The Effect of Hormones on the Estrous Cycle Hypothalmus- primitive part of the brain that controls other endocrine glands. Stimulates the pituitary Pituitary Gland –at the base of the brain. Regulates hormone secretion throughout the body. FSH – Follicle Stimulating Hormone. Causes the follicle to mature. Lutenizing Hormone – causes ovulation and the formation of the corpus luteum.

Hormones Estrogen- Prepares the cow for sexual activity. “Heat” Progesterone, secreted by the corpora lutea, Stops the development of follicles Stops estrogen. Stops cow from coming into heat. prepares the uterus to receive the fertilized egg maintains pregnancy. Follicle stimulating hormone (FSH) and luteninizing hormone (LH) are secreted & travel through the blood to the ovary. FSH and LH are mediated by gonadotropic releasing hormone (GnRH) coming from the hypothalamus to signal their release from the pituitary. FSH stimulates the growth, development and function of the follicle, while LH cause the follicle to rupture during ovulation and causes the subsequent development of the corpus luteum. Hormones http://www.mothercow.org/bull/barnyard/hormones.jpg

Two organs of reproduction are located in the head hypothalamus controls: Body temperature, and the drive to eat and drink are just a few functions. It sends and receives neural signals through the nervous system and hormonal messages through the endocrine system. pituitary gland, at the base of the brain. The pituitary is divided into two regions: the anterior and posterior pituitaries.

We are going to look into the function of the hypothalamus and the pituitary gland.

Follicle produced by FSH

This follicle will soon rupture(ovulation) with the help of LH

CL (Corpus Luteum) takes the place of the follicle CL (Corpus Luteum) takes the place of the follicle. The CL produces the hormone progesterone.

Estrous Heat is the time when a female is receptive to the male and will allow breeding to take place Heat is actually divided into 4 phases of the cycle.

Phases of Estrous Proestrus: ovary is about to release an egg Estrus: female receptivity Metestrus: uterus prepares for pregnancy fertilized egg attaches to uterus Diestrus: longest period of cycle inactive Estrous Cycles stop after conception, and begin soon after Parturition (birth)

Hormones Estrogen – produced by the ovary causes secondary sexual characteristics to develop Causes symptoms of heat Progesterone – produced by the corpus luteum and the uterus in later stages of pregnancy Maintains pregnancy Used to synchronize estrous Progesterone and estrogen are mutually exclusive

Hormones Oxytocin – causes milk letdown and induces labor Prolactin - lactation Adrenaline ( epinephrine) Secreted by the adrenal glands Causes a “flight or fight” syndrome Neutralizes oxytocin

This cycle of egg development in cattle is called the estrous cycle . This cycle of egg development in cattle is called the estrous cycle. The cow is a non seasonal polyestrous species. Which means a cow can multiple estrous cycles throughout the year.   Two prominent structures are present within the ovary, the follicle and corpora lutea. have have

Estrous Cycle The ovarian changes during a typical 21-deay estrous cycle in which pregnancy does not occur. The development and regression of the corpus luteum and of the follicles are continuous processes http://www.cahe.nmsu.edu/pubs/_b/b-212.pdf

The Estrous Cycle Mare Sow Ewe Cow Gyp 18 months 24 months 21 days Animal Age at Puberty Age of First Service Length of Estrous Cycle Length of Estrous Gestation Period in days Mare 18 months 24 months 21 days 5 days 336 Sow 6 months 8-10 months 18 hours 114 Ewe 6-12 months (first fall) First fall Or 2nd 16 days 2 days 150 Cow 6-18 months 14 months 283 Gyp 6-12 months 12 months 6 – 12 months 9 days 63

Methods of Heat Detection Visual Appraisal Gomer Bulls Electronic device Ultrasound machine Marking harness (sheep and goats) Teaser Stallion

Symptoms of Estrous Standing Heat is the best indicator Restlessness Discharge from vulva Swollen vulva Mares will raise tail, and “winking”

Heat symptoms in sows Red, swollen vulva Ears raised with back pressure Stand for back pressure

Heat Detection Device Monitors electrical conductivity changes in vaginal mucous

Gomer Bulls Have had penis diverted to the side May have had vasectomies

Teaser Stallions May be lower quality Are kept near mares to encourage her to “show” heat symptoms

Marking Harness on Rams Ink or chalk filled pad Color changed between cycles

Solar Powered Networked Heat detectors Electronic device on female, reads pressure and sends signal to headquarters