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Title: Oestrus Cycle
Description: University notes on a recurring period of sexual receptivity and fertility in many female mammals A.K.A Heat.
Description: University notes on a recurring period of sexual receptivity and fertility in many female mammals A.K.A Heat.
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Standing heat
Synchronisation of Oestrus
Puberty
Puberty at first oestrus
Puberty and first ovulation
not always synchronous
Silent ovulation
Timing of puberty linked to
growth and weight
Decision to breed
Time of year- to fit in with
calving pattern of herd
Risk of dystocia
Productivity on farm
In Dairy Heifers:
15 mths
350 Kg LW
Calving at c
...
I
...
Freezebranding Aids
Tail paint
Chin ball markers on teasers (vasectomised)
Pressure sensitive indicators on rump of
females Pedometers
2
Cows walk twice as much during oestruscomputerisation required
Oestrus-related odours ( trained dogs )
Best time to breed – am/pm rule
Artificial Insemination Technique - Cow
Control/ Synchronisation of
Oestrus: Why?
Induce early ovulation in season ewe
and mare
Reduce breeding season for management
eg
...
I
Assist with heat detection eg
...
I
...
PG’s
3
Synchronizes oestrus by inducing the regression of
the corpus luteum ( luteolytic )
2
...
variable
Embryo quality nb
Best CR
Two PG’s 11 days apart
Must be on heat the same
day the donor is flushed
Embryo’s transferred on
same day as flushed from
donor
Day 7 - blastocyst
Synchrony is vital
Caesarean birth
Transfer fresh
Freeze excess embryos
Sheep Reproductive Cycle
Sheep are seasonally polyoestrus
i
...
come in oestrus repeatedly over a certain period or season of
the year
Photoperiod- stimulated by shortening daylight hours
5
Early September- February
Melatonin
17 days oestrus cycle Duration of
oestrus = 36 hours Gestation period = 147
days ( approx
...
e
...
of eCG
Early lamb 700-750 i
...
u eCG
Ewes come into oestrus 24-48 hrs later
~95% response Response best during breeding season eCG
PMSG/
‘Sponging’ of Ewes – introduction
of rams
Need more rams:ewe
8
1:8-10
All ewes in oestrus at one time
Introduce at 42 hrs post sponge removal
Not before 36 hrs
CR depends on
Technique/timing
Season
Prolificacy rates lower at beginning and end of breeding season
Lower the CR the >>> cost per ewe lambing
Best CR if you allow 2 nd return (2nd oestrus cycle)
Expense may not be justified in some systems
AI
Artificial Insemination Technique - Sheep
Laparoscopic AI
Cervical AI
Influence of Nutrition on
Conception Rates and Prolificacy
Ewes in good plane of nutrition at start of mating
season have higher conception rates
Scale 1-5
BCS = 3
...
5 for hill ewes
An extra 3
...
5 to 3
...
6kgs
improvement in bodyweight
9
Post Weaning Management & ‘Flushing’
Weaning
Mid season lamb prod = late June/early July
Stock ewes heavily (30-40/ hectare) on bare pasture
Helps ‘dry off’ ewes
Reduce incidence of mastitis
Keep good grass for lambs
Flushing
Ewes should be improving condition in the lead up to the mating season
2-6 weeks depending on BCS
6 weeks of good quality grass = 2
...
5 BCS
Beneficial effect on conception rates and litter size
Keep ewes on good pasture for 6-8 weeks
10
Title: Oestrus Cycle
Description: University notes on a recurring period of sexual receptivity and fertility in many female mammals A.K.A Heat.
Description: University notes on a recurring period of sexual receptivity and fertility in many female mammals A.K.A Heat.