2. Animal Nutrition and Reproductive Physiology (part 1)
Isfahan University of Technology
Animal Nutrition and Reproductive Physiology (part 1)
By: A. Riasi
(PhD in Animal Nutrition & Physiology)
Animal Sci. Dep. Isfahan University of Technology

3. Introduction and general information
Some factors which affect the reproductive performance in mammalians:
Species
Breed
Age
BCS
Nutrition
Introduction
Mammalians reproduction is influenced by many factors as species, breed, age, body condition score (BCS) and nutrition. Among these, nutrition has an important role, because of its direct effects on physiology and reproductive performance. Unfortunately, during the last decades reproductive efficiency of dairy cows has declined. Reproductive decline in dairy cows began in the mid-1980’s and continuing on modern dairy farms (Lucy, 2001). In this regards it is a need to think broadly about the relationship between nutrition and reproduction in postpartum cattle and to discuss the process in its basic components.

4. Introduction and general information
Nutritional factors could be manipulate to ensure positive reproductive performance.
Adequate nutrition could encourage mediocre biological types to reach animals to their genetic potential for reproduction.
Poor nutrition will not only reduce performance below genetic potential, but also exacerbate detrimental environmental effects.
Nutritional factors more than all others, could be manipulate to ensure positive outcomes in reproductive performance.
It appears adequate nutrition could encourage mediocre biological types to reach animals to their genetic potential for reproduction.
Poor nutrition on the other hand, will not only reduce performance below genetic potential, but also exacerbate detrimental environmental effects.

5. Introduction and general information
Several studies and reviews have adequately examined:
Quantitative feed and energy
Qualitative protein and macronutrients intake
Several studies and reviews have adequately examined the effects of quantitative feed and energy, as well as qualitative protein and macronutrients intake on livestock reproductive performance. In general, the results of such studies suggest that poor nutrition caused by inadequate, excess or imbalanced nutrient intake may adversely affect the various stages of the reproductive events: delayed puberty, reduced ovulation and lower conception rates, high embryonic and foetal losses, long post-partum anoestrus, high perinatal mortality and poor neonatal performance.

6. Introduction and general information
Poor nutrition affect the various stages of the reproduction:
Delayed puberty
Reduced ovulation
Long post-partum anoestrus
Lower conception rates
High embryonic and foetal losses
High perinatal mortality
Poor neonatal performance

7. Introduction and general information
Advances in studies enabled researchers to investigate subtle changes in nutrient availability on reproduction:
Growth factor assays (IGFs, FGFs, EGFs, …)
IVM, IVC and IVF stages
Using the ultrasound technique
Molecular studies
Gene expression
Immunohistochemistry
Advances in studies such as growth factor assays (IGFs, FGFs, EGFs, …), IVM, IVC and IVF stages, using the ultrasound technique, and molecular studies have enabled researchers to investigate subtle changes in nutrient availability on reproduction.
On this basis it is appear that not only nutrition affect cyclicity, but also it may impact follicular development, twining, oocyte quality and gene expression in reproductive system. On the other hand, it is well known that the Bcl-2 gene family members are involved in cell proliferation, follicular selection and luteolysis, and the ratio between Bcl-2 (prosurvival molecule)/BAX (pro-apoptotic molecule) shows to be critical for the normal survival of germ cells (the higher the ratio the lower the apoptosis). In the new area of research, short-term nutritional manipulations may be designed to enhance pregnancy and twining rates after mating or artificial insemination and also embryo transfer performance or reduce early embryonic mortality.

8. Introduction and general information
Nutrition not only affect cyclicity, but also it may impact:
Follicular development
Twining rate
Oocyte quality
Gene expression in reproductive system

9. Introduction and general information
The Bcl-2 gene family members are involved:
Cell proliferation
Follicular selection
Luteolysis
The ratio between Bcl-2/BAX is critical for the normal survival of germ cells.

10. Introduction and general information
Short-term nutritional manipulations may affect:
Pregnancy and twining rates
Embryo transfer performance
Early embryonic mortality

11. Introduction and general information
The effect of poor nutrition is depend on the deficiency of:
Energy
Protein
Vitamin
Minerals or trace elements
A complex of nutritional factors
The effect of poor nutrition is defer depending on whether the main deficiency is energy, protein, vitamin, minerals or trace elements or a complex of the nutritional factors. Protein and energy are the nutrient component needed in largest quantities and directly affect body condition score and normal reproductive performance. There is strong link between nutrition and fertility, where nutrient partitioning to the mammary gland in early-lactation , when dry matter intake is reduced, resulting in negative energy balance (NEB) and many associated disorders. Butler and Smith (1989) have shown deleterious impact of NEB on postpartum fertility. Following parturition, DMI needs to increase 4 to 6 folds in order to meet high nutrient demands for milk production. However in high yielding cows, after post calving, cow is not able to increase DMI as fast as the increase the nutrient demands required for lactation. Therefore the cow mobilizes body reserves of fat and protein to cope with this demand. The reduced fertility in modern high yielding dairy cows, is most likely due to alterations in several consecutive steps in the reproductive process.
Vitamin and minerals also play a significant role in fertility by maintaining membrane integrity, and are involved in hormone production and maintenance of strong immune system. Of particular importance are vitamins A, D, E, macro minerals such as calcium, magnesium and phosphorus, and micro minerals such as copper, selenium and zinc.

12. Introduction and general information
Protein and energy needed in largest quantities and directly affect BCS and normal reproductive performance

13. Introduction and general information

14. Introduction and general information
Daniel Luchini, 2014

15. Introduction and general information
Vitamin and minerals also play a significant role in fertility:
Maintaining membrane integrity
Involved in hormone production
Maintenance of strong immune system

16. Introduction and general information
The important vitamins for reproduction are: A E D
The more important minerals are:
Calcium, Magnesium and Phosphorus
Copper, Selenium and Zinc

17. Introduction and general information
Hypothalamus
Progesterone production by CL
(Mg, Mn)
LH and FSH secretion
(Ca, Cu, Zn)
Hypothalamus stimulation for GnRH secretion
(Ca, Cu)
Ovaries
PGF2a secretion by uterus
(Cu)
Estrogen secretion
(Mg, Cu, K, Zn)

18. Introduction and general information
Adapted from: Ferenc Husvéth, 2011
Hypothalamus is the primary target area for sensing and reacting to nutritional status.
The primary target area for sensing and reacting to nutritional status is the hypothalamus. Actually the body is regulated by two basic systems, nervous and endocrine. The endocrine or hormonal system, in general, is specifically concerned with the control of metabolic functions, rate of chemical reactions in cells, transport through cell membranes, and other functions such as growth and secretion. All of this are key components of the total lactation complex.
Hormones are chemical components comprised of steroids, peptides, proteins, and glycoproteins secreted into body fluids at one site with their action on target tissues and organs at adjacent or other sites within the body. The tissue response to the hormone is influenced by the number of receptors present on the cell membrane or within the cell and by the amount of hormone that is present. The amount of hormone presented will be under the influence of blood flow and concentration. Nutrition or perhaps more specifically food nutrients can influence the hormonal status of the animal at several levels.

19. Introduction and general information
The hormonal system is specifically concerned with the control of:
Metabolic functions
Rate of chemical reactions in cells
Transport through cell membranes
Other functions

20. Introduction and general information
The tissue response to the hormone is influenced by
Number of receptors present on the cell membrane or within the cell
The amount of hormone that is present
The amount of hormone presented will be under the influence of:
Blood flow
Hormone concentration

21. Introduction and general information
Potential sites of action of nutrition on ovarian function include systemic effect at:
The hypothalamic level via (GnRH) synthesis and release
The anterior pituitary through control of synthesis and release of FSH, LH and GH
The ovarian level through regulation of follicle growth and steroid synthesis
Pituitary and ovarian responses to endogenous or exogenous hypothalamic stimuli appear to be related to postpartum stage as well as to the severity and duration of nutrient deprivation in dairy cows. Potential sites of action of nutrition on ovarian function include systemic effect at 1- the hypothalamic level via gonadotrophin releasing hormone (GnRH) synthesis and release, 2- the anterior pituitary through control of synthesis and release of FSH, LH and GH, 3- at the ovarian level through regulation of follicle growth and steroid synthesis. The exact mechanism whereby increasing oestradiol concentrations and stimulate a gonadotrophin surge has not been fully established, but it is believed to act on specific neuronal pathways impinging on GnRH neurons within the hypothalamus, leading to an increase in the secretion of GnRH. Some evidence suggests that the pituitary sensitivity to GnRH pulses is decreased during under-nutrition. It is reported that under-nutrition suppressed pituitary synthesis of LH as the concentration of mRNA for both α and β subunits of LH were less in nutritionally restricted ovariectomised ewes. However, pulsatile administration of GnRH was capable of restoring LH synthesis and secretion.

22. Introduction and general information
Low energy availability during the NEB (Butler, 2000):
Suppresses pulsatile secretion LH
Reduces ovarian responsiveness to LH stimulation
NEB during the early pregnancy:
Low progesterone production during the early embryonic period
Adult ewes maintained on low plans of nutrition exhibited reduced ovulation rates.
Butler (2000) reported that low energy availability during the NEB not only suppresses pulsatile secretion LH, but also reduces ovarian responsiveness to LH stimulation. On the other hand it is demonstrated that the case of acute nutritional deprivation, failure of ovulation was always associated with the absence of pre-ovulatory LH and FSH surges though not necessarily associated with the absence of pro-oestrus increase oestradiol. Poor feeding during post-partum reduces luteal function and responsiveness of the ovaries to luteinising hormone. Low progesterone production during the early embryonic period has been suggested as a reason for lowered conception rates related to NEB. Adult ewes maintained on low planes of nutrition exhibited reduced ovulation rates, a response attributed to reduced ovarian follicular development rather than to alteration of the preovulatory surge of LH. Effect on follicular development could result from disruption of pulsatile LH release.
Under-nutrition is associated with elevated growth hormones, reduced IGF-I, and uncoupling of the link between growth hormone and IGF-I and failure of dominant ovarian follicle to produce enough oestradiol to generate the preovulatory surge.

23. Introduction and general information
Under-nutrition is associated with:
Elevated growth hormones
Reduced IGF-I
Uncoupling of the link between growth hormone and IGF-I
Failure of dominant ovarian follicle to produce enough oestradiol to generate the preovulatory surge