100 days after calving), 200-day-not-in-calf
rate (the percentage of cows not pregnant
within 200 days after calving). The drivers
of these rates are: the 80-day submission
rate (the percentage of cows that have been
inseminated by 80 days after calving and the
conception rate (the inverse of the number of
services per conception).
A similar first South African survey was
conducted using about 69 000 service records
in 24 640 lactations from 9 046 cows in 14
Holstein herds. Using calving dates and
service records of cows, the following fertility
traits were derived, i.e. the intervals calving
to first service (CFS) and days open (DO),
services per conception (SPC) and whether
cows were inseminated before 80 days post
partum (FS80d), whether cows were confirmed
pregnant before 100 (Preg100d), and 200 days
post partum (Preg200d). In Table 1 the level
of reproduction management of these herds
is compared to the Australian InCalf survey
guidelines.
Table 1. The mean and standard deviation (SD) of fertility traits of Holstein cows in 14
herds in comparison to InCalf guidelines (DIM: days in milk)
InCalf guidelines
Traits
Calving to first service (days)
First service befor e 80 DIM (%)
Services per conception
Days open (days)
Cows pregnant before 100 DIM (%)
Cows pregnant before 200 DIM (%)
Mean
77
64
2.55
134
36
71
Cows became pregnant in 85% of lactations.
Although average values for traits may be
acceptable from a management point of view,
large variations were observed, i.e. coefficients
of variation for CFS and SPC were 39 and 70%,
respectively. The mean interval for CFS was 77
days, but only 64% of first services occurred
within 80 days after calving. The Australian
survey indicated that 73% of cows are serviced
for the first time within 80 days after calving
by good managers. The DO interval was high
and variable, being 134±74 days. Only in 36
and 71% of all lactations were cows confirmed
pregnant within 100 and 200 days postpartum,
respectively.
With the exception of the percentage of
first services within 80 days after calving,
the means for the different fertility traits
were lower than the values indicated in the
“seek advice” column for Australian dairy
farmers. Based on these values, the average
standard of reproduction management is
SD
30
48
1.79
74
48
45
Good Seek
managers
-
73
1.96
-
58
87 advice
-
<61
>2.32
-
<43
<81
poor; however, variations between herds were
observed indicating the effect of managers on
the reproductive performance of dairy herds.
The effect of farm personnel responsible for
heat detection and/or artificial insemination is
also included here.
The effect of herd and calving year on the
interval traits CFS and DO is presented
in Figure 1. Large differences were found
between herds, i.e. minimum and maximum
intervals were 75 and 142 days for CFS and
115 and 185 days for DO, respectively.
From 1991 to 1994, CFS interval increased by
3.5 days per year. From 1995 onwards, the
interval CFS did not show an annual change
probably indicating that herd managers were
not able to improve this trait or that this level
of reproductive performance was accepted.
Similarly, the interval DO increased from 127
days in 1991 to 153 days in 2006. Results
suggest that farmers seem to have adopted