EBV Explanation

EBV Explanation

Estimated Breeding Values (EBVs)

The EBV is the best estimate of an animal’s genetic merit for that trait.  Each breed’s EBVs are calculated specifically for that breed, for comparisons within the breed, and there can be no cross comparison between breeds.

Single Step Breedplan adds a further dimension to the calculation of EBVs and accuracy, with genomic information now incorporated simultaneously with pedigree and performance data. The analysis takes account of the genomic relationships that exist between all individuals in the genotyped population – which means actual calculated relationships are used rather than “average relationships” based on recorded pedigree.

Accuracy: An accuracy value is presented with every EBV and gives an indication of the amount of information that has been used in the calculation of that EBV.  The higher the accuracy the lower the likelihood of change in the animal’s EBV as more information is analysed for that animal or its relatives.  Low accuracies should be treated with caution.

Calving Ease:  Calving Ease EBVs are based on calving difficulty scores, birth weights and gestation length information.  Negative EBVs mean more difficult calving whilst positive EBVs mean easier calving.

Direct: Direct calving ease indicates how this bull influences the birth of its progeny.  High negatives are bad whilst high positives are good.

Daughters: Daughter’s calving ease indicates how well the animal produces daughters that have easier calving.  This is an important trait if you are breeding your own replacements.  Again, high negatives are bad whilst high positives are good.

Gestation Length: Gestation Length EBVs (days) are based on AI records and observed natural service.  Lower (negative) Gestation Length EBVs indicate shorter gestation lengths which generally relate to easier calving and increased growth after birth.

Birthweight: 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.

Scrotal Size: Scrotal Size EBV (cm) is an indicator of male fertility in regards to semen quality and quantity.  Higher (positive) EBVs indicate higher fertility.  There is also a small negative correlation with age of puberty in female progeny ie, the daughters of bulls with larger testicles may come into season at an earlier 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.  Bulls with high 200 day milk EBVs have more milky daughters.

200-Day Growth: 200-Day Growth EBV (kg) is calculated from the weight of the 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 animal’s genetic merit for growth to early ages.  The higher the 200 day EBV then the higher the suckled calf or weaning weight.

400-Day Growth: 400-Day Weight EBV (kg) is calculated from the weight of progeny 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.  Higher 400 day EBVs indicate earlier maturing progeny with a greater weight at an earlier age.

600-Day Growth: 600-Day Weight EBV (kg) is calculated from the weight of progeny taken between 501 and 900 days of age, adjusted to 600 days and for dam age.  This EBV is the best single estimate of an animal’s genetic merit for growth beyond yearling age.

Mature Cow Weight: Mature Cow Weight EBV (kg) is an estimate of the genetic difference in cow weight at 5 years of age.  Moderate or larger EBVs are generally more favourable.

Carcase Weight: Carcase Weight EBV (kg) estimates the genetic difference in carcase weight at a standard age of 650 days.  An important trait for finished cattle production.

Eye Muscle Area: Eye Muscle Area EBV (cm2) estimates genetic differences in eye muscle area of a 300 kg dressed carcase.  More positive EBVs indicate better muscling on animals.

Fat: Rib Fat EBV (mm) estimates the genetic differences in fat depth at the rib in a 300 kg dressed carcase.  More positive EBVs indicate more subcutaneous fat and earlier maturity, leading to a higher fat classification in slaughtered progeny.

Retail Beef Yield %: Retail Beef Yield Percent EBV (%) represents total (boned out) meat yield as a percentage of a 300 kg dressed carcase.  A more positive EBV indicates higher percentage yield for the 300 kg carcase size.  This is an important trait in finished steers and heifers.

Selection Indexes

Selection indexes provide an overall indication of an animal’s genetic value for profit in a specific production system/target market and are calculated based on weightings placed on individual traits that are deemed to be important for that production system.  The SDHBS currently reports two different selection indexes, the Quality Beef and the Suckler Replacement:

Quality Beef Index

The South Devon Quality Beef Index is a combination of all traits into a single figure and is a measure of a terminal sire’s ability to produce prime steers and heifers for the finished market whilst maintaining calving ease at a reasonable level.

Suckler Replacement Index

The Suckler Replacement Index ranks bulls by their genetic potential for the production of female replacements while producing prime steers and excess heifers for beef production, with emphasis on calving ease and maternal traits.