Page 44 - Woodbank-Matariki ebook

Understanding
Calving Ease EBVs

Calving difficulty has an obvious negative impact on the profitability of a herd
through increased calf & heifer mortality, slower re-breeding performance
& considerable additional labour & veterinary expense.
Whilst many large studies have consistently show birth weight to be the
most important genetic factor influencing calving difficulty, there are also
other aspects that need to be considered. For example, calf shape, pelvic
area & calving “will”. BREEDPLAN Calving Ease EBVs attempt to take
all the factors affecting calving difficulty into consideration & allow the
best possible genetic improvement to be made for ease of calving.

What Calving Ease EBVs are Available?
BREEDPLAN produces two Calving Ease EBVs - Calving Ease Direct &
Calving Ease Daughters.
(1) Calving Ease Direct
Calving Ease (DIR) EBVs are estimates of genetic differences in the ability
of a sires’ calves to be born unassisted from 2 year old heifers. The EBVs
are reported as differences in the percentage of unassisted calvings.
Higher, more positive, Calving Ease (DIR) EBVs are more favourable. For
Example, a bull with an EBV of +5.0% would be expected, on average,
to produce 3% fewer difficult calvings from 2 year old heifers than a bull
with an EBV of -1.0% (6% difference between the sires, then halved as
they only contribute half the genetics).
(2) Calving Ease Daughters

Calving EAse (DTRS) EBVs are estimates of genetic differences in the
ability of a sire’s 2 year old daughters to calve without assistance. The
EBVs are also reported as differences in the percentage of unassisted
calvings.
Higher, more positive, Calving Ease (DTRS) EBVs are more favourable.
For example, a bull with an EBV of +4.0% would be expected to on aver-
age produce 2 year old daughters that have 3% less calving problems than
the daughters of a bull with an EBV of -2.0%.
The challenge when selecting animals is to identify animals who have
both positive EBVs for Calving Ease (DIR) & Calving Ease (DTRS).

42 Woodbank Angus & Matariki Herefords Bull Sale 2021