1.1 Herd fertility

Ideal calving rate

1 calf per cow per year

Calving interval V calving index

• Interval = how long it takes between each calving for an individual

• Index = mean calving interval in herd

  • interference level = >380 days

Interference level

Threshold past which there should be interference

How many days does a cow get to get pregnant in a year?

85 days (cows are pregnant for 280-285)

Minimum voluntary waiting period and most common period, and interference level

• 42 days

• 50 days 

• >60 days

4 factors which could delay VWP

• Lameness or recumbency

• Milk fever

• Twins

• Difficult parturition

Interval between cow oestrus

21 days

Good average times of herd from calving and first service and calving and conceiving

• First service - 65 days

  • interference level - >75 days

• Conceiving - 85 days

  • interference level - >95 days

Which cows aren’t included in calculating key performance indicators?

Culled, dead, unserved or failed pregnancy

3 factors decreasing conception rate

• Malnourishment

• Inadequate heat detection

• Service technique

Oestrus behaviour

Cow in heat gets mounted

What rule is there for timing for first service?

30/40/50/60 rule:

• if cows served 30 days after pregnancy then conception rate will be 30% and so on

First service submission rate

Proportion of cows (eligible for service) served within 3 week (or 24 day) period

• should ideally be 100% since cows should all be in oestrus

2 factors needed for good submission rate

• Cows should cycle normally

• Good heat detection

Why is oestrus detection not done well? (3)

• Often at night

• Often lasts only 15-20mins

• Cannot be done while multitasking since requires focus

2 methods for heat detection

• Dye strip at base of tail - bursts when mounted

• Pedometers

Method for oestrus detection

Test progesterone at time of artificial insemination

• Oestrus → no CL → should have low progesterone

120 day in calf rate definition and ideal range

• % of cows pregnant at 120 days post calving

• >64%

210 day not in calf rate ideal range

<7%

Which time periods for interoestrus intervals should there be peaks?

• Largest at 18-24 days (oestrus interval is 21 days)

• Second largest at 36-48 days (21×2 = 42)