Estrus Cycle and Ovulation in cattle

Hello. I am Shiba Hari Dhakal , undergraduate student of Agriculture science studying 8th semester in Agriculture and Forestry University, Rampur,Nepal. This slide was prepared when I was in Bsc.Ag 5th semester, as an assignment of LPM subject by compiling information from different sources.

1. Estrus Cycle Prepared by: Shiba Hari Dhakal Agriculture and Forestry University

2. Estrus, also called  Oestrus , the period in the sexual cycle of female mammals, except the higher primates, during which they are in heat—i.e. ready to accept a male and to mate The estrous cycle of the cow starts after puberty and occurs approx. every 21 days (17 to 24 days) except for pregnancy, reproductive disease or hormonal disorder  During estrous cycle, the reproductive tract is prepared for heat and ovulation

3. Types of estrus cycle Polyestrus – Cow, buffalo, swine Seasonaly polyestrus Long day breeders eg . Mare Short day breeders eg . Sheep and goat Monoestrus - Dog

4. Two discrete phases of estrous cycle The luteal phase  (14–18 days; metestrus and  diestrus ) and The follicular phase  (4–6 days; proestrus and estrus ) Anestrus - Phase when female does not experience cycle which might be due to pregnancy, reproductive disease or hormonal disorder Follicular Phase Short phase only 20% of cycle Period from regression of corpus luteum to ovulation Pre-ovulatory follicle Dominant hormone is estradiol

5. Luteal Phase Long phase about 80% of the cycle Period from ovulation to corpus luteum regression phase Corpora lutea phase Dominant hormone is progesterone Follicle continue to grow and regress during this phase The cycle is divided into four parts: Proestrus Estrus Metestrus and Diestrus

6. Proestrus Proestrus  is the period between the regression of the corpus luteum of the previous cycle and estrus Start when progesterone decline ( Luteolysis ) and ends at onset of estrus Last for 2 to 5 days FSH and LH are major responsible Ovarian follicle increase in size Estrogen absorbed from the follicle into bloodstream and increase vascularity Preparation for estrus and pregnancy

7. Estrus Estrus  is the period when high amount of estrogen is presents in the blood The estrogen produces the behavioral signs of estrus Period of sexual receptivity Large production of estrogen which stimulate production of LHRH FSH decrease due to estrogen and inhibin Ovulation occur due to LH LH level increase due to LHRH Estrus stopped due to ovulation

8. Metestrus Estrus is followed by a 3 to 4 day period referred to as  metestrus During this period the corpus luteum develops under the influence of LH and starts to produce increasing amounts of progesterone Corpus luteum predominant Increase in Progesterone and decrease in estrogen Diestrus The period between metestrus and the beginning of the regression of the corpus luteum is referred to as  diestrus No reproductive activity Short period CL is fully functional High level of progesterone

9. Animal Estrus Cycle (Days) Pro-estrus (Days) Estrus Metestrus (Days) Diestrus (Days) Cow 21 3-4 12-18 hour 3-4 10-14 Ewe 17 2-3 24-36 hour 2-3 10-12 Sow 21 3-4 48-72 hour 2-3 11-13 Mare 21 2-3 4-8 days 2-3 10-12

10. OVULATION

11. The process in which an oocyte (female germ cell) is released from the Graafian follicle Ovulation  occurs at the ovary surface Ovulation is triggered by the surge of  LH surge from the pituitary Multiple ovulation FSH stimulate the growth of ovarian follicles by which one or more follicle grow rapidly LH help to shedding of the egg and growth of luteal tissue to form CL After the rise of LH level and stimulate ovulation Fertilization is union of sperm and ovum but when ova is not fertilized it degenerate within few days

12. In the natural sequence of mammalian fertilization, the spermatozoa await the arrival of ova in the Fallopian tubes. The time of waiting may vary from 6 hr. (rabbit), 20–30 hr. (pig, sheep and cattle) up to perhaps several months (bat) Cumulus cell is found Acrosomal enzymes is responsible for penetration Gestation period period from the time of conception until birth Gestation length of Cow- 283 days (279-287) Buffalo- 281-334 Sheep-144-152 Goat -148-152 Horse-330-342 Pig -112-120 Donkey – approx. 365 Poultry – 18-21 days incubation period

13. Factor affecting gestation length Age- more age more gestation length. Culling is necessary Sex – male have more GL Birth weight – More weight more gestation length Breed- Jersey have more than Holstein Birth type- multiple birth have short than single birth

14. Thank You