Bovine reproduction 2 Flashcards
Lets start again (57 cards)
Describe the definitive and non definitive behavioural signs associated with oestrus in cows ?
Oestrus behavioural signs
Definitive signs of oestrus
- cow standing to be mounted by another cow
Non-definitive signs of oestrus
- mounting other cows
- vulva mucous dischrage (thin, clear mucous)
- vulva swelling
- sexually active groups (SAG)
- restlessness, increased walking
- sniffing licking and rubbing on other cows
- Flehman response
- chin resting
- poor milk let down
- rubbed pin bones or base of tail
Identify 10 factors which could affect the display of oestrus in cows ?
Factors affecting the display of oestrus in cows
- Environment - hard ground
- Stress
- Lameness
- Health (sick cows are less likely to display oestrus)
- Climate
- Nutrition and milk yeild ( cows experiencing a greater negative energy balance are less likely to display oestrus).
- Age (older cows have a short and less intense heat).
- Breed (Bos indicus cattle are less likely to display oestrus)
- Synchronisation method
- Number of animals simulteneously being in oestrus
- moving of animals
What is a SAG ?
Sexually active group
group of cows engaging in mounting behaviour together.
What is the duration of oestrus ?
The duration of oestrus
- traditionally 18-24hrs
- usually on average 10-15 mounts are recorded per cow per estrus period (intensity)
Describe how you could calculate the positive predictive value (evaluation of heat detection) ?
Positive predictive value
(a measure of accuracy)
Probability of the test being correct, IE the cow truly is in heat.
= number of correct detections / (number of correct and false positive detections) * 100
Describe three different methods of producing a teaser animal ?
Teaser animals
(a chin ball should be applied to detect when a teaser has mounted)
1. Hormonal treatment
- should only be used on culled females or steers.
- Testosterone proprionate 2g IM
- must always be declared as a growth promotant when sold.
- Surgery to create teaser (Gomer) bulls
- vasectomy, epididymectomy
- penile fixation
- penile deviation
Disadvantages
- veneral diseases
- libido may reduce with time
- hazards associated with keeping bulls
Identify the bull:cow ratio when,
A - all the cows are synchronised ?
B - the cows are not synchronised ?
Bull:cow ratio
A when the cows to be mated are synchronised
- use a ratio of 1 bull: 10 - 30 cows
B. In unsynchronised cows
- use a ratio of 1:30-50 cows
Identify six different techniques we could utilise to improve oestrus detection ?
Improving oestrous detection
(the cost of a single missed oestrus = $ 200).
- Improve cow identification and record keeping
- Spend time specifically observing cow behaviour
- minimum of twice daily, 20-30mins each time
- may even be beneficial to start recording heats prior to mating, to assist with predicting the cows comming into heat. - Place suspicious cows into a group of oestrus animals
- Optimise nutrition and health
- Utilisation of detection aids
- Train staff
If farmer is unable to detect oestrus efficiently could consider TAI.
Identify seven aids which could be used to assist in the detection of oestrus ?
Aids which can be utilised for oestrus detection.
- Tail paint, or crayons
- Kamars (capsule broken by pressure during mounting)
- Estrostat (scratchy with fluroscent paint)
- Pedometers
- Progesterone measurement in milk lines and dipstick
- Hormone treated detector animals
- Gomer bulls
A) Define a submission rate ?
B) What is the ideal submission rate in a seasonal / split calving herd ?
C) What is the ideal submission rate in a year-round calving herd ?
A) Submission rate
The percentage of cows detected in oestrus and submitted for AI within a given period.
B) Ideal in a seasonal herd = 86% submission rate over a 3-week period.
C) Ideal in a year-round calving herd = 73% submission rate over an 80 day period.
Anything below the ideal indicates either
- a high proportion of cows not cycling
- poor estrus detection efficiency
Describe the aetiology behind a free martin ?
Free martinism
Definition = The sterile female of a male - female twin pair.
Aetiology
- Vascular connections between placentae of the developing twin (or multiple) foetuses
- results in co mingling of blood supplie occurs
- each foetus becomes a blood chimaera each carries blood cells / DNA from the other foetus
If this happens prior to sexual differentiation (D40) and the twins are male + female
- this results in the development of the female foetus’ reproductive tract under exposure to testosterone and antimullerian hormone (AMH)
- and exposure of the SRY gene in the male
- exposure to AMH induces regression of the mullerian ducts, cranial vagina, cervix, uterus and uterine tubes.
- exposure to testosterone causes varying degrees of musculinisation
What is the effect of freemartinism of the reproductive tract of the female calf ?
Freemartinism
(incidence >90% of female foetuses cotwinned to a male will be freemartins).
- male cotwin usually not affected
The result (internally)
Hypoplasia of the female reproductive tract with varying degress of musculinisation.
- internally short blind ending vagina
- adult freemartin <10cm
- hypoplastic reproductive tract on rectal exam often “uterus hard to find”
- ovaries vary in size from small to normal
- cervix is absent
- occassionally may palpate seminal vesicles
What are the external clinical signs of a free martin ?
External signs of a free-martin
- variable
- non pregnant heifer following a normal breeding period
- externally: tuft of hair from vulva labia
- hypoblastic mammary teats (those normally seen in males)
- clitoris may be prominent
- increased anogenital distance
Describe how you would diagnose and treat a freemartin calf ?
Freemartin
Diagnoses
- history of female twinning with a male
- clinical signs (vaginal length <10cm, hypoblastic reproductive tract, abnormal external vulva (tuft of hair).
- DNA profile (detection of Y chromosome)
- serum AMH high levels >700ng/ml diagnostic
Treatment
- usually culled at birth
- can be used as teasers but will usually require hormonal treatment.
Why are freemartins rare in other species ?
Freemartins
are rare in sheep, horses and pigs
This is because placental fusion occurs later past day 40 (when sexual differentiation occurs).
If you obtain an abnormal semen sample, how long should you leave the bull before you resample ?
Spermatogenesis
- takes around 60 days or a minimum of two months.
Describe the aetiology behind cystic ovarian disease ?
Cystic ovarian disease
Definition
The presence, on one or more ovaries of an anovulatory follicular structure that persist for various periods of time.
- cyst defined follicular structures > 2.5cm in diameter or larger in the absence of a corpus luteum.
- cyst are usually larger than developing follicles but may be of the same size.
COD affects approximately 10% of dairy cows annually.
- is most common during the post partum pariod as cows transition from anoestrous to oestrous cyclicity.
- major cause of infertility
- major cause of increased calving to conception intervals.
There are three possible outcomes of COD without intervention.
Without intervention what isthe possible outcome of COD ?
The outcome of COD
(no intervention)
Cyst are not always static structures
1. Cyst may persist for a prolonged period of time (up to 70 days) and remain dominant over other follicular structures.
- Regression
- the cyst regresses and is replaced by a new follicular structure that often develops into a new cyst (most cyst show this turn over) - Correction
- regresses and is replaced by a new follicular structure that ovulates, resulting in self correction (occurs in about 20% of cows).
Describe the pathology underlying the development of COD ?
Cystic ovarian disease (COD)
Key event = Inadequate development of a preovulatory surge of LH
- COD cows appear refractory to stimulatory effects of GnRH/oestrogen
- increasing oestrodiol normally stimulates a surge of GnRH which in turn stimulates a surge of LH from the pituitary leading to ovulation
- a lack of responsiveness of the GnRH surge centre = an inadequate preovulatory LH surge
The effect; anovulation of ovarian follicles with follicle persistence and an increase in size (>2.5cm)
- follicles persist for >10 days or appear to persist if cyst turnover is taking place.
COD; Describe the two types of follicles which may result ?
COD. Two types of cyst
Follicular cyst (Thin walled)
-systemic P4 is low <1ng/ml
- may secrete oestrodiol
- absence of CL
- most common during the post partum period (days 15-45)
- multiple cyst may occur simultaneously
Luteal cyst (Thick walled)
- systemic high P4 >1ng/ml
- luteinisation of the thecal and granulosa cells has occured and these cells now secrete P4
- difficult to distinguish by palpation from luteinised follicles / may require ultrasound.
Describe the clinical signs of cystic ovarian disease ?
Clinical signs COD
- nymphomania, persistent oestrus
- erratic oestrus behaviour, observed in oestrus more frequently then expected
- “sterility hump” more often seen in chronic cases
- infertility
- follicles >2.5cm felt on rectal palpation (confirmed at sequential examinations).
Describe a sterility hump ?
Sterility hump
(In the vernacular they are called buller cows)
A sterility hump is occasionally seen in cows with chronic cystic ovarian disease.
**
- elevation of the tailhead**
- this occurs due to chronic relaxation of the pelvic ligaments due to chronic exposure to elevated concentrations of oestrogen
- these cows also show frequent oestrus
These cows could be utilised in heat detection programs, however, their behaviour is not entitely consistent.
Describe how you could diagnose a case of cystic ovarian disease ?
Ovarian disease
Presentation
History - irregular cycles / infertility / prolonged anoestrous and delayed conception
- sterility hump
- nymphomania
- palpation of follicles >2.5cm or visualisation on ultrasound
Describe your potential treatments for cystic ovarian disease COD ?
Treatment for COD
- No treatment
- spontaneous recovery < 45 days
- removal of stressors - Manual rupture / aspiration
- there is an increased risk of adhesions with rupture - Hormonal treatments
- PGF2a to induce luteinisation (we can not tell this has occured)
- Induction of an LH surge with GnRH or HCG to induce ovulation or luteinisation
- progesterone can be used to restrore the hypothalmic pituitary sensitivity to oestrodiol.