hi guys my name is Megan bol and today I'm going to be talking about the estrus cycle with the focus on cattle what is the estrus cycle according to the merriam-webster dictionary definition it is the correlated phenomenon of the endocrine and reproductive systems of a female mammal from the beginning of one period of estrus to the beginning of the next when looking at cows specifically they are considered polyester issed meaning that they go through multiple cycles throughout the year the estrus cycle can be broken down into four stages pro estrus estrus med estrus and die Astra's totalling to about 21 days in cattle to be simplified by breaking it down into two parts or two phases the first being the follicular phase which is composed of the pro estrus and estra stages and the primary structure is the follicle and the luteal phase which is composed to the med estrus and diaster stages and the primary structure is the corpus luteum there are many hormones involved in the estrus cycle it's a lot like a recipe with each hormone being an ingredient playing its own unique part and forming the estrus cycle as a whole some of the basic hormones are estradiol or estrogen progesterone LH FSH m PG F 2 alpha first we're going to take a look at estradiol based on this picture we can see that its highest during the estrus and pro extra stages or the follicular phase the job of estradiol is to induce heat in animals leading to an LH surge and it also stimulates the growth of the endometrium and myometrium and the development of the mammary gland next we'll look at progesterone which is highest er than med estrus and diaster stages or the luteal phase pedestrian's main job is to maintain pregnancy as soft LH and FSH being produced to inhibit the animal from going into estrus again and recycling next we'll take a look at LH also called the luteinizing hormone LH has the focus of LH is for there to be a surge before ovulation or to promote ovulation and it's caused by and high levels of estradiol next we'll look at SSH also called the follicle stimulating hormone the main job is SSH is to promote the growth of follicles leading to new ovulations and new cycles finally we'll look at p GF 2 alpha also called prostaglandin F 2 alpha this hormone is released if there is no pregnancy and it causes luteal Isis which is a regression of the corpus luteum and/or prepare for the next cycle however if there is pregnancies and progesterone levels are kept high in order to maintain the pregnancy and go through the reproductive cycle this is just a little sneak peek into the estrus cycle of cattle thank you for listening