Fertility, Subfertility and Infertility in the Cow Flashcards
What is a subfertile cow?
One that fails to achieve its fertility target, or that of the herd or group.
What is an infertile cow?
Incapable of becoming pregnant regardless of how long she is given to achieve pregnancy
How do yield and successful AI% correlate?
Yield is negatively correlated with first AI pregnancy %
What are the 4 causes of subfertility in cattle?
Structural causes
Functional causes
Management causes
Infectious agents
What are the major signs of subfertility in cattle?
No observed oestrus
Regular or irregular returns to oestrus
Presence of abnormal vulval discharge
Abortion and stillbirth
When is it normal to not observe an oestrus?
Pregnancy Immediately postpartum (4-6wks)
What are possible reasons for no observed oestrus?
In heifers congential issues
Acyclical or anoestrus
Ovarian cycsts
Cyclical ovarian activity is occuring but heat detection suboptimal
Cyclical activity occurring but limited behaviour
What is the genetic basis of ovarian aplasia and hypoplasia?
Autosomal recessive gene with incomplete penetrance
How can you diagnose freemartinism?
Test tube or thermometer case - put into vagina will only enter 2-3cm if freemartin
Karyotyping
Why does freemartinism occur?
Blood vessels in the chorion of twin foetuses become fused and interconnected, creating a shared circulation. The male foetus produces male hormones (testosterone and anti-mullerian hormone) and these are introduced to the circulation of the female foetus causing masculinisation of the female.
The effects of the fusion are seen more greatly when it occurs early on in pregnancy.
Freemartinism only occurs in male/female twins, not female/female.
What can cause there to be no observed oestrus in the cow?
Anoestrus or true acyclicity Cystic ovarian disease Persistent CL Pyometra with persistent CL Sub-oestrus Failure to detect oestrus
What causes anoestus or true acyclicity in the cow?
High milks yields Inadequate feeding, particularly energy Poor body condition - may reflect poor nutrition or disease Stress - lameness -- discomfort --- interferes with feeding pattern intercurrent disease
What will you find on clinical examination of a cow in anoestrus, or with true acyclicity?
Rectal examination shows involuted tract; ovaries feel small, smooth and flat
US shows follicles <1.5cm with no CL
Milk progesterone will be low @ 10 day intervals
How does freemartinism affect the female reproductive tract?
The heifer’s reproductive tract is severely underdeveloped and sometimes even contains some elements of a bull’s reproductive tract.
The ovaries of the freemartin do not develop correctly, and they remain very small. Also, the ovaries of a freemartin do not produce the hormones necessary to induce the behavioral signs of heat. The external vulvar region can range from a very normal looking female to a female that appears to be male. Usually, the vulva is normal except that in some animals an enlarged clitoris and large tufts of vulvar hair exist.
How does inadequate nutrition influence fertility through reduced IGF-1 production?
Hypothalamus
- reduced GnRH secretion
- reduced + feedback to oestrus
Pituitary
- reduced LH and FSH secretion
- reduced response to GnRH
Ovary
- decreased granulosa proliferation and differentiation
- decreased LH/FSH supported steroidogenesis
- reduced aromatase activity
- reduced luteal activity and steroidogenesis
Embryo
- decreased embryo growth
- reduced IFN production
How can you treat aneostrus or true acyclicity in cattle?
Wait until milk yield falls, or cow returns to positive energy balance
Hormonal
GnRH
Progesterone such as PRID
PRID alone or with GnRH
What are the normal fluid filled structure in bovine ovaries?
Follicles
1.5-2.0cm diameter during oestrus
<1.5cm diameter rest of cycle
Vaculoated CL
Same size as non-vaculoated CL
Disppears during pregnancy
Usually single
What are abnormal fluid filled structure on the bovine ovaries?
Luteinised follicles
<2.5cm diameter, no sign of ovulation larger cavity than vacuolated CL
Follicular and inactive cysts
Soft, thin walled (<3mm) fluid filled structure >2.5cm diameter. Low P4.
Luteal cysts Thick walled (>3mm) fluid filled structure >2.4cm in diameter. High P4.
What are ovarian cysts and how are they formed?
Fluid filled structures on the ovaries over 2.5cm in diameter. They persist for longer than 10 days.
Develop from anovulatory graafian follicles which fail to ovulate or regress
What are the 3 types of ovarian cysts?
Thin walled, oestradiol secreting follicular cysts
Thick walled, progesterone secreting luteal cysts
Thin walled, functionally undifferentiated inactive cyst
Which is the most common type of cyst?
Inactive
Why does normal ovulation occur?
Ovulation of the dominant follicle is due to LH surge induced by increased secretion of oestradiol by the mature dominant follicle
How do thick walled luteal or luteinised cyst result in acyclicity?
Negative feedback of P4 on anterior pituitary
What can lead a failure of LH surge?
After calving there is a progressive restoration of the ability of the hypothalamus to respond to oestradiol to produce an LH surge.
Failure of oestradiol to elicit a normal + feedback stimulation of LH surge
What are the ovarian causes of cysts?
Reduced number of LH receptors in granulosa cells
Low insulin and IGF-1 and NEB causing >NEFAs which impairs follicular proliferation and function
Why should you not rupture ovarian cysts transrectally?
Can cause damage to other structure of the ovaries, such as adhesions. These may negatively impact fertility.
How should you treat a luteal cyst?
PGF2-alpha - regress CL
How should you treat a follicular cyst?
GnRH or hCG to cause luteinisation, followed by PGF2-alpha or PRID/CIDR for 10-12 days
How does pyrometra lead to CL persistence?
Pathological changes in the uterus interfere with luteolysin production and the CL persists, which perpetuates the disease. Treat with PGF2-alpha
What are the signs of oestrus in the cow?
Restless, not eating, drop in milk yield Searches for other cows, mounting Bellowing Clear vulval elastic mucous discharge Head mouting Standing to be mounted
What is the most important sign of oestrus?
Standing to be mounted
Why may oestrus not be detected?
Cow problem:
Duration of oestrus may be short and signs may be covert
Person problem:
Due to poor facilities for cows to express behaviour and a poor observational regimen
How often should you examine cows for oestrus?
20-30mins at least 3 times per day, other than milking
Use other methods
What are the methods for modifying normal ovarian cyclical activity to implement fixed time AI in cattle?
2 injections of PGF2-alpha 11 days apart with a single AI @ 72-84 hours after 2nd injec. OR double AI @ 72 and 96hrs
Insert PRID or CIDR for 7-9days with PGF2-alpha injected 24 hoyrs before removal and double dixed time AI @ 48 and 72 hours or single @ 56 hours
What are the possible reasons for a cow not calving after service or AI?
Oocytes not fertilised
10-15%
Embryo death before 13 days
15-20%
Embryo dies between 13-42 days
10%
Foetal death after 42 days
5%
What are the causes of fertilisation failures that are not due to bull or poor semen?
Anovulation Delayed ovulation Incorrect AI timing Serving too early postpartum (6weeks to involute) Hormonal imbalances Structual defects Infection of genital tract Stress Nutritional
What are the possible causes of early and late embryonic death?
Luteal deficiency and hormonal imbalance Uterine infection with specific embryopathic micro-organism Infection with opportunistic pathogens Genetics Heat or other stress Nutritional
What are some embryopathic microganisms?
Campylobacter fetus Tritrichomonas fetus Mycoplasma, ureaplasma BVDV IBR Bluetongue Chlamydophila psittaci
What is a repeat breeder cow?
A cow that has returned to oestrus after AI or natural service on 3-4 consecutive occasions
What are some good approaches to treating the repeat breeder cow?
Change sire
Use semen from good bulls
Inseminate at normal time and 24hr later
hCG or GnRH at time of first AI to stimulate a second ovulation to produce an accessory CL to increase progesterone
11-12 days post AI, GnRH IM to enhance CL
11-12 days frollowing AI consider the use of PRID or CIDR
How does uterine infection affect fertility?
Direct pathology on gamete, embryo, foetus
Innate immune signal response in endometrium
Alters endocrine signalling
- CL development
- HPA axis
Influences ovarian function, notably follicular and oocyte development
What are the predisposing factors for endometritis?
Longer or shorter gestation RFM Parity Milk yield Dystocia and trauma Hygiene Season of year Intercurrent disease Nutrtional
What should you check when you look at the vaginal contents when endometritis is present/
Volume
Smell
Colour
What are the non-infectious causes of abortion or stillbirth in cattle?
Genetic factors e.g. abnormalities Endocrine deficiencies and excesses Toxic substanes Heat stress Misuse of therapeutics Stillbirth: dystocia
