Bovine Infertility

Question 1

Estrous cycle of cow (overview)

Answer 1

• cow comes in heat and ovulates
• follicle (produces estradiol making cow come into heat) that was present is gone= no estradiol
• after ovulation, a CL is formed, which produces progesterone by day 5 of heat after estrus
• the lack of estradiol also causes spike in FSH (follicle stim hormone)–> follicle recruitment from ovary –> deviation of dominant follicle
• dominant follicle produces estradiol, but there is presence of progesterone –> high estradiol and progest= small pulses of LH
• follicle goes into atresia–> estradiol falls, new spike in FSH for recruitment of new follicles
• the new dominant follicle produces estradiol, and if cow is not pregnant, there is production of PGF2a (PGF2a lyses the CL)–> drop in progesterone ~17 days
• now, high estradiol produced by dominant follicle is able to induce ESTRUS
• high estradiol allows large LH peak that induces ovulation

Question 2

Reproductive Failure in Cattle

Answer 2

• AI - 5/6 days
  
  • fertilization failure (will see return to estrus)
  • will reduce preg per AI
• 5/6d - 17-24d
  
  • early embryonic loss (will see return to estus)
    
    • prostaglandin causes leuteolysis and drop in progest concentration –> without progest there is no embryo
    • very small embryo may not produce enough interferon tau (normally inhibits prostaglandin)
    • both uterine horns elongate when pregnancy is recognized; if not recognized, PGF2a can be secreted and pregnancy terminated
  • will reduce preg per AI
• 17/24d - 42d
  
  • late embryonic loss (altered inter-estrus interval)
    
    • 42d is end of organogenesis
    • end of embryo, start of fetal phase
  • will reduce pregnancy per AI
• 42d - term
  
  • fetal loss

Question 3

Timing of Estrus and AI

Answer 3

• cow ovulates 27 +/- 5 hours after estrus
• egg lifespan after ovulation is 8 +/- 2 hours
• Optimal time to AI cow
  
  • 8 +/- 4 hours after she comes into heat*
  • sperm capacitation takes ~10hrs
  • high fertility right after ovulation
• major cause of infertility= improper detection of estrus/timing AI**

Question 4

Peripartum Health disorders with first 60 DIM

Answer 4

• dystocia, mastitis, metritis, fever, endometritis, ketosis, lameness
• 85% healthy cows resume cyclicity by 60 DIM
• 1 health disorder= 80% resume cyclicity by 60 DIM
• >1 health disorder= 70% resume cyclicity by 60 DIM

Question 5

Ovarian Recrudescence postpartum

Answer 5

• In early lactaion, there are growths of follices (d/t spikes FSH), but when cow is in negative E balance, her liver doesn’t respond to growth hormone –> doesn’t produce IGF1 (key to development of several cell types including follicles)
• Follicles grow, but not enough to cause peak in estradiol and LH
• When cow passes negative E balance, liver will produce more IGF1 –> allow further growth of follice –> eventual peak of estradiol and LH
• In some species (Brahman), suckling causes release of opioids which block + feedback to estradiol = no LH peak
  
  • estradiol (from follicle) –> noramlly stim GnRH from hypothal–> pituitary gland to induce LH
  • remove calf 2 days before AI

Question 6

Peripartum health disorders affecting embryo quality and preg establishment

Answer 6

• cows that are sick postpartum –>have fewer good embryos; less likely to maintain pregnancy

Question 7

Association among milk yield and estradiol conc and estrus behavior

Answer 7

• high producers
  
  • have less estradiol than low producers/heifers
  • have shorter estrus behavior duration
  • have shorter standing events/time standing

Question 8

at what point during the calving period is a cow most susceptible to disease?

Answer 8

• first 21 days after calving:
  
  • important for early dx, tx and control of diseases
  • maintain BCS
• 21 days before and after-transition period for nutrition

Question 9

estrus expression

Answer 9

• average holstein
  
  • 7 “standing events”
  • 7 hours- 1st to last stand
  • onset occurs equally 24/7

Question 10

Low progesterone and estradiol result in …

Answer 10

• expedited and prolonged follicle growth
• heifers have high progesterone @ end of estrus–> production of prostaglandin reduces progesterone –> follicles grow (not as big as cow) and produce estradiol
  
  • because heifer is eating less than lactating cow, they have higher estradiol levels–> induce estrus much faster
• cows have follicles that must grow very large and they have smaller conc of estradiol –> takes longer for them to come into heat
  
  • follicles have been in ovary for long time which makes oocytes older at time of ovulation = compromises fertility
• low progesterone in cows –> high pulsatlity of LH
  
  • follicles grow faster and oocyte ages faster

Question 11

Comparison of luteal volume and progesterone conc between heifers and lactating cows

Answer 11

• lactating cows (@ 2-14 days in estrous)
  
  • have larger follicles at ovulation
  • have larger CLs
  • have lower progesterone concentrations (increased feed intake)

Question 12

treatments

Answer 12

• Hormones
  
  • GnRH= induce ovulation and increase progesterone concentration before inseminating
  • progest= vaginal iserts avaliable in the US do not result in suff increase in progest conc (may need to use 2)
• Genetic selection

Question 13

infectious causes of infertility

Answer 13

• viruses
  
  • Infectious Bovine Rhinotracheitis
  • Bovine viral diarrhea
• bacteria
  
  • Clostridium
  • Leptospirosis
  • Campylobacter
• Protozoan
  
  • Neospora
• Parasite (Bull)
  
  • Tritrichomonas foetus (trichomonosis)

Question 14

vaccination program

Answer 14

• minimum vax program should include 4 major viral disease
  
  • BVDV (type 1 and 2)
  • herpes virus
  • respiratory syncytial
• also:
  
  • Lepto, Clostridia, core endotoxin vaccines, others according to region