The Oestrous Cycle and Seasonality

Question 1

What are the two types of seasonal cycles?

Answer 1

Short day & long day

Question 2

How can seasonality be manipulated?

Answer 2

Artificial change to photoperiod & physical change to photoperiod

Question 3

What is the difference between oestrus and dioestrus?

Answer 3

Oestrus – female receptive to male, high levels of oestrogen

Dioestrus – female rejects the male, high levels of progesterone

Question 4

What are the four phases of the oestrus cycle?

Answer 4

Proestrus – phase immediately before oestrus
Oestrus – acceptance of the male & ovulation of follicle
Metoestrus – succeeds oestrus, corpus luteum forms
Dioestrus – rejection of the male & period of the CL which secretes progesterone

Question 5

What hormones are involved in controlling the oestrus cycle?

Answer 5

Oestrogen, progesterone, FSH & LH

Question 6

What are the effects of oestrogen on the female?

Answer 6

Behaviour to allow mating, prepares external genitalia & vagina for mating, increases mucus production in cervical glands, stimulates follicular growth & maturation in ovaries, prepares uterine environment for sperm transport & implantation of fertilised oocytes, contributes to growth & development of mammary tissue, prepare uterus for parturition

Question 7

What are the effects of progesterone on the female?

Answer 7

Increased secretion by glands of uterine epithelium, gland secretions contain nutrients for fertilised oocytes, prepares uterus for zygote, behaviour to reject male

Question 8

What are the actions of FSH and LH?

Answer 8

FSH – stimulates maturation of germ cells

LH – stimulates production & secretion of testosterone in the tests and oestrogen & progesterone in the ovaries

Question 9

What events occur after ovulation?

Answer 9

Ciliated epithelium lining the oviduct transports the oocyte, oocyte reaches the ampulla, moves down the oviduct to between the ampulla & isthmus for waiting spermatozoa, after fertilisation ciliary motion & peristalsis move the zygote into the uterus

Question 10

Compare the type of oestrus seen in the common species

Answer 10

Mare – seasonal polyoestrus, long day breeder
Cow – polyoestrus
Ewe – seasonal polyoestrus, short day breeder
Sow – polyoestrus
Bitch – monoestrus
Nanny – seasonal polyoestrus, short day breeder
Queen – seasonal polyoestrus, variable
Jill (ferret) – seasonal polyoestruos