Nutrition and Reproduction (Lecture 1) Prepared by: Dr A. Riasi

1
(No Transcript)
2
??????? ????? ?????? ??????? ??????? ???? ????
???? ???? ??? ????? ? ????? ???
3
Nutrition and Reproduction (Lecture
1)Prepared by Dr A. Riasi
4

• Mammalian reproduction is influenced by many
  factors
• Species
• Breed
• Age
• Body condition score (BCS)
• Nutrition

5

• During the last decades reproductive efficiency
  of dairy cows has declined.

Reproduction problem in USA dairy herds in one
decade
Calving to first service
Open days
6

• Cattle in poor condition or losing body weight
  generally have poor reproductive performance.
• Postpartum cows prioritize their metabolizable
  energy toward production of milk and then toward
  regaining body condition (adipose tissue).

7
(No Transcript)
8

• Optimization of calving intervals can improve
  milk production from the herd.
• The desire of bovine reproductive biologists is
  to establish pregnancy early in lactation when
  seemingly little energy is required for the
  pregnancy.

9
(No Transcript)
10
(No Transcript)
11

• In dairy cow lactation and the reestablishment
  of pregnancy have overlap.
• During the last decades genetic selection and
  improved management have dramatically increased
  milk production of dairy cows and at the same
  time that fertility has decreased

12
(No Transcript)
13
(No Transcript)
14

• An essential question is whether or not dairy
  cows are inherently less fertile?
• Is their infertility a function of their level
  of milk production and nutrient partitioning?

15

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

16

• Negative energy balance affect the metabolic and
  endocrine system.
• The NEB can influence on
• Resumption of ovulatory cycles
• Oocyte and embryo quality
• Form a corpus luteum
• Establishment and maintenance of pregnancy

17
Relationship between the BCS and anovular cows in
a U.S. herd
18
(No Transcript)
19

• 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

20

• In the new area of research, short-term
  nutritional manipulations may be designed to
  enhance pregnancy rates.
• It is appear not only nutrition affect
  cyclicity, but also it may impact follicular
  development, oocyte quality and gene expression.

21

• On the other hand, it is well known that the
  Bcl-2 gene family members are involved in cell
  proliferation, follicular selection and
  luteolysis.
• The ratio between Bcl-2/BAX shows to be critical
  for the normal survival of germ cells.

22
How is the double ovulation rate in high
producing cows?
23

• 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.

24

• 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.

25

• Numerous factors have been recognized as
  possible regulator of twinning rate
• Age of dam
• Season
• Genetics
• Use of reproductive hormones or antibiotics
• Ovarian cysts
• Days open
• Peak milk production

26
Does nutrition affect on postpartum cyclicity
resumption and durationof estrus?

• A preponderance of research has focused on the
  role of nutrition in the control of the
  initiation of estrous cycles.

27

• The onset of lactation creates an enormous drain
  of nutrients in high producing dairy cows, which
  in many cases, antagonizes the resumption of
  ovulatory cycles.
• Anovular cows not only have reduced estrous
  detection and conception rates but also have
  compromised embryo survival.

28

• Resumption of ovarian activity in high producing
  dairy cows is determined by energy status of the
  animal.

29

• Energy deprivation reduces the frequency of
  pulses of luteinizing hormone (LH), thereby,
  impairing follicle maturation and ovulation.
• Furthermore, undernutrition inhibits estrous
  behavior by reducing responsiveness of the
  central nervous system to estradiol by reducing
  the estrogen receptor-á content in the brain
  (Hileman et al., 1999).

30
(No Transcript)