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Reproductive Cyclicity. Repeated Opportunities to Become Pregnant. Definitions. Estrus - noun. Period of time when the female is receptive to the male Usually lasts for a few hours up to a few days. Also called – heat or season. Estrous - adjective.
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Reproductive Cyclicity Repeated Opportunities to Become Pregnant
Definitions Estrus - noun Period of time when the female is receptive to the male Usually lasts for a few hours up to a few days Also called – heat or season Estrous - adjective Estrous Cycle = Period of time from one estrus to the next estrus Repeated opportunities for the female to become pregnant during a breeding season Usually several days or a few weeks in length Anestrus – period of time when the female is not cycling Menstrual Cycle – Period of time from the beginning of one menses to the beginning of the next menses - humans and some nonhuman primates
Types of Estrous Cycles Polyestrus Repeated estrous cycles at specific intervals throughout the year if not pregnant Seasonal Polyestrus Repeated estrous cycles during specific seasons of the year Long day breeders Short day breeders Monoestrus One estrus per year Domestic canids may actually show estrus 2 or 3 times Induced Ovulators Ovulate in response to vaginal stimulation Cat, Rabbit
Brain – Hypothalamus - Pituitary Gland PINEAL Melatonin HYPOTHALAMUS GnRH (Gonadotropin Releasing Hormone) ANTERIOR PITUITARY LH (Luteinizing Hormone) FSH (Follicle Stimulating Hormone) PROLACTIN TSH (Thyroid Stimulating Hormone) ACTH (Adrenal Cortical Tropic Hormone) STH or GH (SOMATOTROPIN) POSTERIOR PITUITARY OXYTOCIN ADH (Antidiuretic Hormone)
Anestrus Gestational Anestrus GnRH is inhibited by progesterone Seasonal Anestrus - increase dark = increase Melatonin Short Day Breeders – GnRH is stimulated by Melatonin from the Pineal Long Day Breeders – GnRH is inhibited by Melatonin from the Pineal Lactational Anestrus Does not occur in the mare and the alpaca Delayed by greater than 2 suckling sessions per day also influenced by visual, auditory, and olfactory stimulus by own calf Effect of lactation may be reduced with extended time post partum Can be confounded by post partum uterine involution Anestrus due to negative energy balance
Brain – Hypothalamus - Pituitary Gland PINEAL Melatonin HYPOTHALAMUS GnRH (Gonadotropin Releasing Hormone) ANTERIOR PITUITARY LH (Luteinizing Hormone) FSH (Follicle Stimulating Hormone) PROLACTIN TSH (Thyroid Stimulating Hormone) ACTH (Adrenal Cortical Tropic Hormone) STH or GH (SOMATOTROPIN) POSTERIOR PITUITARY OXYTOCIN ADH (Antidiuretic Hormone)