Page 6 - Kerrah Catalogue eBook

EBV’s Explained

ESTIMATED BREEDING VALUES (EBV’S) ACTUAL MEASUREMENT:
An EBV is the best estimate of an animal’s genetic merit for that trait. SS: Yearling Scrotal: Scrotal Circumference is an indicator of male
fertility as expressed in semen quality and quantity. The larger the
CALVING EASE: Calving ease are based on calving ease scores, circumference indicates higher fertility. Scrotal Circumference is also
birth weights and gestation length information. More positive EBV’s highly correlated with early puberty in their daughters. This is why
indicate easier calving. we measure bulls as yearlings for their EBVs as this is when we want
DIR: Direct Calving Ease indicated how this animal influences the our female to reach puberty. We also measure them again prior
birth of it’s progeny. to sale, the reason, the bigger they are the more “marbles” in the
pouch, potentially the more cows he can serve. The measurement in
BWT: Birth Weight EBV (kg) is based on the measured birth the catalogue was taken at 18 months.
weight of animals, adjusted for dam age. The lower the value the
lighter the calf at birth and the lower the likelihood of a difficult birth. ACE: Accuracy (%) is based on the amount of performance
This is particularly important when selecting sires for use over heifers. information available on the animal and its close relatives -
potentially the number of progeny analysed. It indicates the
200: 200 Day Growth EBV (kg) is calculated from the weight “confidence level” of the EBV. This is why at Tangiwai both female
of animals taken between 80 and 300 days of age. Values are and male data are analysed. 560 animals to the weaning stage
adjusted to 200 days and for dam age. This EBV is the best single (200 days), 500 to the yearling stage (400 days) and scanning.
estimate of an animals genetic merit for growth to weaning.
UNDERSTANDING THE INDEXES:
400: 400 Day Weight EBV (kg) is calculated from the weight of Index values are provided for each bull. These allow the expected
progency taken between 301 and 500 days of age, adjusted to 400 profitability of the progency of different bulls to be compared.
days and for dam age. This EBV is the best single estimate of an The Maternal Index compares sires on the basis that a proportion
animal’s genetic merit for yearling weight. of their female progency will be retained in the herd as breedin
replacements. The Terminal Index compares sires on the basis that
600: 600-Day Weight EBV (kg) is calculated from the weight all progency will be finished for slaughter (no females retained for
of progency taken between 501 and 900 days of age, adjusted to breeding).
600 days and dam age. This EBV is the best single estimate of an Also to note, is that indexes are a good tool but their
animal’s genetic merit for growth beyond yearling age.
limitation is key traits have a big influence on the index
value and operate on the premise more is always better
Scrotal Size EBV (cm) is calculated from the circumference of the rather than a threshold. At Kerrah we aim to breed
scrotum taken between 300 and 700 days of age and adjusted to balanced cattle trying to avoid extremes of traits as most
400 days of age. This EBV is an estimate of an animal’s genetic often there is an antagonistic trait or traits associated
merit for scrotal size. There is also a small negative correlation with a favourable trait. All said and done, we are still
with age of puberty in female progeny and therefore selection for trying to breed a Polled, phenotypically pleasing, docile
increased scrotal size will result in reduced age at calving of female bull in the top 20% for every trait and index.
progeny.

MILK: 200-Day Milk EBV (kg) is an estimate of an animal’s
milking ability. For sires, this EBV is indicative of their daughter’s Lot 17 Kerrah H410
milking ability as it affects the 200 day weight of their calves.

CWT: Carcase Weight EBV (kg) estimates the genetic difference
in carcase weight at a standard age of 650 days. More positive
EBVs indicate heavier carcases at 650 days of age.

EMA: Eye Muscle Area (cm2) estimates genetic difference in eye
muscle area at the 12/13th rib state of a 300kg dressed carcase.
More positive EBVs indicate better muscling on animals.

RIB FAT: Rib Fat EBV (mm) estimates the genetic differences in fat
depth at the 12/13th rib in a 300 kg dressed carcase. More positive
EBVs indicate more subcutaneous fat and earlier maturity.

P8 FAT: Rump Fat EBV (mm) estimates the genetic differences in
fat depth at the P8 site of a 300kg dressed carcase. More positive
EBVs indicate more subutaneous fat and earlier maturity.

Retail Beef Yield EBV (%) indicates genetic differences between
animals for retail yield percentage in a standard 400 kg carcase.
Sires with larger EBVs are expected to produce progeny with higher
yielding carcases.

4 KERRAH SIMMENTALS BULL SALE 2021