240 S
. Hermesch et al. Livestock Production Science 65 2000 239 –248
aspects of pork are of increasing importance. Histori- Performance records included the animal’s weight
cally, reproductive performance and meat quality at 21 days of age, at 18 weeks of age when the
characteristics were not considered as feasible breed- animal entered the test station and at 22 weeks of age
ing objectives due to low heritabilities, difficulty of recorded shortly before slaughter. The trait recorded
measurement and lack of economic importance before start of test was growth rate from three to 18
McPhee, 1982. However, decline in pork quality weeks of age ADG1. During this period of time
and lack of improvement in reproductive traits animals were group penned in contrast to station
suggests that these areas require greater considera- testing where animals were single penned. Traits
tion Ollivier et al., 1990. recorded in the test station included growth rate
Meat quality has become a major concern in pig ADG2, daily feed intake FDINT and feed conver-
production. In Australia, genetic improvement for sion ratio FCR. Pigs were fed ad libitum in both
meat quality has been achieved by selection against housing systems.
stress susceptible pigs using the halothane test. Carcass traits included real time ultrasound mea-
Studies in Europe showed that in the absence of the surements and measurements taken in the abattoir
halothane gene meat quality characteristics still have with a Hennesy Chong grading machine. Real time
a genetic variation of 20 which could be used in ultrasound measurements were recorded the day
breeding programs de Vries et al., 1994b. Meat before slaughter on the live animal and included fat
quality can be described through a range of charac- depth at the P2 site which is located 6.5 cm of the
teristics but the meat quality deficiency which is of mid line at the last rib LFDP2 and fat and eye
most concern to the consumer is pale, soft and muscle depth between the third and fourth last ribs
exudative meat PSE Jeremiah, 1994. Its signifi- LFD3 4, LMD3 4. After a lairage time of 18 h
cance to the Australian pork industry was shown by pigs were slaughtered and backfat and muscle depth
a PRDC survey PRDC, 1993. The genetic vari- were recorded on the same sites using a Hennesy
ability of traits describing PSE meat is unknown for Chong grading machine FDP2, FD3 4, MD3 4. In
Australian pigs. The objective of this study was to addition, total weight of the left back leg BLW and
obtain genetic parameters for meat quality, carcass lean meat weight of the back leg LMW were
and performance traits as well as reproductive traits obtained on the day after slaughter as additional
of the sow. Within this first paper heritability esti- carcass characteristics. To obtain lean meat weight,
mates for production, carcass and meat quality traits the left back leg was derinded, defatted and slash
obtained from a commercial breeding herd are boned, excluding the hock muscles.
presented. Meat quality traits consisted of pH measured 45
min after slaughter pH45. Meat quality traits recorded 24 h after slaughter were taken on a chop
2. Material and methods including the loin eye area and the belly, which was
taken from the anterior end of the left hand side of 2.1. Data recording and testing procedures
the middle between 5th and 6th thoracic vertebrae. Meat quality traits included pH pH24 and colour of
The study was undertaken in collaboration with the m
. longissimus dorsi and m. multifidus dorsi Bunge Meat Industries where data were recorded
CLD, CMD. Colour measurements were taken with from July 1992 to June 1995 on 1799 Large White
a Minolta Chromameter CR200b recording the L- and 1522 Landrace boars. Each week, two male
value which describes the brightness of meat. A meat piglets per litter were randomly chosen at 21 days of
sample was then cut from the m . longissimus dorsi
age resulting in weekly batches of approximately 30 and suspended in an air filled plastic bag for a further
pigs. The data set included two breeds, Large White 24 h in order to record drip loss percentage DLP.
and Landrace, with 71 and 77 sires, 695 and 608 Intramuscular fat content IMF was determined
dams and 911 and 792 litters, respectively. Further from meat samples of m
. longissimus dorsi with pedigree information was available from 3005 ani-
either the Soxtec solvent extraction method Foster mals comprising four generations.
and Gonzales, 1992 or Near Infrared Spectroscopy
S . Hermesch et al. Livestock Production Science 65 2000 239 –248
241
NIR. Near Infrared Reflectance spectra measure- shown in Table 1. In particular growth rate in the test
ments were performed with a NIR scanning spec- station is characterised by a high phenotypic vari-
trophotometer. This machine was calibrated on 300 ation which exceeds standard deviations presented in
samples resulting in a correlation of above 0.95 other studies i.e. van Steenbergen et al., 1990;
between the two measurement techniques and was Mrode and Kennedy, 1993; von Felde et al., 1996.
additionally used to allow for a quicker analysis of The average muscle depth was 37.8 mm recorded
all samples. Samples were allocated randomly to the with real time ultrasound equipment and 46.6 mm
two measurement techniques resulting in 656 sam- when muscle depth was measured with Hennesy
ples for the Soxtec solvent extraction method and Chong machine. Besides this higher mean for the
1225 samples for the NIR method. No confounding Hennesy Chong measurement, the standard deviation
existed with other systematic effects. was also increased. Gresham et al. 1992 also noted
Means and number of observations per trait are these differences between measurement techniques.
Table 1
a
Number of records, means and raw phenotypic standard deviations for analysed traits Unit
Number of Mean
Standard records
deviation Weight measurements
Weight at start of test kg
3353 73.3
9.3 Weight at end of test
kg 3333
99.5 10.7
Performance traits ADG1
g d 3227
616.0 80.1
ADG2 g d
3227 946.0
185.8 FDINT
kg 3252
2.62 0.43
FCR 3221
2.85 0.58
Carcass traits LFDP2
mm 3223
13.0 2.59
LFD3 4 mm
3203 13.1
2.61 LMD3 4
mm 2895
37.8 4.56
FDP2 mm
2303 12.9
3.13 FD3 4
mm 1383
13.2 3.00
MD3 4 mm
1369 46.5
9.57 BLW
kg 2562
10.6 1.24
LMW kg
2563 5.7
0.73 Meat quality traits
CLD 100 5 white
2535 53.16
4.91 CMD
100 5 white 2581
45.78 4.10
pH45 2221
6.36 0.46
pH24 2479
5.74 0.26
DLP 2705
1.98 1.87
IMF 1881
1.69 0.67
a
Abbreviations for traits: ADG1: Average daily gain from three to 18 weeks; ADG2: Average daily gain in test station from 18 to 22 weeks; FDINT: Feed intake recorded in test station from 18 to 22 weeks; FCR: Feed conversion ratio defined as feed intake over growth rate
18 to 22 weeks; LFDP2: Backfat depth at P2 measured with real time ultrasound; LFD3 4: Backfat depth between the third and fourth last ribs measured with real time ultrasound; LMD3 4: Muscle depth of m
. longissimus dorsi between the third and fourth last ribs on the live animal; FDP2: Backfat depth at P2 measured with Hennesy Chong grading machine; FD3 4: Backfat depth between third and fourth last
ribs measured with Hennesy Chong grading machine; MD3 4: Muscle depth between third and fourth last ribs measured with Hennesy Chong grading machine; BLW: Weight of whole left back leg; LMW: Weight of slash boned left back leg; pH45: pH measured 45 min after
slaughter; pH24: pH measured 24 h after slaughter; CLD: L-value of Minolta chromameter of m . longissimus dorsi; CMD: L-value of
Minolta chromameter of m . multifidus dorsi; DLP: Drip loss percentage; IMF: Intramuscular fat content.
242 S
. Hermesch et al. Livestock Production Science 65 2000 239 –248
2.2. Analysis feed conversion ratio. Significant fixed effects for
carcass traits included week of performance record- Analyses of traits were based on mixed models.
ing, breed and parity of the sow. Liveweight at The fixed effect part of the model was derived using
slaughter and hot carcass weight were included as PROC GLM SAS, 1991. Relevant fixed effects for
linear covariables for backfat and muscle depth production traits as well as the corresponding propor-
measurements while age of the animal at slaughter
2
tion of variation explained by these effects R are was fitted as a linear covariable for weight of the
presented in Table 2. Fixed effects included week of back leg and ham weight.
performance recording, breed of the animal and The main fixed effect influencing meat quality
parity number of the litter the animal was born in. characteristics was date of slaughter which was
Week of recording was used to define management equivalent to recording week since all animals were
groups since it also accounted for possible pen slaughtered on the same day each week Table 2.
effects the animal was housed in before and during This effect explained 38 and 45 of the total
test. Breed was significant for average daily gain variation for pH45 and pH24. Slaughter day was of
recorded before pigs entered the test. Parity number less importance for colour measurements, drip loss
of the litter the animal originated from was signifi- percentage and intramuscular fat content explaining
cant for both growth traits. Weight at test entry was 14 to 20 of the phenotypic variation for these
included as a linear covariable for feed intake and traits. Further fixed effects fitted for meat quality
Table 2
2 a
Fixed and random effects for performance, carcass and meat quality traits and total variation explained by fixed effects R Trait
Fixed effects Random effects
2
R Week
Breed Parity
Weight Age
Method Weight of sample
animal litter
Performance traits ADG1
0.17 ✓
✓ ADG2
0.18 ✓
✓
b
FDINT 0.39
✓
b
FCR 0.22
✓ Carcass traits
c
LFDP2 0.35
✓
c
LFD3 4 0.37
✓
c
LMD3 4 0.31
✓
d
FDP2 0.30
✓
d
FD3 4 0.34
✓
d
MD3 4 0.37
✓ BLW
0.15 ✓
✓ LMW
0.19 ✓
✓ Meat quality traits
pH45 0.38
✓ pH24
0.45 ✓
CLD 0.18
✓ CMD
0.14 ✓
DLP 0.18
✓
d
IMF 0.20
✓
a
For further abbreviations see Table 1.
b
Animal weight at 18 weeks.
c
Animal weight at 22 weeks.
d
Hot carcass weight. P , 0.1; P , 1; P , 5.
S . Hermesch et al. Livestock Production Science 65 2000 239 –248
243
traits included breed and method of measurement for with estimates of 0.27 for model one and 0.10 for
intramuscular fat content. Weight of meat sample and model two while litter effect had a larger importance
2
hot carcass weight were fitted as linear covariables for this breed c : 0.20. In contrast, growth rate was
for drip loss percentage and intramuscular fat con- highly heritable in Landrace with estimates of 0.57
tent. and 0.48 for both models while litter effect was of
2
Estimation of variance components was based on less importance c : 0.08. The design of this project
an animal model applying a Restricted Maximum provided a similar data structure for both breeds in
Likelihood procedure using the DFREML program regard to piglets per litter and management system.
Meyer, 1993. A variance of the likelihood function This excludes systematic effects as a possible reason
2 8
values of less than 10 was chosen as a conver-
for these differences in heritabilities and litter ef- gence criterion. Approximate standard errors of
fects. Results from Klassen 1992, who analysed heritability estimates were obtained as described in
lifetime average daily gain for a number of Aus- Meyer 1989. Significance of random effects was
tralian herds, confirm higher heritabilities for Aus- tested through a likelihood ratio test. Based on this
tralian Landrace in comparison with Australian likelihood ratio test, litter effect was only significant
Large White. Klassen 1992 who did not fit litter for growth rate, weight of the back leg and lean meat
effect as an additional random effect estimated weight of the back leg as an additional random effect
heritabilities ranging from 0.23 to 0.40 for Large Table 2.
White and from 0.32 to 0.61 for Landrace pigs. It is also possible that the size or structure of data
sets in this study did not allow a reliable simulta-
3. Results and discussion neous estimation of additive genetic effects and litter
