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Livestock Production > Repro: Puberty > Flashcards

Repro: Puberty Flashcards

(42 cards)

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1
Q

Define female puberty.

A
  • the first oestrus leading to ovulation
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2
Q

When is female puberty achieved/finished?

A
  • when the brain (hypothalamus) is able to respond to high levels of oestrogen produced in the ovaries by eliciting ovulation
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3
Q

When does puberty in females occur?

A

The age of puberty varies between animal species and breed

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4
Q

What physical changes occur during female puberty?

A
  • development of secondary sexual characteristics and dimorphism
  • body fat distribution
  • mammary gland development
  • body hair distribution and coloration
  • bone and muscular growth
  • pelvic structure
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5
Q

Why is the first ovulation accompanied by a silent heat?

A
  • due to a lack of prior exposure to progesterone
  • females require progesterone-priming before oestrogen can induce full oestrus behaviour
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6
Q

When, if ever, do some organs grow faster than others in females?

A

Reproductive organs and mammary glands grow faster during puberty

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7
Q

Define puberty in males.

A
  • T production increases greatly and spermatogenesis commences

Several definitions:
- time of first production of viable sperm
- time at which the male first develops the ability to fertilise the female (produces sperm, shows libido, can copulate, etc)

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8
Q

What is one of the most important factors that determines the age of puberty in bulls?

A
  • early rise in LH between 10 and 20 weeks old
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9
Q

What are the other actions of increased testosterones at puberty?

A
  • development of sex organs
  • development of primary sex characteristics, internal and external genitalia
  • development of secondary sex characteristics
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10
Q

What are the secondary characteristics in males?

A
  • libido
  • pheromones
  • musculature
  • antlers or horns
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11
Q

What factors effect the onset of puberty?

A
  • body weight
  • environment
  • nutrition
  • season of birth
  • genetics
  • socialisation
  • hormones
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12
Q

What is the most important factor in the onset of puberty?

A
  • body weight
  • puberty is reached between 40% and 60% mature weight
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13
Q

In females, live weight indicates what?

A
  • whether they are capable of handling pregnancy and lactation
  • whether they are large enough to give birth safely
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14
Q

How does live weight (in reference to puberty) differ between breeds?

A
  • larger breeds have heavier weight requirements
  • ex: beef heifers reach puberty at 55-65% mature weight, while dairy heifers mature when they are at 30-40% mature weight
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15
Q

At what age (months), percentage of adult body weight, and size in KG does puberty occur in female cows (heifers)?

A
  • 8 to 12 months
  • 40% to 45% adult body weight
  • 160 to 270 kg
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16
Q

At what age (months), percentage of adult body weight, and size in KG does puberty occur in female sheep?

A
  • 7 to 12 months
  • 40% adult body weight
  • 27 to 34 kg
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17
Q

At what age (months), percentage of adult body weight, and size in KG does puberty occur in female goats?

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A
  • 7 to 12 months
  • 40% adult body weight
  • 25 to 40 kg
18
Q

At what age (months), percentage of adult body weight, and size in KG does puberty occur in female pigs?

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A
  • 4 to 7 months
  • 35% to 40%
  • 68 to 90 kg
19
Q

At what age (months), percentage of adult body weight, and size in KG does puberty occur in female horses?

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A
  • 15 to 24 months
  • 60% adult body weight
  • size in KG varies with breed
20
Q

What is the average age and range (in months) of puberty in male bovine?

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A
  • 11 months
  • 7 to 18 months
21
Q

What is the average age and range (in months) of puberty in male ovine/sheep?

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A
  • 7 months
  • 6 to 9 months
22
Q

What is the average age and range (in months) of puberty in male porcine/pigs?

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A
  • 7 months
  • 5 to 8 months
23
Q

What is the average age and range (in months) of puberty in male equine?

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A
  • 14 months
  • 10 to 24 months
24
Q

What factors of body weight will also inhibit the onset of puberty?

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A
  • birth/rearing status (single vs twin)
  • dam age (offspring from young dams tend to grow more slowly)
  • environmental conditions
  • nutrition/trace mineral deficiencies
  • parasitism
25
Why is the season of birth particularly important in seasonal species?
- seasonal species (sheep/goat/mare) born in late spring/summer will not reach puberty until its second autumn
26
In non-seasonal species, what affect does the season of birth have on puberty?
- can affect when puberty occurs based on the availability of feed (ie: cattle born in spring reach puberty faster than those born in autumn due to having more pasture)
27
How does genetics affect the onset of puberty?
- prolific breeds (produces many young) reach puberty earlier and at a lower proportion of mature weight
28
How does socialisation affect the onset of puberty?
- interaction with the other animals can affect the onset of puberty (gilts reared with young boars reach puberty fasters, and gilts reared in isolation reach puberty later) - introduction of male (teasing) can be used to induce puberty in females that are near achieving it naturally
29
What is the male/ram/buck effect?
- exposure to the male (or its odours) can induce cyclic activity and a certain degree of synchronised cyclicity
30
When is the ram/buck effect used?
- in seasonal anoestrus period (only effective towards the end) - pre-puberty period (close to target weight) - post-partum anoestrus interval (PPAI)
31
How can stress affect the onset of puberty?
- stress can delay puberty - cortisol can interfere with the normal HPG axis function - nutritional stress has direct effects on growth rates and BW - feed quality decreases in the hot season
32
What are some kinds of stresses that affect puberty?
- short duration: shearing just prior to puberty - long duration: undernutrition, diseases, environmental events (such as draught or heat)
33
When does sexual maturity occur?
- when the animal reaches its full reproductive potential
34
Why are young females not yet at sexual maturity?
- can have irregular oestrus cycles, lower ovulation rate increased fertilisation failure, and embryo loss - do not show intense oestrus behaviour, do not seek or stand as readily for the male - have shorter oestrus
35
Why breed females at a young age?
- increases lifetime performance - increases performance of total flock/herd within a given year - more efficient use of feed (product produced per kg eaten) - allows detection of those predisposed to early breeding and potentially multiple births - increases annual genetic gain because of decreased generation interval
36
Why not to breed young females?
- can have negative affects of she's too small or underfed - increased feed requirements during early life (to reach target weights and for pregnancy and lactation while still growing) - variable reproductive performance - progeny born to young dams can be lighter at birth and have slower growth rate - might not have expressed desirable/undesirable traits yet
37
What can poor management while breeding young females cause?
- light birth weights - higher death rates of dam and her young - poor lactational performance - reduced live weight at weaning of the young dam
38
Management of breeding young females should aim to achieve...
satisfactory reproductive performance without negatively affecting lifetime production
39
When/why would knowing the timing of puberty be important?
- when there is an interest in breeding young females as soon as possible - to identify animals that achieve puberty early, selection of replacement - to ensure they do not get pregnant
40
What is the proper mating management of young females?
- only using females that are well grown - prior exposure to a male can increase performance levels - mate with an experienced male - use higher male:female ratio than used with mature females - small, flat paddocks are best - competition from older, more experienced females should be avoided - sire breed is important in relation to birth difficulties (like lower calving weight) - ensure adequate levels of nutrition - consider timing of breeding in to anoestrus period
41
Why mate a young male?
- reduce the generation interval to increase genetic gain - cheaper source of mating males
42
How should you manage a young male for breeding?
- should have prior contact with the females - lower F:M ratios than used with mature males - used for shorter breeding periods only - small, flat paddocks are best - not used in teams with mature males - teams of young males can help ensure higher performance levels

Livestock Production (10 decks)

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