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The Estrous Cycle of Mare its Manipulation & Artificial Control Dr. Hatem Atalla D.V.M PhD An-Najah National University Faculty of Veterinary Medicine.

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Presentation on theme: "The Estrous Cycle of Mare its Manipulation & Artificial Control Dr. Hatem Atalla D.V.M PhD An-Najah National University Faculty of Veterinary Medicine."— Presentation transcript:

1 The Estrous Cycle of Mare its Manipulation & Artificial Control Dr. Hatem Atalla D.V.M PhD An-Najah National University Faculty of Veterinary Medicine 2009

2 Seasonality Their season is initiated as the ratio of daylight to darkness increases and ends during decreasing day lengths. Their season is initiated as the ratio of daylight to darkness increases and ends during decreasing day lengths. The average season for horses, extending from February(2) to November(11). Peak fertility is obtained if mares are bred between May(5) and July(7). The average season for horses, extending from February(2) to November(11). Peak fertility is obtained if mares are bred between May(5) and July(7). Behavioral estrus occurring during short-day months (January to April) is frequently not accompained by ovulation. Behavioral estrus occurring during short-day months (January to April) is frequently not accompained by ovulation.

3 Seasonality The physiologic (natural) breeding season of the mare occurs in late spring and summer. During the Transition from anestrus to physiologic polyestrus, the mare will frequently have variable length periods of behavioral signs of estrus without developing follicular structures or ovulating. During the Transition from anestrus to physiologic polyestrus, the mare will frequently have variable length periods of behavioral signs of estrus without developing follicular structures or ovulating.

4 Receptors in eye Pineal gland Hypothalamus Anterior pituitary Ovaries Increasing day length Light Stimulus Decreasing day length Neuropathway Decreasing melatoninIncreasing melatonin Increasing GnRH Decreasing GnRH Increasing Gonadotropins (FSH, LH) Decreasing gonadotropins J F M A M J J A S O N D

5 Anestrus Anestrus is caused by the secretion of melatonin, which is secreted in response to increasing darkness. The melatonin inhibits GnRH, so the FSH and LH are low. Anestrus is caused by the secretion of melatonin, which is secreted in response to increasing darkness. The melatonin inhibits GnRH, so the FSH and LH are low. Anestrus occurs around Winter solstice. Anestrus occurs around Winter solstice. About 80% of mares undergo anestrus. About 80% of mares undergo anestrus. Mares in anestrus are passive to the stallion advances. Mares in anestrus are passive to the stallion advances. On rectal palpation the ovaries are small, smooth, and inactive. On rectal palpation the ovaries are small, smooth, and inactive. The cervix and uterus are flaccid. The cervix and uterus are flaccid. Vaginoscopic exam reveals a cervix that is pale and dry, and the cervix may even be open. Vaginoscopic exam reveals a cervix that is pale and dry, and the cervix may even be open. The hormones are all at very low concentrations. The hormones are all at very low concentrations. If the is nutrition poor, the mare may not cycle back in the spring. If the is nutrition poor, the mare may not cycle back in the spring.

6 Spring transition The increasing daylight length in the spring brings about a series of changes in the mare. The increasing daylight length in the spring brings about a series of changes in the mare. Decrease of Melatonin secretion  Decrease of Melatonin secretion  As the melatonin decreases, GnRH resumes secretion, and FSH and LH also increase. As the melatonin decreases, GnRH resumes secretion, and FSH and LH also increase. With increased FSH, follicles start to grow. With increased FSH, follicles start to grow. Most of these follicles are not steroidogenically competent so they do not produce estrogen. Most of these follicles are not steroidogenically competent so they do not produce estrogen. They also do not ovulate. In fact, an average of 3.7 waves of follicular development occur before the first ovulation. They also do not ovulate. In fact, an average of 3.7 waves of follicular development occur before the first ovulation. After several waves, an estrogen producing follicle finally develops and ovulates. After several waves, an estrogen producing follicle finally develops and ovulates. The first ovulation of the season, on the average, occurs about April 8 The first ovulation of the season, on the average, occurs about April 8

7 Physiological Breeding Season 21 day inter-ovulatory interval (estrous cycle) 21 day inter-ovulatory interval (estrous cycle) Estrus (heat): 5 – 7 days Estrus (heat): 5 – 7 days Ovulation: 24 to 48 hours prior to end of heat Ovulation: 24 to 48 hours prior to end of heat Diestrus: 14 – 16 days Diestrus: 14 – 16 days

8 Fall transition Fall transition mirrors spring transition. Fall transition mirrors spring transition. You see: You see: prolonged heats, prolonged heats, irregular cycles, irregular cycles, large 'hung' or 'autumn' anovulatory follicles. large 'hung' or 'autumn' anovulatory follicles. These follicle become atretic and the mare goes into anestrus. These follicle become atretic and the mare goes into anestrus. This is caused from the low LH release because melatonin is taking its grip again as the day length decreases. This is caused from the low LH release because melatonin is taking its grip again as the day length decreases. There is no treatment for fall transition. There is no treatment for fall transition.

9 Estrous Cycle of the Mare

10 Endocrinology of the Estrous Cycle

11 Mating Behavior (Estrus signs) Mating Behavior (Estrus signs) The mare will allow the stallion to smell and bite. The mare will allow the stallion to smell and bite. She will She will extend her hind legs, extend her hind legs, lift her tail to the side and lift her tail to the side and lower her rump. lower her rump. The erect clitoris will be exposed frequently by contractions (winking) of the labia. The erect clitoris will be exposed frequently by contractions (winking) of the labia. The vulva will be elongate and swollen, with the labia partly everted. The vulva will be elongate and swollen, with the labia partly everted. The mare should be teased by a stallion for accurate detection. The mare should be teased by a stallion for accurate detection. Attempts to fight the stallion indicate she is not in estrus even though some other signs of estrus are apparent. Attempts to fight the stallion indicate she is not in estrus even though some other signs of estrus are apparent.

12 Timing of Insemination “Mares” Best results without palpation are obtained by multiple breedings starting on the third day and repeating at 48-hours intervals until the mare is no longer in estrus. Best results without palpation are obtained by multiple breedings starting on the third day and repeating at 48-hours intervals until the mare is no longer in estrus. When only one breeding is desired it is recommended that the mare be palpated and bred when she has a 35mm follicle. She should be palpated 2 days later to see if ovulation occurred and if not, she should be rebred. When only one breeding is desired it is recommended that the mare be palpated and bred when she has a 35mm follicle. She should be palpated 2 days later to see if ovulation occurred and if not, she should be rebred. When two large follicles are detected by palpation, mares should not be bred, since pregnancies involving twins are usually terminated by abortion. When two large follicles are detected by palpation, mares should not be bred, since pregnancies involving twins are usually terminated by abortion. Some breeders inject LH at the time of breeding to insure ovulation while sperm are viable. Some breeders inject LH at the time of breeding to insure ovulation while sperm are viable.

13 Foal Heat Mares will come into estrus from 7 to 12 days after parturition (foaling heat) and can frequently be bred with good results. Mares will come into estrus from 7 to 12 days after parturition (foaling heat) and can frequently be bred with good results. However, mares should be bred at this time only if they have been given a careful examination to determine if there has been adequate recovery since parturition. However, mares should be bred at this time only if they have been given a careful examination to determine if there has been adequate recovery since parturition. If there is any question about recovery, wait until the next estrus, which will occur about 30 days postpartum. If there is any question about recovery, wait until the next estrus, which will occur about 30 days postpartum.

14 Criteria Mares Should Meet In Order to Be Bred During Foal Heat u u Delivery of foal without significant difficulty. u u Pass placenta within 3 hrs after birth u u A healthy foal that stands and nurses within 1 hr. u u A cervix free from bruises and abnormal discharges. u u A uterus significantly reduced in size, without fluid accumulations.

15 Estrus Manipulation Methods u Artificial lighting u Shortening Late Transition u Inducing Ovulation u Estrus synchronization u Estrus Synchronization & Ovulation Induction

16 Manipulation Methods: Light watts for a 12 x 12 Stall X 60 days, start Dec watts, 12 x 12 Stall X 75 days Aged mares (greater than 10 yrs) take ~12-18 days longer Aged mares (greater than 10 yrs) take ~12-18 days longer No advantage to starting before Dec 1 No advantage to starting before Dec 1 Light can be supplemented in the afternoon and evening to give a total of 16 hours light each day.

17 Hormone Management - Progestagens Regumate Oral Suppresses estrus by forming an artificial luteal period. Dose - 1 ml/50 kg orally or in feed for 14 days. Heat occurs 4-5 days after withdraw Injectable progesterone Estrus suppression 100 mg/day prevents estrus and ovulation.

18 Progesterone or related compounds l Regumate – most common l Normalization of estrus l Regulation of estrus l Estrus synchronization l Long-term suppression of estrus l Delay foal heat l Pregnancy maintenance

19 PGF 2  Lutalayse or Estrumate u Shorten the interval between estrous periods u Treatment of a maintained corpus luteum u After foal heat u Estrous synchronization with prostaglandins

20 Hormone Management Prostglandins Only works on mature corpus luteum (~ 5 d after ovulation) Mare will come into heat 2-5 days later. Ovulation in days Ovulation in days The time to estrus varies depending on follicular development on the ovary. Lutalyse Dose is 5-10 mg (1-2 cc/mare) IM. Side effects Estrumate Dose is 200 mcg/mare IM. Fewer side effects Side effects can be sever in mare Sweating Abdominal cramps, increased motility of GI tract and/or colic Increased heart rate Muscle weakness and balance problems All side effects begin at minutes and last until 60 minutes after injection

21 Induction of Ovulation hCG Dose 1,500-3,000 IU IV 3.5 cm follicle Ovulation normally occurs within hours. 80% of mares will ovulate within 48 hr Older Mares loose % More you use it, the less effective it becomes on subsequent heats 10% less effective Feb, Mar, Apr Deslorelin Deslorelin 3.5 cm follicle, ovulate hrs, 90% As effective as hCG without antibodies

22 Estrogen  Limited use: “Induction of estrus” for jump mare “Induction of estrus” for jump mare Estradiol cypionate; 5-10 mg Estradiol cypionate; 5-10 mg Start 3-4 days prior to wanting mare showing signs of estrus Start 3-4 days prior to wanting mare showing signs of estrus “Enhance signs of estrus” in silent heats “Enhance signs of estrus” in silent heats Estradiol 17B; 1-2 mg Estradiol 17B; 1-2 mg

23 Suppress Estrous Sterile, 30 to 35 mm diameter glass marble into the uterus within 24 hrs after ovulation Increases the interovulatory interval from 21 days to ~ 90 days for about 40 to 70% of mares Appears to be no discomfort, nor any detrimental effects on future breeding prospects


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