The oestrus cycle and seasonality

Question 1

Describe Pro-oestrus and Oestrus, and the behaviours associated with them

Answer 1

Pro-oestrus and Oestrus: ovarian follicles mature, secrete increasing concentrations of E2 into the blood. Ostrogens result in oestrus behaviour, prepare external genitalia and vagina for mating, increased mucous production by the cervix, follilcular growth and maturation in the ovaries, uterine environment prepared for sperm transport and implantation (hypertrophy of endometrial epithelium and glandular enlargement), growth and development of mammary tissue, prepares uterus for parturition
Oestrus behaviour is seen: standing to be mounted, clitoral winking

Question 2

Describe Dioestrus and Metoestrus, and the behaviours associated with them

Answer 2

• ovarian follicles ovulate to produce a corpus luteum, which secretes progesterone into the bloods, ends in luteolysis of the CL by PGF2A, during this time follicles continue to develop but fail to ovulate
  Progesterone caused increased secretions by glands of the uterine epithelium, secretions contain nutrients for fertilised oocytes, prepares uterus for zygote
  Dioestrus/metoestrus: violent towards male, not receptive

Question 3

Discuss the oestrus cycle of the mare

Answer 3

• Seasonal polyoestrus
• Long day breeder
• Oestrus= 6 days
• Dioestrus= 15 days
• Total cycle length= 21-23 days
• Ovulation: last day of oestrus/before end of oestrus

Question 4

Discuss the oestrus cycle of the cow

Answer 4

• Polyoestrus
• Oestrus= 8 hours
• Dioestrus= 19-20 days
• Total cycle length= 18-24 days
• Ovulation= 12 hours after the end of oestrus (24-32h after onset)
• Some variation with maturity, breed, season, bull presence, milk yield, nutrition, lactation, cohorts in season

Question 5

Discuss the oestrus cycle of the ewe

Answer 5

• Seasonal polyoestrus
• Short day breeder (October – February)
• Oestrus= 30 hours
• Dioestrus = 15-16 days
• Total cycle length- 17 days
• Ovulation= towards the end of oestrus

Question 6

Discuss the oestrus cycle of the sow

Answer 6

• Polyoestrus (wild pigs may be seasonal)
• Oestrus= 53 hours
• Dioestrus= 19 days
• Total cycle length= 21 days
• Ovulation= 35-45 hours after the start of oestrus

Question 7

Discuss the oestrus cycle of the nanny

Answer 7

• Seasonal polyoestrus
• Short day breeder (August to February)
• Oestrus= 30-40 hours
• Dioestrus= 20-21 days
• Total cycle length= 21-22 days
• Ovulation= 12-36 hours after the start of oestrus

Question 8

Discuss the oestrus cycle of the bitch

Answer 8

• Pro-oestrus= 9 days
• Oestrus= 9 days
• Ovulation= 1-2 days after onset of oestrus
• Met-oestrus
  70-80d if measured by regression of CL
  130-140d if measured by endometrium repair
• Anoestrus= 3 months
• Interoestrus=7 months

Question 9

Discuss the oestrus cycle of the queen

Answer 9

• Seasonal polyoestrus - variable
• Oestrus 7-10 days
• Dioestrus 10-14 days
• Total cycle length 21 days
• Ovulation dependent on mating (induced ovulator)

Question 10

Discuss the oestrus cycle of the jill

Answer 10

• Seasonal polyoestrus
• Oestrus
  if mated ~14 days
  if unmated <6 months
• Ovulation
  dependent on mating (induced ovulator)
  30-40h after mating