Reproduction - Comparative Oestrus Cycles & Pharma Flashcards
What is the total length of oestrus (ovulation to ovulation) for the mare?
21 days
How long is oestrus in the mare (standing behaviour as Day 1)?
4-8 days
What is the length of the oestrus cycle in the sow?
21 days
What is the length of oestrus in the ewe?
17 days
Every 17 days in the fall & winter, te ewe will ovulate (if she isn’t impregnated right away).
What is the length of oestrus in the bitch?
93 days.
What is the length of oestrus in the queen?
It’s variable.
What is the length of the oestrus cycle in the woman?
28 days.
However, women don’t mark their ovarian cycles by the start of oestrus, but by the appearance of menses, and thus they mark the menstrual cycle rather than the oestrus cycle. Ovulation occurs in the MIDDLE of the woman’s menstrual cycle, whereas ovulation typically occurs a few days after the start of the oestrus cycle in domestic animals.
In domestic animals, is the follicular phase of the oestrus cycle longer or shorter than the luteal phase?
How does this compare with the two phases in the woman?
In domestic animals, the follicular phase is much shorter than the luteal phase.
In humans, the follicular & luteal phases are the same length (14 days & 14 days).
How long does oestrus last during the oestrus cycle (ie., when the animal is receptive) in the mare?
4-8 days
How long does oestrus last during the oestrus cycle (ie., when the animal is receptive) in the cow?
4-24 hours
(also cited as 12-36 hours)
In cow, oestrus tends to be nocturnal; oestrus must be observed, marked by standing when mounted, Flehmen, lordosis, swollen vulva, etc.
How long does oestrus last during the oestrus cycle (ie., when the animal is receptive) in the ewe?
24-48 hours
The ram has to be fast!
How long does oestrus last during the oestrus cycle (ie., when the animal is receptive) in the sow?
48-96 hours
(2-4 days)
How long does oestrus last during the oestrus cycle (ie., when the animal is receptive) in the bitch?
7-13 days
Note that the bitch only ovulates one every 93 days, so if she doesn’t become pregnant during the 7-13 days she’s in heat, then she has a very long period – almost three months – before she will ovulate again. In reality, the bitch goes through a very long period of anoestrus when she won’t come into heat at all, so she might come into heat less than once a year.
How long does oestrus (heat) last during the oestrus cycle in the queen?
4-10 days. This is when you hear queens yowling.
How long does oestrus (heat) last in women?
There is no “oestrus period” in the same way domestic animals go into heat.
The follicular phase of the oestrus cycle is when oestrogen is dominant; it is rising as the dominant follicles prepare to ovulate and the granulosa cells continue to convert testosterone from the theca cells, using aromatase, into oestrogen.
When the oestrogen plasma concentration reaches a threshold, oestrogen will switch from providing negative feedback to the hypothalamus for GnRH production and the anterior pituitary for LH secretion to positive feedback.
In the mare, how long is this follicular stage?
Variable, but about 7 days.
The follicular phase of the oestrus cycle is when oestrogen is dominant; it is rising as the dominant follicles prepare to ovulate and the granulosa cells continue to convert testosterone from the theca cells, using aromatase, into oestrogen.
When the oestrogen plasma concentration reaches a threshold, oestrogen will switch from providing negative feedback to the hypothalamus for GnRH production and the anterior pituitary for LH secretion to positive feedback.
In the cow, how long is this follicular stage?
4 days
The follicular phase of the oestrus cycle is when oestrogen is dominant; it is rising as the dominant follicles prepare to ovulate and the granulosa cells continue to convert testosterone from the theca cells, using aromatase, into oestrogen.
When the oestrogen plasma concentration reaches a threshold, oestrogen will switch from providing negative feedback to the hypothalamus for GnRH production and the anterior pituitary for LH secretion to positive feedback.
In the ewe, how long is this follicular stage?
Three days
The follicular phase of the oestrus cycle is when oestrogen is dominant; it is rising as the dominant follicles prepare to ovulate and the granulosa cells continue to convert testosterone from the theca cells, using aromatase, into oestrogen.
When the oestrogen plasma concentration reaches a threshold, oestrogen will switch from providing negative feedback to the hypothalamus for GnRH production and the anterior pituitary for LH secretion to positive feedback.
In the sow, how long is this follicular stage?
Seven days
The follicular phase of the oestrus cycle is when oestrogen is dominant; it is rising as the dominant follicles prepare to ovulate and the granulosa cells continue to convert testosterone from the theca cells, using aromatase, into oestrogen.
When the oestrogen plasma concentration reaches a threshold, oestrogen will switch from providing negative feedback to the hypothalamus for GnRH production and the anterior pituitary for LH secretion to positive feedback.
In the bitch, how long is this follicular stage?
18 days
The follicular phase of the oestrus cycle is when oestrogen is dominant; it is rising as the dominant follicles prepare to ovulate and the granulosa cells continue to convert testosterone from the theca cells, using aromatase, into oestrogen.
When the oestrogen plasma concentration reaches a threshold, oestrogen will switch from providing negative feedback to the hypothalamus for GnRH production and the anterior pituitary for LH secretion to positive feedback.
In the queen, how long is this follicular stage?
Variable
NB the luteal phase is 40 days, and the entire oestrus cycle is variable, so it’s definitely less than 40 days! Probably a few days.
The follicular phase of the oestrus cycle is when oestrogen is dominant; it is rising as the dominant follicles prepare to ovulate and the granulosa cells continue to convert testosterone from the theca cells, using aromatase, into oestrogen.
When the oestrogen plasma concentration reaches a threshold, oestrogen will switch from providing negative feedback to the hypothalamus for GnRH production and the anterior pituitary for LH secretion to positive feedback.
In the woman, how long is this follicular stage?
14 days. Same as the luteal phase.
Physiological interventions can be used to achieve cyclical synchronisation in a herd or to induce ovulation (can be for an individual animal or in a herd). The ways these physiological interventions work are not all completely known, but in general, they stimulate or inhibit endogenous reproductive hormones via the hypothalamus-pituitary-gonadal axis.
Give an example of a physiological intervention used to achieve cyclical synchronisation in a herd of ewes.
State how it works, as well as the advantages & disadvantages.
**Ram effect. **
- remove rams from ewes during anoestrus up to six weeks before expected oestrus
- isolate rams for 3-4 weeks, then re-introduce to ewes
- majority ewes ovulate w/i 6 days
-
priming & then removal of progesterone (sponges, IM
injections) pre-intro ↑ ewes in oestrus - priming extends the luteal phase, then removing the sponge at the same time – sudden reduction in progesterone, like luteolysis – causes them to start ovulating together - *Advantages**: cheap, can affect whole herd
- *Disadvantages**: only works @ certain times of year (ie., just before start of natural breeding season); doesn’t work in deep anoestrus (eg., July)
What type of physiological intervention can be used to induce ovulation in ewes?
Ram effect. Same idea as in achieving synchronization in a herd.