Define puberty
Process of acquiring reproductive competence
Age of the first expression of oestrus with ovulation
The onset of puberty depends on _____
specific hypothalamic neurons to produce sufficient GnRH for gametogenesis
What is normally the weight at which puberty is reached?
45-50% of the mature weight and then breeding happens at 65%
For dairy cows it is 35-45% of the mature weight and breeding happens at 55%
Shortly describe the hormone functions to reach puberty
- Increase GnRH, increases the release of FSH and LH, this causes an increase in ovary stimulation
- High GnRH and LH initiate follicular growth, oocyte maturation and ovulation.
- Initially waves of follicular growth would result in degeneration.
Name the factors that affect the age at which puberty is reached.
Species breed size>genetically exposure to males Environmental: nutrition, temp. changes, management
Define monoestrous
Oestrus cycle once a year
Define polyestrous
Oestrus cycle more than once a year
Define seasonal polyestrous
Cycle happens more than once, but only during a breeding season.
How can you manipulate the time it takes for an animal to reach puberty?
Use pigs as example:
- When using large groups (more than 10) of animals normal puberty =28 weeks
- In small groups ( 2-3 days) puberty is delayed =32 weeks
- When the females is exposed to a male the puberty is accelerated, it does not matter if the boar is in the kraal next to them or in the same kraal = 24 weeks
What is the average daily gain of high-, moderate- and low plane of nutrition?
High plane= 2lb/day
Moderate= 1.5lb/day
low= 1.2lb/day
Name the 4 stages of the oestrus cycle.
Proestrus, oestrus, metestrus and diestrus
Which stages of the oestrus cycle fall under the follicular phase?
Proestrus
Oestrus
Which stages of the oestrus cycle fall under the luteal phase?
Metestrus
Diestrus
Describe the proestrus stage
- Day 17-21
- CL regresses
- P4 drops
Reproductive system is preparing for mating - Behavioural characteristics of oestrous are beginning to be expressed.
Describe the oestrus stage
- Day 1
- E2 levels are high
- female is receptive to male and will stand for mating
- Length of this stage varies between species and individuals
- Ovulation associated with oestrus occurs a couple of hours later
Affected by temp.
Describe the metestrus phase:
- Day 2-4
- Cessation of oestrus
- Period of CL formation
- Transition from E2 dominance to P4 dominance
- Ovulation happens during this stage for cows and does
- Metestrus bleeding in cows, during late proestrus and oestrus E2 increases the endometrial vascularity.
- The vascularity reaches its peak 1 day after oestrus ends.
- With a declining E2 breakage of capillaries may occur resulting in the loss of a little blood
Describe the diestrus stage:
- Day 5-16
- Fully functional CL
- Increase in P4
- Uterus prepares for embryo
- Ends with the regression of the CL
- Period of preparation of the uterus for pregnancy
Define lordosis
A female is receptive to males and will stand for mating.
What is the effect of time of insemination on conception rate in cattle?
The conception rate is at its highest when insemination is about 10 hrs from the beginning of estrus.
Follicular development is a ______ and _____ process.
progressive and recurring
What was used to characterise the patterns of follicular growth?
Trans-rectal ultrasonography
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mating behaviour23
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Ovigenesis and fertilization39
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Gestation38
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Oestrous cycle21
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1. PARTURITION AND POSTPARTUM RECOVERY32
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2. introduction to AI11
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3. SEMEN COLLECTION5
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5. AI, semen processing and handling15
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4. SEMEN AND ITS COMPONENTS21
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6. oestrus sync8
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8. reproductive management19
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9. Environmental management5
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10. Nutritional management0
