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Advanced reproductive Physiology (part 2)

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فیزیولوژی تولید مثل پیشرفته. Advanced reproductive Physiology (part 2). By: A. Riasi (PhD in Animal Nutrition & Physiology). What is early embryonic loss?. From conception to the time of maternal recognition of pregnancy, e mbryonic loss is high. The early embryonic loss is affected by:

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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 cyclesbut 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