Repro: Conception Rates & Foetal Loss

Question 1

What is conception rate?

Answer 1

the percentage of females that become pregnant after being bred (or inseminated) once

Question 2

What is pregnancy rate?

Answer 2

conception rate x submission rate (% detected in heat)

Question 3

What factors affect conception rate?

Answer 3

• genetics
• stage of the breeding season
• nutrition
• temperature
• live weight and BCS
• reproductive tract health
• post-partum anoestrus and time since postpartum
• oestrus detection and timing of mating

Question 4

How does live weight and BCS affect conception rate?

Answer 4

• low live weight and/or low BCS can reduce CR
• very high BCS can reduce BCS
• within each species/breed, there will be an optimum live weight and/or BCS range to maximise OR

Question 5

How can the stage of the breeding season affect conception rate?

Answer 5

• outside of breeding season, the female will not be cycling
• CR can be lower during the first cycle of the season

Question 6

How can age affect conception rate?

Answer 6

• use of young animals can result in lower CR
• CR can be lower during the first cycle after puberty
• old females will have lower CR

Question 7

How can nutrition affect conception rates?

Answer 7

• severe underfeeding at the time of breeding may depress CR
• mineral deficiencies can reduce CR
• phytoestrogens can reduce CR
• mycotoxins can reduce CR

Question 8

What are the factors in embryonic mortality in cows?

Answer 8

• genetic factors
• stress factors
• age of animal
• internal environmental factors
• endocrine factors
• external environmental factors
• nutritional factors
• chromosomal abnormalities

Question 9

What are the common causes of early embryo loss?

Answer 9

• genetic defects
• infectious diseases
• unfavourable uterine conditions
• heat stress
• nutritional deficiencies
• twinning (depending on the species)
• generally higher loss with higher OR
• generally higher in young and very old females

Question 10

What are the mechanisms involved in heat stress leading to embryo loss in cattle?

Answer 10

• direct effects
  
  • elevated temperatures can damage the embryo
  • early embryos are more susceptible to heat stress
• hormonal imbalance
• oocyte quality
• oxidative stress (can damage the embryo)

Question 11

What are the impacts foetal loss has on fertility?

Answer 11

• female will take longer to return to cyclicity
• uterine clearance and repair post-foetal loss takes time
• foetal loss predisposes the female to uterine diseases (retained foetal membranes, metritis, endometritis)
• if foetal mummification occurs, female will remain “pregnant” and still not produce and offspring