1. Reproductive Management of Dairy Cattle
Important Records for Reproductive Management

2. 1st breeding – anytime after VWP
Later breedings
Conception
Voluntary waiting period
Cycle from one calving until the next calving
Calving
Gestation
The Reproductive Cycle

3. Voluntary Waiting Period – (VWP)
- Determined by herd owner.
- Fixed period following calving before attempting to breed cow.
- Often the same for all cows in the herd although some have a longer VWP for 1st lactation animals.
- Usually between 40 and 70 days

4. Option Interval or Voluntary Waiting Period
Two factors seem to play a role in the cow’s calving interval.
- High producers tend to have silent heat more often than low producers.
- Dairy farmers may give high producers a longer wait period before being bred back.

5. Option Interval or Voluntary Waiting Period
This may vary depending upon individual cow’s production.
- High producing cows – Bred at first estrus 60 day postpartum – 13 month calving interval may be optimal.
- Medium/Low producing cows – Breed at first estrus 40 days postpartum – 12 month calving interval may be optimal.

6. Dairy cattle reproductive cycle
Voluntary waiting period
Breed after this date
Calves

7. Days to first service
Number of days between calving and when the animal is bred for the first time.
Calculated on a herd basis – not for an individual animal.
Animal may or may not conceive to this breeding/service.

8. Dairy reproductive terms – linear display
Days to 1st service
Bred for 1st time
Calves

9. Days Open Number of days between calving and conception.
Calculated on a herd basis – not for an individual animal.

10. Days open & Days to first service - linear display
Days to 1st service
Bred for 1st time and conceives
Calves

11. Days open + Days to first service - linear display
Days to 1st service
Bred again and conceives
Bred for 1st time
Calves

12. Dairy reproductive terms – linear display
Days open
Days to 1st service
Bred again (3rd service) and conceives
Bred again
- 2nd service
Bred for 1st time
- 1st service
Calves

13. Gestation period Number of days that a cow is pregnant.
Number of days from conception to birth of the fetus.
Average gestation: 279 days-there are breed differences

14. Calving Interval Period from one calving until the next.
Measured in months.
Calculated on a herd basis – not for an individual animal.
Days open Gestation period
Calving interval

15. Dairy reproductive terms – linear display
Calving interval
Calves again
Calves

16. Measures of Reproductive Efficiency
Days to first service
Days open
Calving interval
Services per conception
Conception rate
Heat detection rate
Pregnancy rate

17. Services per conception
S/C =
Total number of services (breedings)
Total number of pregnant cows
Calculated on a herd basis – not for an individual animal.
Inverse of conception rate.

18. Conception Rate Total number of pregnant cows
CR =
Total number of pregnant cows
Total number of services (breedings)
Calculated on a herd basis – not for an individual animal.
Inverse of services per conception.

19. Heat detection rate Also known as service rate.
Percentage of eligible cows detected in heat during a 21-day period.

20. Calculated in two ways:
Pregnancy Rate
Calculated in two ways:
PR =
Total number of cows pregnant
Total number of opportunities to get cows pregnant
PR =
Conception Rate x Service Rate