Dairy Herd Fertility

Question 1

What is VWP?

Answer 1

Voluntary waiting period: earliest service date after calving

• too soon after calving -> v pregnancy rates, too late prolongs calving interval
• generally 30d = 30% success, 40d = 40% etc. up to 60 optimum.

Question 2

What is the calving index? What are the limitations of this?

Answer 2

• average of all calving intervals

- cows that dont calve are NOT included so some problems may be hidden if oly this figure is looked at

Question 3

What is the target calving index? Interfereence level?

Answer 3

365d, interference >380d

Question 4

What is the target earliest service date (VWP?) Interference level?

Answer 4

50d, interfere <42d

Question 5

What is the the target calving-first service interval?

Answer 5

65d, interfere >75d

Question 6

What is the target calving-conception interval?

Answer 6

85d interfere >95d

Question 7

What is the target conception rate at first service and all services? Define these parameters. Intereference level?

Answer 7

• definition: off 100 straws on AI, how many result in pregnancy?
• target 60 at first service, 55 all services
• interfere <50%

Question 8

How is timing of 1st service measured (2 ways?) Downsides to these methods?

Answer 8

1. Mean interval calving -> 1st service
   - cows not served are missed out, if large spread of values this is not seen as average each other out, unusual VWP
2. first service submission rate (proportion of cows served within 24d/3 weeks of earliest allowed service date (50d post calving) ie. VWP = start of time when service can occour, submission rate = no. cows served 74d post-calving)

Question 9

What is the target submission rate at 42d? What can impact submission rates?

Answer 9

85%

- poor heat detection v submission rates

Question 10

What are inter-oestrus intervals? How are these commonly depicted?

Answer 10

• Bar chart - if flat = poor detection of heat

- majority of inter-oestrus intervals should be _____ ** LOOK UP ***

Question 11

How may oestrus detection accuracy be tested?

Answer 11

Milk P4 at time of AI

- should be <5 (if in season, P4 will be low)

Question 12

What is a cu-sum graph?

Answer 12

Plot every AI service date on graph - colour higher square when service is successfull and lower square when unsuccessful.
- helps to identify trends and times/patches of poorer conception rates and link to temporal causes

Question 13

What is the 120d in calf rate? Aim?

Answer 13

% cows pregnanct at 120d post calving

- Aim for >64%

Question 14

What is the 210d not in calf rate?

Answer 14

% cows not pregnant 210d post calving

• should be drying off by now so should have noticed before!!
• should be <7%

Question 15

Why may pre-breeding checks no longer be advocated?

Answer 15

• sticking hand in cow -> stress and contamination

- not very useful

Question 16

What is the gestation length of a cow?

Answer 16

282d

Question 17

Why do cows not cycle immediately post-partum?

Answer 17

• need to involute uterus
• hypothalamus refractory to oestradoil -> v GnRH release
• hence VWP

Question 18

What may extend the earliest service date?

Answer 18

• metiritis, BCS, mastitis, retained foetal membranes >24hrs

Question 19

What is ESD?

Answer 19

Earliest service date (==VWP?)

- should be 42d post calving

Question 20

What is S1?

Answer 20

1st service

- should be d65

Question 21

What is Cn?

Answer 21

Conception

- should have occourred by d85 post calving (to allow for 280d gestation and maintain 365d calving cycle)