Nutritional Effects on Reproduction Flashcards
When is primordial follicle number determined and what influences it?
Prenatally, influenced by nutrition
When should a heifer fed on moderate nutrition reach puberty?
9-11 months
Why can fat covering the testes be a problem?
Decreases cooling
How are sex hormones synthesised?
Cholesterol -> pregnenolone -> progesterone -> testosterone -> oestradiol
What metabolic hormones can have an effect on reproduction?
Insulin – direct action on antral follicle growth and steroid production
IGF – enhances ovarian action of gonadotrophins (IGF I) & directly effects follicle growth and steroidogenesis (IGF I & II)
Leptin – at physiological levels, inhibits oestradiol secretion and increases folliculogenesis
How does nutrition affect ovulation?
Via reproductive hormones (LH)
What nutritional problems can cause pregnancy loss in the cow?
Deficiencies in vitamin A, selenium, phosphorus & copper, negative energy balance, high intake of rumen-degradable protein, ingestion of dietary oestrogens/anti-oestrogens
How does chronic undernutrition during early gestation affect the placenta weight?
Reduces placental weight in early gestation but increases its weight when measured at term
What problems relating to nutrition occur around parturition?
Dystocia (fat cows) & milk fever
What is flushing?
Moving ewes onto fresh good pasture or supplementary feed 2 weeks prior to start of tupping, usually results in an increased fecundity
How does selenium deficiency affect females?
Increases incidence of retained placenta, cystic ovaries & endometritis, high embryo mortality, decreased conception rates, birth of premature, weak or dead calves
What is the effect of dietary molybdenum and iron on plasma copper concentrations in heifers?
Plasma copper reduced for both iron fed and molybdenum fed heifers, but only molybdenum fed are showing clinical symptoms
What other effects does molybdenum have on the heifer?
Increases age of puberty, decreases peak LH concentration & decreases conception rate
What are the clinical symptoms of copper deficiency?
Delay of puberty, failure to display oestrus, irregular oestrus and ultimately anoestrus, reduces conception rates, reduced peak ovulatory LH, reduced feed intake and conversion efficiency, hair pigmentation and texture, reduced energy utilisation, swayback
What is the actual cause of a copper deficiency?
Thiomolybdate toxicity
What have thiomolybdates also been found to cause?
Gross alterations in pathology and function of pituitary, ovarian somatic cell effects (decreased steroidogenesis), reduced postovulatory progesterone (reduced MRP)
Why does reduced progesterone increase pregnancy failure?
Decreased progesterone -> decreased interferon tau -> decreased MRP -> increased pregnancy failure
How does zinc deficiency affect males?
Essential for spermatogenesis
Deficiency gives decreased libido and testicular size
How does zinc deficiency affect females?
Mild deficiency decreases number born, birth weight and leads to increased pregnancy toxaemia
Severe deficiency in early pregnancy leads to teratogenic effects
What are the reproductive symptoms of iodine deficiency?
Lowered conception rates, irregular oestrus & ultimately anoestrus, retained placenta, abortions, still births & birth of weak and/or hairless calves, cystic ovaries, in male decreased libido and semen quality
What are the last trimester effects of iodine deficiency?
Abnormal brain development, thyroid hormones produce lung surfactants – decreased newborn viability, increased post natal susceptibility to hypothermia
