PTA mobility was highly correlated with udder composite.

PTA mobility showed a moderate, positive correlation with production, productive life, and net merit.

n Phenotypic and genetic correlation of mobility with 16 linear type traits and final score

Genetic evaluation of mobility for Brown Swiss dairy cattleG. R. Wiggans1, J. R. Wright*1, C. J. Muenzenberger2, and R. R. Neitzel2

1Animal Improvement Programs Laboratory, Agricultural Research Service, USDA, Beltsville, MD 20705-23502Brown Swiss Cattle Breeders Association of the USA, Beloit, WI, USA

50 53 56 59 62 65 68 71 74 77 80 83 86 89 92 950

1,000

2,000

3,000

4,000

5,000

Abstr.T43

INTRODUCTION Ability of a cow to easily move about is a

vital aspect to her health and production

Brown Swiss Cattle Breeders Association (BSCBA) began scoring mobility in June 2007 as a potential addition / correction to foot and leg composite

Defined as a global measure indicating the ease of movement and comfort while standing

Evaluated while the cow is walking, when possible

Scored on a scale from 50 to 99 by BSCBA appraisers

Estimate genetic parameters for mobility

Determine the relationship between mobility and linear type traits

Calculate genetic evaluations for mobility

CONCLUSIONS & APPLICATIONS Use of mobility trait evaluations may

increase the accuracy of predictions of productive life by increasing the accuracy of the foot and leg composite (FLC).

PTA mobility seems to more accurately reflect ideal body structure than the current FLC since it accounts for ease of movement, flex to hock, rear leg rear view, and correct thurl placement.

Field observations of sire daughters’ feet and leg traits seem to be more consistent with PTA mobility than with FLC.

BSCBA will replace FLC with PTA mobility in the calculation of their breed index ranking (Progressive Performance Ranking; PPR) beginning August 2012.

A study conducted with 6,152 Milking Shorthorn records from 4,213 cows yielded similar results, including a h2 of 0.18.

http://aipl.arsusda.gov

OBJECTIVES

DATA & METHODSEDITS:

Appraisal scores from June 2007 to June 2011

Cow must be < 69 month old and have been scored in first or second lactation

No missing scores for final score, 16 linear traits, and mobility (variance estimation only)

After edits, 32,710 records of 19,472 cows in 819 herds

VARIANCE COMPONENT MODEL:

Multi-trait analysis using canonical transformation, multiple diagonalization, and a decelerated expectation-maximation REML algorithm

Fixed effects for:

herd – appraisal date (2,109 groups)

appraisal age within parity (46 groups)

lactation stage within parity (21 groups)

Random effects for:

animal, permanent environment, residual

GENETIC EVALUATION MODEL:

Multi-trait animal model with same effects as variance component estimation plus addition of herd-sire interaction effect

RESULTS (cont.)RESULTS RESULTS (cont.)

•Distribution of mobility scores (2007 to 2011)

•Distribution of PTA mobility for 840 bulls with at least 1 daughter scored

Mobility scoreTh

ou

san

ds o

f re

cord

s

Mean=83.7Std dev=4.3

Phenotypic correlation

Genetic correlation

Final score 0.63 0.78Stature 0.14 0.17Strength 0.14 0.22Dairy Form 0.13 0.40Foot angle 0.30 0.47Rear leg (side view) -0.10 -0.10Body depth 0.20 0.34Rump angle -0.07 -0.13Thurl width 0.12 0.20Fore udder attachment 0.19 0.31Rear udder height 0.23 0.46Rear udder width 0.24 0.51Udder depth 0.02 -0.01Udder cleft 0.09 0.23Front teat placement 0.10 0.18Teat length 0.01 0.03Rear legs (rear view) 0.38 0.72

-2 -1.7 -1.4 -1.1 -0.8 -0.5 -0.2 0.1 0.4 0.7 1 1.3 1.60

10

20

30

40

50

60

70

80

90

Mean=0.0Std dev=0.5

Num

ber

of

bu

lls

Milk 0.41 Final score 0.69Fat 0.36 Stature 0.48Protein 0.40 Strength 0.24Productive life 0.31 Dairy Form 0.54Somatic cell score -0.07 Foot angle 0.41Protein percent -0.12 Rear leg (side view) -0.13Fat percent -0.17 Body depth 0.33Net merit 0.39 Rump angle -0.12

Thurl width 0.32Composites: Fore udder attachment 0.53 Feet / legs 0.35 Rear udder height 0.59 Udder 0.51 Rear udder width 0.55 Size 0.43 Udder depth 0.37

Udder cleft 0.36Milking speed 0.29 Front teat placement 0.43

Teat length -0.29Rear legs (rear view) 0.50

● Correlation of PTA mobility with PTA of other traits

2012

● Phenotypic estimated standard deviation (SD), repeatability (R) and heritability (h2) for mobility, final score, and 16 linear type traits

SD R h2

Final score 3.0 0.74 0.33Stature 6.9 0.57 0.37Strength 6.7 0.26 0.13Dairy Form 7.6 0.29 0.14Foot angle 6.7 0.21 0.09Rear leg (side view) 6.3 0.29 0.14Body depth 6.5 0.37 0.21Rump angle 6.7 0.31 0.18Thurl width 6.0 0.28 0.16Fore udder attachment 7.7 0.40 0.20Rear udder height 6.8 0.37 0.18Rear udder width 6.6 0.29 0.15Udder depth 5.5 0.49 0.27Udder cleft 7.6 0.40 0.20Front teat placement 7.3 0.42 0.24Teat length 6.9 0.50 0.34Rear legs (rear view) 6.2 0.13 0.06Mobility 4.2 0.46 0.21

Heritabilities ranged from 0.06 (rear legs rear view) to 0.37 (stature) and were similar to the values used in the present Brown Swiss type evaluation system.

Heritability of mobility was moderate (0.21), as was the repeatability (0.46).

Phenotypic SD was somewhat lower in final score and mobility than in the linear traits, likely due to difference in scoring method.

Less than 5% of mobility scores were below 75 or above 90.

Evaluated bulls with ≥1 daughter differed by as much as 3.4 points.

PTA mobility of Active AI bulls ranged from -0.7 to+1.2 (not shown).

Traits most highly correlated with mobility were final score, rear legs rear view, rear udder height and rear udder width.

PTA mobility