Transcript Lecture 9 - Fatty Acid Metabolism

‫فیزیولوژی تولید مثل پیشرفته‬
Advanced reproductive
Physiology
By: A. Riasi
(PhD in Animal Nutrition & Physiology)
 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?
 Infertility in Dairy cows
 The reproductive genotype of dairy cows is
normal and their reproductive phenotype is a
function of lactation.
 Dairy cows faced to negative energy balance
during the early lactation period.
 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
Relationship between the BCS and anovular cows in a U.S. herd
Increase milk
production
Endocrine change
Prolactin
Somatotropin
Insulin
 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.
 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
 It is appear nutrition affect:
 Cyclicity
 Follicular development
 Oocyte quality
 Gene expression
Short-term
nutritional
manipulations
designed to enhance pregnancy rates.
may
be
 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.
 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.
 Numerous factors that regulate twinning rate:
Age of dam
 Season
 Genetics
 Use of reproductive hormones or antibiotics
 Ovarian cysts
 Days open
 Peak milk production *
 Effect of parity on twining rate (%) and relative risk of twining in
dairy cattle.
Adapted from Wiltbank et al., 2000
Adapted from Wiltbank et al., 2000
Does nutrition affect postpartum
cyclicity resumption and duration of
estrus?
 Anovular cows have:
Reduced estrous detection
Reduced conception rates
Compromised embryo survival
 Energy deprivation reduces the frequency of pulses
of LH.
 Under-nutrition inhibits estrous behavior.
What are physiological changes in
postpartum dairy cows?
 There
are
two
phases
in
postpartum
reproduction recovery:
Resumption
of
FSH
and
LH
pulsatility
reestablishment of LH surge mechanism
Uterine involution
and
 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
 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
 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
 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
 The increased incidence of anestrus and
abnormal estrous cycles:
 LH secretion
 Metabolic growth factors
 Follicular development
 Estradiol secretion
 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?
What is early embryonic loss?
 From conception to the time of maternal
recognition of pregnancy, embryonic loss is high.
 The early embryonic loss is affected by:
 Nutritional factors
 Reproductive management
 The relationship of body condition score and
early embryonic loss (Mapletoft et al. 1986)
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.
 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.
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.
 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.
 The primary nutrients that should be considered
in providing for good reproduction are:
 Energy
 Protein
 Minerals
 Vitamins
 Fiber
 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
 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).
Poor nutrition
Lower metabolic hormones:
• Somatotropin
• Insulin
• IGF-I
Low energy intake
Smaller and less estrogenic dominant follicle
Lower sroidogenic capacity of corpora lutea
Smaller corpora lutea
Lower progesterone concentration in blood
Lower reproduction performance
 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
 Feeding diets that promote greater insulin
concentrations are benefit for fertility.