2. Advanced reproductive Physiology By: A. Riasi (PhD in Animal Nutrition & Physiology) فیزیولوژی تولید مثل پیشرفته

3.  At the end of this section students will be able to reply  How NEB affect the reproductive performance of dairy cows?  Which factors may affect the twining rate in dairy cattle?  Does nutrition affect postpartum cyclicity resumption and duration of estrus?  What are physiological changes in postpartum dairy cows  How leptin affect the hypothalamus and pituitary gland?  What is early embryonic loss?

4.  Infertility in Dairy cows  The reproductive genotype of dairy cows is normal and their reproductive phenotype is a function of lactation.

5.  Dairy cows faced to negative energy balance during the early lactation period.

6.  Infertility in Dairy cows  The metabolic and endocrine cues associated with negative energy balance impair: Resumption of ovulatory cycles Oocyte and embryo quality Formation a corpus luteum Establishment and maintenance of pregnancy

7. Relationship between the BCS and anovular cows in a U.S. herd

9.  We need to know how nutrition can affect reproduction, for better or for worse. Providing a balanced diet to females is most critical  During the last trimester of pregnancy  Through the breeding season Among the functions fueled by nutrients, reproduction typically takes a back seat.

10.  Some nutritional solution for thin dairy cows Maximizing DMI during the transition period Minimizing the incidence of peri-parturient problems Adding supplemental fat to diets Manipulating the FA content of fat sources

11.  It is appear nutrition affect: Cyclicity Follicular development Oocyte quality Gene expression  Short-term nutritional manipulations may be designed to enhance pregnancy rates.

12.  The Bcl-2 gene family members are involved in: Cell proliferation Follicular selection Luteolysis  The ratio between Bcl-2/BAX shows to be critical for the normal survival of germ cells.

13.  One of reproductive trait that has been directly linked to milk production is double ovulation rate.  For a more complete review see Lopez et al., 2005; Wiltbank et al., 2000.

14.  Numerous factors that regulate twinning rate: Age of dam Season Genetics Use of reproductive hormones or antibiotics Ovarian cysts Days open Peak milk production *

15.  Effect of parity on twining rate (%) and relative risk of twining in dairy cattle. Adapted from Wiltbank et al., 2000

17. Does nutrition affect postpartum cyclicity resumption and duration of estrus?

18.  Anovular cows have: Reduced estrous detection Reduced conception rates Compromised embryo survival

20.  Energy deprivation reduces the frequency of pulses of LH.  Under-nutrition inhibits estrous behavior.

22. What are physiological changes in postpartum dairy cows?

23.  There are two phases in postpartum reproduction recovery: Resumption of FSH and LH pulsatility and reestablishment of LH surge mechanism Uterine involution

24.  Follicular development begins shortly after calving with a transient increase in FSH.  However the first postpartum dominant follicle undergoes one of three fates: Ovulation Atresia and turnover Cyst formation

25.  Some endocrine hormones can influence GnRH secretion.  The actions may be on: GnRH neurons The neuronal pathways that impinge upon GnRH neurons The pituitary gonadotroph

26.  The hormonal control arises from tissues that respond to the metabolic or nutritional status: Pancreas with secretion insulin Liver with secretion IGF-I Adipose tissue with secretion leptin

27.  The metabolites and hormones that influence on GnRH may act directly on sensitivity of the ovary to LH and FSH.  Insulin and IGF-1 may affect the ovaries independent of LH and FSH

28.  The increased incidence of anestrus and abnormal estrous cycles: LH secretion Metabolic growth factors Follicular development Estradiol secretion

29.  Lower metabolic hormone concentrations may contribute to a decrease in ovarian LH responsiveness.  Lactating cows had larger preovulatory follicles than heifers but lower preovulatory concentrations of estradiol in blood. Why?

30. What is early embryonic loss?

31.  From conception to the time of maternal recognition of pregnancy, e mbryonic loss is high.  The early embryonic loss is affected by:  Nutritional factors  Reproductive management

32.  The relationship of body condition score and early embryonic loss (Mapletoft et al. 1986)

33.  Energy deficiency should be considered as a problem in herds, in this condition:  Cows lose excessive amounts of body condition during early lactation.  Cows are not cycling normally by 30-40 days after calving.

34.  Cows in better energy balance had greater intrafollicular IGF-I and plasma progesterone levels and produce more oocytes graded as good.  Therefore, NEB not only delays resumption of ovulatory cycles but it might also influence the quality of occytes once cows are inseminated.

35.  When heifers are fed inadequate amounts of energy, they reach sexual maturity later.  If energy deficient rations are fed to heifers that have begun to have normal estrous cycles, they may stop cycling.

36.  The first key is to understand the nutrient needs of cattle at different phases of production and reproduction.  The second key is to know the nutrition content of the predominate feedstuff and supplement as needed.

37.  The primary nutrients that should be considered in providing for good reproduction are: Energy Protein Minerals Vitamins Fiber

38.  Energy intake may be the most important nutritional factor affecting reproduction.  Excessive energy intake during late lactation and the dry period can cause “fat cow” problems

39.  In cows with NEB, blood concentration of NEFA icrease and at the same time IGF-I, glucose and insulin are low.  It has shown cyclic cattle that are underfed have progressively smaller and less estrogenic dominant follicles (Bossis et al., 1999).

40. Poor nutrition Low energy intake Lower metabolic hormones: Somatotropin Insulin IGF-I Lower progesterone concentration in blood Smaller and less estrogenic dominant follicle Smaller corpora lutea Lower sroidogenic capacity of corpora lutea Lower reproduction performance

41.  Expression of hepatic growth hormone receptor (GHR-1A) is thought to be responsible for the concentrations of IGF-I in plasma of cows.  IGF-I is an important hormonal signal that influences reproductive events: Stimulation of cell mitogenesis Hormonal production Embryo development

42.  Feeding diets that promote greater insulin concentrations are benefit for fertility.