Estimates of Breed Differences and Genetic Parameters of Pig Temperament Scores during a Performance Test and its Relationship with Performance Traits
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2010-04-12
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Abstract
YODER, CHAD LEWIS. Estimates of Breed Differences and Genetic Parameters of Pig
Temperament Scores during a Performance Test and its Relationship with Performance
Traits. (Under the direction of Dr. M. Todd See).
The objective of this study was to estimate breed differences for temperament scores
during a performance test, and estimate the genetic parameters associated with temperament
and performance traits. Chester White (CW), Duroc (D), Landrace (L), and Yorkshire (Y)
boars and gilts (n=4,774) were used to estimate breed differences in temperament and genetic
parameters. Adjusted backfat (BF), adjusted loin depth (LD), days to 113.4 kilograms
(DAYS), estimated percent fat-free lean (LEAN), and three temperament scores: load score
(LS), scale score (SS), and vocal score (VS) were recorded. All scores ranged from 1 (calm)
to 5 (highly excited). While loading into the scale LS was recorded; SS and VS were
recorded while in the scale as ultrasound measurements were taken.
Temperament scores were evaluated as categorical traits with statistical models
including fixed effects of breed, sex, contemporary group (barn-farm-test date), and off-test
weight as a covariate. Order in which pigs were loaded into the scale was included in the
model for LS. After initial analysis it was determined VS was best described as two
categories, vocal and non-vocal, and was analyzed as a binary trait. Statistical models for BF,
LD, DAY, and LEAN included fixed effects of breed, sex, and LS, SS, or VS. Growth rate
was adjusted to 113.4 kilograms, while BF and LD were adjusted to the mean weight of the
respective breed. Breed differences for LS, SS, and VS were estimated as odds ratios.
The odds of increased LS were greater for L (1.62, 1.30; P < 0.01) than D and Y
respectively. Landrace had a greater (P < 0.01) probability of a higher SS and VS compared
to CW (1.77, 2.37), D (3.31, 3.94) and Y (2.51, 2.46). Yorkshire had greater odds of
increased LS (1.25), SS (1.32), and VS (1.60) than D. Chester White had a greater
probability of increased LS and SS than D (1.58, 1.87) and Y (1.26, 1.42). Chester White
were 1.66 (P < 0.01) times more likely to have a higher VS than D.
Genetic models for LS, SS, VS and performance traits were the same as those used to
estimate breed differences. However, breed as a fixed effect was excluded and separate
analysis was conducted for each breed, and temperament scores were not included in models
for performance traits. Variance components were estimated using THRGIBBS1F90 with
150,000 cycles, a 20,000 cycle burn in period, and every 20th sample was stored. Estimates of
parameters of interest were obtained as statistics of their respective posterior distributions.
Direct heritability estimates were (CW, D, L, Y): LS (0.05, 0.06, 0.06, 0.05), SS
(0.22, 0.09, 0.09, 0.10), and VS (0.27, 0.24, 0.37, 0.21). Estimated heritability of LS was low
regardless of breed. Heritability estimates for SS, were low with the exception of CW.
Heritability estimates for VS were moderate. Direct genetic correlations between SS and VS
obtained in a bivariate model were positive and moderate (0.30 to 0.75) indicating that pigs
that are more active in the scale are also more vocal. Genetic correlations between
temperament traits varied between breed, but were generally moderate and positive. The
genetic correlations between LS, SS, and VS with BF, LD, DAYS, and LEAN ranged from -
0.78 to 0.56, and varied among breeds. Based on these results selection for temperament
scores collected during a performance test provide potential to alter pig behavior. However,
progress in performance traits may be affected if selection for temperament is practiced,
while current selection criteria may result in changes in temperament.
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Keywords
pigs, temperament, performance, breeds
Citation
Degree
MS
Discipline
Animal Science