Managing fertility and manipulating the breeding season 1

Question 1

What are the aims of efficient reproductive management?

Answer 1

• Cattle: aim to produce one live calf once a year
• Sheep: aim to produce one - two live lambs each year
• Pigs: aim to produce > 20 live piglets each year (≥ 2 litters)

Question 2

What are ewe factors affecting reproductive performance in sheep?

Answer 2

Failure to breed
* Body condition score
* General health
* Stage in annual cycle
* Season
* Anatomical/congenital abnormalities
* Errors in synch protocols
* Ram problems

Failure to conceive/maintain pregnancy
* Reproductive pathology
* Early embryonic death / abortion
* Errors in synch protocols

Question 3

What are ram factors affecting reproductive performance in sheep?

Answer 3

Failure to breed
* Low/absent libido
* Pathologies of the penis/prepuce affecting intromission
* Lameness
* Inexperience
* Too high ewe:ram ratio

Failure to conceive
* Pathologies causing orchitis/epididymitis
* Penile abnormalities
* Inadequate testicular circumference
* Sperm abnormalities

Question 4

What are cow factors affecting reproductive performance?

Answer 4

Failure to breed
* Body condition score
* General health
* Milk yield (dairy)
* Anatomical/congenital abnormalities
* Errors in synch protocols
* Bull problems

Failure to conceive/maintain pregnancy
* Reproductive pathology
* Early embryonic death / abortion
* Errors in synch protocols
* AI errors –> AI commonly used in dairy herds

Question 5

What are bull factors affecting reproductive performance?

Answer 5

Failure to breed
* Low/absent libido
* Pathologies of the penis/prepuce affecting intromission
* Lameness
* Inexperience
* Too high cow:bull ratio

Failure to conceive
* Pathologies causing orchitis/epididymitis
* Penile abnormalities
* Inadequate testicular circumference
* Sperm abnormalities
* AI errors –> AI commonly used in dairy herds

Question 6

What are important breeding and lambing targets in sheep?

Answer 6

• Ewe:ram ratio = < 45 - 50 (dependent on age and type of ram)
• Abortion = < 2%
• Sheep –> primarily aiming to maximise numbers of lambs reared

Question 7

What are important breeding and calving targets in beef cattle?

Answer 7

• Calving interval - 365 days
• Cow:bull ratio = 30-50
• Abortion = < 5%
• Beef –> Aiming to minimise variation in calf size at weaning
  
  • Achieved through compact calving season

Question 8

What are the important targets in dairy heifers?

Answer 8

Age at first breeding = 13.5 months
Weight at breeding = 397 kg
Age at first calving = ≤ 24 months, (not < 22 months)

Question 9

What are the important breeding and year round calving targets for adult dairy cattle?

Answer 9

• Calving interval = 365 days
• Conception rate = > 35 - 40%
  
  • (Number of cows pregnant ÷ number of cows bred) x 100
• Abortion = < 5%

Question 10

What are the important breeding and block calving targets for adult dairy cattle?

Answer 10

• Conception rate = > 60%
  
  • (Number of cows pregnant ÷ number of cows bred) x 100
• Calving interval = 365 days
• Dairy –> primarily aiming to achieve one calf per year
  
  • Seasonal herds aiming to have all cows calving/dry at the same time… again means a compact calving season needed

Question 11

What have we seen a global phenomenom of increased yield but decreased fertility?

Answer 11

• Genetic selection
• Problems with postpartum resumption of cyclicity
• Reduced oestrus behaviour
• Oocyte and embryo quality
• Lower ability to cope with adverse events (e.g. heat stress)