CBL 9: The Routine Fertility Farm Animal Visit

What are the main factors impacting the onset of puberty in cows?

genetics, nutrition, body composition and weight

How can poor nutrition be caused in cows?

bullying and competition from other cows

Does poor nutrition delay or cause early onset of puberty?

delay

Does good nutrition delay or cause an early onset of puberty?

early onset

Does seasonality affect puberty?

yes

How do longer daylight hours affect puberty?

delay puberty

How does shorter daylight hours affect puberty?

accelerate it

Do higher temperatures in the summer delay or cause early onset of puberty?

delay

What is the site of secretion of oestrogen?

granulosa cells of the ovarian follicles

What effect on the ovaries does high levels of oestrogen cause?

LH surge during oestrus

What is the site of secretion of progesterone?

corpus luteum

What are the effects of progesterone on the ovaries?

prepares uterus for initiation and maintenance of pregnancy

How does progesterone affect other hormones?

inhibits FSH, LH & oestrogen

What is the site of secretion of FSH?

anterior pituitary gland

What are the effects of FSH on the ovaries?

stimulates follicle growth

What is the site of secretion of LH?

anterior pituitary gland

What effect does LH have on the ovaries?

maintenance of the corpus luteum

What is the site of secretion of PGF2α?

uterus

What effect does PGF2α have on the ovaries?

induces regression of corpus luteum (luteolysis)

What is the site of secretion of GnRH?

hypothalamus

What effect does GnRH have on the ovaries?

stimulates ant pit to release FSH and LH

What is the site of secretion of inhibin?

granulosa cells of the ovarian follicles

What effects does inhibin have on the ovaries?

inhibits release of FSH

What hormones are involved in the reproductive cycle?

oestrogen, progesterone, FSH, LH, PGF2α, GnRH, inhibin

Outline the steps of the process of ovulation

1. hypo secrete GnRH

2. FSH & LH released from pit

3. follicle maturation

What happens after follicle maturation?

follicle reaches max size & ruptures to release ovum

Where does the oocyte pass post ovulation?

down uterine tube into uterus

How does the oocyte pass down the uterine tube?

muscular contractions and cilia

What does the remaining tissue from the follicle become after being fertilised in the uterus?

CL

Outline the places the female gametes are transported to prior to fertilisation

ovaries - fimbriae of infundibulum - uterine tube - uterotubal junction - uterine horns

What is the fimbriae of infundibulum?

ovarian end of uterine tube/oviduct

What does the fimbriae of infundibulum do after ovulation?

engulf oocyte and prevent it being lost into abdominal cavity

How many parts does the uterine tube/oviduct have?

3

What are the 3 parts of the uterine tube called?

infundibulum, ampulla and isthmus

Where does fertilisation most commonly occur?

ampulla

Outline the places the sperm is transported prior to fertilisation

seminiferous tubules of testes - rene testis - epididymus - deferent duct - pelvic urethra (cervix - uterine body - uterine horns - uterine tubes)

Where is sperm produced?

seminiferous tubules of testes

Where does sperm mature?

epididymus

What happens to the sperm at the epididymus?

it matures

How does sperm move through the epididymus?

peristaltic contractions of muscular duct and hydrostatic pressure

What are the 5 stages of fertilisation?

1. contact

2. acrosome reaction (& completion of zona pellucida penetration)

3. fusion of plasma membranes and entry of sperm into nucleus

4. cortical reaction

5. fertilisation

acrosome

membrane which surrounds the anterior part of the sperm nucleus

What is the acrosome reaction triggered by?

penetration of cumulus and zona pellucida

What enzymes are involved in the acrosome reaction during fertilisation?

hydrologic enzymes

What does the cortical reaction block during fertilisation?

polyspermy

What happens during the cortical reaction?

cortical granules in egg fuse with plasma membrane

Where are cortical granules found?

egg cytoplasm

What does the embryo release when it attaches to the uterine lining in implantation to communicate its existence to the mother?

proteins and hormones

What does embryo signalling prevent?

luteolysis (CL breakdown)

Implantation

embryo comes into contact with the receptive parts of the uterus

What are the 2 types of implantation?

invasive and non-invasive

What is the role of progesterone in pregnancy and parturition?

maintain uterus, maintain quiescence of myometrium, promote cervical closure

What is oestrogen’s role in pregnancy and parturition?

increase contractive potential of uterus

What is the role of prolactin in pregnancy and parturition?

alveolar development during prepartum period

When and why do prolactin levels rise during pregnancy and parturition?

latter part of gestation because of oestrogen

What is the role of ACTH in pregnancy and parturition?

adrenal cortex becomes more sensitive to foetal ACTH

What is the role of cortisol in pregnancy and parturition?

changes in secretion by foetus causes release of PGF2a from uterus

What is the role of PGF2a in pregnancy and parturition?

increases (due to increased oestrogen) and initiates parturition

What is the role of oxytocin in pregnancy and parturition?

stimulates uterine contractibility softening cervix and relaxation of birth canal

What is the role of relaxin in pregnancy and parturition?

enhance luteal activity and support pregnancy

follicle

small pocket-like sac located inside ovary

What are follicles responsible for?

monthly growth, maturation and release of an egg

What species are monovular?

horse, cow

What species are polyovular?

sheep, pig, dog, cat

What do you do to identify dominant follicles of an animal?

rectal palpation

How are follicles detected during rectal palpation?

fluctuating, turgid, fluid-filled bodies usually smooth and protruding slightly from the surface

What does a corpus luteum when fully formed feel like during rectal palpation?

firm, solid unyielding body embedded in ovary

What is the optimal sign for mating/AI?

12 hours after primary oestrus signs are observed

What are the behavioural signs of proestrus?

increasingly restless, mount other heifers, calling

What hormones do the behavioural signs of proestrus occur due to?

oestrogens

Are primary or secondary heat signs seen during proestrus?

secondary

Are primary or secondary heat signs seen during oestrus?

primary

What are the behavioural signs of oestrus seen during oestrus?

stand to be mounted, display bulling string of mucus from vulva

What is the function of the corpus luteum?

progesterone secretion to prepare the uterus for pregnancy

Luteolysis

regression of CL

Why is cows being seasonally polyoestrous good regarding maximising productivity in cattle?

there can be almost constant reproduction of new offspring

How can optimising fertility reduce environmental impacts?

decrease methane emissions

What is rectal palpation important for diagnosing in cows?

pregnancies

What body condition score should replacement heifers have?

3 when weaned at 8 months

What percentage of their mature weight should replacement heifers be at at their first mating?

60%

What age are heifers served at?

15 months

When should heifers have their first calving?

24 months

How are vaginal exams in cows performed?

vulvar lips parted and speculum with lubricant inserted into vestibule

What direction should the speculum be inserted into the vestibule during a vaginal exam?

dorsocranially

Why should the speculum be inserted into the vestibule dorsocranially during a vaginal exam?

to avoid external urethral orifice

What is the role of vaginal examination in assessment of a cow?

detect infection from birthing process (find any abnormal discharge)

What could finding abnormal discharge in a vaginal examination be a sign of?

endometrius, metritis or cervicitis

What does a normal cow’s vaginal discharge look like?

clear

What does abnormal cow’s vaginal discharge look like?

purulent, malodorous, blood

What is post partum lochia?

normal discharge after calving

What diagnostic imaging can be used to identify pregnancy in cows?

trans-rectal ultrasonography

Corpus luteum or follicles?

corpus luteum

Corpus luteum or follicles?

follicles

Corpus luteum or follicles?

Corpus luteum

Corpus luteum or follicles?

follicles

What colour is CL on ultrasound?

grey (hypoechoic)

What colour are follicles on ultrasound?

black (anechoic centre)

What does CL look like on ultrasound?

grey with black “lacuna” in centre

Does CL have a thin or thick wall?

thick

Do follicles have a thick or thin wall?

thin