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MMFS Manual

Tool 9.1 ASBV explanations and examples

ASBV explanations and examples

Sheep Genetics analyses and reports over 90 traits between the MERINOSELECT, DOHNE, LAMBPLAN Maternal and LAMBPLAN Terminal databases, which are reported as Australian Sheep Breeding Values (ASBVs).

ASBVs are a prediction of an animal’s genetic merit for a particular trait and an indication of how an animal’s progeny will perform based on the genes they will pass on. ASBVs are generated from the data, pedigree and genomic information collected by Sheep Genetics members to provide a prediction of genetic merit, accounting for heritability and correlations, as well as non-genetic factors (known environmental factors), to determine an animal’s genetic merit for a range of important traits.

ASBVs are comparable across flocks, though an ASBV may be different to the animal's actual performance, as actual performance is a combination of both genetic and environmental influences.

Most ASBVs are reported and displayed with the same units used to measure the trait. For example, the ASBV for fibre diameter (FD) is reported in microns, the ASBV for weight (WT) is reported in kilograms, and the ASBVs for traits that are measured in visual scores are reported using scores. Some traits, like clean fleece weight (CFW) and fibre diameter coefficient of variation (DCV) are provided as percentages.

There are ASBVs for many different traits that impact the performance and profitability of sheep enterprises. These include:

  • reproduction
  • growth
  • carcase
  • eating quality
  • wool
  • health and welfare.

Examples of traits from each of these categories follows, with an explanation of the trait, correlations and associated information.

Reproduction traits

Trait

Reproduction trait group

Conception

Scrotal Circumference

Condition Score

Litter Size

Gestation Length

Lambing Ease

Ewe Rearing Ability

Weaning Rate

ASBV trait code

YCON

CON

PSC

YSC

CS

YLS

LS

GL DIR

GL DTR

LE DIR

LE DTR

YERA

ERA

YWR

WR

Example ASBV

0.32

0.09

6.38

4.96

0.67

0.26

0.41

0.62

-0.41

1.22

0.31

0.05

0.03

0.48

0.15

Example Acc (%)

58

46

59

54

54

48

51

64

64

48

50

38

44

51

57

Example Av

0.24

0.03

3.77

2.95

0.12

0.14

0.15

-0.2

-0.26

-1.29

-3

0.03

0.01

0.37

0.15

Age stages available

Yearling

Adult

Post-weaning

Yearling

Adult

Yearling

Adult

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

Definition

The genetic difference between sires to produce daughters that in turn conceive more lambs.

The genetic difference in scrotal circumference measured either at post-weaning or yearling.

The condition of the ewe at joining.

The genetic difference between rams to sire daughters who have larger litters.

The difference between sires for the gestation length of their progeny.

The difference between sires for the gestation length of their daughters’ subsequent pregnancies.

The genetic difference between rams in the ease of their progeny to be born.

The genetic difference between rams or the ease of their daughters during lambing.

The genetic difference between animals for rearing ability

The genetic difference between animals for the number of lambs weaned per ewe joined, as a yearling.

The genetic difference between animals for the number of lambs weaned per ewe joined, as an adult.

Unit

Number of lambs per ewe joined

Centimetres (cm)

Body condition score

Number of lambs per ewe lambing

Percentage (%)

Percentage (%)

Number of lambs per ewe lambing

Number of lambs per ewe joined

Number of lambs per ewe joined

Favourable correlation

Better lifetime reproductive success
Smaller adult weight
High early growth

Improved reproductive rate

Improved conception rates

Better lifetime reproductive success
Shorter gestation length
Lower birth weight
Less lambing difficulty

N/A

N/A

Higher lamb survival

N/A

N/A

Unfavourable correlation

N/A

N/A

N/A

Higher adult weights

Lower muscle

N/A

N/A

N/A

N/A

N/A

 

Growth traits

 

Growth trait group 

Trait

Birth Liveweight

Weaning Liveweight

Post-weaning Liveweight

Yearling Liveweight

Adult Liveweight

ASBV trait code

BWT

WWT

PWT

YWT

AWT

Example ASBV

0.2

10.51

19.5

15.78

18

Example Acc (%)

63

65

60

59

55

Example Av

0.34

9.56

14.56

14.92

17.46

Age stages available

Birth, weaning, post-weaning, yearling, hogget, adult

Definition

The genetic difference in liveweight measured at birth.

The genetic difference in liveweight measured at weaning.

The genetic difference in liveweight measured at post weaning.

The genetic difference in liveweight measured at yearling.

The genetic difference in liveweight measured at adult

Unit

Kilograms (kg)

Kilograms (kg)

Kilograms (kg)

Kilograms (kg)

Kilograms (kg)

Favourable correlation

Higher lifetime growth

Marketable at earlier ages, higher reproductive output, higher lean meat yield, higher fleece weight

Marketable at earlier ages, higher reproductive output, higher lean meat yield, higher fleece weight

Marketable at earlier ages, higher reproductive output, higher lean meat yield, higher fleece weight

Marketable at earlier ages, higher reproductive output, higher lean meat yield, higher fleece weight

Unfavourable correlation

too low – lower lamb survival
too high – longer gestation length & higher lambing difficulty

increase in adult weight, lamb birthweight increases, fibre diameter goes up

increase in adult weight, lamb birthweight increases, fibre diameter goes up

increase in adult weight, lamb birthweight increases, fibre diameter goes up

increase in adult weight, lamb birthweight increases, fibre diameter goes up

 

Carcase traits

 

Carcase trait group

Trait

Eye Muscle Depth

Fat

Carcase Weight

ASBV trait code

EMD

FAT

CWT

Example ASBV

3.32

0.14

6.02

Example Acc (%)

64

64

59

Example Av

1.87

-0.39

5.08

Age stages available

Post-weaning, yearling,
hogget

N/A

Definition

The genetic difference between animals for eye muscle depth at the C site.

The genetic variation of fat depth at the C site.

The genetic difference in weight measured on the carcase.

Unit

Millimetres (mm)

Kilograms (kg)

Favourable correlation

Lean meat yield, dressing percentage, worm resistance

Improved reproductive rate, CV of Fibre diameter goes down, intramuscular fat improves, eating quality improves

Marketable at earlier ages, higher reproductive output, higher lean meat yield, higher fleece weight

Unfavourable correlation

Growth, eating quality

Carcase fatness goes up and fleece weight goes down

Increase in adult weight, birth weight increases, eating quality

 

Eating quality traits

 

Eating quality trait group

Trait

Lean Meat Yield

Intramuscular Fat

Shear Force

Dressing Percentage

ASBV trait code

LMY

IMF

SHEARF5

DRESS

Example ASBV

4.37

-0.55

5.26

2.86

Example Acc (%)

53

48

52

55

Example Av

3.24

-0.46

2.42

2.12

Age stages available

N/A

N/A

N/A

N/A

Definition

The genetic difference between animals for the amount of lean meat yield derived from the carcase.

The genetic difference between animals for the amount of intramuscular fat or marbling expressed in the meat.

A measure of the force required to cut through the loin muscle after 5 days of aging, indicating tenderness.

The genetic difference between animals for dressing percentage as measured at slaughter.

Unit

Percentage (%)

Percentage (%)

Newton-metre (nM)

Percentage (%)

Favourable correlation

Growth increases, higher proportion of saleable meat

Reduced birth weight, shear force decreases

IMF increases

Growth increases, increased lean meat yield

Unfavourable correlation

Intramuscular fat decreases, shear force increases and birthweight increases

Growth decreases, carcase decreases and lean meat yield decreases

Growth decreases, lean meat yield decreases, worm resistance decreases

Intramuscular fat decreases, shear force increases, birthweight increases

 

Wool traits

Trait

Wool trait group

Greasy Fleece Weight

Clean Fleece Weight

Fibre
Diameter

Staple Strength

Fibre
Diameter CV

Staple
Length

ASBV trait code

GFW

CFW

FD

SS

DCV

SL

Example ASBV

24.23

11.38

-3.76

-4.61

0.13

3.84

Example Acc (%)

70

66

82

56

72

62

Example Av

14.06

16.67

-0.99

0.66

-0.87

8.13

Age stages available

Post-weaning, yearling, hogget, adult

Definition

The genetic differences between animals for greasy fleece weight.

The genetic difference a between animals for clean fleece weight.

The genetic difference between animals for fibre diameter.

The genetic difference between animals for staple strength.

The genetic difference between animals for fibre diameter CV.

The genetic difference between animals for staple length.

Unit

Percentage (%)

Percentage (%)

Micron (µm)

Newtons per kilotex (N/kt)

Percentage (%)

Millimetres (mm)

Favourable correlation

Body weight, growth and improved staple length

Body weight, growth and improved staple length

NA

Higher fleece weight, lower fibre diameter CV

Resistance to worms, staple strength, reduced fleece rot, less body strike

Increased fleece weight, higher growth, less fleece rot

Unfavourable correlation

Higher fibre diameter, increased wrinkle, reduced fat, reduced reproduction

Higher fibre diameter, increased wrinkle, reduced fat, reduced reproduction

Lower fleece weight, lower body weight, reduced staple strength, reduced staple length

Higher fibre diameter

Lower fleece weight

Reduced reproduction, higher fibre diameter

 

Health and welfare traits

Trait

Health and welfare trait group

 

Breech Wrinkle

Dag

Breech Cover

Worm Egg Count

ASBV trait code

BWR

DAG

BCOV

WEC

Example ASBV

-2.11

-0.19

-0.47

-53.13

Example Acc (%)

64

66

69

51

Example Av

-0.21

-0.1

-0.1

-15.37

Age stages available

Early

Late

Early

Weaning, post-weaning, yearling, hogget

Definition

The genetic difference between animals for the amount of wrinkle in the breech area.

The genetic difference between animals for the amount of dag in the breech area.

Genetic difference between animals for the amount of bare cover in the breech area.

The genetic difference between animals for worm egg count measured

Unit

Score

Percentage (%)

 

Favourable correlation

Reduced fly strike susceptibility, higher staple length, improved reproduction

Reduced fly strike susceptibility, reduced crutching, more saleable wool, less costs due to wool washing etc.

Reduced flystrike
Improved reproduction

Higher muscling, higher staple strength

Unfavourable correlation

Lower fleece weight

N/A

N/A

N/A