Oestrous cycle

Question 1

Define puberty

Answer 1

Process of acquiring reproductive competence

Age of the first expression of oestrus with ovulation

Question 2

The onset of puberty depends on _____

Answer 2

specific hypothalamic neurons to produce sufficient GnRH for gametogenesis

Question 3

What is normally the weight at which puberty is reached?

Answer 3

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%

Question 4

Shortly describe the hormone functions to reach puberty

Answer 4

• 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.

Question 5

Name the factors that affect the age at which puberty is reached.

Answer 5

Species
breed
size>genetically
exposure to males
Environmental: nutrition, temp. changes, management

Question 6

Define monoestrous

Answer 6

Oestrus cycle once a year

Question 7

Define polyestrous

Answer 7

Oestrus cycle more than once a year

Question 8

Define seasonal polyestrous

Answer 8

Cycle happens more than once, but only during a breeding season.

Question 9

How can you manipulate the time it takes for an animal to reach puberty?

Answer 9

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

Question 10

What is the average daily gain of high-, moderate- and low plane of nutrition?

Answer 10

High plane= 2lb/day
Moderate= 1.5lb/day
low= 1.2lb/day

Question 11

Name the 4 stages of the oestrus cycle.

Answer 11

Proestrus, oestrus, metestrus and diestrus

Question 12

Which stages of the oestrus cycle fall under the follicular phase?

Answer 12

Proestrus

Oestrus

Question 13

Which stages of the oestrus cycle fall under the luteal phase?

Answer 13

Metestrus

Diestrus

Question 14

Describe the proestrus stage

Answer 14

• Day 17-21
• CL regresses
• P4 drops
  Reproductive system is preparing for mating
• Behavioural characteristics of oestrous are beginning to be expressed.

Question 15

Describe the oestrus stage

Answer 15

• 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.

Question 16

Describe the metestrus phase:

Answer 16

• 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

Question 17

Describe the diestrus stage:

Answer 17

• 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

Question 18

Define lordosis

Answer 18

A female is receptive to males and will stand for mating.

Question 19

What is the effect of time of insemination on conception rate in cattle?

Answer 19

The conception rate is at its highest when insemination is about 10 hrs from the beginning of estrus.

Question 20

Follicular development is a ______ and _____ process.

Answer 20

progressive and recurring

Question 21

What was used to characterise the patterns of follicular growth?

Answer 21

Trans-rectal ultrasonography