Name the common primordium of the repro/urinary systems.
- Pronephroi - form the primitive urinary system
- Mesonephroi - Caudal to the pronephros, other segmental tubes unite the pronephric duct to form the ‘Mesonephros’ or ‘wolffian body’. Mesonephroi are part of the urinary system (later) –> develop into relatively large, ovoid structures
- Metanephroi –> form the definitive kidneys
What makes up the indifferent stage of genital development?
Internally:
- 1 pair of gonads (develop into testes/ovaries)
- 2 pairs of tubular tracts (mesonephric ducts & paramesonephric ducts)
Externally:
- 1 genital tubercle
- 1 pair genital swellings
- Bilateral urogenital folds
T/F. The female phenotype is the default phenotype.
T. As a result of the absence of androgenic and inhibiting hormones.
The differentiation of the gonads is dependent upon the expression of a gene on the Y chromosome. Under the influence of this gene, the gonads develop into testes.
The male genital tract and external genitalia develop in response to androgenic hormones produced by the interstitial endocrine (Leydig) cells of the testes. Foetal Leydig cells function for a limited period then involute – Leydig cells reappear in association with sexual maturity at which time they stimulate spermatogenesis. The Sertoli cells of the foetal testes produce a nonsteroidal inhibiting substance that causes regression of the paramesophric ducts.
What ducts arising from the repro/urinary primordium regress in the male?
Paramesonephric ducts.
Where as, in the female the paramesonephric ducts give rise to the uterine tubes, the uterus and the cr portion of the vagina
***[ to remember think P for paramesonephric = paternal, they regress in male & M for maternal = mesonephroi regress in female]
What is the fate of the urogenital folds in the male & female?
- In the male, urogenital folds fuse throughout their length, thereby contributing to the formation of the penile urethra
- In the female, the urogenital folds fail to fuse and form the labia
What is the fate of the pair of genital swellings in the male & female?
- In both male & female, a pair of superficial swellings forms over the site of the inguinal canal – genital swellings
- In the male, these swellings move toward the median plane, caudal to the elongating genital tubercle. The swellings fuse, giving rise to the scrotum
- In the female, the swellings disappear.
What is the fate of the Mesonephric ducts in the female?
Regress. Where as in the male the mesonephric ducts give rise to the epididymis and deferent ducts
What are the 3 different levels of development in sexual differentiation?
- Chromosomal Sex
- Gonadal sex
- Phenotypic sex
Explain the importance of the Y chromosome in sexual differentiation.
- Chromosomal sex (development)
- Sex-determining region Y (SRY) gene –> testis determining factor production by sex cords in ‘indifferent’ gonads
- leads to testis development
- Sertoli cells secrete anti-mullerian factor which causes regression of paramesonephric development
- In the absence of TDF –> female genital tract
Explain the Gonadal sex development in sexual differentiation.
- Gonadal ridges - arise on medial sides of mesonephroi, fuse with cells of mesonephros in early development
- Primordial germ cells & sex cord formation - primary germ cell migration (embryonic disc -> yolk sac -> gonadal ridges)
- Sex cords -> break into clusters, germ cell division (female) -> germ cells become follicles of the ovary –> oocyte. In male, seminiferous tubules arise from sex cords, the germ cells from the gonadal ridge develop to the early sperm
- Gubernaculum - associated with testicular descent - (male) pulls the testis down to where the scrotum is - remnants in male = proper lig. of the testis and lig. of the tail of the epididymis; In the female, gubernaculim is associated with the proper lig. of the ovary and round lig. of the uterus
Describe the sequence of events during normal breeding in the dog/cat.
Normal breeding – dog
• Observation, interest
• Erection – incl enlargement of bulbus glandis
• Positioning & riding
• Tie (+/- change of position)
• Ejaculation – pre sperm/rich sperm/post sperm fractions
Normal breeding – cat • Neck biting • Mounting • Positioning & pelvic thrusting • Intromission (multiple; penile spines) • Induced ovulation (24 to 48 hr post breeding
What are some structural changes during pregnancy?
- Ovaries - retencion of CL, CL of pregnancy may increase in size
- Uterine tube - fertilisation at junction of ampulla and isthmus. Contractions of muscular tunic of isthmus regulate (delay) passage of early embryo (takes 4-5d to enter uterus)
- Uterus - Early embryo floats freely in uterine lumen. CL of pregnancy may increase in size
- Implantation of embryo - Spacing of embryos - role of uterine contraction. Membrane interactions with endometrium.
- Vascular flow increases
- Hypertrophy muscle fibres within broad ligament
- Uterine growth
- foetal position changes during pregnancy
How to detect pregnancy?
Dog: From ovulation (day) - Abdo palps (28-30) - Xray (42) - USS (22) - Acute phase proteins (25) - Relaxin (25) From mating - Urine Oestrogen (21 d) From fertilisation - Serum FSH (28d)
Cat: From breeding(day) - Enlarged mamm glands (21) - Abdo palp (21-25) - X-ray (38-40) - USS (16-25) - Relaxin? (25) - No pregnancy if P4 < 1ng/ml
What are the physiological changes to the bitch/ foetus during pregnancy?
- Placenta -> increase risk of exposure to pathogens/ds (mum +foetus); increase risk of septicaemia due to foetus loss
- Foetal growth (trimesters 2/3); increase wt of mum
- Endocrine -> increase protein production (liver), change in excretion of metabolites (liver, urinary, placenta)
- Circulatory changes -> increas O2 consumption, anaemia, Ig, Preg oedema
- Digestive system -> hormones, motility, insulin resistance
Maintenance/Keeping the pregnancy. What to do/avoid?
- Preventatice treatments before mating
- Avoid stress (exp. to diseases/ physical activity)
- Diet (energy adjustment - ad lib puppy food to mum; folic acid?; calcium)
- Monitor (weekly weighting/physical examination +/- USS)
- Avoid unnecessary drugs/ preventive treatments!
What is the gestation period of the dog?
58 - 68 days (about 9 weeks)
What is the gestation period of the cat?
64 - 67 days
What is the average oestrus interval in a cow?
21 days
What is the gestation period of the cow?
282 - 285 days (around 9 mo)
What is an acceptable abortion rate in beef cattle?
3-5% is an acceptable abortion rate. most losses occur before 80 days
What are some reasons for early losses in pregnant cows?
- Failure to conceive:
- Bull infertility or sub-fertility
- Inadequate bull power
- Poor AI
- Nutrition/-ve energy balance
- Poor transition (increased metritis, endometritis, pyometra)
- BVDV (pesti)
- Vibriosis
- Trochomoniasis - Early losses:
- BVDV
- Campylobacter fetus spp. venerealis (Vibriosis)
- Trichomoniasis
- Leptospirosis
- Iatrogenic (prostaglandin)
What are the 5 parts of the BBSE?
Bull Breeding Soundness Examination: o Physical examination (Testes, Penis, Seminal Vesicles, legs, joints, gait, eyes, BCS) o Scrotal circumference o Semen motility o Sperm morphology o Serving capacity (rarely done)
what pathogen causes Vibriosis? What are the repercussions in the animal? How is Vibriosis prevented in practice?
- Campylobacter fetus spp. venerealis
- (bulls are the main source of infection)
- Infection prevents implantation of the embryo or loss of the developing embryo –> repro wastage
- Cows return to oestrus with prolonged/irregular cycles
- Abortions occasionally occur around 6 months gestation
Dxx by PCR of preputial wash from the bulls or IgA ELISA of vaginal mucus from infected cows - Prevention by vacc bulls annually
Outline the characteristics of BVDV and its transmission.
Bovine viral diarrhoea virus (pestivirus)
- Enveloped DNA
- transmission via close contact e.g. PIs shed virus from all body secretions (saliva, tears, milk, urine, semen and faeces)
- In non-preg cattle –> BVDV causes mild illness brfore an immune response clears virus
- Foetal immune system matures at 4 mo
- A foetus <4mo either aborts or becomes a PI –> denpend on stage of gestation (0-45d -> embryonic death/decreased conception; <125d –> PI calf; 100-150d –> congenital defects; >125 d –> immune response to virus (ag neg, ab pos)
- Cull PIs, test new bulls for BVDV ag before purchase, vacc herd wth Pestigard before joining
