What are Wagyu Breeding Values?
Wagyu Breeding Values (WBVs) provide an estimate of an animal’s genetic merit for a range of important traits. They help us compare the genetics of animals that will be displayed in progeny. In turn this allows breeders to make more informed selection decisions rather than relying on visual assessment or pedigree information alone.
WBVs currently provide information across several key categories, including:
- Calving
- Growth traits
- Maternal
- Fertility
- Carcase
By understanding these values, breeders can select animals that best align with their breeding objectives and production systems.
Understanding WBV Values
“What does a positive or negative WBV actually mean?”
WBVs estimate an animal’s genetic merit for a specific trait relative to the Wagyu population. They do not predict the exact performance of the animal itself, but rather the genetic contribution it is expected to pass on to its progeny.
In simple terms, WBVs help answer the question:
“How much higher or lower do we expect this animal’s progeny to perform for a trait, compared with the progeny of another animal, due to genetics alone?”
WBVs are expressed relative to a breed baseline. As a result, WBVs may be either positive or negative, reflecting whether an animal’s genetic merit for a trait is above or below the baseline. This should not be confused with the breed average WBV or percentiles which are more relevant for comparing and benchmarking genetics.
A common source of confusion is the interpretation of negative WBVs. For example, a negative Rump Fat WBV does not mean an animal has “negative fat”. Rather, it indicates the animal is genetically expected to produce progeny with less rump fat than an animal with a positive WBV.
Likewise, a positive WBV indicates an animal is genetically expected to produce progeny with higher levels of that trait compared to an animal with a negative WBV. The further a WBV sits above or below the breed baseline, the greater the expected genetic difference.
It is also important to remember that a WBV estimates genetic potential, not actual performance. The eventual performance of an animal will still be influenced by factors such as nutrition, management, health and environment. WBVs estimate only the animal’s genetic contribution to the result.
Importantly, negative WBVs do not indicate a poor animal, nor do positive WBVs indicate a superior animal in every situation. The most desirable WBV will depend on your breeding objectives, production system and target market requirements.
Comparing Animals Using WBVs
WBVs are most useful when comparing animals. The expected differences described by WBVs assume progeny are managed under similar environmental and management conditions. This allows breeders to assess the genetic difference between animals separately from the influence of factors such as nutrition, health and management.
Example 1: 200-Day Weight (200D)
| Animal | 200D WBV |
| Bull A | +25 |
| Bull B | +5 |
The difference between Bull A and Bull B is 20 kg.
Because each parent contributes half of its genetics to its offspring, the expected difference in progeny performance is approximately half the WBV difference.
In this example, progeny from Bull A would be expected to weigh approximately 10kg more at 200 days of age than progeny from Bull B, assuming they are raised under similar environmental and management conditions.
While both bulls have positive values, the important point is that Bull A is genetically superior for 200-day growth when compared directly with Bull B.
Example 2: Net Feed Intake
| Animal | NFI WBV |
| Bull C | 0.71 |
| Bull D | -0.79 |
The difference between the two bulls is 1.50.
Because each parent contributes half of its genetics to its offspring, the expected difference in progeny performance is approximately half the WBV difference.
Unlike many growth traits, lower NFI values are generally more desirable, as they indicate animals that consume less feed than expected for their size and growth rate.
In this example, progeny from Bull D would be expected to be genetically more feed efficient than progeny from Bull C, assuming they are managed under similar environmental and management conditions.
Although Bull C sits above the breed average of -0.08 and Bull D sits below it, Bull D has the more favourable NFI WBV because it is lower. This highlights an important point when using WBVs: higher is not always better. The preferred direction of a trait will depend on what the trait measures and your breeding objectives.
What the Traits Mean
Calving Traits
Gestation Length (GL)
Gestation Length WBVs estimate genetic differences between animals in the number of days from conception to calving.
Shorter gestation lengths are generally associated with:
- Lower birth weights
- Improved calving ease
- Better re-breeding performance of dams
- In some cases, heavier weaning weights due to additional days of post-natal growth
It is important to note that while natural matings may be observed, the exact date of conception cannot be confirmed. As a result, gestation length analyses are based on AI and controlled mating records rather than natural matings.
Birth Weight (BW)
Birth Weight WBVs estimate genetic differences between animals in expected calf weight (kg) shortly after birth.
Animals with lower Birth Weight WBVs are expected to produce progeny with lighter birth weights. Birth weight is an important trait because it can influence:
- Calving ease
- Calf survival
- Heifer survival
- Costs associated with assisted or difficult births
Growth Traits
200– Day Weight (200D)
200-Day Weight WBVs estimate genetic differences between animals in expected live weight (kg) at 200 days of age.
Higher 200D WBVs indicate an animal is likely to produce progeny with heavier weights at 200 days. This is a key measure of early growth and reflects calf performance before weaning.
400– Day Weight (400D)
400-Day Weight WBVs estimate genetic differences between animals in expected live weight (kg) at 400 days of age.
Higher 400D WBVs indicate an animal is likely to produce progeny with heavier 400-day growth weights. This trait provides an indication of growth performance through the yearling stage and how animals continue to perform after weaning.
600- Day Weight (600D)
600-Day Weight WBVs estimate genetic differences between animals in expected live weight (kg) at 600 days of age.
Higher 600D WBVs indicate an animal is likely to produce progeny with heavier 600-day growth weights. This measure helps assess growth performance beyond early development and provides insight into how animals perform within a production system over a longer period.
Net Feed Intake (NFI)
Net Feed Intake WBVs estimate genetic differences in feed efficiency.
NFI measures the difference between an animal’s actual feed intake and the amount of feed it is expected to consume based on its size and growth rate.
Animals that consume less feed than expected have a lower NFI and are considered more feed efficient. Feed efficiency is particularly important in long-fed production systems where feed costs represent a significant proportion of total production expenses.
Maternal Traits
Mature Cow Weight (MCW)
Mature Cow Weight WBVs estimate genetic differences between animals in expected live weight (kg) of mature females, based on weights recorded between 870 and 3,900 days of age that fit the genetic evaluation model.
Higher MCW WBVs indicate an animal is likely to produce female progeny with heavier mature weights, while lower MCW WBVs indicate female progeny are likely to be lighter at maturity.
Mature Cow Weight is an important trait because it provides an indication of a cow’s mature size and associated maintenance requirements. Larger cows generally require more feed and energy to maintain body condition, which can increase production costs. Conversely, moderate weight cows may be more efficient in environments where feed availability is limited. As a result, MCW should be considered alongside other economically important traits to ensure cow size aligns with the production system and breeding objectives.
200- Day Maternal (200DM)
200-Day Maternal WBVs estimate genetic differences between animals in the maternal contribution to calf weight at 200 days of age (previously known as Milk).
Higher 200DM WBVs indicate an animal is likely to produce female progeny that wean heavier calves due to their superior maternal performance.
Maternal performance includes factors such as:
- Milk production
- Mothering ability
- Maternal behaviour and temperament
- The dam’s ability to support calf growth through to weaning
Fertility Traits
Scrotal Circumference (SC)
Scrotal Circumference WBVs estimate genetic differences between animals in scrotal circumference (cm) at 400 days of age.
Higher SC WBVs are generally associated with improved fertility and reproductive performance.
Bulls with larger scrotal circumferences tend to:
- Reach puberty earlier
- Produce greater volumes of semen
- Demonstrate improved semen quality
Research has also shown favourable relationships between scrotal circumference and female fertility, with daughters often reaching puberty earlier and exhibiting improved reproductive performance.
Carcase Traits
Carcase Weight (CW)
Carcase Weight WBVs estimate genetic differences between animals in expected hot carcase weight (kg), based on records collected from animals aged between 300 and 1,400 days that fit the genetic evaluation model.
Higher CW WBVs indicate an animal is likely to produce progeny with heavier hot carcase weights, while lower CW WBVs indicate progeny are likely to produce lighter carcases.
Carcase Weight is an important production trait as it directly influences the amount of saleable product and an animal’s ability to meet market specifications. Selecting for increased carcase weight can improve productivity and profitability, particularly in markets where heavier carcases attract premium returns. However, carcase weight should be considered alongside other economically important traits to ensure it aligns with overall breeding objectives and market requirements.
Eye Muscle Area (EMA)
Eye Muscle Area WBVs estimate genetic differences between animals in the area of the eye muscle (cm²), measured from carcase or ultrasound records collected on animals aged between 300 and 1,400 days that fit the genetic evaluation model.
Higher EMA WBVs indicate an animal is likely to produce progeny with larger eye muscle areas and greater muscling. EMA is an important indicator of lean meat yield, as animals with higher EMA measurements generally produce carcases with a greater proportion of saleable meat relative to bone and fat, contributing to improved carcase value and processing efficiency.
Rump Fat
Rump Fat WBVs estimate genetic differences between animals in expected rump fat depth (mm), measured from carcase or ultrasound records collected on animals aged between 300 and 1,400 days that fit the genetic evaluation model.
Higher Rump Fat WBVs indicate an animal is likely to produce progeny with greater fat depth at the rump site. Rump fat is an important carcase trait that influences fat cover, market suitability and overall carcase composition. Adequate fat cover helps protect the carcase during chilling, reducing the risk of cold shortening, and contributing to improved eating quality outcomes.
Marble Score (MS)
Marble Score WBVs estimate genetic differences between animals in the amount of visible intramuscular fat (marbling) within the eye muscle, collected from animals aged between 300 and 1,400 days that fit the genetic evaluation model.
Higher Marble Score WBVs indicate an animal is likely to produce progeny with greater marbling. Marble score is assessed visually using recognised grading systems or via correlated marbling percent from MIJ camera and is a key determinant of carcase quality and value in premium beef markets.
Marble Fineness (MF)
Marble Fineness WBVs estimate genetic differences between animals in the size and distribution of marbling particles within the eye muscle, measured from carcase records collected on animals aged between 300 and 1,400 days that fit the genetic evaluation model.
Higher Marble Fineness WBVs indicate an animal is likely to produce progeny with a finer and more evenly distributed marbling pattern. Finer marbling is characterised by a greater number of smaller intramuscular fat flecks dispersed throughout the muscle, rather than fewer, larger flecks.
Marble fineness is an important trait in premium beef markets, particularly Wagyu, where a fine and consistent marbling pattern is often associated with enhanced visual appeal and consumer preference. When considered alongside Marble Score, Marble Fineness provides additional information about marbling quality and overall carcase value.
Using WBVs Effectively
While WBVs provide valuable information about an animal’s genetic merit, no single trait should be considered in isolation. The most effective selection decisions balance multiple traits to align with breeding objectives, production systems and target market requirements.
When used alongside pedigree information, performance records and selection indexes, WBVs provide a powerful tool for achieving long-term genetic improvement within a herd.
