Directory UMM :Data Elmu:jurnal:S:Small Ruminant Research:Vol36.Issue3.2000:
Small Ruminant Research 36 (2000) 275±283
The effect of breed slaughter weight and nutritional management
on cholesterol content of lamb carcasses
G. Arsenosa,*, D. Zygoyjannisb, D. Ku®disc, N. Katsaounisb, C. Stamatarisb
a
Department of Management and Health, Animal Biology Division, Scottish Agricultural College, Bush-Estate, Penicuik,
EH26 OPH, Scotland, UK
b
Department of Animal Husbandry, Faculty of Veterinary Medicine, Aristotle University, 54006 Thessaloniki, Macedonia, Greece
c
Laboratory of Animal Nutrition, Faculty of Veterinary Medicine, Aristotle University, 54006 Thessaloniki, Macedonia, Greece
Accepted 11 August 1999
Abstract
This study was carried out to assess the effect of breed, sex, post-weaning nutrition, live weight at slaughter and their interactions
on the cholesterol content in carcass fat of lambs. The carcasses were obtained from lambs of three indigenous Greek dairy breeds of
sheep, the Boutsko (B), Serres (S) and Karagouniko (K) breed. After weaning (at approximately 42 days), the lambs of the three
breeds had been reared under different conditions of housing and nutritional management in three consecutive experiments between
1992 and 1994. In experiment 1, lambs (males and females) were individually penned and fed ad libitum on a concentrate ration
(11.3 MJ Metabolizable Energy (ME)/kg DM and 192 g crude protein (CP)/kg DM) together with 100 g per day of Lucerne hay
(8.3 MJ ME/kg DM and 182 g CP/kg DM). In experiment 2, lambs (males only) were also individually penned but were fed on three
different levels of concentrate and ad libitum on Lucerne hay. In experiment 3, lambs (males only) were initially group fed indoors
for 63 days on three different levels of concentrate together with ad libitum Lucerne hay, and thereafter the lambs ®nished on
irrigated, sown pasture (Lolium perrene Trifolium repens). Lambs were assigned to be slaughtered at one of ®ve standard
proportions of estimated mature weight for each breed in experiment 1; at three ®xed live weights, common for all breeds in
experiment 2 and at two ®xed proportions of breed mature weight in experiment 3. The right-hand side of the lamb carcasses was
minced and 150 lamb carcasses were selected out of a total of 300 minced carcasses. The concentration of total cholesterol content
in carcass fat was determined by HPLC in samples of these 150 lamb carcasses. Mean cholesterol content of carcass fat in the three
breeds, B, S and K, extracted from the whole ground carcasses samples, was 3.33, 4.41, 3.34 mg/g of carcass fat (s.e.d. 0.18),
respectively in experiment 1, whereas this content was 3.42, 4.50, 3.59 mg/g of carcass fat (s.e.d. 0.19) in experiment 2 and 4.38,
3.47, 3.78 mg/g of carcass fat (s.e.d. 0.22) in experiment 3. Cholesterol content differed signi®cantly (P < 0.001 in experiments 1
and 2, P < 0.05 in experiment 3) between breeds. It was also signi®cantly affected (P < 0.05) by the sex of lambs (experiment 1).
Live weight of lambs at slaughter had a signi®cant effect on cholesterol content (P < 0.001 in experiment 1 and P < 0.05 in
experiment 2). There was a general trend for cholesterol content to be lower in fat samples extracted from carcasses as target
slaughter weight increased. The different levels of concentrate feed affected signi®cantly (P < 0.00l) the cholesterol content in
carcass fat in experiment 2. The results suggest that there are possibilities of modifying body composition by manipulation of postweaning nutrition, especially reducing the cholesterol content, in carcass fat of lambs slaughtered at a wide range of live weights. In
such a situation, however, as nutritional management and degree of maturity change, breed remains the main factor that determines
the cholesterol content in carcass fat. # 2000 Elsevier Science B.V. All rights reserved.
Keywords: Carcass fat; Lambs; Cholesterol content; Slaughter weight; Breeds
*
Corresponding author. Tel.: 44-131-5353200; fax: 44-131-5353121.
E-mail address: g.arsenos@ed.sac.ac.uk (G. Arsenos)
0921-4488/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 9 2 1 - 4 4 8 8 ( 9 9 ) 0 0 1 0 7 - 8
276
G. Arsenos et al. / Small Ruminant Research 36 (2000) 275±283
1. Introduction
Despite the extended and continuous research on
growth, development and meat production in sheep
there is little information concerning the overall quality of the ®nal product (Zygoyiannis et al., 1997).
Cholesterol content in carcasses of meat producing
animals has long been identi®ed as the single most
important characteristic of overall meat quality (Newman, 1993). In view of the role of animal fats in human
health, consumer's concerns are increasingly re¯ecting their awareness of the link between health and
nutrition (Brewer, 1994). To our knowledge, most of
the available information regarding the cholesterol
content in carcass of lambs are hardly relevant to
the consumer because pertinent studies have been
focused mainly on the determination of cholesterol
content either in individual muscles or in speci®c fat
depots rather than in lamb carcasses as a whole
(Honikel and Arneth, 1996).
The results described in this paper formed part of a
wider series of studies, supported by the European
Commission, designed to assess the quality and marketability of sheep meat produced in the less favoured
areas (LFA) of the community. Our objectives in the
current study were: (i) to determine the content of
total cholesterol in the carcass fat of lambs of three
indigenous Greek dairy breeds of sheep, and (ii) to
investigate whether the cholesterol content in carcass
fat was affected by breed, sex, nutritional management and live weight (LW) at slaughter. More
speci®cally, the following factors were examined:
(i) breed, sex and degree of maturity at slaughter
in experiment 1, (ii) breed, feeding treatment and
slaughter weight in experiment 2 and (iii) breed,
and slaughter weight of lambs reared under a different
®nishing treatment (grazing on irrigated pasture) in
experiment 3.
2. Materials and methods
2.1. General experimental procedures
The experimental procedures regarding sample preparation and cholesterol determination were identical
for all samples. Speci®c design and methods are
detailed below.
2.1.1. Animals
The study was carried out by using 150 samples
from lamb carcasses which were selected out of a total
of 300 lambs that were used in three consecutive
experiments (for details see Section 2.2). All the lambs
were weaned at approximately 42 days. They belonged
to three indigenous dairy breeds of sheep, which were
chosen as representatives of the most common breeds
of sheep in Greece. They were: the Boutsko breed (B),
a mountain breed with an initially estimated mature
weight of 50 and 38 kg for males and females respectively, the Serres breed (S), a lowland breed with an
initially estimated mature weight of 60 kg for males
and 50 kg for females and the Karagouniko breed (K),
a lowland breed with an initially estimated mature
weight of 70 kg for males and 55 kg for females.
2.1.2. Feeds
The same two feeds (concentrate and Lucerne hay)
were used throughout the three experiments. The ingredients and chemical composition of these feeds are
shown in Table 1. The concentrate feed was made into
pellets (3 mm) and contained 192 g crude protein (CP)
per kg of dry matter (DM) and 11.3 MJ Metabolizable
Energy (ME)/kg DM. The Lucerne hay contained 182 g
CP/kg DM and 8.3 MJ of ME/kg DM. The concentrate
Table 1
Ingredients and chemical composition of the experimental feeds
Feeds
Concentrate
Lucerne hay
Ingredients (g/kg)
Barley
Maize
Sugar beet pulp
Soybean
Salt
Vitamin mineral premix
NH4Cl
Sodium sulphate
542
100
135
200
10
10
2.6
0.75
±
±
±
±
±
±
±
±
Component (g/kg DM)
Dry matter
ME (MJ/kg DM)a
Crude protein
Ash
Acid detergent fibre
Natural detergent fibre
Acid hydrolysed ether extract
900
11.3
192
74
106
246
28
888
8.3
182
93
312
250
±
a
ME calculated from feed compostion tables.
G. Arsenos et al. / Small Ruminant Research 36 (2000) 275±283
feed was formulated to be relatively high in CP content
and was expected to support the potential growth of the
animals when offered ad libitum (ARC, 1990).
2.1.3. Measurements
Lambs in all experiments were weighed at the start
of each experiment and subsequently at 7-day intervals
(every Monday). Those found to be approaching target
live weight were then weighed daily until the nominated
weight was recorded and were slaughtered on the same
day. 6 h after slaughter the carcasses were refrigerated
at 18C and kept at this temperature until sampling.
2.1.4. Sampling procedures
The carcass samples (n 150) used in this study,
were selected (randomly within sub-classes) out of a
total number of 300 minced half (1/2) carcasses covering the whole range of the live weights achieved and
the feeding treatments for the B, S, and K breeds
respectively. The refrigerated carcasses were sawn
down at the middle line through the centre of the
vertebral column and the right-hand side (RHS) of
each carcass was minced and thoroughly mixed. One
random sub-sample, each of approximately 200 g was
taken from each minced carcass and stored in a deep
freezer (ÿ258C). All frozen samples were freeze-dried
(Leybold-Heraus GT2) and were ground, in a small
mill, to pass through a 1 mm mesh screen. From the
ground samples, a quantity of 2 g was taken for lipid
extraction.
2.1.5. Cholesterol determination
Concentration of total cholesterol in carcass fat was
determined by HPLC using a modi®cation of the
procedure suggested by Klatt et al. (1995). Total lipids
from carcass samples were extracted and puri®ed
according to the method of Folch et al. (1957). A
quantity of approximately 100 mg (1 mg) of the
puri®ed lipid was accurately weighed in a glass tube
(40 ml capacity) equipped with a Te¯on coated screwup. A 4 ml volume of 95% aqueous ethanol and 0.8 ml
of a freshly prepared solution of KOH (50%) were
added and the tube was sealed, well shaken in a vortextype mixer and heated for 90 min in a water bath
(508C). At 15 min intervals, the tube was shaken
brie¯y using a vortex mixer. Immediately after the
samples were removed from the water bath, 6 ml of
aqueous (95%) ethanol were added and the tubes were
277
allowed to cool at room temperature. Subsequently,
10 ml of toluene and 11 ml of 1 N KOH solution were
added and the tubes were shaken vigorously using the
vortex for 2 min. The solution was then allowed to
separate into two layers, the aqueous layer (bottom)
was discarded and the organic (upper) layer was
washed with 4 ml of 0.5 N KOH solution. The tubes
were again shaken and allowed to stand until the
separation of the two layers. If an emulsion was
formed, a small amount of 1±2 ml of 95% ethanol
was added to facilitate the separation of the layers. The
bottom layer was again discarded whereas the upper
one was washed successively three times with a total
volume of 12 ml of distilled water. Afterwards, a small
amount of anhydrous Na2SO4 was added to remove
traces of moisture and the tubes were centrifuged for
5 min. The whole amount of the upper layer was
transferred carefully to a small ¯ask with a cover of
Te¯on. The solvent was evaporated to dryness under a
steam of nitrogen and the remaining dry residue was
re-dissolved in an exact amount of 3 ml isopropanol-2.
Sample solutions were then kept frozen (ÿ258C) until
HPLC analysis. After thawing, an exact amount of
30 ml from each sample was injected into the high
performance liquid chromatograph (Perkin-Elmer,
Series 3) equipped with a Rheodyne injection valve
(170 ml sample-loop), a 250 4.6 mm column packed
with 10 mm Spherisorb C18, a UV absorbance detector
set at 214 nm and an integrator (Shimazu Chromatopak C-R3A). The mobile phase was a mixture of
isopropanol-2-acetonitrile; ACN 40/60) for the quantitative determination of total cholesterol. Recoveries
were determined by employing cholesterol calibration
standard (SRM 911b, National Bureau of Standards,
US Department of Commerce) which were run daily.
2.2. Speci®c experimental design
2.2.1. Experiment 1
This experiment reported by Zygoyiannis et al.
(1997) was carried out using 20 male and 20 female
lambs of each breed. After weaning, the lambs were
reared at the Institute of Reproduction and Arti®cial
Insemination (IRAI) of the National Agricultural
Research Foundation (NARF), in Thessaloniki, Northern Greece. They were offered daily fresh concentrate
feed ad libitum together with a small amount (100 g)
of unchopped Lucerne hay to allow normal digestive
278
G. Arsenos et al. / Small Ruminant Research 36 (2000) 275±283
function and avoid rumen acidosis. Lambs were
slaughtered at one of ®ve standard proportions of
estimated mature weight (PMW), i.e., 20%, 30%,
45%, 60% and 90%. The cholesterol determination
was carried out by using only two carcass samples out
of four minced carcasses of lambs of each breed and
sex, slaughtered at each of the ®ve stages of PMW.
These samples were selected at random, within the
above sub-classes, to give a total of 60 samples.
2.2.2. Experiment 2
In this experiment, described in detail by Zygoyiannis et al. (1999), 36 exclusively male lambs from each
breed were used. The experimental work was carried
out in individual pens at the same location (IRAI) as in
experiment 1. The lambs were randomly allocated to
3-target slaughter live weights (TSLW), i.e., 23. 28
and 33 kg, common to all breeds. The TSLW were
selected to correspond to the carcass weights at which
the B, S and K lambs, respectively, were found to
produce the most market acceptable carcasses from
the results of experiment 1. Lambs were fed both
Lucerne hay, which was offered ad libitum in speci®c
designed metal troughs, and restricted amounts of
concentrate. The concentrate allowances (CA) were
offered daily at high (H), medium (M) and low (L)
levels. The H level was set to correspond to 80% of the
mean ad libitum intake as it was measured in experiment 1, whereas the M and L levels were set to 67%
and 33% of the H level, respectively. The amounts
offered were increased each week by feed quantities
of 33, 22, 11 g in B, 48, 32, 16 g in S and 54, 36, 18 g
in K lambs for the H, M and L level of CA respectively. The cholesterol determination was carried out
by using only two carcass samples out of four minced
carcasses of lambs from each breed, TSLW and CA.
These samples were selected at random, within the
above sub-classes, to give a total of 54 samples.
2.2.3. Experiment 3
In this experiment also reported by Zygoyiannis
et al. (1999), only male lambs (24 from each breed)
were used. The experiment consisted of two phases:
an indoor phase that lasted 63 days and a grazing
phase. During the indoor phase the design of the
feeding treatments was similar to that used in experiment 2 and the levels of CA were derived from the
intakes recorded in experiment 2. The maximum level
of CA (H) was set equal to the M level used in experiment 2 for both K and S lambs while for the B lambs,
the H level was only 60% of the M level used in
experiment 2. The M level for experiment 3 was
intermediate between M and L levels used in experiment 2 for each breed. Finally the L level was set at a
nominal 50 g per day for all breeds. Initial offerings
were increased weekly by ®xed amounts. These CA
were assigned to achieve three de®ned live weights for
each breed prior to turnout to the grazing phase.
Lambs were to be slaughtered off pasture when they
attained one of two nominated PMW. These had been
set at 48% and 54% of the mature weight for each
breed. The irrigated, sown pasture consisted of tetraploid ryegrass (Lolium perenne) and white clover
(Trifolium repens) in a proportion of 10 : 1, respectively. Pasture management was based on maintaining
a relatively constant sward surface height throughout
the grazing season using change in grazing area or
adding of non-experimental lambs as required (mean
6 cm with a maximum tolerance of 2 cm). The
lambs were slaughtered when they reached the de®ned
PMW. The cholesterol determination was carried out
by using only two carcass samples out of ®ve minced
carcasses of lambs from each breed, CA and PMW.
These samples were selected at random, within the
above sub-classes, to give a total of 36 samples.
2.3. Statistical analyses
All statistical analyses were performed using Minitab statistical package (Minitab version 11). Data were
analysed separately for each experiment using the
general linear model (GLM). The model used accounting for the main effects and interactions of breed, sex,
degree of maturity (TSLW) in experiment 1, breed,
CA, TSLW in experiment 2, and breed and PMW in
experiment 3. The signi®cance of all main effects and
interactions was tested against the error mean squares.
3. Results
3.1. Experiment 1
Mean values of cholesterol content in carcass fat of
lambs are shown in Table 2. Analysis of variance of
cholesterol content (mg/g fat of carcass DM) showed
signi®cant (P < 0.001) effects of breed and degree of
279
G. Arsenos et al. / Small Ruminant Research 36 (2000) 275±283
Table 2
Mean cholesterol content (mg/g of carcass fat) of lamb carcasses by breed, sex and degree of maturity in experiment 1
Breed
Sex
Degree of maturity
Overall means
20%
30%
45%
60%
90%
B
Male
Female
4.77
4.05
5.43
4.85
2.64
2.22
2.42
1.96
3.26
1.77
3.33
S
Male
Female
5.06
7.36
7.33
6.09
4.33
3.14
3.23
2.38
3.45
1.74
4.41
K
Male
Female
4.39
5.49
3.19
3.96
3.37
4.17
3.00
2.38
1.95
1.55
3.34
Overall means
5.18
S.e.d. for comparing overall Breed means: 0.18
S.e.d. for comparing overall Degree of maturity means: 0.24
Overall sex means are: male, 3.85; female, 3.54; s.e.d., 0.15
5.14
3.31
2.56
2.28
Source of variation
d.f.
m.s.
F-value
P
Breed
Sex
Degree of maturity
Breed Sex
Breed Degree of maturity
Sex Degree of maturity
Breed Sex Degree of maturity
Error
2
1
4
2
8
4
8
30
7.63
1.48
23.18
1.62
2.32
1.77
0.83
0.34
22.44
4.35
68.18
4.76
6.82
5.21
2.44
***
Total
59
*
***
*
***
**
*
*
P < 0.05.
P < 0.01.
***
P < 0.001.
**
maturity (TSLW). This ®nding suggests that these two
factors are of major importance in terms of cholesterol
deposition (content) in carcass fat. Cholesterol content
was also signi®cantly affected (P < 0.001) by the
interaction between breed and TSLW (Table 2). Small
but signi®cant differences (P < 0.05) were found
between carcasses of male and female lambs. It is
interesting to note the inverse proportional relationship between TSLW and cholesterol content. It seems
that the mean cholesterol content decreased as the
degree of maturity approached the mature weight of
each breed. This pattern was consistent for all breeds.
In general, the intermediate-sized breed S seemed to
deposit the most cholesterol in carcass fat.
3.2. Experiment 2
Mean cholesterol values in respect of breed,
PMW and CA are shown in Table 3. The results
suggest that diet restrictions can result in signi®cant
changes in cholesterol content of carcass fat. Thus,
as the proportion of CA decreased and that of
Lucerne hay increased in the diet of lambs, the
cholesterol content in their carcass fat increased
(P < 0.001). Analysis of variance showed that breed
had a signi®cant effect (P < 0.001) similar to that
observed in experiment 1. The effect of PMW was
also signi®cant (P < 0.05), but this signi®cance
could be attributed to the fact that, although lambs
were slaughtered at the same LW, their carcasses
were at a different degree of maturity. Unlike experiment 1, there were no signi®cant interactions between
any of the main factors. It is important to note
that, generally, carcasses from lambs at the ®rst
slaughter point had a higher cholesterol content in
all breeds and that lambs fed on L levels of CA
appeared to deposit more cholesterol than those fed
on H levels.
280
G. Arsenos et al. / Small Ruminant Research 36 (2000) 275±283
Table 3
Mean cholesterol content (mg/g of carcass fat) of lamb carcasses by breed target slaughter live weight (TSLW) and concentrate allowances
(CA) in experiment 2
Breed
TSLW
Concentrate allowances
Overall means
H
M
L
B
23
28
33
2.59
2.63
3.25
3.71
3.21
3.70
4.40
3.77
3.52
3.42
S
23
28
33
4.20
3.78
3.43
4.78
4.53
4.05
5.74
4.56
5.42
4.50
K
23
28
33
2.65
2.53
3.11
4.16
4.16
4.17
4.64
3.02
3.90
3.59
Overall means
3.13
4.05
S.e.d. for comparing overall Breed means: 0.19
S.e.d. for comparing overall CA means: 0.18
Overall means for the 23, 28 and 33 TSLW are: 4.10,3.57 and 3.84; s.e.d. 0.19, respectively
4.33
Sources of variation
d.f.
m.s.
F-value
P
Breed
TSLW
CA
Breed TSLW
Breed TSLW
TSLW CA
Breed TSLW CA
Error
2
2
2
4
4
4
8
26b
6.04
1.22
7.11
0.17
0.52
0.50
0.28
0.31
19.48
3.94
22.94
0.55
1.68
1.61
0.90
***
Total
52b
*
***
NSa
NSa
NSa
NSa
a
NS: not signi®cant.
One sample was missing.
*
P < 0.05.
***
P < 0.001.
b
3.3. Experiment 3
4. Discussion
Table 4 shows the mean values of the cholesterol
content of carcass fat of lambs ®nished on irrigated
pasture. Cholesterol content in carcass fat differed
signiticantly (P < 0.01) between breeds. There was
no apparent effect of dietary treatment during the
indoor phase. This implies that the nutritional treatment before turnout to grazing appears to be of minor
signi®cance. There was a slight indication of a
decrease in cholesterol content in the carcasses of
heavier lambs but the differences between PMW were
non-signi®cant. However, there were small differences between breeds when compared at the same
PMW, with the B breed showing consistently higher
values.
This study was conducted to determine the cholesterol content in whole carcass fat of edible lamb meat
by comparing results of three different systems of
production. We discuss ®rst the effects of breed of
lambs and subsequently the effects of sex since this
factor was examined only in experiment 1. The effects
of feeding treatment and live weight at slaughter,
alternatively de®ned as proportion of mature weight
are then addressed.
4.1. Effects of breed and sex
The results indicate that the effect of breed was
apparent throughout the three experiments. Among
281
G. Arsenos et al. / Small Ruminant Research 36 (2000) 275±283
Table 4
Mean cholesterol content (mg/g of carcass fat) of lamb carcasses by breed, proportion of mature weight (PMW) and concentrate allowances
(CA) in experiment 3
Breed
PMW
Concentrate allowances
Overall means
1
2
3
B
0.48
0.55
3.31
4.36
5.01
3.90
5.07
4.66
4.38
S
0.48
0.55
4.55
2.89
3.53
2.96
3.25
3.67
3.47
K
0.48
0.55
3.56
4.04
3.68
3.72
4.40
3.30
3.78
Overall means
3.78
3.80
S.e.d. for comparing overall Breed means: 0.21
S.e.d. for comparing overall CA means: 0.21
Overall means for the 0.48 and 0.52 PMW are: 4.04, and 3.72; s.e.d. 0.19, respectively
4.06
Sources of variation
d.f.
m.s.
F-value
P
Breed
PMW
CA
Breed PMW
Breed CA
PMW CA
Breed PMW CA
Error
2
1
2
2
4
2
4
18
2.56
0.91
0.28
0.19
0.52
0.20
1.39
0.29
8.83
3.14
0.97
0.66
1.79
0.69
4.79
NSa
NSa
NSa
NSa
NSa
Total
35
a
**
**
NS: not signi®cant
P < 0.01.
**
the other factors that have been studied, breed seems
to be the most important regarding the effects on
carcass fat and its cholesterol content. This is in
agreement with the results of other studies (Zygoyiannis et al., 1992; Nurnberg et al., 1998; Matthes et al.,
1998). The above was more evident from the results in
experiment 3 in which, apart from breed factor, none
of the others had any signi®cant effect. Similar ®ndings with our results were reported by Abutarboush
and Dawood (1993), Sevi et al. (1997) and Demise
et al. (1998). Reported values ranged from about 135
to 184 mg per 100 g adipose tissues. The results of the
current study support the belief that the indigenous
Greek breeds produce carcasses with better eating
quality (Zygoyiannis et al., 1990; Arsenos, 1997),
as far as its savour is concerned. They also suggest
that there is a chance for the producers to choose
between the breeds studied here in terms of cholesterol
content in carcass fat, when attempts are made to
improve the overall quality of lamb carcasses. How-
ever, there was no clear indication of a consistent
difference between sex types within breeds (experiment 1) and it was not feasible to have a further
indication on these effect as the following experiments
were carried out with male only lambs.
4.2. Effects of nutritional management
In experiment 2, feeding treatment seems to be
important when comparisons are made at similar
carcass weights with respect to differences in the
degree of maturity between breeds. The different
levels of CA and that of Lucerne hay fed ad libitum
resulted in increased amount of cholesterol content in
carcass fat in response to reduction in the CA. The
highest amounts were observed in breed S and the
lowest in breed K. Mean cholesterol content was
signi®cantly decreased due to H levels of CA in S
and K breeds, but not in the slower maturing breed
B. In contrast, results from carcasses of lambs fed
282
G. Arsenos et al. / Small Ruminant Research 36 (2000) 275±283
on medium levels of CA were more similar across
PMW.
The results, also, indicate that the cholesterol content is lower in carcass fat samples obtained from
lambs ®nished on pasture (under the present system,
experiment 3) than those obtained from other lambs
(of the same breed) which were reared indoors in
individual pens on a diet of restricted amounts of CA
and ad libitum Lucerne hay (experiment 2). As
expected from the results in experiments 1 and 2, B
lambs tended to contain higher levels of cholesterol in
their carcass fat than those of the other two breeds.
These lambs, were grazing for a shorter period of time
since they belong to an early maturing breed. The
results from experiment 3 suggest that, irrespectively
of feeding treatment during indoor phase, increasing
the duration of grazing period could improve the
carcass quality of lambs. Zygoyiannis et al. (1999)
suggested that grazing on irrigated pasture would
allow reaching the optimal growth of muscles of
fattening lambs. Thus, lambs reared on irrigated pasture could be a source of low-fat, low-cholesterol
carcasses throughout the year. These observations
support the belief that the slower rearing systems
may result in a lower concentration of cholesterol
in carcass fat at equivalent weights (Demise et al.,
1998) and may also help to explain the decrease in fat
content in carcasses of grazing lambs (Sanudo et al.,
1996). However, Solomon et al. (1992), found that diet
had no effect on cholesterol content of lean tissue and
Rule et al. (1997) suggested that different growing®nishing strategies in beef cattle production systems
did not alter cholesterol in meat. Nevertheless, great
variability in cholesterol content was reported by Park
et al. (1991) in carcasses from post-weaned kids fed a
high quality concentrate diets and by Lough et al.
(1993) in various fat depots of lambs fed forage diets.
4.3. Effects of live weight at slaughter
The LW of lambs at slaughter (de®ned either as
degree of maturity or as proportion of mature weight)
affected signi®cantly the cholesterol content of their
carcasses. Given the range of PMW used in this study,
results suggest that the high levels of cholesterol
content in carcasses must have been deposited before
lambs reach the ®rst half of their mature LW. In
experiment 1, cholesterol content in carcass fat
decreased with advancing carcass maturity. For the
two younger maturity groups, the cholesterol content
was higher between the three breeds with the S lambs
having consistently the highest levels in experiments 1
and 2. In experiment 3, the cholesterol content did not
seem to be different between carcasses of lambs
slaughtered at the two PMW. The lack of signi®cance
due to PMW in experiment 3 may be attributed to the
fact that there were no signi®cant differences in
carcass traits when carcasses were compared at similar
degree of maturity (Hopkins and Nicholson, 1999).
Based on PMW differences, as well as on differences in fat content, one would thus expect that the
mature carcasses would contain more cholesterol.
However, this was not the case either in carcass
samples from experiment 1 or from experiment 2
(Tables 3 and 4). It seems that the cholesterol content
is not attributable to the differences in the amount of
fat in the carcasses. Similarly, Hoelscher et al. (1988)
suggested that cholesterol content does not depend
directly to the ether-extractable fat content of the
carcasses. Nevertheless, there was a general trend
for cholesterol content to be lower in fat samples
extracted from carcasses as TSLW increased.
5. Conclusion
The results suggest that there are possibilities of
modifying body composition by manipulation of postweaning nutrition, especially reducing the cholesterol
content in carcass fat, in lambs slaughtered at a wide
range of live weights. In such situation, however, as
nutritional management and degree of maturity
changes, breed remains the main factor determining
the cholesterol content in carcass fat. Results also
suggest that the provision of irrigated, sown pasture,
could be used to produce consumer acceptable carcasses at much heavier weights than those which are
traditionally preferred in Greece with a considerable
lower cholesterol content.
Acknowledgements
The work was supported by the European Community (DG VI) project No CAMAR 8001 CT 91-0308)
as a part of a collaborative program between the UK,
G. Arsenos et al. / Small Ruminant Research 36 (2000) 275±283
Greece and Spain. The assistance, also, of the farmer
Mr G. Zygoyiannis and his family is gratefully
acknowledged.
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The effect of breed slaughter weight and nutritional management
on cholesterol content of lamb carcasses
G. Arsenosa,*, D. Zygoyjannisb, D. Ku®disc, N. Katsaounisb, C. Stamatarisb
a
Department of Management and Health, Animal Biology Division, Scottish Agricultural College, Bush-Estate, Penicuik,
EH26 OPH, Scotland, UK
b
Department of Animal Husbandry, Faculty of Veterinary Medicine, Aristotle University, 54006 Thessaloniki, Macedonia, Greece
c
Laboratory of Animal Nutrition, Faculty of Veterinary Medicine, Aristotle University, 54006 Thessaloniki, Macedonia, Greece
Accepted 11 August 1999
Abstract
This study was carried out to assess the effect of breed, sex, post-weaning nutrition, live weight at slaughter and their interactions
on the cholesterol content in carcass fat of lambs. The carcasses were obtained from lambs of three indigenous Greek dairy breeds of
sheep, the Boutsko (B), Serres (S) and Karagouniko (K) breed. After weaning (at approximately 42 days), the lambs of the three
breeds had been reared under different conditions of housing and nutritional management in three consecutive experiments between
1992 and 1994. In experiment 1, lambs (males and females) were individually penned and fed ad libitum on a concentrate ration
(11.3 MJ Metabolizable Energy (ME)/kg DM and 192 g crude protein (CP)/kg DM) together with 100 g per day of Lucerne hay
(8.3 MJ ME/kg DM and 182 g CP/kg DM). In experiment 2, lambs (males only) were also individually penned but were fed on three
different levels of concentrate and ad libitum on Lucerne hay. In experiment 3, lambs (males only) were initially group fed indoors
for 63 days on three different levels of concentrate together with ad libitum Lucerne hay, and thereafter the lambs ®nished on
irrigated, sown pasture (Lolium perrene Trifolium repens). Lambs were assigned to be slaughtered at one of ®ve standard
proportions of estimated mature weight for each breed in experiment 1; at three ®xed live weights, common for all breeds in
experiment 2 and at two ®xed proportions of breed mature weight in experiment 3. The right-hand side of the lamb carcasses was
minced and 150 lamb carcasses were selected out of a total of 300 minced carcasses. The concentration of total cholesterol content
in carcass fat was determined by HPLC in samples of these 150 lamb carcasses. Mean cholesterol content of carcass fat in the three
breeds, B, S and K, extracted from the whole ground carcasses samples, was 3.33, 4.41, 3.34 mg/g of carcass fat (s.e.d. 0.18),
respectively in experiment 1, whereas this content was 3.42, 4.50, 3.59 mg/g of carcass fat (s.e.d. 0.19) in experiment 2 and 4.38,
3.47, 3.78 mg/g of carcass fat (s.e.d. 0.22) in experiment 3. Cholesterol content differed signi®cantly (P < 0.001 in experiments 1
and 2, P < 0.05 in experiment 3) between breeds. It was also signi®cantly affected (P < 0.05) by the sex of lambs (experiment 1).
Live weight of lambs at slaughter had a signi®cant effect on cholesterol content (P < 0.001 in experiment 1 and P < 0.05 in
experiment 2). There was a general trend for cholesterol content to be lower in fat samples extracted from carcasses as target
slaughter weight increased. The different levels of concentrate feed affected signi®cantly (P < 0.00l) the cholesterol content in
carcass fat in experiment 2. The results suggest that there are possibilities of modifying body composition by manipulation of postweaning nutrition, especially reducing the cholesterol content, in carcass fat of lambs slaughtered at a wide range of live weights. In
such a situation, however, as nutritional management and degree of maturity change, breed remains the main factor that determines
the cholesterol content in carcass fat. # 2000 Elsevier Science B.V. All rights reserved.
Keywords: Carcass fat; Lambs; Cholesterol content; Slaughter weight; Breeds
*
Corresponding author. Tel.: 44-131-5353200; fax: 44-131-5353121.
E-mail address: g.arsenos@ed.sac.ac.uk (G. Arsenos)
0921-4488/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 9 2 1 - 4 4 8 8 ( 9 9 ) 0 0 1 0 7 - 8
276
G. Arsenos et al. / Small Ruminant Research 36 (2000) 275±283
1. Introduction
Despite the extended and continuous research on
growth, development and meat production in sheep
there is little information concerning the overall quality of the ®nal product (Zygoyiannis et al., 1997).
Cholesterol content in carcasses of meat producing
animals has long been identi®ed as the single most
important characteristic of overall meat quality (Newman, 1993). In view of the role of animal fats in human
health, consumer's concerns are increasingly re¯ecting their awareness of the link between health and
nutrition (Brewer, 1994). To our knowledge, most of
the available information regarding the cholesterol
content in carcass of lambs are hardly relevant to
the consumer because pertinent studies have been
focused mainly on the determination of cholesterol
content either in individual muscles or in speci®c fat
depots rather than in lamb carcasses as a whole
(Honikel and Arneth, 1996).
The results described in this paper formed part of a
wider series of studies, supported by the European
Commission, designed to assess the quality and marketability of sheep meat produced in the less favoured
areas (LFA) of the community. Our objectives in the
current study were: (i) to determine the content of
total cholesterol in the carcass fat of lambs of three
indigenous Greek dairy breeds of sheep, and (ii) to
investigate whether the cholesterol content in carcass
fat was affected by breed, sex, nutritional management and live weight (LW) at slaughter. More
speci®cally, the following factors were examined:
(i) breed, sex and degree of maturity at slaughter
in experiment 1, (ii) breed, feeding treatment and
slaughter weight in experiment 2 and (iii) breed,
and slaughter weight of lambs reared under a different
®nishing treatment (grazing on irrigated pasture) in
experiment 3.
2. Materials and methods
2.1. General experimental procedures
The experimental procedures regarding sample preparation and cholesterol determination were identical
for all samples. Speci®c design and methods are
detailed below.
2.1.1. Animals
The study was carried out by using 150 samples
from lamb carcasses which were selected out of a total
of 300 lambs that were used in three consecutive
experiments (for details see Section 2.2). All the lambs
were weaned at approximately 42 days. They belonged
to three indigenous dairy breeds of sheep, which were
chosen as representatives of the most common breeds
of sheep in Greece. They were: the Boutsko breed (B),
a mountain breed with an initially estimated mature
weight of 50 and 38 kg for males and females respectively, the Serres breed (S), a lowland breed with an
initially estimated mature weight of 60 kg for males
and 50 kg for females and the Karagouniko breed (K),
a lowland breed with an initially estimated mature
weight of 70 kg for males and 55 kg for females.
2.1.2. Feeds
The same two feeds (concentrate and Lucerne hay)
were used throughout the three experiments. The ingredients and chemical composition of these feeds are
shown in Table 1. The concentrate feed was made into
pellets (3 mm) and contained 192 g crude protein (CP)
per kg of dry matter (DM) and 11.3 MJ Metabolizable
Energy (ME)/kg DM. The Lucerne hay contained 182 g
CP/kg DM and 8.3 MJ of ME/kg DM. The concentrate
Table 1
Ingredients and chemical composition of the experimental feeds
Feeds
Concentrate
Lucerne hay
Ingredients (g/kg)
Barley
Maize
Sugar beet pulp
Soybean
Salt
Vitamin mineral premix
NH4Cl
Sodium sulphate
542
100
135
200
10
10
2.6
0.75
±
±
±
±
±
±
±
±
Component (g/kg DM)
Dry matter
ME (MJ/kg DM)a
Crude protein
Ash
Acid detergent fibre
Natural detergent fibre
Acid hydrolysed ether extract
900
11.3
192
74
106
246
28
888
8.3
182
93
312
250
±
a
ME calculated from feed compostion tables.
G. Arsenos et al. / Small Ruminant Research 36 (2000) 275±283
feed was formulated to be relatively high in CP content
and was expected to support the potential growth of the
animals when offered ad libitum (ARC, 1990).
2.1.3. Measurements
Lambs in all experiments were weighed at the start
of each experiment and subsequently at 7-day intervals
(every Monday). Those found to be approaching target
live weight were then weighed daily until the nominated
weight was recorded and were slaughtered on the same
day. 6 h after slaughter the carcasses were refrigerated
at 18C and kept at this temperature until sampling.
2.1.4. Sampling procedures
The carcass samples (n 150) used in this study,
were selected (randomly within sub-classes) out of a
total number of 300 minced half (1/2) carcasses covering the whole range of the live weights achieved and
the feeding treatments for the B, S, and K breeds
respectively. The refrigerated carcasses were sawn
down at the middle line through the centre of the
vertebral column and the right-hand side (RHS) of
each carcass was minced and thoroughly mixed. One
random sub-sample, each of approximately 200 g was
taken from each minced carcass and stored in a deep
freezer (ÿ258C). All frozen samples were freeze-dried
(Leybold-Heraus GT2) and were ground, in a small
mill, to pass through a 1 mm mesh screen. From the
ground samples, a quantity of 2 g was taken for lipid
extraction.
2.1.5. Cholesterol determination
Concentration of total cholesterol in carcass fat was
determined by HPLC using a modi®cation of the
procedure suggested by Klatt et al. (1995). Total lipids
from carcass samples were extracted and puri®ed
according to the method of Folch et al. (1957). A
quantity of approximately 100 mg (1 mg) of the
puri®ed lipid was accurately weighed in a glass tube
(40 ml capacity) equipped with a Te¯on coated screwup. A 4 ml volume of 95% aqueous ethanol and 0.8 ml
of a freshly prepared solution of KOH (50%) were
added and the tube was sealed, well shaken in a vortextype mixer and heated for 90 min in a water bath
(508C). At 15 min intervals, the tube was shaken
brie¯y using a vortex mixer. Immediately after the
samples were removed from the water bath, 6 ml of
aqueous (95%) ethanol were added and the tubes were
277
allowed to cool at room temperature. Subsequently,
10 ml of toluene and 11 ml of 1 N KOH solution were
added and the tubes were shaken vigorously using the
vortex for 2 min. The solution was then allowed to
separate into two layers, the aqueous layer (bottom)
was discarded and the organic (upper) layer was
washed with 4 ml of 0.5 N KOH solution. The tubes
were again shaken and allowed to stand until the
separation of the two layers. If an emulsion was
formed, a small amount of 1±2 ml of 95% ethanol
was added to facilitate the separation of the layers. The
bottom layer was again discarded whereas the upper
one was washed successively three times with a total
volume of 12 ml of distilled water. Afterwards, a small
amount of anhydrous Na2SO4 was added to remove
traces of moisture and the tubes were centrifuged for
5 min. The whole amount of the upper layer was
transferred carefully to a small ¯ask with a cover of
Te¯on. The solvent was evaporated to dryness under a
steam of nitrogen and the remaining dry residue was
re-dissolved in an exact amount of 3 ml isopropanol-2.
Sample solutions were then kept frozen (ÿ258C) until
HPLC analysis. After thawing, an exact amount of
30 ml from each sample was injected into the high
performance liquid chromatograph (Perkin-Elmer,
Series 3) equipped with a Rheodyne injection valve
(170 ml sample-loop), a 250 4.6 mm column packed
with 10 mm Spherisorb C18, a UV absorbance detector
set at 214 nm and an integrator (Shimazu Chromatopak C-R3A). The mobile phase was a mixture of
isopropanol-2-acetonitrile; ACN 40/60) for the quantitative determination of total cholesterol. Recoveries
were determined by employing cholesterol calibration
standard (SRM 911b, National Bureau of Standards,
US Department of Commerce) which were run daily.
2.2. Speci®c experimental design
2.2.1. Experiment 1
This experiment reported by Zygoyiannis et al.
(1997) was carried out using 20 male and 20 female
lambs of each breed. After weaning, the lambs were
reared at the Institute of Reproduction and Arti®cial
Insemination (IRAI) of the National Agricultural
Research Foundation (NARF), in Thessaloniki, Northern Greece. They were offered daily fresh concentrate
feed ad libitum together with a small amount (100 g)
of unchopped Lucerne hay to allow normal digestive
278
G. Arsenos et al. / Small Ruminant Research 36 (2000) 275±283
function and avoid rumen acidosis. Lambs were
slaughtered at one of ®ve standard proportions of
estimated mature weight (PMW), i.e., 20%, 30%,
45%, 60% and 90%. The cholesterol determination
was carried out by using only two carcass samples out
of four minced carcasses of lambs of each breed and
sex, slaughtered at each of the ®ve stages of PMW.
These samples were selected at random, within the
above sub-classes, to give a total of 60 samples.
2.2.2. Experiment 2
In this experiment, described in detail by Zygoyiannis et al. (1999), 36 exclusively male lambs from each
breed were used. The experimental work was carried
out in individual pens at the same location (IRAI) as in
experiment 1. The lambs were randomly allocated to
3-target slaughter live weights (TSLW), i.e., 23. 28
and 33 kg, common to all breeds. The TSLW were
selected to correspond to the carcass weights at which
the B, S and K lambs, respectively, were found to
produce the most market acceptable carcasses from
the results of experiment 1. Lambs were fed both
Lucerne hay, which was offered ad libitum in speci®c
designed metal troughs, and restricted amounts of
concentrate. The concentrate allowances (CA) were
offered daily at high (H), medium (M) and low (L)
levels. The H level was set to correspond to 80% of the
mean ad libitum intake as it was measured in experiment 1, whereas the M and L levels were set to 67%
and 33% of the H level, respectively. The amounts
offered were increased each week by feed quantities
of 33, 22, 11 g in B, 48, 32, 16 g in S and 54, 36, 18 g
in K lambs for the H, M and L level of CA respectively. The cholesterol determination was carried out
by using only two carcass samples out of four minced
carcasses of lambs from each breed, TSLW and CA.
These samples were selected at random, within the
above sub-classes, to give a total of 54 samples.
2.2.3. Experiment 3
In this experiment also reported by Zygoyiannis
et al. (1999), only male lambs (24 from each breed)
were used. The experiment consisted of two phases:
an indoor phase that lasted 63 days and a grazing
phase. During the indoor phase the design of the
feeding treatments was similar to that used in experiment 2 and the levels of CA were derived from the
intakes recorded in experiment 2. The maximum level
of CA (H) was set equal to the M level used in experiment 2 for both K and S lambs while for the B lambs,
the H level was only 60% of the M level used in
experiment 2. The M level for experiment 3 was
intermediate between M and L levels used in experiment 2 for each breed. Finally the L level was set at a
nominal 50 g per day for all breeds. Initial offerings
were increased weekly by ®xed amounts. These CA
were assigned to achieve three de®ned live weights for
each breed prior to turnout to the grazing phase.
Lambs were to be slaughtered off pasture when they
attained one of two nominated PMW. These had been
set at 48% and 54% of the mature weight for each
breed. The irrigated, sown pasture consisted of tetraploid ryegrass (Lolium perenne) and white clover
(Trifolium repens) in a proportion of 10 : 1, respectively. Pasture management was based on maintaining
a relatively constant sward surface height throughout
the grazing season using change in grazing area or
adding of non-experimental lambs as required (mean
6 cm with a maximum tolerance of 2 cm). The
lambs were slaughtered when they reached the de®ned
PMW. The cholesterol determination was carried out
by using only two carcass samples out of ®ve minced
carcasses of lambs from each breed, CA and PMW.
These samples were selected at random, within the
above sub-classes, to give a total of 36 samples.
2.3. Statistical analyses
All statistical analyses were performed using Minitab statistical package (Minitab version 11). Data were
analysed separately for each experiment using the
general linear model (GLM). The model used accounting for the main effects and interactions of breed, sex,
degree of maturity (TSLW) in experiment 1, breed,
CA, TSLW in experiment 2, and breed and PMW in
experiment 3. The signi®cance of all main effects and
interactions was tested against the error mean squares.
3. Results
3.1. Experiment 1
Mean values of cholesterol content in carcass fat of
lambs are shown in Table 2. Analysis of variance of
cholesterol content (mg/g fat of carcass DM) showed
signi®cant (P < 0.001) effects of breed and degree of
279
G. Arsenos et al. / Small Ruminant Research 36 (2000) 275±283
Table 2
Mean cholesterol content (mg/g of carcass fat) of lamb carcasses by breed, sex and degree of maturity in experiment 1
Breed
Sex
Degree of maturity
Overall means
20%
30%
45%
60%
90%
B
Male
Female
4.77
4.05
5.43
4.85
2.64
2.22
2.42
1.96
3.26
1.77
3.33
S
Male
Female
5.06
7.36
7.33
6.09
4.33
3.14
3.23
2.38
3.45
1.74
4.41
K
Male
Female
4.39
5.49
3.19
3.96
3.37
4.17
3.00
2.38
1.95
1.55
3.34
Overall means
5.18
S.e.d. for comparing overall Breed means: 0.18
S.e.d. for comparing overall Degree of maturity means: 0.24
Overall sex means are: male, 3.85; female, 3.54; s.e.d., 0.15
5.14
3.31
2.56
2.28
Source of variation
d.f.
m.s.
F-value
P
Breed
Sex
Degree of maturity
Breed Sex
Breed Degree of maturity
Sex Degree of maturity
Breed Sex Degree of maturity
Error
2
1
4
2
8
4
8
30
7.63
1.48
23.18
1.62
2.32
1.77
0.83
0.34
22.44
4.35
68.18
4.76
6.82
5.21
2.44
***
Total
59
*
***
*
***
**
*
*
P < 0.05.
P < 0.01.
***
P < 0.001.
**
maturity (TSLW). This ®nding suggests that these two
factors are of major importance in terms of cholesterol
deposition (content) in carcass fat. Cholesterol content
was also signi®cantly affected (P < 0.001) by the
interaction between breed and TSLW (Table 2). Small
but signi®cant differences (P < 0.05) were found
between carcasses of male and female lambs. It is
interesting to note the inverse proportional relationship between TSLW and cholesterol content. It seems
that the mean cholesterol content decreased as the
degree of maturity approached the mature weight of
each breed. This pattern was consistent for all breeds.
In general, the intermediate-sized breed S seemed to
deposit the most cholesterol in carcass fat.
3.2. Experiment 2
Mean cholesterol values in respect of breed,
PMW and CA are shown in Table 3. The results
suggest that diet restrictions can result in signi®cant
changes in cholesterol content of carcass fat. Thus,
as the proportion of CA decreased and that of
Lucerne hay increased in the diet of lambs, the
cholesterol content in their carcass fat increased
(P < 0.001). Analysis of variance showed that breed
had a signi®cant effect (P < 0.001) similar to that
observed in experiment 1. The effect of PMW was
also signi®cant (P < 0.05), but this signi®cance
could be attributed to the fact that, although lambs
were slaughtered at the same LW, their carcasses
were at a different degree of maturity. Unlike experiment 1, there were no signi®cant interactions between
any of the main factors. It is important to note
that, generally, carcasses from lambs at the ®rst
slaughter point had a higher cholesterol content in
all breeds and that lambs fed on L levels of CA
appeared to deposit more cholesterol than those fed
on H levels.
280
G. Arsenos et al. / Small Ruminant Research 36 (2000) 275±283
Table 3
Mean cholesterol content (mg/g of carcass fat) of lamb carcasses by breed target slaughter live weight (TSLW) and concentrate allowances
(CA) in experiment 2
Breed
TSLW
Concentrate allowances
Overall means
H
M
L
B
23
28
33
2.59
2.63
3.25
3.71
3.21
3.70
4.40
3.77
3.52
3.42
S
23
28
33
4.20
3.78
3.43
4.78
4.53
4.05
5.74
4.56
5.42
4.50
K
23
28
33
2.65
2.53
3.11
4.16
4.16
4.17
4.64
3.02
3.90
3.59
Overall means
3.13
4.05
S.e.d. for comparing overall Breed means: 0.19
S.e.d. for comparing overall CA means: 0.18
Overall means for the 23, 28 and 33 TSLW are: 4.10,3.57 and 3.84; s.e.d. 0.19, respectively
4.33
Sources of variation
d.f.
m.s.
F-value
P
Breed
TSLW
CA
Breed TSLW
Breed TSLW
TSLW CA
Breed TSLW CA
Error
2
2
2
4
4
4
8
26b
6.04
1.22
7.11
0.17
0.52
0.50
0.28
0.31
19.48
3.94
22.94
0.55
1.68
1.61
0.90
***
Total
52b
*
***
NSa
NSa
NSa
NSa
a
NS: not signi®cant.
One sample was missing.
*
P < 0.05.
***
P < 0.001.
b
3.3. Experiment 3
4. Discussion
Table 4 shows the mean values of the cholesterol
content of carcass fat of lambs ®nished on irrigated
pasture. Cholesterol content in carcass fat differed
signiticantly (P < 0.01) between breeds. There was
no apparent effect of dietary treatment during the
indoor phase. This implies that the nutritional treatment before turnout to grazing appears to be of minor
signi®cance. There was a slight indication of a
decrease in cholesterol content in the carcasses of
heavier lambs but the differences between PMW were
non-signi®cant. However, there were small differences between breeds when compared at the same
PMW, with the B breed showing consistently higher
values.
This study was conducted to determine the cholesterol content in whole carcass fat of edible lamb meat
by comparing results of three different systems of
production. We discuss ®rst the effects of breed of
lambs and subsequently the effects of sex since this
factor was examined only in experiment 1. The effects
of feeding treatment and live weight at slaughter,
alternatively de®ned as proportion of mature weight
are then addressed.
4.1. Effects of breed and sex
The results indicate that the effect of breed was
apparent throughout the three experiments. Among
281
G. Arsenos et al. / Small Ruminant Research 36 (2000) 275±283
Table 4
Mean cholesterol content (mg/g of carcass fat) of lamb carcasses by breed, proportion of mature weight (PMW) and concentrate allowances
(CA) in experiment 3
Breed
PMW
Concentrate allowances
Overall means
1
2
3
B
0.48
0.55
3.31
4.36
5.01
3.90
5.07
4.66
4.38
S
0.48
0.55
4.55
2.89
3.53
2.96
3.25
3.67
3.47
K
0.48
0.55
3.56
4.04
3.68
3.72
4.40
3.30
3.78
Overall means
3.78
3.80
S.e.d. for comparing overall Breed means: 0.21
S.e.d. for comparing overall CA means: 0.21
Overall means for the 0.48 and 0.52 PMW are: 4.04, and 3.72; s.e.d. 0.19, respectively
4.06
Sources of variation
d.f.
m.s.
F-value
P
Breed
PMW
CA
Breed PMW
Breed CA
PMW CA
Breed PMW CA
Error
2
1
2
2
4
2
4
18
2.56
0.91
0.28
0.19
0.52
0.20
1.39
0.29
8.83
3.14
0.97
0.66
1.79
0.69
4.79
NSa
NSa
NSa
NSa
NSa
Total
35
a
**
**
NS: not signi®cant
P < 0.01.
**
the other factors that have been studied, breed seems
to be the most important regarding the effects on
carcass fat and its cholesterol content. This is in
agreement with the results of other studies (Zygoyiannis et al., 1992; Nurnberg et al., 1998; Matthes et al.,
1998). The above was more evident from the results in
experiment 3 in which, apart from breed factor, none
of the others had any signi®cant effect. Similar ®ndings with our results were reported by Abutarboush
and Dawood (1993), Sevi et al. (1997) and Demise
et al. (1998). Reported values ranged from about 135
to 184 mg per 100 g adipose tissues. The results of the
current study support the belief that the indigenous
Greek breeds produce carcasses with better eating
quality (Zygoyiannis et al., 1990; Arsenos, 1997),
as far as its savour is concerned. They also suggest
that there is a chance for the producers to choose
between the breeds studied here in terms of cholesterol
content in carcass fat, when attempts are made to
improve the overall quality of lamb carcasses. How-
ever, there was no clear indication of a consistent
difference between sex types within breeds (experiment 1) and it was not feasible to have a further
indication on these effect as the following experiments
were carried out with male only lambs.
4.2. Effects of nutritional management
In experiment 2, feeding treatment seems to be
important when comparisons are made at similar
carcass weights with respect to differences in the
degree of maturity between breeds. The different
levels of CA and that of Lucerne hay fed ad libitum
resulted in increased amount of cholesterol content in
carcass fat in response to reduction in the CA. The
highest amounts were observed in breed S and the
lowest in breed K. Mean cholesterol content was
signi®cantly decreased due to H levels of CA in S
and K breeds, but not in the slower maturing breed
B. In contrast, results from carcasses of lambs fed
282
G. Arsenos et al. / Small Ruminant Research 36 (2000) 275±283
on medium levels of CA were more similar across
PMW.
The results, also, indicate that the cholesterol content is lower in carcass fat samples obtained from
lambs ®nished on pasture (under the present system,
experiment 3) than those obtained from other lambs
(of the same breed) which were reared indoors in
individual pens on a diet of restricted amounts of CA
and ad libitum Lucerne hay (experiment 2). As
expected from the results in experiments 1 and 2, B
lambs tended to contain higher levels of cholesterol in
their carcass fat than those of the other two breeds.
These lambs, were grazing for a shorter period of time
since they belong to an early maturing breed. The
results from experiment 3 suggest that, irrespectively
of feeding treatment during indoor phase, increasing
the duration of grazing period could improve the
carcass quality of lambs. Zygoyiannis et al. (1999)
suggested that grazing on irrigated pasture would
allow reaching the optimal growth of muscles of
fattening lambs. Thus, lambs reared on irrigated pasture could be a source of low-fat, low-cholesterol
carcasses throughout the year. These observations
support the belief that the slower rearing systems
may result in a lower concentration of cholesterol
in carcass fat at equivalent weights (Demise et al.,
1998) and may also help to explain the decrease in fat
content in carcasses of grazing lambs (Sanudo et al.,
1996). However, Solomon et al. (1992), found that diet
had no effect on cholesterol content of lean tissue and
Rule et al. (1997) suggested that different growing®nishing strategies in beef cattle production systems
did not alter cholesterol in meat. Nevertheless, great
variability in cholesterol content was reported by Park
et al. (1991) in carcasses from post-weaned kids fed a
high quality concentrate diets and by Lough et al.
(1993) in various fat depots of lambs fed forage diets.
4.3. Effects of live weight at slaughter
The LW of lambs at slaughter (de®ned either as
degree of maturity or as proportion of mature weight)
affected signi®cantly the cholesterol content of their
carcasses. Given the range of PMW used in this study,
results suggest that the high levels of cholesterol
content in carcasses must have been deposited before
lambs reach the ®rst half of their mature LW. In
experiment 1, cholesterol content in carcass fat
decreased with advancing carcass maturity. For the
two younger maturity groups, the cholesterol content
was higher between the three breeds with the S lambs
having consistently the highest levels in experiments 1
and 2. In experiment 3, the cholesterol content did not
seem to be different between carcasses of lambs
slaughtered at the two PMW. The lack of signi®cance
due to PMW in experiment 3 may be attributed to the
fact that there were no signi®cant differences in
carcass traits when carcasses were compared at similar
degree of maturity (Hopkins and Nicholson, 1999).
Based on PMW differences, as well as on differences in fat content, one would thus expect that the
mature carcasses would contain more cholesterol.
However, this was not the case either in carcass
samples from experiment 1 or from experiment 2
(Tables 3 and 4). It seems that the cholesterol content
is not attributable to the differences in the amount of
fat in the carcasses. Similarly, Hoelscher et al. (1988)
suggested that cholesterol content does not depend
directly to the ether-extractable fat content of the
carcasses. Nevertheless, there was a general trend
for cholesterol content to be lower in fat samples
extracted from carcasses as TSLW increased.
5. Conclusion
The results suggest that there are possibilities of
modifying body composition by manipulation of postweaning nutrition, especially reducing the cholesterol
content in carcass fat, in lambs slaughtered at a wide
range of live weights. In such situation, however, as
nutritional management and degree of maturity
changes, breed remains the main factor determining
the cholesterol content in carcass fat. Results also
suggest that the provision of irrigated, sown pasture,
could be used to produce consumer acceptable carcasses at much heavier weights than those which are
traditionally preferred in Greece with a considerable
lower cholesterol content.
Acknowledgements
The work was supported by the European Community (DG VI) project No CAMAR 8001 CT 91-0308)
as a part of a collaborative program between the UK,
G. Arsenos et al. / Small Ruminant Research 36 (2000) 275±283
Greece and Spain. The assistance, also, of the farmer
Mr G. Zygoyiannis and his family is gratefully
acknowledged.
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