Sexual Cycle in Sheep
• Age of puberty is 6-9 months in sheep.
• Domestic breeds can be used for breeding starting from 16-18 months of age but good maintenance and nutrition reduces it to 7-15 months of age.
• In sheep, which are among the seasonally polyestric animals, the onset of sexual activity is related to daylight length.
• The reduction of light exposure with the day length decrease results in increasing the melatonin release from the pineal gland.
• Increase of blood melatonin level stimulates GnRH release from the hypothelamus and the increased GnRH release stimulates FSH release by affecting the frontal lobe of hypophysis.
• FSH travels to the ovaries through blood and initiates follicular developments.
Sexual cycle in sheep:
• Proestrus (2-3 days)
• Estrus (30-36 hours)
• Metaestrus (2 days)
• Diestrus (10-12 days)
• Anestrus (seasonal)
Sexual Cycle in Sheep
Proestrus
• Lasts 2-3 days.
• is faint.
• Outer changes may not be observed.
Sexual Cycle in Sheep
E strus
• Lasts 30-36 hours (depending on ram effect, age and race of sheep, light exposure time)
• Ovulation occurs closer to the end of estrus.
• Determining the sheep in estrus morning and evening with teaser rams is a necessity.
• Behaviour of sheep in estrus is evident when there is a ram and the distinct sign is smelling rams testicles.
Sexual Cycle in Sheep
• Detection of estrus by observation is not as easy as it is in cows.
• The most distinct sign of sheep in estrus; smelling rams scrotum and standing in front of the ram.
• Other than these; restlessness, tail wagging, vulvar swelling and edema, open cervix and sometimes a cervical originated mucous discharge may be observed throughout estrus.
• Usage of teaser ram is needed for correct detection of estrus.
Sexual Cycle in Sheep
Metaestrus
• Lasts 2 days.
• Corpus Luteum is active and progesterone release is initiated.
• Not very important.
Sexual Cycle in Sheep
Diestrus
• is the longest phase of the cycle and lasts 10-12 days.
• With the effect of progesterone secreted from Corpus Luteum uterine milk is secreted from the uterine glands and it prepares the uterus for gestation.
• If there a viable embryo does not exist by day 13, corpus luteum begins regressing with the effect of PGF
2 secreted from the uterus.
Sexual Cycle in Sheep
Anestrus
is the sexual rest period of sheep and lasts from mid-winter to mid-summer in the nothern hemisphere.
Sexual Cycle in Sheep
Sexual Cycle in Goats
• Goats reach; puberty at approximately 6-9 months of age and breeding age at 9-15 months of age.
• In goats, which are among the seasonally polyestric animals, the onset of sexual activity is related to daylight length.
• The reduction of light exposure with the day length decrease results in increasing the melatonin release from the pineal gland.
• Increase of blood melatonin level stimulates GnRH release from the hypothelamus and the increased GnRH release stimulates FSH release by affecting the frontal lobe of hypophysis.
• FSH travels to the ovaries through blood and initiates follicular developments.
Sexual cycle phases in goats:
• Proestrus (2-3 days)
• Estrus (36-48 hours)
• Metaestrus (2 days)
• Diestrus (14-16 days)
• Anestrus (seasonal)
Sexual Cycle in Goats
Proestrus
• Lasts approximately 2-3 days.
• is more active when compared to sheep, the buck starts to show interest to the sheep.
Sexual Cycle in Goats
Estrus
• Lasts approximately 30-36 hours.
• Signs observed; vocalization, restlessness, vulvar swelling, redness, mucous discharge, tail wagging, decrease in apetite, reduction in lactation yield, frequent urination and defecation and smelling genital areas of other goats.
• Ovulation occurs closer to the end of estrus, 2-3 oocytes may be ovulated at once.
Sexual Cycle in Goats
Metaestrus
• is considered to be the phase in which corpus luteum is formed and lasts approximately 2 days.
Diestrus
• Lasts approximately 14-16 days.
• In this phase progesterone is released from the corpus luteum and uterus is prepared for gestation.
Anestrus
• is the sexual rest period for goats and lasts from mid- winter to mid-summer in the nothern hemisphere.
