Sheep Breeding Values Explained
Australian Sheep Breeding Values (ASBV's) are an estimate of an animal’s true breeding value based on pedigree and performance recorded information. They are essentially a projection of how that animals progeny will perform for a range of traits. This is more effective than raw data as it accounts for environmental (i.e. feed, management, seasonal) effects.
We select with both ASBVs and visually, as both are equally as important. We make sure to collect all this data in the most accurate way possible, ensuring the ASBVs generated from this data are of high accuracy.
Growth Breeding Values
Weaning Weight (kg) WWT
Estimates the genetic difference between animals in live-weight at 100 days of age. The higher the better.
Post Weaning Weight (kg) PWT
Estimates the genetic difference between animals in live-weight at 225 days of age. The higher the better.
Yearling Weight (kg) YWT
Estimates the genetic difference between animals in live-weight at 360 days of age.
Post Weaning Fat Depth (mm) PFAT
Estimates the genetic difference in GR fat depth at 45kg live-weight Desired level depends on breeding aims. Should not be extreme either way.
Post Weaning Eye Muscle Depth (mm) PEMD
Estimates the genetic difference in eye muscle depth at the C site in a live-weight animal. The higher the better.
Yearling Eye Muscle Depth (mm) YEMD
Estimates the genetic difference in EMD at the C site at 60kg live-weight Level depends on breeding aims.
Yearling Fat Depth (mm) YFAT
Estimates the genetic difference in GR fat depth at 60kg live-weight Level depends on breeding aims. Should not be extreme either way.
Birth Weight (kg) BWT
Estimates the genetic difference between animals in weight at birth. In terminal (White Suffolk) sires, the lower the better, as this decreases the chance of having lambing issues. But extremely low can also be a problem (more so in non-terminal breeds).
Maternal Weaning Weight (kg) MWWT
Estimates the genetic difference between the animals daughters weaning weights and their potential to provide milk and a better maternal environment. The higher the better.
Number of Lambs Weaned (%) NLW
Estimates the genetic difference between animals for number of lambs weaned at each lambing opportunity. This not only accounts for fertility, but also survivability. The higher the better.
Yearling Number of Lambs Weaned (%) YNLW
Rams with more positive YNLW ASBVs will sire daughters that wean a higher percentage of lambs as ewe lambs. Ideal for people looking to maximise their ewe lamb joining.
Lambing Ease Direct (%) LE DIR
Describes how easily a sire’s lambs will be born, with a positive number preferred. LE DAU is how easily the sires daughters lambs will be born. The higher the better for both.
Wool Breeding Values
Yearling Fleece Weight (%) YGFW or YCFW
Estimate the genetic difference in fleece weight at 360 days of age. The higher the Better. (picture on right is raw data collection from 7 months growth on ewe lambs)
Yearling Fibre Diameter (micron) YFD
Estimates the genetic difference in fibre diameter at 360 days of age. Depends on breeding aims, usually the lower the better.
Yearling Fibre Diameter Coefficient of Variation (%) YFDCV
Estimates the genetic difference in fibre diameter coefficient of variation at 360 days of age. Animals with a lower YFDCV will genetically have a lower variation in fibre diameter (preferred).
Yearling Staple Strength (N/Kt) YSS
Estimates the genetic difference in staple strength at 360 days of age. The higher the better.
Yearling Staple Length (mm) YSL
Estimates the genetic difference in staple length at 360 days of age. Level depends on breeding aims.
Management / Ease Of Care Traits
Adult Weight (kg) AWT
Estimates the genetic difference between animals in live-weight as adults. A small to medium sized animal (with the same production breeding values as a bigger animal) is more efficient and easier to handle.
Worm Egg Count (%) PWEC & YWEC
Value of an animals genes for carrying worm burdens – a combination of being genetically less likely to pick up worms & being able to cope immunologically with the worm burden. The lower the better.
Early Breech Wrinkle (EBWR)
Wrinkle trait ASBVs have been developed by using breech and body wrinkle score & estimates the genetic difference. Negative is the preferred trait to reduce breech wrinkle. Useful to move away from mulesing.
Dag Score (LDAG)
Estimates the genetic difference of the likelihood of dags. A more negative ASBV is desirable.
Breach Cover (BCOV)
Refers to animals’ ability to produce less wool around the breach area. A more negative ASBV is desirable.
Eating Quality and Meat Yield
Lean Meat Yield (%) LMY
Rams with more positive LMY ASBVs produce lambs that have a higher Lean Meat Yield percentage at slaughter.
Intramuscular Fat (%) IMF
Rams with more positive IMF ASBVs produce progeny with higher levels of intramuscular fat. (IMF is a measure of the chemical fat percentage in the loin muscle of a lamb and is often referred to as marbling. IMF has been shown to have a significant impact on the flavor, juiciness, tenderness and overall likeability of lamb).
Shear Force (kg) SF5
Rams with more negative SF ASBVs produce lambs with more tender meat. (Shear Force is a measure of the force or energy required to cut through the loin muscle of lamb after 5 days of ageing, the ASBV is reported in deviations of kilograms of force.
Lamb 2020 Eating Quality Index (LEQ)
The Lamb 2020 Eating Quality index is targeted at terminal producers interested in improving the meat eating quality of their prime lambs while continuing to improve production traits in a balanced way. The LEQ index is based on the same production targets as TCP but adds worm egg count (WEC).
Terminal Carcass Production Index (TCP)
This index has been created to assist producers to achieve both gains in their major production traits, such as post-weaning weight and muscling, as well as ensuring consumer satisfaction from lamb is maintained through focusing on key eating quality traits such as shear force (tenderness) and intramuscular fat (marbling). Unlike LEQ this does not include worm resistance (WEC).
Maternal Dollar Index (Mat$)
This index is aimed at maternal breeds in place of the breed specific indexes such as Border$ and Coopworth$ The MAT$ index balances the key economic traits relevant to most maternal breeds.
Maternal Carcass Production Plus (MCP+)
The Maternal Carcase Production + (MCP+) index targets self-replacing production systems where maintaining the same adult weight and fleece weights are seen as important at the same time as improving carcase traits. A slight increase in clean fleece weight is expected. This index aims to reduce WEC as it is assumed in the index most enterprises are located in high rainfall areas and/or high input management systems. The contribution of each trait to economic gain is expressed in the graph along with the predicted genetic gain over 10 years.
Fibre Production Indexes (FP & FP+)
The Fibre Production (FP & FP+) indexes rank animals on their ability to produce merinos for a wool production operation.
The index is aimed at those producers whose majority of sheep income come from their wool clip. It is for self-replacing merino flocks who keep their wethers as part of their wool producing flock.
What makes up the FP and FP+ indexes? See the table.
Merino Production Index (MP & MP+)
The Merino Production (MP & MP+) indexes rank animals on their ability to produce progeny for a fine wool operation that has significant surplus sheep sales.
The index is aimed at those producers whose sheep income is a balance of both wool and surplus sheep sales. It is for self-replacing merino flocks who do not keep their wethers to produce wool.
What makes up the MP and MP+ indexes? See the table.
Dual Purpose Index (DP & DP+)
The Dual Purpose (DP & DP+) indexes rank animals on their ability to produce merinos for a dual purpose operation.
These indexes are aimed at those producers whose majority of sheep income comes from sheep sales. It is for self-replacing merino flocks that do not keep their wethers and also join a portion of their ewes to terminal sires for lamb production.
What makes up the DP and DP+ indexes? See the table.
Other Abbreviations in the Catalogue
RT: Rear Type: Single (S), Twin (TW), Triplet (TR)
CM: Conception Method: Natural (N),
Artificial Insemination (AI), Pen Mate (PEN),
Embryo Transfer (ET)