An animal's breeding value describes its genetic merit, half of which will be passed on to its progeny, the other half being passed on by its other parent. While we will never know the exact breeding value for performance traits it is possible to make accurate estimates. These estimates are called Estimated Breeding Values (EBVs).
In the calculation of EBVs, the performance of individual animals within a contemporary group is directly compared to the average of other animals in that group. A contemporary group consists of animals of the same sex and age range within a herd, run under the same management conditions and treated equally. Indirect comparisons are made between animals reared in different contemporary groups, through the use of pedigree links between the groups and the standard heritabilities for each trait.
EBVs are expressed in the units of measurement for each particular trait. They are shown as positive or negative values and compare an animal's genetics difference with the average of the genetic base to which the animal is compared. For example, a bull with an EBV of +30 kg for Yearling Weight is estimated to have a genetic merit 30 kg above the breed base of 0 kg. Since the breed base is set to an historical benchmark, the average EBVs of animals born in each year changes over time as a result of genetic progress within the breed. So the current breed average might be +25kg which means an EBV of +30kg is only 5kg better than the current average.
The absolute value of any EBV is not critical, but rather the differences in EBVs between animals. Particular animals should be viewed as being "above or below breed average" for a particular trait. The breed average and percentiles are calculated for the current two year old animals and their parents.
Whilst EBVs provide the best basis for the comparison of the genetic merit of animals reared in different environments and management conditions, they can only be used to compare animals of the same breed and analysed within the same analysis. Consequently, Stabiliser EBVs cannot be compared with EBVs for any other breed.
EBVs are published for a range of traits including fertility, calving ease, milking ability, growth and carcase merit. When using EBVs to assist in selection decisions it is important to achieve a balance between the different groups of traits and to place emphasis on those traits that are important to the particular herd, markets and environment. One of the advantages of having a comprehensive range of EBVs is that it is possible to avoid extremes in particular traits and select animals with balanced overall performance.
Birth Weight EBV (kg) is based on the measured birth weight of progeny, adjusted for dam age. The lower the EBV value, the lighter will be the calf at birth and the likelihood of a difficult birth will be reduced. This is particularly important when selecting sires for use on heifers. Remember, there is always a spread of birth weights from all sires, and the breed of dam will also influence the birth weight of her calf. Eg heavy continental cows tend to have heavier calves whatever sire is used.
Weaning Weight EBV (kg) is calculated from the weight of progeny taken between 100 and 300 days of age. Values are adjusted to 200 days and for age of dam. This EBV is the best single estimate of an animal's genetic merit for early growth. It is often referred to as Weaning Weight EBV.
Yearling Weight EBV (kg) is calculated from the weight of progeny taken between 301 and 500 days of age, adjusted to 400 days and for age of dam. This EBV is the best single estimate of an animal's genetic merit for yearling weight.
Milk EBV (kg) is an estimate of an animal's milking ability. For sires, this EBV indicates the effect of the daughter's milking ability, inherited from the sire, on the weaning weights of her calves. For dams, it indicates her individual likely milking ability.
Mature Cow Weight EBV (kg) is based on the cow weight when the calf is weighed at weaning, adjusted to 5 years of age and body condition. This EBV is an estimate of the genetic difference in cow weight at 5 years of age and is an indicator of growth at later ages and potential feed maintenance requirements of the females in the breeding herd.
Scrotal Size EBV (cm) is calculated from the scrotal circumference of individuals measured between 300 and 500 days of age and adjusted to 400 days of age. This EBV is an estimate of an animal's genetic merit for scrotal size. There is a small negative correlation with age of puberty in female progeny and therefore selection for increased scrotal size will result in reduced age at calving of female progeny.
Rib Fat EBV (mm)is calculated from measurements of subcutaneous fat depth at 3 sites across the rib (from live animal ultrasound scans and from abattoir carcases) and is adjusted to a standard 300 kg carcase. This EBV indicates the genetic difference in fat distribution on a standard 300 kg carcase. Sires with a low, or negative, fat EBV are expected to produce leaner progeny at any particular carcase weight than will sires with higher EBVs.
Eye Muscle Area EBV (sq cm) is calculated from measurements of live animal ultrasound scans and from abattoir carcase data, adjusted to a standard 300 kg carcase. This EBV estimates genetic differences in eye muscle area at the 12/13th rib site of a 300 kg dressed carcase. More positive EBVs indicate better muscling on animals. Sires with relatively higher EMA EBVs are expected to produce better muscled and higher percentage yielding progeny at the same carcase weight than will sires with lower EMA EBVs.
Intramuscular Fat (IMF) EBV (%) is an estimate of the genetic difference in the percentage of intramuscular fat at the 12/13th rib site in a 300 kg carcase. Depending on market targets, higher positive values are generally more favourable.
Feed to Gain EBV (ratio) is calculated from individual daily feed intake and weight gain records and indicates the feed conversion efficiency of animals. Animals with larger negative figures are more favourable because they require less feed per kg of gain.
DM Feed Intake EBV (kg) is an estimate of the amount of feed that the bull s progeny will consume over a 112 day feeding period. Animals with higher intake will consume more throughout their life. Animals with lower intake will consume less. This is the best prediction of the feed needs for a bull s steer offspring and for the feed needs of daughters.
£Weaning Index
Estimates the profitability of the cow and calf unit up to the point of weaning and is expressed per animal. It includes fertility, calving and milk traits as well as growth to weaning and cow maintenance costs.
The index tends to highly rate moderate, highly fertile cows with good feed efficiency that give birth to small calves which then grow quickly to meet market specification.
This index prioritises maternal traits and should be used by breeders wishing to improve the maternal characteristics of their herds.
£Finisher Index
Estimates the profitability of the weaned calf through to finishing for slaughter and is expressed per animal. Included are growth and carcase traits which combine to achieve target specifications.
This index prioritises terminal sire traits and should be used by breeders wishing to breed animals for slaughter.
£Profit Index
The UK Stabiliser £Profit index is a customised version of the Leachman $Profit Index to suit UK market conditions. It is a multi-trait index that is designed to identify the most profitable animals in the Stabiliser breed.
£Profit is based on data collected from Stabiliser breeders and the UK beef industry. The model assumes one bull will sire 140 calves in his lifetime and that 30% of these calves will be kept as replacements, and the remaining 70% will be retained through to slaughter. These assumptions are used to weight the relationship between Economically Relevant Traits (ERT) and corresponding farm costs such as pasture, feed and premiums/discounts associated with the EUROP carcase grading scheme and associated payments to the farmers.
The result is a single £Profit figure used to accurately compare bulls against each other based on relative differences in profitability over their expected productive life. For example, if one sire has a £Profit of £15,000 and another has a £Profit of £10,000, the model predicts a lifetime advantage of £5,000 from the higher bull.
Selecting bulls using £Profit, £Weaning and £Finisher.
It is important when selecting bulls to study all 3 Indexes and then use them to identify the appropriate bulls to suit the intended breeding strategy as described above.
Bulls that rank highly for all 3 Indexes are the favoured choice for recorded pedigree breeders as their use will ensure multi-trait improvement across the whole herd.
A star rating system can be seen in the Accuracy box below the Index values that shows how animals rank in the Indexes.
| Star Rating | Percentile |
| 5* | Top 5% |
| 4* | Top 10% |
| 3* | Top 15% |
| 2* | Top 25% |
| 1* | Top 50% |
Accuracy (%) is based on the amount of performance information available on the animal and its close relatives - particularly the number of progeny analysed. Accuracy is also based on the heritability of the trait and the genetic relationships (correlations) with other recorded traits. Hence accuracy indicates the "confidence level" of the EBV. The higher the accuracy value the lower the likelihood of change in the animal's EBV as more information is analysed for that animal or its relatives. Even though an EBV with a low accuracy may change in the future, it is still the best estimate of an animal's genetic merit for that trait at that time. As more information becomes available, there is an equal likelihood that an EBV will increase in value, as it is to decrease.
As a rule, animals should be compared on EBVs regardless of accuracy. However, where two animals have similar EBVs, the one with higher accuracy could be the better choice, assuming other factors are equal.
For further information please contact the StabiliserTM Cattle Company