 Dear student, in this study you will learn about astro-cycle and its different stages. I will also discuss the effect of hormones and breeding season. Astro-cycle is a set of recurring physiological changes that are induced by reproductive hormones in all mammalian females except some higher primates. This cycle starts after sexual maturity and it continues until death and interrupted by during pregnancies. A female becomes actually receptive during this phase and allow male for mating. The length of this cycle is 21 days. Now we will discuss its different stages. So, I have 4 stages, pro-stress, astress, metastress and anestress. First, we will discuss pro-stress. Pro-stress phase is called follicular phase. As follicles grow, astrogen hormone starts to produce. Astrogen hormone is called uterine line development. Second stage in this cycle is estress. This stage is called heat period. Female is actually receptive. This phase is called evolution phase. When the follicle is released, this phase is called evolution phase. This phase is called evolution phase. Female is actually receptive. And male is attracted for mating purpose. Third stage is metastress phase. This stage is called luteal phase. This phase is called follicle rupture. Last stage is evolution phase in which egg follicles are released. The rupture follicle develops corpus luteum. This is called luteal phase. Corpus luteum progesterone hormone is released. This progesterone hormone prepares uterus for implantation purpose. It suppresses the contractions of uterus and plays a role in maintaining pregnancy. If pregnancy is not present in this stage, the line of uterus is reorganized. For the next cycle, this body is not discarded or shared. That is the main difference between menstrual cycle and the estress cycle. The main difference between menstrual cycle and the rest of the high primaries is that the lining of the body, in the absence of pregnancy, is discarded. In the estress cycle, the lining of the body is not shared but reorganized. The next stage is anestress phase. It is also called sexual inactive phase. It is called resting phase in which female is not sexually active. This phase is induced by age, pregnancy, weakness and time of the year during breeding season. During breeding season, it is controlled by the exposure of light which influence the production of melatonin hormone through pineal gland. Now we will look at this figure which shows different ovarian changes. Along with this, we are looking at different phases and stages of the estress cycle. This cycle is starting from this point, from ovulation. This is the day 1 mention. What is happening in this stage? As the ovulation is being released from the follicle, you can see an egg being released from the follicle. This is a rupture follicle. There are some small follicles which are not growing in the growing stage. Old corpus luteum is shown here which has been regenerated from the previous cycle. This is day 1 in which there is no ovulation. Next is day 2 to day 4. The rupture follicle will make a new corpus luteum. As shown here, a new corpus luteum. The old corpus luteum will be regressed. It will be regenerated from the previous cycle. Next, from 5 days to 15 days, the follicle has matured. As the old corpus luteum has matured, it releases the progesterone hormone. In the next stage, from day 19 to 20 days, the corpus luteum is regressing. It is going towards the degeneration. As the corpus luteum is degeneration, the production of the progesterone will decrease. As the production of the progesterone will decrease, the new follicles will develop and grow. This is a new follicle which is starting to develop. The follicle which was developing has matured. This cycle will end here. In the next cycle, the mature follicle will be ruptured and released. After release, the rupture follicle will make corpus luteum and corpus luteum. Once it is matured, the cycle will continue like this. Now we will discuss the hormones which are controlling the cycle. There are three major parts of this cycle. One is hypothalamus, one is anterior pituitary and the other is ovary. Hypothalamus is a special region in our brain. It secretes the corpus luteum in releasing hormones. This corpus luteum targets the pituitary gland. There are two lobes of pituitary gland, the anterior lobe and the posterior lobe. We will discuss the anterior lobe here. The anterior lobe produces two hormones, follicle-stimulating hormone and latinizing hormone. These hormones are targeted by ovaries through blood circulation. Now we will discuss the function of follicle-stimulating hormone and FSH. As the FSH will target the ovary, the follicles in the ovary will start growing. As I mentioned earlier, when follicle grows, it produces estrogen hormone. As the follicle grows, it will start producing estrogen in the body. As the estrogen level increases in the blood, it will give a positive feedback to the hypothalamus. What will the hypothalamus do with this positive feedback? Again, it will produce gonitropin-releasing hormone, which secretes the luteum with anterior pituitary. The luteum secretes the luteum. The animal in this phase, if we take a cow's example, the cow's nervous system affects it. It shows different signs like restlessness, phonation, mounting, and most importantly, willingness to be mounted by any other animal. The estrogen that is increasing in the blood will contract the uterus. It will cause uterus contraction and it will allow the sperm transport in the female tract after insemination. Along with this, the estrogen level increases blood circulation through the genital organs. It secretes the mucus glands in the vagina and cervix. There are different signs of the cow. The cow will show different signs when it is receptive or when it is in a heat period. Let's talk about the luteinizing hormone. As the luteinizing hormone is produced, the female has shown signs of ovulation. As the ovulation egg is released, the corpus luteum will stay behind. The ruptured follicle has developed the corpus luteum. As the corpus luteum is produced, it will produce the pregesterone hormone. As the pregesterone hormone level increases, it gives negative feedback to the hypothalamus. All the procedures that have been done to produce the luteinizing hormone will stop. When the new follicle is not produced, the new follicles will not start growing. This cycle will stop. The pregesterone hormone will prepare the luteinizing for implantation. It will suppress the contraction of the luteinizing hormone and maintain the pregnancy. There is another hormone involved in the luteinizing hormone, the prostaglending F2-alpha. The luteinizing hormone produces the luteinizing hormone and affects the ovary. Basically, this hormone initiates the ovulation. How does this hormone generate the corpus luteum? When the corpus luteum is degenerated, the pregesterone's synthesis will stop. As the pregesterone's synthesis stops, the cycle will start again. The porous hypothalamus will produce the luteinizing hormone. It will target the anterior pituitary. The follicle-stimulating hormone will be released. It will start the growth and development of the follicles. The prostaglending F2-alpha has a positive feedback of the high level of the pregesterone. As the level of the pregesterone increases, the luteinizing hormone will produce the luteinizing hormone. The luteinizing hormone will degenerate the corpus luteum and reduce the level of the pregesterone. These were the hormones that control the luteinizing hormone. These are the types of mammals. Some animals are monostrous and some animals are monostrous animals. These animals have a seasonal cycle. We can say that they have one seasonal cycle in which there are wolves and bears. Similarly, there are some polyesters. In polyesters, they have many cycles. The male remains sexually active throughout the year. Dear student, understanding the biological mechanism associated with getting a cow or any mammal breed can be a significant management tool for increasing income or for increasing yield. I hope now you have a clear understanding of this extra cycle, its different stages and different hormones which are involved in this cycle. Thank you.