kidney) to the urogenital sinus. These ducts will originate the efferent ducts system of the male reproductive tract. Specifically, the mesonephros is drained by mesonephric tubules, 5-15 of which will penetrate into the primitive gonad, connecting to the sex cord via the rete testis. The mesonephric tubules converge into a larger mesonephric duct that will originate the epididymis and ductus deferens. In females, the mesonephric ducts regress and only remnants can be found by dissecting the floor of the vestibule of the vagina in adult animals (Gartner's ducts)

Answer 19

Some hormones can be orally administered (e.g., steroids), whereas others cannot (e.g., glycoproteins). Glycoproteins cannot be orally administered because they are polypeptide chains with carbohydrate moieties that are easily degraded into the digestive system.

Answer 20

The cremaster muscle is a striated muscle that is the continuation of the oblique internal abdominal oblique muscle and it passes within the spermatic cord, contributing to the wall of the scrotum. Being a striated muscle, is it not capable of sustained contractions, and its function is to have short rhytmic contraction pumping the venous blood back to the main circulation. However, it may be involved in short elevation of the scrotum due to fear. It is responsible for rhytmic movements of the testicles in bulls and ram during sexual excitation.

Answer 21

Spermatozoa maturation (acquisition of abitilty to move and fertilize), storage of spermatozoa (in the cauda), movement of spermatozoa to the ductus deferens,

Answer 22

Ewe, cow, sow

Answer 23

Mechanism: melatonin is an endogenous hormone secreted by the pineal gland and it is mainly produced at night, when the enzymes involved in the synthesis of this hormone have higher functionality. Melatonin acts on the suprachiasmatic nucleus of the hypothalamus by linking to MT1 and MT2 receptors. In long-day breeders (e.g., cat, horse), high melatonin levels suppress kisspeptin production, inhibiting GnRH release and thus suppressing reproductive activity. Conversely, when nights are shorter, melatonin levels drop, allowing kisspeptin to increase, thereby triggering reproductive activity. The opposite pattern may be observed in short-day breeders (e.g., sheep). Therefore, the photoperiod affects reproduction in seasonal breeders and altering light-darkness proportions may be used as a tool to control the estrus cycle in these species. Mare: exposure of mares to a stimulatory artificial photoperiod is commonly used to anticipate the onset of the breeding season. The duration from the onset of artificial light exposure and the first ovulation of the year is about 60-90 days. The objective should be a daily light exposure of about 15-16 hours. This works better than a 24-hour light exposure. In Europe, the artificial photoperiod can be started at the beginning of December. Mares can be exposed to natural light from sunrise to late afternoon (before dusk), when lights are turned on to extend the exposure to 16 hours. This allows 8 hours of darkness. Minimum light intensity is approximately 100 lux. Different approaches can be used: - Exposure of anestrous mares to 35 days of artificial photoperiod (14.5 hours of light and 9.5 hours of dark, light intensity of 100 lux). Mares will start ovulating about 76 days after the onset of the artificial photoperiod. - ‘Skeletal lighting’ protocol: exposure of mares to two hours of light 8-9.5 hours after the onset of darkness. This interrupts the course of melatonin exposure, thus modulating the inhibitory effect of melatonin on GnRH secretion. This has been reported to stimulate follicular development in anestrus mares. - Blue light mask: mares can be exposed to a LED blue light with wavelength of 468 nm and intensity of 10 lux. This is normally done using a mask emitting a low-level blue glow on a single eye. Advantages of light masks include the possibility of programming it to start light exposure at a specific time and the possibility to keep the mare in external paddocks. Queen: the minimum number of hours per day reported to stimulate follicular activity in queens is 12h. A daily dark-light cycle of 12h:12h lead to continuous cycling in queens. Light exposure can be increased to 14 h to induce estruses and were reported to be optimal to stimulate the hypothalamic-pituitary axis. However, continuous exposure for 24h per day causes a decrease in the frequency of cycles. Moreover, phases with lower light exposure (i.e., < 8 hours per day) seem to optimize the response to light exposure (> 12h). The best protocol to induce estrus is to extend the natural photoperiod to 12-14h hours by exposing the queen to 300 lux intensity light and introduce an estrus female or a tomcat, this should cause cyclicity to start within 30-45 days. Cats are common pets living indoor and can be exposed to artificial light with variable intensity and duration. However, majority of intact pet cats in Europe do not cycle between October and December. Small ruminants (sheep and goat): in these species, decreasing daylight will stimulate cyclicity. This can be achieved in spring and summer either by housing the animals in daylight proof facilities or by exposing the animal to artificially longer days (e.g., 22 hours light exposure) for at least one month and then returning to natural day length. Sow: in domesticated animals housed in breeding facilities, food availability and controlled environment suppress seasonality. However, wild pigs are seasonally anestrous. For this reason, a seasonal decrease in fertility is sometimes observed in gilts and sows in summer and autumn. This can be avoided by optimizing nutrition and light exposure. Specifically, it is advised to use a light program consisting of 16 hours of light (light intensity of 200 lux) and 8 hours of darkness in the breeding area, whereas the proportion can be inverted (8 hours of light and 16 hours of darkness) in the lactation area.

Answer 24

Vulva, vestibular-vaginal fold, cervix

Answer 25

The Gartner's ducts are remnants of the Wollfian ducts located in the floor of the vestibule of the vagina.

Answer 26

The cervix is an hollow organ located between the uterus and the vagina. It is relatively thick-walled and the lumen is differently shaped among domestic species. In bitches and queens the mucosa is relatively smooth and a single fold of mucosa protrude within the cranial vagina; in cowe, ewes, sows, and mares there are multiple folds protruding within the cranial vagina. Specifically, in cows and ewes the folds form interlocking finger-like projections (i.e., cervical rings), the surface is rich in crypts and folds and mucous secretion is cospicuous depending on the stage of the cycle; in the mare there are cospicuous cervical folds protruding into the vagina, mucous production is lower, the cervical tone is increased under the influence of P4, otherwise the cervix is relatively soft in mares; in sows the mucosa forms interdigitating prominences, requiring a special conformation of the glans penis of the boar (corckscrew spiral twist; in this species the semen is ejaculated in the cervix and the high volume of 200-500 mL, causes the semen to quickly progress to the uterus). The cervix is a barrier to sperm transport in cows, ewes, bitches, queens but not in mares and sows. In all species, the mucosal epithelium is capable of secreting the mucus forming the cervical seal of pregnancy, isolating the pregnant uterine environment from the vagina and external environment, thus preventing ascenting contamination from potentinally pathogenic bacteria.

Answer 27

Ruminants post-scrotal, boar = pre-scrotal

Answer 28

Lactational anestrus is the absence of cyclicity in lactating dams, due to mechanical (suckling), auditory, visual, and olfactory stimuli associated with maternal care of newly born offspring. This happens in most domestic species, except for the mare and alpaca. Moreover, bitches do not show a proper lactational anestrus, since they would anyway be in the anestrus phase of the cycle that follows diestrus. In queens, lactational anestrus is present in some animals and not in others and cyclicity is mainly restored in 7-10 days. Sows present lactational anestrus and display estrus and ovulate 4-8 days after weaning, making time at weaning a key breeding management tool in this species. Cows normally show lactational anestrus, although newborns from dairy cows are removed from their dam immediately or few hours afrer birth, thus dairy cows do not show a proper lactational anestrus as beef cows do. Suckling seem to be a major mechanical stimulation involved in lactational anestrus and a suckling frequency of less than 2 times per day promote the increase in amplitude and frequency of LH pulses and the return to cyclicity, whereas a number equal to or higher than 3 keeps LH pulses with low amplitude and frequency, thus mantaining lactational anestrus.

Answer 29

A normal CL should be visible in pregnant mares up to day 45 of gestation. During early pregnancy it is important to evaluate the size of the CL, since CL smaller than normal could indicate an insufficient P4 production (in that case, P4 should be supplemented: e.g., altrenogest 0.088 mg/kg per os). Secondary corpora lutea may be identified in pregnant mares after 45-60 days of gestation, although these do not form in every pregnant mare.

Answer 30

Ejaculation is an example of simple neural refles involved in reproduction. When sensory terminals in the glans penis are mechanically stimulated, afferent nerves with body cells located in the spinal cord synapse with interneurons in the spinal cord that will synapse with efferent nerves and the axons of these neurons will convey the signal to muscles involved in ejaculation causing this event. Similarly, when temperature sensitive terminals on the skin of the scrotum are stimulated by a descrease in the temperature, the message is conveyied to the spinal cord via afferent nerves with body cells in the spinal cord, these will synapse with an interneuron that will synapse with an efferent neuron conveying the information to the smooth muscle of the tunica dartos causing a contraction that will bring the scrotum closer to the body.

Answer 31

The implantation socket is a depression within the posterior nucleus hosting the capitulum of the flagellum.

Answer 32

Periventricular, preoptic, arcuate

Answer 33

Ovariectomized bitches cannot carry a pregnancy to term, since the CL is needed to produce P4, therefore ovariectomy at any stage of pregnancy causes abortion in bitches. Many queens will abort as well. However, some queens ovariectomized after 45 dop, will carry the pregnancy to term, probably because the the placentae can produce some P4 by converting pregnenolone to P4. This matter is still controversial, and ovaries are still considered the main source of P4 in pregnant queens.

Answer 34

Dopaminergic substances can promote folliculogenesis by modulating GnRH producting neurons thus GnRH secretion that in turn modulare FSH and LH secretion. This is proved by iatrogenic administration of dopaminergic agenst (e.g., cabergoline and bromocriptine) during anestrus: this can stimulate GnRH production thus shortening the anestrus.

Answer 35

Primordial germ cells migrate by ameboid movement from the endoderm of the yolk sac to the genital ridge, where undergo replication by mitosis and locally stimulate the proliferation of the connective tissue that will form the primitive sex cords, that will push towards the mesonephros (primordial kidney). Precursors of the Sertoli cells migrate from the coelomic epithelium to the genital ridge. Precursors of the Leydig cells are formed in the mesonephros. Male mammals have a Y chromosome carryin a gene named SRY (Sex Determining Region) controlling the synthesis of the SRY protein. When the SRY protein is produced by the sex chords, the development of the male reproductive system is stimulated. This will lead to the development of the testes, in which Sertoli cells carry a Desert Hedgehog Gene (DHH) and produce AMH and dihydrotestosterone, which will cause degeneration of the paramesonephric ducts. DHH causes the differentiation of Leydig cells that will produce testosterone and dihydrotestosterone, promoting the development of the male reproductive system.

Answer 36

Reproductive organs develops in retroperitoneal position, they then grow pushing the peritoneum until they are completely enveloped by it and a portion of the peritoneum eventually fuses forming a double layered sheet of connective tissue named 'broad ligament'. The broad ligament privide vascular supply, limphatics, and nerves to the reproductive organs and suspends them to the dorsal body wall. The cranial portion of the broad ligament is called mesovaium: it attaches and supports the ovary and vehiculate vessels and nerves to the organ, forming the ilus of the ovary. Most species also have a utero-ovarian ligament (also called proper ligament of the ovary) that connect the ovary to the uterus (these ligaments are not part of the broad ligament!). The thinner serous portion of the broad ligament that supports the oviduct and forms the ovarian bursa (nearly complete in bitches) is named mesosalpinx. This ligament has also the function to orient the infundibulum of the salpinx towards the ovary in order to enhance the chances that oocytes will reach the infundibulum. Finally, the largest part of the broad ligament is called 'mesometrium'. It supports the uterine horns and body and it is continuous with the dorsal peritoneum, so that it literally hangs from the dorsal body wall. There are also intercornual ligaments (dorsal and ventral) connecting the two uterine horns.

Answer 37

The pituitay originate from the embryonic ectoderm. It consists of two lobes (adenohypohysis and neurohypophysis). The anterior lobe (adenohypophysis) originates from the dorsal wall of the stomodeum that forms a diverticulum named Rathke's pouch, that grows dorsally. The posterior lobe (neurohyphysis) originate from the floor of the third ventricle of the embryonic brain (infundibulum) and grows towards the Rathke's pouch. The posterior lobe contains the axons and nervous terminals (telodendra) of the hypothalamus. Whe the two lobes are almost completely formed, the sphenoid bone starts growing around the two lobes, that will then be contained in the sella turcica of the sphenoid bone, which works as a protective case.

Answer 38

Acrosome reacrion is an organized and highly specialized exocytosis allowing the release of acrosomal enzymes to penetrate the oocyte during fertilization.

Answer 39

Bitch, cow, mare

Answer 40

STAR (steroidogenic acute regulatory)

Answer 41

It starts at 20% of the gestation and it is completed at 33%.

Answer 42

Hormones can be classified based on their mode of action in the following way. (i) neurohormones: these hormones are produced by neurons and released in the blood (oxytocin, GnRH); (ii) gonadotropins: these hormones act on the gonads (FSH, LH); (iii) sexual promoters: promote sexual behavior and secondary sex characteristics (steroids); (iv) pregnancy manteinance hormones: eCG, hCG, P4; (v) lactogenic hormones (placental lactogen); (vi) general metabolic hormones (thyroxin, somatotropin); (vii) luteolytic hormones (PGF2α).

Answer 43

Multiple ovulations producting multiple follicles in one estrus and allowing to fertilizations from different matings

Answer 44

The uterus is the organ of pregnancy. Its primary functions are: luteolysis and control of cyclicity (in some species); sperm transport to the oviduct, where fertilization happens (ampulla); environment for embryo attachment; maternal contribution to the placenta; expulsion of the fetus and fetal annexes at the end of pregnancy.

Answer 45

Hormones can be classified based on the tissue of origin as follows (i) hypothalamic (GnRH); (ii) pituitary (FSH, LH, PRL); (iii) gonadal (female: estrogens, progesterone, inhibin, testosterone, oxytocin, relaxin; male: testosterone, other androgens, estrogens, inhibin); uterine and placental (PGF2α, estrogens, P4, eCG, hCG).

Answer 46

Biochemically, hormones can be classified as (i) peptides (chains of amino acids). These can be relatively small, as GnRH that is a decapeptide, or larger as prolactin (198 amino acids) and relaxin (two polypeptide chanins connected by disulfide links). (ii) glycoproteins: these are polypeptide chains with carbohydrate moieties. These guarantee protection to the hormone because only glycosilation sites are damaged. The higher the glycosilation, the longer the half-life of the hormone. Normally, glycoproteins are made of two chains. For instance, glycoproteins produced by the anterior pituitary within one species (including the gonadotropins FSH and LH) share the same structure of the alpha chain, that is connected (by hydrogen bonds and van der Waals forces) to a beta chain that is characteristic of the specific hormone. Other glycoproteins are inhibin (alpha and two typer of beta chains (A and B) with similar biological activity), activin (two beta chains), and follistatin. (iii) steroid hormones are synthetized from cholesterol and they all share a nucleus of cyclopentanoperhydrophenanthrene. Finally, (iv) prostaglandins are lipids consisting of 20 carbon-unsaturated hydroxy fatty acids synthetized from arachidonic acid. They have extremely short half-life (seconds, for instance PGF2α is completely removed in one pass thorugh the pulmonary circulation in about 30 seconds). There are at least six prostaglandins and several biologically active metabolites. The most important are PGF2α and PE2.

Answer 47

The acrosome is a membrane-bound lysosome containing enzymes such as acrosin, esterases, zona lysin, hyaluronidase, and acid hydrolases that are needed to digest and penetrate the zona pellucida of the oocyte during fertilization.

Answer 48

Canids, felids (rudimentary), primates (e.g., spider monkey), mustelids (ferret, skunk, otter, weasel), bears, raccons, bats, squirrels, mole, hedgehogs, shrews, guinea pig, rats, mice, hamsters, decu, gerbils, chichilla

Answer 49

Hormones with short half-life are prostaglandins (seconds to minutes, almost all PGF2α disappears after one complete passage in the pulmonary circulation - about 30 seconds), also gonadotropins such as LH and FSH have relatively short half-lives (ranging from 20 to 120 minutes depending on the hormone and species), whereas other glycoproteins such as eCG and hCG have longer half-life (hours to days) and steroids have even longer half-lives (days to weeks).

Answer 50

LH has a basal pulsatile pattern during anestrus, with pulses of low frequency and low amplitude. Frequency and amplitude start increasing at the end of anestrus and beginning of proestrus, under the effect of GnRH, which has increased pulse frequency and amplitude itself. The surge center, under the positive effect of estradiol produced by the developing follicles, produces a peak in GnRH that causes a peak in LH obout 24h after a peak in estradiol. In bitches the LH peak lasts longer compared to other species (mean 36 +/- 55h). About 48-60h after the peak in LH ovulation occurs. In metestrus LH has a pulsatile pattern characterized by higher amplitude and frequency compared to anestrus.

Answer 51

Proliferation, meiosis, differentiation

Answer 52

Paraventricular nucleus (oxytocin), surge center (mainly in the preoptic area = medial preoptic nucleus and anteroventeal periventricular nucleus), tonic center (arcuate nucleus and median eminence); also the periventricular nucleus, preoptic nucleus (contains neurons that secrete GnRH and kisspeptin), and arcuate nucleus (contains neurons that secrete GnRH and kisspeptin) can influence reproduction by secreting kispeptins which act on the surge and tonic centers of the hypothalamus.

Answer 53

Primary spermatocytes are the cells with the longest life-span (e.g., in bulls it is 18-19 days over 61 days of spermatogenesis). Secondary spermatocytes have a shorter life-span between 1.1 and 1.7 days, depending on the species.

Answer 54

Lactational anestrus is a period of absence of cyclicity associated with lactation in most domestic species. Specifically, it is associated with mechanical (suckling), olfactory, visual, and auditory stimuli associated with the presence of the offspring. It is present in cows, sows, small ruminants, sometimes in queens (variable), it is not detectabe in bitches as they woudl anyway be in anestrus following diestrus. It is not present in mare and alpaca. Dairy cows do not display lactational anestrus as the calf is removed immediately or a few hors after birth.

Answer 55

The menstrual cycle differs from the estrus cycle in the following ways: (i) the follicular phase is 50% of the cycle, whereas it is only 20% in domestic species; (ii) as a consequence, the luteal phase is 50% of the menstrual cycle, whereas it is 80% of the estrous cycle; (iii) sexual receptivity is homogeneous throughout the cycle (it is not affected by progesterone), while it is displayed only during estrus of the estruous cycle; (iv) ovulation happens halfway through the menstrual cycle, whereas it is the beginning of the estrous cycle; (v) the fertile period is 18% of the menstrual cycle, whereas on average, it is 5% of the estrous cycle; (vi) follicular depletion lead to the interruption of the menstrual cycle (menopause), this does not happen in animals displaying an estrous cycle.

Answer 56

Half-life, receptor density, pattern and duration of the secretion, receptor-hormone affinity

Answer 57

It may indicate an insufficient P4 production. It may be necessary to supplement P4.

Answer 58

The hymen is a remnant of tissue of the Müllerian ducts fusing with the urogenital sinus, it is therefore located at the vestibular-vaginal junction

Answer 59

From the outer to the inner: serosa (simple squamous cells layer; in the uterus it is called perimetrium); muscolaris (outer longitudinal layer, inner circular layer; in the uterus it is called myometrium); submucosa (conncetive tissue, vases, lymphatics and nerves); mucosa (epithelial layer with different characteristics based on the tract of the reproductive system. e.g., columnar ciliated within the salpinx, columnar and highly secretory in the cranial part of the vagina, stratified squamous in the vestibulum of the vagina); the uterine mucosa and submucosa are named emndometrium, with different cellular characteristics based on the stage of the estrus cycle.

Answer 60

Continuous supply of male gametes, providing genetic diversity, maximize reproductive success by producing spermatozoa daily, provide an immunological privileged site for germ cells development

Answer 61

Freemartinism is a sex differentiation condition affecting heifers twins of a bull. Specifically, if two bovine embryos are conceived and they have genetically different sexes, the sex differentiation process in the male causes abnormalities in that of the female, because the two embryos will share the same chorion and cotyledons, thus the same blood and hormone milieu. Sex differentiation in males start around 40 days of gestation in males, whereas in females this process starts later. In males, the sertoli cells of the testes produce anti-Müllerian hormone, inhibiting the development of the paramesonephric ducts, hence the formation of the female reproductive organs and the development of germ cells that are likely to produce abdonrmally high amounts of testosterone and androstenedione. The heifer calf is therefore sterile, whereas the bull is fertile. Therefore, freemartin heifers often presents with incomplete cavitation of the reproductive organs, abnormally developed ovaries, and male sex characteristics and behavior.

Answer 62

Pituitary gonadotropins have a half-life that range from 20 to 120 minutes depending on the hormone and species.

Answer 63

Stallion and boar (higher than a pregnant mare or sow), however these molecules have low biological activity

Answer 64

>Fetometry (ICC and OUD outer uterine diameter until 30 dop) at least 3 fetuses. CRL crown-rump length (from the most rostral part of the head to the base of the tail), BPD, BD body diameter (two transverse diameters at the level of stomach-liver = widest), DPTV deep portion of the diencephalo-telencephalic vesicle, FL femur-length, GD gastric diameter.

Answer 65

Defeminization of the hypothalamus is a process happening during fetal and early neonatal life, leading to inactivation of the GnRH surge center in the hypothalamus. This is caused by testosterone crossing the hemato-encephalic barrier and being aromatised to estradiol within the brain of the male. Therefore, defeminization itself is mainly caused by estradiol and happens in males due to higher levels of testosterone that can reach the brain, cross the hemato-encephalic barrier and be converted in estradiol. In females, although blood concentrations of estradiol are higher, defeminization of the hypothalamus does not take place, as estradiol cannot cross the hemato-encephalic barrier due to the action of the alpha-ferroprotein, which binds estradiol. Alpha-ferroprotein is produced both in males and females, earlier by the embryonic yolk sac, later by the liver. Early post-natal exposure to androgens is important to complete the process of defeminization of the hypothalamus, as it has been reported that it is still possible to stimulate high GnRH pulses from the surge center of bulls castrated immediately after birth.

Answer 66

Protein hormones travel in the blood stream and interstitium until they reach a target cell expressing a receptor for the hormone on the surface of its plasma membrane. Once the hormone binds to the receptor, a transformation of a G protein coupled with that receptor is induced. The transformation causes tha activation of adenylate cyclase, an enzyme promoting the conversion of ATP in cAMP. cAMP is a second messenges (the first being the hormone) that when present in the cytoplesm, binds to a proteine kinase, another enzyme consisting of two subunit. The cAMP binds to the regulatory subunit that will activate the catalytic subunit that will promote the conversion of existing substances to new products.

Answer 67

The hypothalamo-hyphophyseal portal system allows circulation of hormones from the hypothalamus to the anterior pituitary before dilution into the systemic blood stream. It consist of a superior hypohyseal artery, dividing in small capillaries and forming a primary portal plexus at the stalk region of the pituitary. At this level, the terminals of neurons with body cells located in the hypothalamic nuclei, make contact with capillaries of the plexus and hormones are secreted in the blood stream of these capillaries. Then the blood circulates in a second portal plexus in the anterior pituitary and finally exit the organ through venous blood vessels.

Answer 68

The testicular artery (originating from the abdominal aorta and directed to the testicle) convey blood at body temperature (about 39°C) to the testicle. However, in most species, testicular temperature must be 4-6° below that of the body in order to have successful spermatogenesis. The arterial blood is therefore cooled by a countercurrent heaht exchange. Specifically, the venous blood in the testes contained in the scrotum has a temperature of about 33°C. Venous vessels form finger-like wrappings around the testicular artery (pampiniform plexus). Therefore, the arterial blood has a decreased temperature when it reaches the testicle. Moreover, the testicular artery becomes convoluted (loos of pulse pressure). The intimate relationship between the pampiniform plexus and the testicular artery also guarantee some testosterone to be recirculated within the testes (passed from the vanous blood to the arterial blood). The pampiniform plexus and the testicular artery pass in the spermatic cord.

Answer 69

Insuline-like 3 is a factor secreted by the islets of the pancreas and by Leidyg cells with various functions. Among these, INSL-3 and its receptor (Lgr8) control the transabdominal phase of the testes descent to the scrotum.

Answer 70

Countercurrent heath exchange, which is also favored by the contractions of the cremaster muscle that pumps venous blood of the pampiniform plexus, moreover the tunica dartos can operate sustained contractions to keep the scrotum closer to the body. The skin of the scrotum is also important becouse has terminations of thermal sensory nerves that convey information to the thermosensitive neurons within the hypothalamus. If T°C is increased a signal from the hypothalamus increases the activity of sweat glands on the scrotal skin and relax the tunica dartos so the testes are moved away from the body. Moreover, the hypothalamus sends signals to the respiratory center so respiratory rate increases if the testicular T°C is increased.

Answer 71

Macroscopic: color, volume Microscopic: concentration (manual using Burker's chamber, Makler's chamber, or Toma's chamber, or automated systems as the Nucleocounter), motility (subjective evaluation or Computer-Assisted-Sperm-Analyzers = CASA), morphology (evaluation of at lease 200 sperm per slide, on eosin-nigrosine stained smears).

Answer 72

1)Cycle length: 21 days in all species, except ewe (17 days). 2)Estrus length: shorter in cows (average 15 h), ewes 30 h, sows 48 h, longer in mares (7 days). 3) Cows and sows have non-seasonal polyestrous cycle (although sows would have seasonality in the wild, with fertility in autumn); Ewes and mares have a seasonal polyestrous cycle, ewes are short-days breeders, whereas mares are long-days breeders. 4) Cows, mares, ewes have follicular waves, whereas sows have no follicular waves.

Answer 73

Obesity can impact fertility and reproductive success. 1. Hormonal Imbalances Leptin Dysregulation: Leptin, a hormone produced by fat cells, plays a critical role in regulating appetite and energy balance but also affects reproductive hormones. Obesity leads to leptin resistance, which can disrupt the hypothalamic-pituitary-gonadal axis and impair reproductive hormone secretion, leading to: Reduced Gonadotropin Release: Impaired secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), essential for normal reproductive function. Consequently, the secretion of estrogens, pregesterone, and testosterone is affected as well. 2. Reduced Fertility Females: (i)Failure to ovulate and Irregular Estrous Cycles: Obesity can lead to hormonal imbalances, particularly affecting estrogen, progesterone, and leptin levels. This can result in irregular estrous cycles, failure to ovulate or prolonged periods of anestrus (absence of heat cycles). (ii)Dystocia: Obese animals, particularly females, are at increased risk of dystocia due to excess body fat around the pelvic region, fat deposits may reduce the space available for passage through the birth canal. Males: (i)Lower Sperm Quality: In obese males, there can be reduced sperm motility and morphological abnormalities in sperm. This results from hormonal imbalances, including decreased testosterone levels and increased estrogen production from adipose tissue. (ii)Decreased Libido: Obesity can lead to reduced interest in mating due to lethargy and hormonal imbalances. 3. Increased Risk of Gestational Diabetes: Excessive body fat can predispose females to gestational diabetes, which can result in poor pregnancy outcomes and may affect fetal development. 4. Postpartum Problems: Obese females may have reduced lactation capacity and can be prone to complications like uterine infections or mastitis postpartum. 5. Poor Neonatal Health Offspring born to obese mothers may be at risk for low birth weight, neonatal death, or developmental problems. Obesity may affect placental function, limiting nutrient supply to the fetus, or cause metabolic disturbances that negatively affect the fetus. 6. Increased Risk of Reproductive Cancers Females: Obesity has been linked to an increased risk of reproductive cancers such as mammary tumors in dogs and cats, especially if they are intact (not spayed). This risk is compounded by high levels of circulating estrogen due to excess body fat. Males: Obese males may be more prone to testicular tumors or prostate disease, partly due to hormonal imbalances and the inflammatory effects of obesity. 7. Difficulty in Spaying or Neutering Obesity makes surgical procedures such as spaying (ovariohysterectomy) The excess fat can obscure anatomical landmarks, increase surgical time, and heighten the risk of complications like infections or poor wound healing.

Answer 74

Pseudopregnancy is a paraphysiologic condition in bitches. The cycle of the bitch is characterized by a long luteal phase (about 70 days). Progesterone is produced by the corpus luteum and its blood concentrations increase until day 25 after ovulation, from that moment, in non pregnant bitches, it starts decreasing. The decline in P4 is associated with a rise in prolactin. Bitches can show clinical or non-clinical pseudopregnancy. The latter may be characterized just by the presence of slight mammary enlargment and modest lactogenesis, whereas the clinical condition is also associated with behavioral signs (nervousness, anorexia, nursing of inanimate objects, nesting, aggressiveness, mock parturition) and heavier lactogenesis. This condition is self-limiting, however the clinical presentation can lead to mastitis. Therefore, medical treatment using Cabergoline, bromocriptine, metergoline is possible.

Answer 75

Glycoprotein hormones are polypeptide chains with carbohydrate meioties. This group of hormones includes LH, FSH, eCG, hCG, inhibin, activin, follistatin.

Answer 76

Effective management of neonatal diarrhea in lambs requires prompt treatment to address dehydration, the underlying cause, and supportive care. Preventive measures such as proper colostrum management, sanitation, and vaccination are critical to reduce the incidence of diarrhea in lambs. Causes = infectious or non-infectious 1.Infectious agents: (i) Bacteria: E. coli, Salmonella, Clostridium perfringens. (ii)Viruses: Rotavirus, Coronavirus. (iii)Protozoa: Cryptosporidium parvum, Eimeria spp. (coccidia). 2.Non-infectious causes (i)Nutritional causes (overfeeding, sudden changes in diet, poor-quality milk replacers or inadequate nutrition from the ewe). (ii)Environmental causes: cold or unsanitary environments increase the risk of diarrhea. Treatment: 1. Supportive care Neonatal diarrhea ==> dehydration, electrolyte imbalances, and acidosis = fatal if not addressed promptly. (i)Fluid therapy: Oral rehydration solutions (ORS)(commercial electrolyte solutions designed for livestock or prepare a homemade solution - e.g., NaCl + bicarbonate + glucose). For mild to moderate dehydration, give 50-100 mL/kg of oral electrolyte solution every 6-8 hours until the lamb improves. In cases of severe dehydration = intravenous fluids. (ii). Warmth: Heat lamps or blankets. NB cold lambs may not be able to suckle properly, which worsens dehydration. (iii). Nutritional Support: Continue feeding colostrum in the first 24-48 hours of life. Colostrum should be given within 1-2 hours of birth if possible, at about 50 mL/kg body weight. Avoid overfeeding. 2.Specific Treatments (i)Antibiotics if bacterial infection (e.g. E. coli). Broad-spectrum antibiotics such as amoxicillin, trimethoprim-sulfamethoxazole, or neomycin may be used especially for septicemia. (ii)For protozoal infections like Cryptosporidium or coccidiosis, use specific anti-parasitic drugs: Cryptosporidium: Halofuginone lactate. Coccidiosis: Toltrazuril or sulphamides. Probiotics: Preventive Measures: (i). Proper Colostrum Management: high-quality colostrum soon after birth to provide passive immunity. Dose: 50 mL/kg body weight within the first 2 hours of life, and every 6 hours for the first day (at least 200 mL/kg in the first 24 hours). (ii). Hygiene and Sanitation: Maintain a clean, dry, and warm environment for the lambing area. Avoid overcrowding. (iii). Nutrition: avoid overfeeding or sudden changes in diet. Ensure that ewes are properly fed during gestation and lactation, as poor maternal nutrition can result in weak lambs that are more prone to infections. (iv). Vaccination: Vaccination of ewes during late pregnancy (with multivalent vaccines) can protect lambs through maternal antibodies, particularly against pathogens like Clostridium perfringens (which causes enterotoxemia) and E. coli.

Answer 77

Ovaries are paired dense paired organs responsible for female gametes and hormones production. Each ovary is surrounded by tunica albuginea (connective tissue) covered by a single layer of cuboidal cells referred as ' germinal epithelium' (although the name is misleading as this is not involved in gamete production!). Underneath the tunica albuginea, there is the ovarian cortex (except in mares). This contains the oocyte population and the cells surrounding the oocytes that forms follicles at different stages of development. The cortex also contains the corpus luteus/corpora lutea and the corpora albicantia (which are degenerated corpora lutea enriched in connective tissue from previous estrus cycles). The inner part of the ovary is referred as medulla that consists mainly of connective tissue and hosts blood and lymphatic vessels and nerves. In mares the cortex and medulla are inverted and ovulation can only take place at the ovulation fossa (random location in any part of the cortex in other species), which is a depression on the ventral border of the ovary and it is not covered by the tunica albuginea.

Answer 78

Because germ cells are connected by intercellular bridges that guarantee the communication between the cytoplasm of cells belonging to the same cohort.

Answer 79

Noakes chapter 4

Answer 80

When produced by gonadal cells, steroid hormones exit the cell by diffusion (as they are lipo soluble), although they to bind with transport protein to travel within the blood circulation and in the interstitium. When they reach target cells, they unbind from the transport protein and can act in two different ways. (i) steroid can enter the target cell, diffusing through the plasma membrane and the nuclear memebrane to bind with nuclear receptors within the nucleus. The bind between the hormone and the nuclear receptor is a transcription factor that will promote the synthesis of mRNA that will then exit the nucleus, reach the ribosomes and promote the synstesis of specific proteins. This mechanism takes long time (hours to days). An example is the effect of estradiol on the cell of the cervix, causin the production and secretion of mucous; another example is the progesterone causing increased endometrial secretion using the same mechanism (ii) steroid can also bind to plasma membrane receptors. The bond causes the transformation of a G protein that will activate adenylate cyclase, which is an enzyme that converts ATP to cAMP. cAMP will then bind to the regulatory subunit of a proteine kinase enzyme that will cause the activation of the catalytic subunit of the same enzyme. This will cause a change in permeability of the calcium channels. This mechanism is faster (seconds to minutes). Examples are the effect of estradiol on myometrial cells, causing a change in permeability of calcium channel that favors myometrial contraction; conversely, progesterone has a similar mode of action, although inhibiting myometrial contractions.

Answer 81

The meiosis phase of spermatogenesis takes place in the adluminal compartment of the seminiferous tubule. It starts when primary spermatocytes enter the first meiotic division, that guarantee genetic heterogeneity, meaning that each secondary spermatocyte and then spermatid will have unique genetic material. This is possible thanks to the formation of tetrads after complete DNA replication. Tetrads fuse at random spots (i.e., chiasmata) and crossing-over takes place, allowing segments of chromosomes to cross-over to the homologous chromosome. At the end of meiosis, secondary spermatocytes are formed.

Answer 82

Metaestrus is the phase of the estrus cycle that follow the estrus. In this phase, progesterone levels start rising as the corpus luteum develops.

Answer 83

The excurrent duct system is part of the male reproductive system responsible for the transport, maturation, and storage of sperm after they leave the testis and before they are ejaculated through the urethra. It includes the efferent ducts (transporting the sperm from the rete tesis to the head of the epididymis), the epididymis (where spermatozoa acquire motility and fertilizing capacity and is stored until ejaculation occurs; the epididymis is divided in three regions: head, body, and tail) the ductus deferens (a muscular tube that convey the sperm to the urethra during ejaculation).

Answer 84

Bovine: Male 11 months (7-18), Female 11 months (9-24) Ovine: Male 7 months (6-9), Female 7 months (4-14) Caprine: Male 7 months (6-9), Female 7 months (4-14) Equine: Male 12-18 months, Female 12-24 months Swine: Male 7 months (5-8), Female 6 months (5-7) Canine: Male 9 months (5-12), Female 12 months (6-24) Feline: Male 9 months, Female 8 months (4-15, depending on the month of birth) Camel: Male 3-5 years, Female 3 years Llama and Alpaca: Male 2-3 years, Female 1 year Rat: 4-8 weeks (both male and female) Mouse: Male 30-42 days, Female 24-28 days Hamster: 6-12 weeks (both male and female) Rabbit: Male 4-8 months, Female 4-6 months

Answer 85

Vertical vulva, with 70-80% of the vulva located below the pelvic birm (otherwise predisposition to uterine infections)

Answer 86

The paramesonephric ducts are ducts that develop parallelly to the mesonephric ducts (ducts connecting the mesonephros to the urogenital sinus in the early fetus). The female reproductive system (oviducts, uterus, cervix, cranial part of the vagina) develops from the paramesonephric ducts, whereas in males these ducts regresses. The paramesonephric ducts have a cranial opening and caudally connect with the dorsal wall of the urogenital sinus, the cranial vagina will originate from the caudal part of the paramesonephric ducts, whereas the vestibule will originate from the urogenital sinus. During development of the fetus, the two paramesonephric ducts will merge medially. The degree of fusion between the two ducts will determine the type of uterus of the animal. The degree of fusion is the highest in species with simplex uteurs (one vagina, one cervix, one uterine body, no uterine horns), it is variable in species with bicornuate uterus (from the highest to the lowest degree of fusion: mare, cow and small ruminants, sow, bitch and queen), and it is the lowest in species with duplex uterus (e.g., marsupials and rabbits).

Answer 87

Rfamide Related Protein 3 is a peptide involved in in regulation of kiss neurons. Specifically, when melatonin decreases due to increase of the photoperios, RFRP-3 increases determining either a stimulation of kiss neurons in producing kisppeptin-10 (in long-days breeders) or an inhibition of these neurons (in short-day breeders). For this reason, in long-day breeders, when kisspeptin-10 is increased, it stimulates GnRH-producing neurons to release more GnRH that will then stimulate the release of LH and FSH from the anterior pituitary, leading to cyclicity. In short-day breeders, low kisspeptin-10 lead to low GnRH and seasonal anestrus.

Answer 88

It may indicate an insufficient P4 production. It may be necessary to supplement P4.

Answer 89

Based on the degree of fusion of the paramesonephric ducts: - Simplex: highest degree of fusion of the paramesonephric ducts. One uterine body, no/rudimental uterine horns. Humans. - Bicornuate: a) High degree of fusion of the paramesonephric ducts = short uterine horns = Mare. b) Intermediate degree of fusion of the paramesonephric ducts = Cow, Ewe, Doe c) Low degree of fusion of the paramesonephric ducts = long uterine horns = Bitch, Queen, Sow - Duplex = two uterine bodies, either two cervical canal and two vaginal canals (opossum) or two cervical canals and one vagina (rabbit)

Answer 90

Elephant, sloth, armadillo, whale, dolphin, birds

Answer 91

It can cause abdominal descent of the ovaries

Answer 92

An increase in androstenedione and testosterone

Answer 93

Pulsatile GnRH, LH receptors on the Leydig cells, high concentration of testosterone in the seminiferous tubules, low concentration of testosterone in the systemic circulation (100-500 times lower than in the seminiferous tubules, otherwise high systemic testosterone concentrations would cause a downregulation of the GnRH/LH system and would remove the negative feedback on FSH, that guarantees stimulation of Sertoli cells). Moreover, a pulsatile secretion of LH optimize the number of LH-receptors on the Leydig cells, as a continuous secretion would cause the Leydig cells to become refractory.

Answer 94

It is important to detect, map, and measure endometrial cysts before breeding a mare, in order not to confuse them with an embryonic vesicle. Cyst do not move and do not grow. If there is doubt for pregnancy diagnosis between endometrial cyst and embryo => re-scan around day 25 of gestation to check for the heartbeat.

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