Estimated Breeding Values

Estimated Breeding Values (EBVs) are estimates of an animals’ genetic merit for a particular trait and an indication of how an animal’s progeny will perform. EBVs are expressed as the difference between an individual animal’s genetics and the genetic base to which the animal is compared (a historic genetic level for each breed). All EBVs are reported in the units in which the measurements are taken e.g. kilograms for weight EBVs and millimetres for fat depth EBVs. BREEDPLAN currently reports EBVs for a range of economically important traits. These traits include:

To find out more about EBVs, watch a short ‘how-to’ animated video, produced by Meat & Livestock Australia, on what are Estimated Breeding Values.

It should be noted that EBVs will only be available if sufficient data has been recorded for that trait and as such, the full range of EBVs may not be available for each particular Breed Society/Association.

Only EBVs for animals within a particular breed can be compared, not EBVs from different breeds.

Always compare an EBV to the current breed average EBV for that trait. This will give you an indication of how the animal compares with the current genetic level for the breed for each trait and if it is above or below average for the breed. This can be taken further by comparing the animal’s EBV to the Percentile Bands Table to assess exactly where the animal ranks within the breed for each trait e.g. top 20%.

It is also important to look at the accuracy of each EBV as this provides a measure of its reliability. The higher the accuracy the lower the likelihood of change in the animals EBV as more information is analysed for that particular animal, its progeny or relatives.

Selection of animals should be based on both EBVs and a visual assessment for other important traits such as structural soundness. Bull fertility should also be tested using BULLCHECK^TM or a Veterinary Bull Breeding Soundness Evaluation.

EBVs are available for a wide range of traits, which can result in a dilemma when trying to select animals for use in a particular breeding program. In an ideal situation, it would be desirable to select animals that excel in all traits, but rarely will an animal be superior for all the available EBVs. So which traits should producers put most emphasis on? How much emphasis should be placed on each trait?

BreedObject is a tool that can help solve this dilemma. BreedObject combines the BREEDPLAN EBVs for an animal with an economic weighting (based on costs of production and returns on outputs), to produce a single Selection Index. Selection Indexes enable cattle producers to make “balanced” selection decisions, taking into account the relevant growth, carcase and fertility attributes of each animal to identify the animal that is most profitable for their particular commercial enterprise.

To find out more about indexes, watch a short ‘how-to’ animated video, produced by Meat & Livestock Australia, on what are beef indexes?

Beef producers wanting to learn more are encouraged to attend a Breeding EDGE workshop to help develop or improve their breeding program.

Practical examples using EBVs

When comparing two bulls, Bull A with an EBV for 600 day weight of +40kg and Bull B with an EBV of +10 for the same trait, the difference in their EBVs is 30kg. As a result, the progeny of Bull A would expected to be 15kg heavier than those of Bull B at 600 days of age.

The expected progeny difference is half the difference in the EBVs of the parents, since the progeny receives half the genes from the sire and half from the dam. It is also the average expected over a large number of progeny (it is not what is expected for each, and every, progeny).

In determining which bull to buy or use in a herd, or which cows to use to breed replacement heifers, it is not always the animal with the highest EBV that should be selected. For example, with birth weight often a bull with a low, or even negative EBV might be selected, depending on the potential in the herd for problems with high birth weight and dystocia. In many tropical herds, breeders look for bulls with adequate, but not the highest EBV for milk, as high milk production, in some herds, is thought to be associated with lowered fertility. Even for the growth rate traits depending on the market, breeders may choose bulls without the highest EBVs as the best to use in their herds.

Watch some short ‘how-to’ animated videos, produced by Meat & Livestock Australia, to help you find bulls on the BREEDPLAN website and how to search sales catalogues on the BREEDPLAN website.

Watch a short ‘how-to’ animated video, produced by Meat & Livestock, Australia that steps you through how to go about buying a high performing bull.

Specific BREEDPLAN EBVs

Fertility/calving

Scrotal Size

Scrotal Size EBVs are estimates of the genetic differences between animals in scrotal circumference at 400 days of age. Scrotal Size EBVs are expressed in centimetres (cm) and are calculated from scrotal circumference measurements taken on bulls between 300 and 700 days of age. Increased scrotal circumference is associated with increased semen production in bulls, and earlier age at puberty of bull and heifer progeny.

Increased scrotal circumference also has a favourable relationship with days to calving, such that bulls with larger scrotal circumference tend to have daughters with shorter days to calving.

Larger, more positive, Scrotal Size EBVs are generally more favourable.

Days to Calving

Days to Calving EBVs are estimates of genetic differences between animals in time from the start of the joining period (i.e. when the female is introduced to a bull) until subsequent calving. Days to Calving EBVs are expressed in days and are calculated from the joining records submitted for females.

The Days to Calving EBV promotes those cows that calve earlier in the season compared to those that calve later, while penalizing those cows that do not calve. Variation in days to calving is mainly due to differences in the time taken for females to conceive after the commencement of the joining period. Lower, or more negative, Days to Calving EBVs are generally more favourable. Females with shorter Days to Calving EBVs also tend to be those that show early puberty as heifers and return to oestrous earlier after calving.

Gestation Length

Gestation Length EBVs are estimates of genetic differences between animals in the number of days from the date of conception to the calf birth date. Gestation Length EBVs are expressed in days and are calculated from the joining date and birth date records for calves conceived by either AI or hand mating. Shorter gestation length is generally associated with lighter birth weight, improved calving ease and improved re-breeding performance among dams. In addition, calves born with a shorter gestation length are often heavier at weaning due to more days of growth. Consequently, lower or more negative Gestation Length EBVs are considered to be more favourable.

Calving Ease

EBVs are provided for calving ease, an important characteristic for cattle. Calving difficulty has an obvious negative impact on the profitability of a herd through increased calf and heifer mortality, slower re-breeding performance and considerable additional labour and veterinary expense. EBVs for traits related to calving ease are calculated from three main sources of information – calving difficulty score, birth weight and gestation length data. BREEDPLAN produces two calving ease EBVs – Calving Ease Direct and Calving Ease Daughters.

(i) Calving Ease Direct

Calving Ease (DIR) EBVs are estimates of genetic differences in the ability of a sire’s calves to be born unassisted from two 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.

(ii) Calving Ease Daughters

Calving Ease (DTRS) EBVs are estimates of genetic differences in the ability of a sire’s daughters to calve at two years of age 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.

Weight

Birth Weight

Birth Weight EBVs are estimates of genetic differences between animals in calf birth weight. Calf birth weight is the biggest genetic contributing factor causing calving difficulty in heifers. Birth Weight EBVs are expressed in kilograms (kg) and are calculated based on weights of calves taken at birth. Small, or moderate, Birth Weight EBVs are more favourable.

Please note, whilst low Birth Weight EBVs are favoured for calving ease they are also generally associated with lower overall growth potential. Consequently, birth weight and growth need to be carefully balanced. Fortunately, animals can be found that have both moderate Birth Weight EBVs and above average EBVs for later growth.

200 Day Milk

200 Day Milk EBVs are estimates of an animal’s maternal effect on the 200 day weight of its calf. In the case of sires, this estimates the maternal effect that his daughters will have on the 200 day weight of their progeny. The 200 Day Milk EBV is expressed as kilograms (kg) of calf live weight at 200 days (i.e. the expected difference in the weight of the calf at 200 days due to the maternal effect (milk) of the cow). The 200 Day Milk EBV is calculated by partitioning the difference in the 200 day weight of calves into growth and milk components. Larger, more positive 200 Day Milk EBVs are generally more favourable, depending upon the environment.

The optimum level of milk production potential among beef cows depends on the production system and environment in which the cows are run. Selection for increased milk production may be warranted when cows are run under good nutritional conditions and calves are sold as weaners. However, some environments may not support high milking cows.

Growth

In general, with all other things being equal, higher growth rates will lead to higher profitability. In most economic analyses conducted, positive emphasis on growth is warranted. BREEDPLAN calculates three growth EBVs – 200 Day Growth, 400 Day Weight and 600 Day Weight. These EBVs are the best prediction of the animal’s ability to grow to weaning (200 day), yearling (400 day) and later ages (600 day). 200 Day Growth EBVs are therefore important to vealer breeders, 400 Day Weight EBVs for yearling breeders and 600 Day Weight EBVs for breeders of heavy steers. These EBVs are closely linked genetically but there is some scope to select for them individually.

(i) 200 Day Growth

200 Day Growth EBVs are estimates of the genetic differences between animals in liveweight at 200 days of age due to their genetics for growth. 200 Day Growth EBVs are expressed in kilograms (kg) and are calculated from the weights of calves taken between 80 and 300 days of age.

This EBV is a measure of an animal’s early growth to weaning. It is an important trait for breeders turning off animals as vealers or weaners. Larger, more positive, 200 Day Growth EBVs are generally more favourable.

(ii) 400 Day Weight

400 Day Weight EBVs are estimates of the genetic differences between animals in liveweight at 400 days of age. 400 Day Weight EBVs are expressed in kilograms (kg) and are calculated from the weights of calves taken between 301 and 500 days of age.

This EBV is an important trait for breeders turning off animals as yearlings. Larger, more positive, 400 Day Weight EBVs are generally more favourable.

(iii) 600 Day Weight

600 Day Weight EBVs are estimates of the genetic differences between animals in liveweight at 600 days of age. 600 Day Weight EBVs are expressed in kilograms (kg) and are calculated from the weights of calves taken between 501 and 900 days of age.

This EBV is an important trait for breeders targeting the production of animals suited for heavyweight grass or grain fed markets. Larger, more positive, 600 Day Weight EBVs are generally more favourable.

Mature Cow Weight

Mature Cow Weight EBVs are estimates of the genetic differences between cows in liveweight at five years of age. Mature Cow Weight EBVs are expressed in kilograms (kg) and are calculated from weights taken on the cow when her calf’s 200 day (weaning) weight is being measured.

Mature Cow Weight EBVs are an indicator of:

• cow feed requirements – in general, lighter cows will tend to eat less and consequently have lower feed requirements and be less expensive to maintain
• cull cow values – the major determinant in the value of cull cows in a commercial herd is liveweight. Consequently, heavier cows may provide higher returns from the sale of cull cows.

Carcase

BREEDPLAN combines both live animal ultrasound scanning information with abattoir chiller carcase data to calculate EBVs that provide information regarding the genetic differences in carcase composition between animals. Carcase EBVs provide a useful tool to assist breeders in targeting animals that meet market requirements.

Carcase Weight

Carcase Weight EBVs are estimates of the genetic differences between animals in hot standard carcase weight (as defined by AUS-MEAT) at 650 days of age. Carcase Weight EBVs are expressed in kilograms (kg).

Larger, more positive, Carcase Weight EBVs are generally more favourable.

Carcase Weight should not be confused with yield. The Carcase Weight EBV is an indication of the animal’s carcase weight and not an indication of the animal’s yield percentage.

Eye Muscle Area

Eye Muscle Area (EMA) EBVs are estimates of the genetic differences between animals in eye muscle area at the 12/13th rib site in a standard weight steer carcase. EMA EBVs are expressed in square centimetres (cm²).

Larger, more positive, EMA EBVs are generally more favourable.

Rib Fat

Rib Fat EBVs are estimates of the genetic differences between animals in fat depth at the 12/13th rib site in a standard weight steer carcase. Rib Fat EBVs are expressed in millimetres (mm).

More positive or more negative Rib Fat EBVs may be more favourable, depending on your breeding goals relating to the finishing ability of your animals.

Rump Fat

Rump Fat EBVs are estimates of the genetic differences between animals in fat depth at the P8 rump site in a standard weight steer carcase. Rump Fat EBVs are expressed in millimeters (mm).

More positive or more negative Rump Fat EBVs may be more favourable, depending on your breeding goals relating to the finishing ability of your animals.

Stock with positive fat EBVs are likely to produce progeny that are fatter, or more earlier maturing, on average than stock with lower or negative fat EBVs. Increasing fat depth leads to a decrease in retail beef yield, however most market specifications require a minimum fat depth. Breeders aiming to breed leaner, higher yielding cattle may select for lower fat EBVs. Breeders wishing to finish their animals earlier may tend to select animals with moderate fat EBVs.

Caution should be placed on selecting for extremely low fat EBVs for replacement females as this may indicate females that are more difficult to get in calf.

Differences between Rib Fat EBVs and Rump Fat EBVs can indicate differences in fat distribution among animals.

Retail Beef Yield

Retail Beef Yield (RBY) EBVs are estimates of genetic differences between animals in boned out retail beef yield in a standard weight steer carcase. RBY EBVs are reported as differences in percentage (%) yield.

Larger, more positive, RBY EBVs are generally more favourable.

Intramuscular Fat

Intramuscular Fat (IMF) EBVs are estimates of genetic differences between animals in intramuscular fat (marbling) at the 12/13 rib site in a standard weight steer carcase. IMF EBVs are reported as differences in percentage (%) IMF.

Larger, more positive, IMF EBVs are generally more favourable.

For markets where marbling is important (e.g. Japanese B2/B3 market, restaurant trade, MSA etc..), higher IMF EBVs can contribute significantly to carcase value.

Shear Force

Shear Force EBVs are estimates of genetic differences between animals in meat tenderness. Shear Force EBVMs are expressed as differences in the kilograms of shear force that are required to pull a mechanical blade through a piece of cooked meat and are calculated from shear force measurements (i.e. objective abattoir measures of meat tenderness), gene marker information and flight time records.

Lower, more negative, Shear Force EBVs are more favourable. That is, lower EBVs indicate that less shear force is required and hence the meat is more tender.

Other

Net Feed Intake

Feed efficiency is recognised as one of the most economically important production traits, both in grazing enterprises and feedlot operations. Research has shown that large variation exists in feed efficiency between animals, and that a proportion of this variation is due to genetic differences.

BREEDPLAN produces two EBVs relating to feed efficiency –Net Feed Intake (Post Weaning) and Net Feed Intake (Feedlot Finishing). Both EBVs are calculated from information collected in feed efficiency trials. Whilst there is a positive relationship between the two EBVs, some animals do rank differently for feed efficiency in the two different scenarios.

(i) Net Feed Intake (Post Weaning)

Net Feed Intake Post Weaning (NFI-P) EBVs are estimates of genetic differences between animals in feed intake at a standard weight and rate of weight gain when animals are in a growing phase, and is expressed as kilograms (kg) of feed intake per day.

Lower, or more negative, NFI-P EBVs are more favourable.

(ii) Net Feed Intake (Feedlot Finishing)

Net Feed Intake Feedlot Finishing (NFI-F) EBVs are estimates of genetic differences between animals in feed intake at a standards weight and rate of weight gain when animals are in a feedlot finishing phase, and is expressed as kilograms (kg) of feed intake per day.

Lower, or more negative, NFI-F EBVs are more favourable.

Structural Soundness

Animals should conform to certain structural requirements to ensure high levels of production and adaptability to the environment. When structural integrity is not maintained, substantial financial loss can occur. These losses could be due to such things as complete bull breakdown, bulls not being able to cover the allocated cows resulting in lower conception rates, steers being unable to finish a long feeding program, or cows with badly structured udders being unable to rear their calves properly.

Structural Soundness EBVs are provided for five important structural traits:
• Front Feet Angle (FA)
• Front Feet Claw Set (FC)
• Rear Feet Angle (RA)
• Rear Leg Hind View (RH)
• Rear Leg Side View (RS).

Structural Soundness EBVs are reported as an estimate of genetic differences between animals in the percentage of progeny that will have a desirable score for a particular structural trait and are calculated from structural scores recorded on animals by an accredited scorer when the animals are younger than 750 days of age.

Higher Structural Soundness EBVs are more favourable. That is, higher EBVs indicate a greater percentage of progeny with a desirable score for that particular trait.

Animals with very low (i.e. negative) EBVs for each trait are identified with an additional flag to indicate the nature of their structural fault:

• Front Feet Angle and Rear Feet Angle EBVs are identified with a flag of ‘ST’, indicating increased probability of steep feet angle and ‘SH’, indicating increased probability of shallow feet angle.
• Front Feet Claw Set EBVs are identified with a flag of ‘OD’, indicating increased probability of open divergent claws and ‘SC’, indicating increased probability of scissor claws.
• Rear Leg Hind View EBVs are identified with a flag of ‘BL’, indicating increased probability of bow legged rear legs and ‘CH’, indicating increased probability of cow hocked rear legs.
• Rear Leg Side View EBVs are identified with a flag of ‘SR’, indicating increased probability of straight rear legs and ‘SI’, indicating increased probability of sickle hocked rear legs.

Docility

Docility EBVs are estimates of genetic differences between animals in temperament. Docility EBVs are expressed as differences in the percentage of progeny that will be scored with acceptable temperament (i.e. either ‘docile’ or ‘restless’) and are calculated from temperament scores recorded on animals using either a crush or yard test when the animals are between 60 and 400 days of age (preferably at weaning).

Docility in cattle is the way cattle behave when being handled by humans or put in an unusual environment such as being separated from the mob in a small yard. What we define as poor docility is a survival trait in the wild – fear of anything unusual and the desire to escape. In domesticated cattle it is exhibited as flightiness.

Importantly, docility is a highly heritable trait and so can be improved genetically.

Higher, more positive, Docility EBVs are more favourable.

Flight Time

Flight Time EBVs are estimates of genetic differences between animals in temperament. Flight Time EBVs are expressed as differences in the number of seconds taken for an animal to travel approximately two metres after leaving the crush. They are calculated from flight time measurements that have been recorded on animals using specialised flight time equipment.

Flight time is a simple, cost-effective and easy to record objective measurement of temperament. Research has shown that in addition to the obvious benefits for ease of handling and management, animals with longer flight time (i.e. superior temperament) also have superior meat tenderness Higher (i.e. longer) Higher Flight Time EBVs are more favourable. That is, higher EBVs indicate a longer time taken to exit the crush and hence better temperament.

Adapted from ‘A Basic Guide to BREEDPLAN EBVs’ .

Further information

BREEDPLAN

Website: www.breedplan.une.edu.au
Ph: (02) 6773 3555
Email: breedplan@abri.une.edu.au

Tropical Beef Technology Services

Website: www.tbts.une.edu.au
Ph: (07) 4927 6066
Email: office@tbts.une.edu.au

Meat & Livestock Australia’s genetics hub

Website: www.genetics.mla.com.au including short ‘how-to’ animated videos on:
• Getting started with breeding values
• Using breeding values to find bulls on BREEDPLAN
• Putting breeding values into practice