Under large numbers of animals we have seen the EBVS of animals change over time to accurately reflect their expected performance. EBVS are only as good as the information put into them and only estimate the performance of a particular trait. The accuracy level reported under an EBV reflects how much information there is about an animal and its relatives. We have heard of people using low birth weight bulls and been disappointed only to look up accuracy levels of below 50%. Rest assured the majority of Kerrah Simmental Bulls are higher than 70%. You can look up internet solutions on any breed a bulls accuracy and what traits have had data submitted for e.g. BW ,400 etc or whether the EBVS are just an estimate from other relations.
For us an animal has to be balanced in as many of the traits as possible and we try to avoid extremes and understand the antagonisms and relationships between the different traits. This is where indexes are helpful but you still need to eliminate the animals which have extremes that don’t fit your farming system, e.g. a bull with great growth and low birth with low eye muscle and low fat covers has often been referred to as a bull that had “great EBVS but looked terrible and lean so EBVS can’t work”. EBVS can be divided into four blocks; calving block, growth, reproductive and carcass. Used in a balanced perspective with structure and temperament overriding them they are still our best proven tool we have for making genetic progress as seed stock producers and you as a beef producer.
Calving ease: are based on calving ease scores, birth weights and gestation length information. More positive EBV’s indicate easier calving. DIR: Direct Calving Ease indicated how this animal influences the birth of it’s progeny.
BWT: Birth Weight EBV (kg) is based on the measured birth 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. This is particularly important when selecting sires for use over heifers.
200: 200 Day Growth EBV (kg) is calculated from the weight of animals taken between 80 and 300 days of age. Values are adjusted to 200 days and for dam age. This EBV is the best single estimate of an animals genetic merit for growth to weaning.
400: 400 Day Weight EBV (kg) is calculated from the weight of progency taken between 301 and 500 days of age, adjusted to 400 days and for dam age. This EBV is the best single estimate of an animal’s genetic merit for yearling weight.
600: 600-Day Weight EBV (kg) is calculated from the weight of progency taken between 501 and 900 days of age, adjusted to 600 days and dam age. This EBV is the best single estimate of an animal’s genetic merit for growth beyond yearling age.
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 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 subcutaneous fat and earlier maturity.
SS: Yearling Scrotal: Scrotal Circumference is an indicator of male fertility as expressed in semen quality and quantity. The larger the circumference indicates higher fertility. Scrotal Circumference is also highly correlated with early puberty in their daughters. This is why we measure bulls as yearlings for their EBVs as this is when we want our female to reach puberty. We also measure them again prior to sale, the reason, the bigger they are the more “marbles” in the pouch, potentially the more cows he can serve. The measurement in the catalogue was taken at 15 months.
ACE: Accuracy (%) is based on the amount of performance information available on the animal and its close relatives - potentially the number of progeny analysed. It indicates the “confidence level” of the EBV. This is why at Tangiwai both female and male data are analysed. 560 animals to the weaning stage (200 days), 350 to the yearling stage (400 days) and scanning.
Understanding the indexes
Index values are provided for each bull. These allow the expected profitability of the progency of different bulls to be compared.
The Maternal Index compares sires on the basis that a proportion of their female progency will be retained in the herd as breedin replacements.
The Terminal Index compares sires on the basis that all progency will be finished for slaughter (no females retained for breeding).